Plastics Materials (PD-PMD-I)

 CHAPTER - 01 

(INTRODUCTION OF POLYMER)

Can you live without Plastics......Think It.......🤔🤔

(BASICS OF POLYMER )

Polymer: 

• Poly(Many)+Mer(Unit)
• Polymers are large molecules also known as macromolecule. 
• Those are made up of long sequences of smaller units 
• They occur widely in natural and synthetic polymers are a very popular manufacturing material.

Monomer: Polymers are built up by the linking together of a large number of small molecules known as monomer. 

Dimer: Formed from the combination of two monomer units.

Oligomer: It is a complex molecule that is made out of a few monomer units.

Polymerization: The process by which, monomer combine to form polymers is known as polymerization

Degree of polymerization: The numbers of repeating unit known as degree of polymerization. It represent by Dp.

PROPERTIES OF POLYMERS

• Low Density. 
• Transparent or in different colours. 
• Good mechanical properties. 
• Low coefficient of friction. 
• Good corrosion resistance. 
• Good Thermal properties 
• Good mould ability. 
• Excellent surface finish 
• Good dimensional  tolerances.

APPLICATIONS OF POLYMERS

• Household Items 
• Medical Applications 
• Personal Protective Equipment 
• Clothing 
• Car Parts 
• Paints, Lubricants 
• Constructions 
• Packaging and Containers 
• Electronics

TYPES OF POLYMERS

THERMOPLASTIC V/S THERMOSET

AMORPHOUS V/S CRYSTALLINE POLYMER

TYPES OF POLYMERIZATION

Addition Polymerization: When molecules just add and to form the polymer, the process is known as addition polymerization. In this process the molecular weight of the polymer is approx equal, to that of all the molecules, which are used to make that polymer.

Condensation polymerization: When molecules do not just add on but also undergo some reaction formed the polymer and releases bypass product such as H2O, CO2. The process is called condensation polymerisation. In this process the molecular weight of the polymer is lesser than the total weight of monomers.

PROPERTIES OF POLYMER

• Low Density. 
• Transparent or in different colours. 
• Good mechanical properties. 
• Low coefficient of friction. 
• Good corrosion resistance. 
• Good Thermal properties 
• Good mould ability. 
• Excellent surface finish 
• Good dimensional  tolerances.

APPLICATIOS OF POLYMER

• Household Items 
• Medical Applications 
• Personal Protective Equipment 
• Clothing 
• Car Parts 
• Paints 
• Lubricants 
• Constructions 
• Packaging and Containers 
• Electronics

TYPES OF POLYMERIZATION TECHNIQUES

• Bulk Polymerization 
• Solution Polymerization 
• Suspension Polymerization 
• Emulsion Polymerization

BULK POLYMERIZATION

It is also known as mass polymerization and is formed by adding a radical initiator to the pure monomer. However, the monomer must be in a liquid state, and the radical initiator should be soluble. The reaction is exothermic.

SOLUTION POLYMERIZATION

In this industrial polymerization method, a monomer is to be dissolved in the non-reactive solvent having an initiator or catalyst, which increases the speed of reaction. The polymer formed in the process is also soluble in the same non-reactive solvent..

SUSPENSION POLYMERIZATION

In this process of heterogeneous radical polymerization, mechanical agitation is used for mixing monomers in their liquid state.

EMULSION POLYMERIZATION

In this process of heterogeneous radical polymerization, mechanical agitation is used for mixing monomers in their liquid state.

NATURAL POLYMERS

Natural polymers are large molecules that are found in nature. They are formed by the joining of smaller molecules, called monomers, through chemical processes. Natural polymers are essential to the structure and function of living organisms, and they are also used in a variety of industrial applications.

• Cellulose 
• Starch 
• Chitin 
• Proteins 
• Lignin 
• Shellac 
• Natural Resin (Rosin) 
• Natural Fibers 
• Natural Rubber

 CELLULOSE

Cellulose is a natural polymer and the main component of the cell walls of plants. It is a polysaccharide consisting of long chains of glucose units linked together. Cellulose is the most abundant organic compound on Earth and serves as a structural material in plants, providing strength and rigidity to cell walls. 

Source: Cellulose is primarily derived from plant sources. It is found in the cell walls of all plant tissues, with particularly high concentrations in wood, cotton fibers, and certain types of grasses.

Manufacturing : The manufacturing of cellulose typically involves the following steps- 

• Harvesting: Plants rich in cellulose (e.g., wood, cotton) are harvested.
• Pulping: The harvested material undergoes a pulping process to separate the cellulose fibers from other components such as lignin and hemicellulose. This can be achieved through mechanical processes (like grinding and pressing) or chemical processes (such as digestion with chemicals like sodium hydroxide).
• Processing: The cellulose fibers are further processed and purified to produce cellulose in various forms.

Formation of Cellulose :

• In the leaf of a plant, the simple compounds carbon dioxide and water are combined to form the sugar glucose. This process, known as photosynthesis, requires catalysis by the green coloring matter chlorophyll, and requires energy in the form of light. 
• Plants synthesize carbohydrates through photosynthesis-

6CO2 + H2O →602 + C6H12O6 (Glucose)→ Starch, Cellulose + H2O

• Thousands of glucose molecules can then be combined to form the much larger molecules of cellulose, which constitutes the supporting framework of the plant.

Properties of Cellulose:

• Chemical Formula- (C6H10O5)n
• No taste and No odour
• Melting point- 260-270 °C
• Density -1.5 g/cc
• Insoluble in water.
• Soluble in few organic solvents
• Crystalline solid having a white powdery appearance
• High Molecular weight.
• High tensile strength due to formation of hydrogen bonds between the individual chains.

Applications of Cellulose :

• Used in the diet as a fibre supplement
• Used to produce paperboard and paper products
• Used as an additive in various food items
• Used in the production of rayon
• Used as a preservative in cheese as it plays the role of an anti-clumping agent
• Used in making explosives (nitrocellulose)

STARCH

Starch is a complex carbohydrate and natural polymer that is a key part of many plants, including fruits, vegetables, and grains. It is made up of long chains of glucose molecules that are joined together by covalent bonds.

Source: Starch is manufactured in the green leaves of plants from excess glucose produced during photosynthesis and serves the plant as a reserve food supply. Starch is stored in chloroplasts in the form of granules and in such storage organs as the roots of the cassava plant; the tuber of the potato; the stem pith of sago; and the seeds of corn, wheat, and rice.

Structure of Starch

Manufacturing : The manufacturing of starch typically involves the following steps-

• Raw Material Selection: Starch is derived from various raw materials such as corn, wheat, potatoes, and cassava
• Extraction: The extraction process varies slightly depending on the raw material but generally follows these steps-
• Cleaning
• Milling/Grinding
• Slurrying
• Separation: Separation techniques vary based on the raw material but typically include the following methods.
• Centrifugation
• Sieving
• Hydro-cycloning
• Purification: Purification involves several washing steps to remove any residual non-starch components. The starch is repeatedly washed and centrifuged to ensure high purity..
• Dewatering: The purified starch is still in a slurry form and needs to be dewatered. This is typically done using vacuum filters or centrifuges to remove as much water as possible.
• Drying: The dewatered starch is then dried to achieve the desired moisture content. Common drying methods include:
• Air Drying
• Spray Drying
• Grinding and Sieving: Dried starch may be ground and sieved to obtain the desired particle size and consistency.
• Packaging and Storage: The final product is packaged in appropriate containers to protect it from moisture and contamination. It is then stored in a cool, dry place until it is ready for distribution.

Properties of Starch:

• White, odorless powder,
• Density-1.5g/cc
• Melting-256-258 °C
• 20–30% amylose (Linear) and 70–80% amylopectin (Branched)
• Insoluble in cold water and alcohol, forms a gel in hot water.
• Varies by source, swells and thickens upon heating with water, with different gelatinization temperatures.
• Comprised of amylose and amylopectin, with varying ratios depending on the source.
• High molecular weight polymers
• Absorbs and retains water
• Provides carbohydrates and energy
• Environmentally friendly and can be modified for specific uses.
• Varies in stability to high temperatures and viscosity changes with temperature, shear, and concentration.

Applications of Starch:

• Food Industry: Used as a thickener, stabilizer, and gelling agent in products like sauces, soups, and desserts.
• Paper Industry: Used as a binder and coating agent to improve paper quality.
• Textile Industry: Used in textile sizing and finishing to provide strength and smoothness to fabrics.
• Pharmaceutical Industry: Used as a binder and disintegrant in tablet formulations.

CHITIN

Chitin is the second most abundant polysaccharide in nature. An estimated 1 billion tons of chitin are produced each year in the biosphere. It is a primary component of cell walls in fungi.

Source: chitin is extracted from the shells of crabs, shrimps, shellfish and lobsters, which are major by-products of the seafood industry.

Properties of Chitin:

• Structure: Long-chain polymer, similar to cellulose.
• Abundance: Second most abundant natural polymer, sourced from crustaceans, insects, and fungi.
• Mechanical Properties: Strong, flexible, high tensile strength, and toughness.
• Chemical Properties: Insoluble in water/organic solvents, dissolvable in acids/alkalis.
• Antimicrobial Properties: Prevents microbial growth, useful in medical and packaging applications.
• Biodegradability: Naturally biodegradable, environmentally friendly.
• Biocompatibility: Suitable for medical uses like wound dressings and tissue engineering.

Applications of Chitin:

• Medical: Wound dressings, sutures, tissue engineering, drug delivery, anti-inflammatory/antimicrobial agents.
• Agriculture: Biopesticides, seed coatings, soil conditioners, plant growth enhancers.
• Industrial: Water purification, biodegradable films/packaging, textile finishing, bioplastics.
• Food Industry: Edible coatings, food preservatives, thickeners, stabilizers.
• Cosmetics: Moisturizers, skin care, hair care, anti-aging products.
• Environmental: Biodegradable materials, oil spill remediation.
• Biotechnology: Enzyme immobilization, microencapsulation of cells/bioactive compounds.

PROTEIN

Proteins are known as the building blocks of life because they are the most abundant molecules present in the body and form about 60% of the dry weight of cells.

Source: Primary protein sources include animal products (meat, poultry, fish, dairy, eggs) and plant-based options (legumes, nuts, seeds, grains, soy products, vegetables).

Structure: A polymeric chain of amino acid residues constitutes proteins. A protein’s structure is primarily made up of long chains of amino acids. The arrangement and placement of amino acids give proteins certain characteristics. All amino acid molecules contain an amino (-NH2) and a carboxyl (-COOH) functional group.

Properties of Protein:

• Proteins are made of amino acids and have complex structures (primary to quaternary).
• They perform various functions like enzymes, transport, and structural support.
• Proteins can be either soluble or insoluble in water.
• Heat, pH, or chemicals can denature proteins, altering their structure and function.
• Each protein is highly specific to its role and interactions in the body.

Applications of Proteins:

• Medical: Therapeutic drugs (e.g., insulin), diagnostics, nutritional supplements.
• Food Industry: Functional ingredients, protein-rich foods.
• Biotechnology: Recombinant protein production, industrial enzymes.
• Agriculture: Animal feed supplements, plant proteins.
• Cosmetics: Skincare, hair care products with proteins.

LIGNIN

Lignin, complex oxygen-containing organic polymer that, with cellulose, forms the chief constituent of wood. It is second to cellulose as the most abundant organic material on Earth.

Source: It is primarily found in plants, where it acts as a glue to hold together cellulose fibers in the cell walls. This gives plants their rigidity and resistance to decay. Trees and woody plants are especially rich in lignin.

Structure:

It is a complex, irregular polymer made from phenylpropane units linked by various bonds, forming a strong, three-dimensional network. Its structure is highly cross-linked and amorphous, providing rigidity and water resistance to plant cell walls. Lignin varies across plants and is challenging to break down, contributing to the strength and durability of wood.

Properties of Lignin:

• Provides mechanical strength and rigidity to plant cell walls.
• Shows hydrophobic properties, aiding in water retention and transport.
• It is a highly cross-linked, amorphous polymer with an irregular structure.
• Resistant to microbial and enzymatic degradation due to its complex bonding.
• Its structure varies across different plant species, tissues, and environmental conditions.

Applications of Lignin:

• Lignin is removed to produce white paper, with the byproduct often used as biofuel.
• Lignin can be converted into renewable biofuels.
• Creating durable composite materials for construction and automotive industries.
• Producing chemicals like vanillin and as a component in resins and adhesives.

SHEELAC

Unlike other natural resins, shellac does not originate from plants, but is produced from the secretion of an insect. It is a purified form of lac and is the most widely known as lac product.

Source:

Shellac is produced by the female lac bug, Kerria lacca (Laccifer lacca), which lives on trees in India and Thailand. The bugs secrete the resin as they feed on tree sap, and it is then harvested from the tree branches.

Structure & Compositions: 

Shellac is primarily a mixture of aliphatic poly hydroxy acids in the form of lactones and esters. It has an acid number of 70, a saponification number of 230, a hydroxyl number of 260, and an iodine number of 15. Its average molecular weight is about 1000.

Properties:

• Non-toxic and safe for food, pharmaceuticals, and cosmetics.
• Easily dissolves in alcohol for application as a coating.
• Dries quickly to form a hard, durable, glossy finish.
• Provides a smooth, moisture-resistant protective layer.
• Softens with heat and hardens when cooled, allowing for versatile use

Applications:

• Wood Finish: Provides a protective, glossy coating for wooden surfaces.
• Food Coating: Used to create a shiny, moisture-resistant layer on candies and fruits..
• Pharmaceutical Coating: Coats pills and tablets to protect from moisture and improve taste.
• Adhesive:Serves as a natural adhesive in industrial and crafting applications.
• Cosmetics and Insulation: Applied in nail polish and as an insulating material in electronics

NATURAL RESIN / ROSIN

Rosins are known as gum, wood, or tall oil rosin, based on the method of isolation and the source. It is a versatile natural resin with sticky, adhesive properties 

Source: 

It is derived from the oleoresin (a mixture of resin and volatile oils) exuded by pine trees, particularly from species like Pinus. The process involves collecting the raw resin, which is then heated to evaporate the volatile oils (turpentine), leaving behind the solid rosin.

Structure-

• Natural rosin is primarily composed of diterpene resin acids like abietic acid, with a complex, amorphous structure, that is hydrophobic and thermoplastic. 
• Its molecular structure includes a diterpene backbone with carboxylic acid groups, contributing to its reactivity and versatility.

Properties- 

• Hard and brittle at room temperature.
• Repels water and does not dissolve in water.
• Dissolves in organic solvents like alcohol and acetone.
• Strong adhesive properties, suitable for glues and coatings.
• Softens when heated and hardens upon cooling

Applications- 

• Adhesives: 
• Varnishes and Coatings 
• Ink Production
• Rubber Compounding
• Musical Instruments

NATURAL FIBERS

Natural fibres such as jute and coir have been computing the properties of cellulose fibres. Fibres commonly used in composites materials, carpet, ropes, coir and geotextile. 

Source: 

Cellulose fibres are obtained from different parts of vegetables plants for e.g. jute are obtained from the stem; sisal, banana and pineapple from leaf, cotton from seed, coir from fruit etc.

Structure: 

• Plant-based fibers-such as cotton and flax, are made of cellulose and have a hollow, twisted structure.
• Animal-based fibers-like wool and silk, are composed of proteins, with wool providing insulation and silk being smooth and shiny.

Properties: 

• Natural fibers decompose naturally over time, minimizing environmental impact.
• Cotton and linen fibers are breathable, offering comfort in warm climates. 
• Cotton is highly absorbent, ideal for towels and bed linens.
• Wool provides excellent insulation and has natural elasticity, making it suitable for winter clothing and comfortable to wear. 
• Fibers like flax are strong and durable, perfect for heavy-duty uses such as ropes and sacks.

Appications: 

• Textiles and Clothing: Cotton, wool, silk, and linen are used in various fashion items and home textiles. 
• Home Furnishings: Cotton, jute, and sisal are popular for curtains, carpets, bed linens, and upholstery. 
• Industrial Applications: Hemp and jute are used for ropes, sacks, and composite materials in automotive and construction.
• Medical and Hygiene Products: Cotton is widely used in bandages, gauze, and other medical products for its absorbency. 
• Eco-friendly Products: Natural fibers are increasingly used in biodegradable and sustainable products like reusable bags and packaging

NATURAL RUBBER

Natural rubber (NR) (cis-1,4-polyisoprene) occurs in over 200 species of plants. The Hevea brasiliensis tree accounts for over 99% of the world's natural rubber production.

Latex Composition:

• Freshly tapped Hevea latex- 
• pH of 6.5-7.0, 
• Density of 0.98 g/cm3, 
• Surface free energy of 4.0-4.5 μJ/cm2 (0.96-1.1 μcal/cm2). 
• The total solids of fresh field latex vary typically from 30 to 40%, depending on the clone, weather, stimulation, tapping frequency, and other factors. copper.
• The dry rubber content is 3 wt % less than the total solids. 
• The rubber phase typically contains 96 wt % rubber hydrocarbon, 1 wt % protein, and 3 wt % lipids along with trace amounts of magnesium, potassium, and copper.

Latex Processing: 

• Collection of Latex: Latex is harvested from rubber trees through a process called tapping, where shallow cuts in the tree bark allow the latex to flow out and be collected. 
• Preservation: To prevent the latex from spoiling or coagulating prematurely, preservatives like ammonia are added immediately after collection to stabilize the latex during storage and transportation. 
• Centrifugation: The latex is concentrated by spinning it in a centrifuge, which separates the rubber particles from water and other non-rubber components, increasing the rubber content to about 60% for further processing.

       

Types and Grades: 

The type of rubber is defined by the raw material and the method of production, whereas the grade refers to quality subdivisions within a type- 

• Visually Graded Rubber (VGR)- Visual inspection is the oldest method of grading rubber) 
• Technically Specified Rubber (TSR)- All versions of TSR are analysed with the same set of tests to determine quality, but small differences exist in the specification limits and the permissible raw materials. 

Aspect	Technically Specified Rubber (TSR)	Visually Graded Rubber (VG Rubber)
Grading Method	Based on technical specifications and measurable properties (e.g., dirt content, ash content, viscosity)	Based on visual inspection of appearance (color, cleanliness, visible impurities)
Quality Consistency	High consistency due to precise, measurable testing criteria	Variable consistency, relies on subjective visual assessment
Processing	Involves controlled processes with washing, shredding, drying, and laboratory testing	Processed mainly through traditional methods with basic cleaning and visual inspection
Uses and Applications	Used in industries needing high-quality, consistent rubber (e.g., automotive tires, conveyor belts, industrial products)	Used for general-purpose applications where minor quality variations are acceptable (e.g., rubber bands, mats, general rubber goods)
Cost	Generally more expensive due to additional processing and quality control	Typically cheaper due to less stringent processing and testing
Purpose	Ensures predictable properties like strength, elasticity, and durability	Suitable for applications where exact properties are less critical

Processing of Natural Rubber- 

The processing of natural rubber involves several technical steps to convert raw latex from rubber trees into a usable form.type. Steps divided into four key stages- 

• Mastication 
• Mixing or Incorporation 
• Shaping/Forming 
• Vulcanization (Curing) 

1. Mastication- 

• It involves mechanically working the rubber to break down its molecular structure, making it softer, more plastic, and easier to mix with other ingredients. 
• This is typically done using a two-roll mill or an internal mixer (Banbury mixer). 
• This process reduces the rubber's viscosity, making it easier to process.

2. Mixing or Incorporation- 

After mastication, various additives are mixed into the rubber to achieve the desired properties for the final product. These additives may include- 

• Fillers (e.g., carbon black, silica)- to reinforce the rubber and improve strength. 
• Plasticizers- to improve flexibility. 
• Accelerators and Activators- to control the vulcanization process. 
• Antioxidants and Stabilizers- to prevent degradation from heat, light, or oxygen.

3. Shaping/Forming- In this stage, the compounded rubber is shaped into the desired form of the final product. There are several methods of shaping, depending on the type of product being made. 

• Extrusion- To produce long, continuous shapes such as tubes and strips. 
• Calendering- to create thin sheets or coatings for flat products. 
• Molding- for complex shapes like tires and seals. 
• Dipping- To form thin rubber films for products like gloves and balloons.

4. Vulcanization- 

• It is a critical process that converts the rubber from a plastic, flexible material into a durable, elastic product. 
• This chemical process involves heating the rubber compound with sulfur or other curing agents to create cross-links between the rubber molecules. 
• These cross-links improve the rubber elasticity, strength, and heat resistance. 

Basic Steps in Vulcanization- 

• Preparation- The natural rubber is first compounded with various additives, including sulfur (the primary curing agent), accelerators (to speed up the curing reaction), and other chemicals (like antioxidants and fillers) to achieve the desired properties.
• Mixing- The compounded rubber is thoroughly mixed to ensure that the additives are evenly distributed throughout the rubber. This mixture is then shaped into the desired form using methods like extrusion, molding, or dipping. 
• Heating- The rubber is heated in a curing or vulcanization chamber. The heat activates the sulfur and other curing agents, leading to a chemical reaction that forms cross-links between the rubber molecules. 
• Cooling- After vulcanization, the rubber is cooled to solidify the cross-linked structure. This step is essential to stabilize the rubber and make it ready for use.

Types of Vulcanization- 

• Sulphur Vulcanization 
• Efficient (EV) Vulcanization

1. Sulphur Vulcanization- 

Sulfur vulcanization is a chemical process used to improve the properties of natural rubber. 

• Sulfur vulcanization creates cross-links between rubber polymer chains, strengthening and stabilizing the material. 
• This process enhances rubber’s durability, elasticity, and resistance to heat, chemicals, and wear. 
• The amount of sulfur and vulcanization conditions can be adjusted to control the rubber hardness and flexibility.

2. Efficient (EV) Vulcanization- 

Efficient Vulcanization (EV) in natural rubber refers to a process that optimizes the sulfur cross-linking reaction to improve rubber properties

• EV systems have low sulfur content (0.3-1.0 parts) and high accelerator concentration (2.0-5.0 parts). This reduces the formation of polysulfide cross-links, focusing on stronger monosulfide bonds. 
• Semi-EV systems are a compromise, with moderate sulfur (1.0-1.8 parts) and accelerator levels (1.0-2.5 parts). 
• EV vulcanizates predominantly form monosulfide cross-links, offering superior thermal stability and oxidation resistance.

VULCANIZATION CHEMICALS USED IN NATURAL RUBBER-

 

Sulfur and Accelerators	Natural rubber is mainly vulcanized using sulfur and accelerators. Lower sulfur levels require more accelerator for cross-link density. Semi-EV  with 0.5-1.5 phr sulfur optimize mechanical properties.
Metal Oxides	Zinc oxide is the primary metal oxide used to enhance the effect of accelerators. Magnesium oxide and lead oxide are sometimes used for specific purposes like acidic compounds or reducing water absorption.
Activators	Fatty acids (e.g., stearic acid) and amine salts act as activators in many accelerator systems. Activators like glycol and triethanolamine are used in silica-filled compounds.
Vulcanization Inhibitors	Used to prevent premature vulcanization (scorching). Phthalimide sulfenamides are common inhibitors, delaying the onset and completion of vulcanization.

 

Protective Agents	Aromatic amines (e.g., p-phenylenediamine) protect against oxidation, dynamic fatigue, and ozone. Lighter vulcanizates use bisphenols or polymeric hindered phenols to avoid discoloration.
Fillers	Reinforcing fillers (e.g., carbon black, silica) enhance tensile and tear strength. Non-reinforcing fillers (e.g., kaolin, calcium carbonate) are used to adjust properties like hardness, processability, and price.
Oxidation	Oxidation breaks down rubber chains, reducing physical properties. Oxidation is influenced by processing conditions, metal catalysts, and temperature.
Ozone Attack	Ozone reacts with double bonds in NR, leading to surface cracks. Wax and chemical antiozonants are used to prevent this degradation.

 

Softeners	Mineral oils, animal, and vegetable oils are common softeners. NR uses fewer softeners than synthetic rubbers. Migration and blooming potential must be considered when choosing softeners.
Resins	Resins are not typically necessary for NR but can be added for tack (e.g., rosin, tar). Resins developed for synthetic rubbers are less relevant for NR.

Properties- 

• Density: Typically has a density of around 0.9 g/cm³, making it lightweight. 
• Elasticity: High elasticity allows for stretching (up to 600-800%) and returning to its original shape. 
• Tensile Strength: Good tensile strength (21-28 MPa or 3000-4000 psi) provides durability under tension. 
• Resilience: Excellent resilience enables absorption of energy and return to shape after deformation. 
• Abrasion Resistance: Fair abrasion resistance makes it suitable for wear and tear applications. 
• Thermal Stability: Moderate thermal stability; can degrade at high temperatures without proper vulcanization.
• Weather Resistance: Prone to degradation from UV light, ozone, and oxidation; requires protective agents for better aging resistance. 
• Chemical Resistance: Limited resistance to certain chemicals; can swell or degrade in oils, solvents, and some acids. 
• Processability: Easily processed through methods like molding, extrusion, and calendering due to good flow properties. 
• Adhesion: Good adhesion properties, suitable for bonding with other materials in various applications

Applications- 

• Tires: Commonly used in tires for vehicles, including cars, trucks, and aircraft, due to durability and heat resistance. 
• Industrial Products: Employed in conveyor belts, hoses, gaskets, and seals, providing flexibility and abrasion resistance. 
• Footwear: Used in shoe soles for comfort, grip, and resilience. 
• Adhesives: Utilized in various adhesives, including surgical, masking, and packaging tapes for excellent bonding properties. 
• Sports and Household Items: Found in sports equipment like tennis balls and household products like rubber mats and toys for cushioning and durability. 

 

Percentage of Rubber used in various applications-- 

CHAPTER - 02

(COMMODITY PLASTICS)

Why we use thermoplastic ?

• Performance and Durability: Enhanced performance with good strength-to-weight ratio, toughness, and durability.
• Cost and Process Efficiency: Reduces costs through parts consolidation, net shape formation, and elimination of processes like painting and machining. 
• Material Properties: Properties can be tailored to specific needs, offering corrosion resistance, chemical and moisture resistance, and fire retardancy. 
• Ease of Use: Easy to process, non-toxic, and practically maintenance-free with attractive colors and good weatherability. 
• Sustainability: Reusable, recyclable, and resistant to microbes, contributing to environmentally friendly applications.

COMMODITY PLASTICS

• Commodity plastics are a category of plastics that are produced in large quantities and are used in a wide range of everyday applications. 
• Also known as general purpose plastics. 
• Commodity plastics play a crucial role in various industries due to their affordability, versatility, and availability. 
• Examples- 
• Low Density Polyethylene (LDPE) 
• Linear Low Density Polyethylene (LLDPE) 
• High Density Polyethylene (HDPE) 
• Polypropylene (PP) 
• Polyvinyl chloride (PVC) 
• Polystyrene (PS).

Properties-

• Enhanced Cost-Effectiveness: Produced in large quantities, keeping costs low and making them affordable for mass production. 
• Lightweight: Contributes to reduced transportation costs and enhances energy efficiency in various applications. 
• Versatility: Can be molded into diverse shapes and sizes, suitable for a wide range of industries. 
• Chemical Resistance: Many exhibit good resistance to chemicals, making them ideal for packaging and containers. 
• Ease of Processing: Easily processed through common manufacturing techniques like injection molding and extrusion.

Applications-

• Produced Packaging: Widely used in flexible packaging materials, such as bags, films, and containers. 
• Consumer Goods: Found in household items like toys, kitchenware, and cleaning products. 
• Automotive Parts: Utilized for components like bumpers and interior panels due to durability and lightweight properties.
• Construction: Commonly used in pipes, fittings, and flooring materials for their strength and corrosion resistance. 
• Electronics: Used in housings, insulation, and connectors in electronic devices for their electrical insulation properties.

MATERIAL SELECTION CRITERIA

POLYETHYLENE (PE)

                               

Where: 

• CH₂=CH₂ is the ethylene monomer. 
• [-CH₂-CH₂-]n is the repeating unit of the polyethylene polymer, with "n" representing the number of repeating units.

Types of Polyethylene- 

• LDPE (Low-Density Polyethylene)
• HDPE (High-Density Polyethylene)
• LLDPE (Linear Low-Density Polyethylene)
• VLDPE (Very Low-Density Polyethylene)
• MDPE (Medium-Density Polyethylene)
• UHMWPE (Ultra-High Molecular Weight Polyethylene)

LDPE (Low-Density Polyethylene)

Low-Density Polyethylene (LDPE) is produced through free-radical polymerization. This process typically involves: 

• High Pressure: The polymerization is carried out at high pressures (1000-3000 atmospheres). 
• High Temperature: The reaction takes place at elevated temperatures (around 200-300°C). 
• Free Radicals: Organic peroxides or oxygen are used to initiate the free-radical chain reaction, which results in the formation of LDPE 

Properties- 

• Low density- 0.915 ~ 0.925 g/cc 
• Low melting range- 115°C~120°C 
• Tg  is well below the room temperature 
• Free from odour and toxicity 
• Very low cost & FDA compliant 
• Good tensile strength, elongation & impact resistance 
• Low brittleness 
• Good insulating properties 
• Excellent chemical resistance
• Easy processability 
• Water repellent 
• Low gas & water vapour permeability

Limitations- 

• Susceptible to environmental stress cracking 
• Low strength, stiffness and maximum service temperature. 
• High gas permeability, particularly carbon dioxide 
• Poor UV resistance 
• Highly flammable 
• High-frequency welding and joining impossible 
• Poor scratch and abrasion resistance

Processibility- 

• Injection Molding-
• Melt temperature : 160-260°C 
• Post mold shrinkage lies between 1.5 and 3.5 %
• Extrusion-
• Melt temperature : 180-240°C 
• Higher melt temperatures are needed for extrusion-coating (280-310°C). 
• A three zone screw with a L/D ratio of around 25 is recommended

Applications- 

• Packaging: Bags for grocery, garbage, shopping, milk pouches, liners for woven sacks, garment packing, cellular foams for packaging. 
• Medical: Bottles for packing fluids, Saline. Bottle caps and inner seals. Tubes for saline sets, gases, fluids, etc.
• Agriculture: Irrigation Pipes, film for greenhouses, nursery bags, canal liners, mulching films etc. Electrical: Wire coating, electrical  and telephone cable sheathing.

LLDPE (Linear Low-Density Polyethylene)

LLDPE is made through copolymerization of ethylene with α-olefins (like butene, hexene, or octene).

• Catalysts Used:
• Ziegler-Natta catalysts 
• Metallocene catalysts
• Pressure and Temperature: Low to medium pressures (compared to LDPE) and at mild temperatures (about 70-90°C)

Properties-

• Higher Density (0.910 ~ 0.925) 
• Higher Melting Range.(125˚C) 
• Very good Puncture resistance 
• High ESCR 
• Good tensile strength, stiffness & creep 
• Excellent temperature toughness 
• Moderate thermal stability 
• Excellent water vapour barrier

Limitations- 

• Lower gloss than LDPE 
• Narrower heat-sealing temperature range than LDPE 
• Lower processability compared to LDPE 
• Susceptible to stress cracking 
• Lower stiffness than polypropylene 
• High mold shrinkage 
• Poor UV resistance 
• Low heat resistance 
• Not suitable for high-frequency welding and joining

Processibility- 

• Injection Molding-
• Melt temperature : 160-260°C
• Extrusion-
• Melt temperature : 205-260°C 
• A three zone screw with a L/D ratio of around 25 is recommended

Grade- 

• Opalene-ONGC-OPAL 
• Polysure-HMEL 
• SABIC LLDPE 
• G-Lene- GAIL
• ExxonMobil LLDPE

Applications- 

• Bags and Pouches: Used for packaging. 
• Films for Food Packaging: Suitable for frozen and dry goods.
• Agriculture: Used for agricultural films.
• Pipes & Fittings: Suitable for water pipes.
• Wiring & Cables: Used for cable jacketing and insulators.

High Density Polyethylene (HDPE)

HDPE is produced through polymerization of ethylene monomers (C₂H₄) in a reactor.

• Catalysts Used: 
• Ziegler-Natta catalysts under low pressure 
• Philips process 
• Pressure and Temperature: Low to medium pressures (1–3 MPa) and at mild temperatures (about 70-110°C)

Properties-

• Higher Density: 0.940–0.965 g/cm³ 
• Melting range: 135°C 
• Tg well below room temperature 
• FDA compliant 
• Good thermal stability 
• High tensile, stiffness, creep and abrasion resistance (superior to LDPE) 
• Higher impact strength, wear resistance, and stress crack resistance 
• Higher heat deflection temperature 
• Very low water absorption 
• Non-polar with excellent chemical resistance 
• Good insulation properties and water vapor barrier 

Limitations- 

• Limited Heat Resistance 
• Poor UV and Weather Resistance 
• Lower processability compared to LDPE 
• Higher Cost than PE 
• Susceptible to Creep

Applications- 

• Agriculture: Drip irrigation drippers, sprinkler parts, agricultural nets.
• Automotive: Fuel tanks, wheel covers, door interiors, petrol cans and caps. 
• Industrial: Gasoline and chemical storage tanks, industrial drums, cable jacketing. 
• Household: Grocery bags, pipes, mugs, soap boxes, knife handles, bottles, nets, dust bins, buckets. 
• Packaging: Milk crates, beverage bottles, paint pails, bread trays, bottle caps, fertilizer and cement sacks.

POLPROPYLENE (PP)

Polypropylene (PP) is a linear polymer, composed of repeating units of isopropane.

                                       

• Catalysts Used: 
• Ziegler-Natta Polymerization.((titanium trichloride with aluminum trialkyls) 
• Metallocene Polymerization

Processing-

• Medium: Naphtha under a nitrogen atmosphere, forming a slurry (10% catalyst, 90% naphtha). 
• Molecular Weight Control: Hydrogen is used as a chain transfer agent to control molecular weight. 
• Process Type: Suspension polymerization. 
• Polymerization Conditions: Propylene is charged under pressure into the polymerization vessel, with separate metering of the catalyst and reaction diluent.

Structure Property Relationship-

• PP is a linear polymer with minimal or no branching. 
• The methyl group in the chain increases the melting point and causes chain stiffening. 
• The tertiary carbon atom in PP provides a site for oxidation, making it less stable than polyethylene (PE) in the presence of oxygen. 
• The presence of the methyl group results in products with varying tacticity. 
• Commercial polypropylene typically has about 90-95% isotactic structure.

Tacticity- It refers to the arrangement of side groups (e.g., methyl groups) relative to the polymer backbone in a polymer chain

• Isotactic 

• Syndiotactic 

• Atactic 

General Properties-

 

Name Of Property	Value	Unit
Specific gravity	0.90	--
Tensile Strength	35.5	MPa
Tensile modulus	1380	MPa
Flexural modulus	1690	MPa
Elongation at break	35-350	%
Impact Strength (Izod )	37	J/m
Hardness	R100	---
HDT (under 1.82 MPa load.)	55	°C
Glass transition temperature	5	°C
Melting point	164	°C
Dielectric Strength	24-28	KV/mm

Properties- 

• Very Low Density (0.890 - 0.905 g/cm3) 
• Melting range (160°C~165°C) 
• PP burns slowly and has an odor of crude oil
• Tough with good impact resistance.
• Good surface hardness and scratch resistance. 
• Outstanding hinge properties. 
• FDA compliant
• Excellent insulator due to its non-polarity.
• Good chemical resistance to most inorganic acids, alkalis, salts,

Grades-

MFI (gm/10 min)	Grade
3-5	Blown film grade
9-11	Cast film grade
16	Extrusion coating grade
11	General purpose injection grade
1.9	Bottle grade

Trade Name:

Name Of Company	Grade Name
Haldia Petrochemicals Ltd, India	Halene PP
IPCL, India	Koylene
Reliance, India	Repol
Exxon Mobil, US	Escorene
Mitsui petrochemical, Japan	Sunlet PP
Mobil Chemical, US	Bicor PP
Sumitomo, Japan	Esprene
Mitsubishi , Japan	Noblen

Processability-

• Injection Molding
• Melt temperature : 210-275°C
• Pressure- 100-150 MPa. (Depending upon grade)
• Extrusion
• Melt temperature : 220-230°C
• L/D Ratio- 30:1

Applications-

• Household: Buckets, thermo flask cases, microwave trays, baby bottle warmers, hair dryers.
• Appliances: Dish racks, washing machine parts, air cleaners, pump housings, silverware baskets. 
• Automotive: Bumpers, steering wheel covers, radiator grills, spoilers, fenders. 
• Packaging: Candy wrappers, tobacco packaging, contact lens cases, first aid kits, tool boxes. 
• Electrical/Electronics: Cable connectors, transformer housings, switch gears, capacitors, control knobs. 

Modification in Polyolefins- 

• Ethylene-vinyl acetate (EVA) copolymer. 
• Ethylene-ethyl acrylate (EEA) copolymer. 
• Ethylene-methyl acrylate (EMA) copolymer. 
• Ethylene-acrylic/methacrylic acid copolymer. 
• Ethylene-propylene copolymer. 

POLYVINYL CHLORIDE (PVC)

It is the most versatile thermoplastic with a wide range of applications..

Historical Timeline- Vinyl Chloride was first synthesized by Reghawlt in 1835. Commercial production of PVC resin began in 1931 in Germany. In India, PVC manufacturing started in 1961 when Calico began its plant in Mumbai.

Commercial Method- 

• Vinyl chloride monomer is prepared by cracking 1,2-dichloroethane.

                                    

                           

• Vinyl Chloride may be produced by the addition of HCl to acetylene.

    
               

Polymerization-

• Suspension Polymerization 
• Emulsion Polymerization

• Suspension Polymerization: 
• 85% of the world's PVC production is done by suspension polymerization.
• The technique was developed by Dr. Berg at Wacker-Chemie Polymerization in 1935.
• Vinyl chloride is dispersed in water with stirring during the process.
• Monomer-soluble organic peroxides are used as initiators for polymerization.
• Protective colloids, such as cellulose ethers, are added to prevent the monomer droplets from coalescing.
• After polymerization, unreacted vinyl chloride is removed and sent to the monomer recovery plant.
• The polymer is then centrifuged to remove free water, and the resulting wet polymer is dried by hot air.
• The particle size of PVC resin is about 100-150µm.

• Emulsion Polymerization-  
• The system consists of the monomer- water containing emulsifier and water soluble initiator. 
• In presence of the emulsifier, agitation of the charge in the autoclave disperse the monomer into very fine droplets. Initiator starts polymerization. 

Structure Property Relationship-

• PVC is polar due to the presence of the C-Cl dipole.
• It is resistant to non-polar solvents.
• PVC is flame retardant and self-extinguishing.
• The presence of the chlorine atom increases inter-chain attraction, enhancing hardness and stiffness of the polymer.

Properties- 

Name Of Property	Value	Unit
Specific gravity	1.18-1.70	--
Tensile Strength	5.5-26.2	MPa
Tensile modulus	4.8-12.4	MPa
Flexural modulus	30	MPa
Elongation at break	150-450	%
Hardness	A85	---
Glass Transition Temperature	80-85	°C
Dielectric Strength	9.9-15.8	KV/mm

• Density (1.38 g/cm3) 
• Melting point (210 °c) 
• Good strength.
• Good abrasion resistance.
• Excellent water and chemical resistance. 
• Unlimited compounding possibilities. 
• Self extinguishing characteristics. 
• Good weather resistance. 
• Good electrical properties

Dilute Solution Viscosity (DSV)/(K Value Of PVC) : PVC is heat-sensitive, so instead of melt flow index, its K-value is calculated. 

• The K-values for PVC used in processing typically range between 55 and 60. 
• Higher K-values improve mechanical and electrical properties of the molded material but reduce processability. 
• Optimum results in processing are achieved by using PVC with the appropriate K-value for each specific application.

Calculation of DSV / K-Value-

• The value of ‘k’ is calculated by the relationship
  

From K-value one will know the grade of PVC material.
K-Value- 

• 60-65 Injection Moulding
• 65-67 Extrusion Process
• 67-70 Calendering Process

Additive and Compounding of PVC- A PVC compound may contain the following ingredients:

• Stabilizers
• Fillers & Plasticizers
• Polymeric processing aids
• Impact modifiers
• Pigments

Other miscellaneous materials may include:

• Flame retardants
• Optical bleaches
• Blowing agents

Stabilizers-

• PVC degrades at temperatures above 70°C, especially during processing (150-200°C), making the product unusable.
• Stabilizers prevent degradation during processing.
• Compounds of Cd, Ba, Ca, and Zn are commonly used as stabilizers in PVC.

Lubricants-

• Two types of lubricants are used in PVC:
• External lubricants: Prevent sticking to processing equipment by forming a film.
• Internal lubricants: Improve flow behavior during processing.
• Common lubricants include Calcium Stearate, Lead Stearate, Dibasic Lead Stearate, and Graphite.

Plasticizers-

• Used to reduce processing temperature and modify properties like flexibility and processability.
• Plasticizers must have a solubility parameter similar to PVC.
• Key plasticizers: Di-iso-octyl phthalate (DIOP) and Di-ethylhexyl phthalate (DEHP).

Extenders-

• Extenders are cheaper than plasticizers and improve compatibility when mixed with plasticizers.
• Common extenders include Chlorinated paraffin waxes, Chlorinated liquid paraffin, and Oil extracts.

Fillers

• Used to reduce costs or improve specific properties, such as:
• Increasing hardness (e.g., for flooring compounds).
• Reducing tackiness.
• Improving electrical insulation.
• Enhancing hot deformation resistance (e.g., in cables).
• China clay is used for electrical insulation, and carbonates for general-purpose applications.

Pigments

• Considerations for pigments:
• Potential for decomposition, fading, or bleeding.
• Impact on stabilizers, lubricants, and electrical properties.

Polymeric Impact Modifiers & Processing Aids-

Impact modifiers improve the processability of unplasticized PVC and reduce brittleness.

• Common impact modifiers-
• ABS graft copolymers,
• MBS (Methacrylate-butadiene-styrene) terpolymers,
• Chlorinated Polyethylene,
• EVA-PVC graft polymers.

NOTE: Chlorinated Polyethylene is widely used for impact resistance, especially when good aging properties are needed.

Flexible Pipe Formulation-

The given formulation is a general guide for a flexible PVC pipe compound, consisting of the following components:-

• Suspension polymer (K-65): 100 parts 
• DIOP (Plasticizer): 40 parts ( for flexibility)
• Trixylyl Phosphate (Plasticizer/Processing aid): 20 parts 
• China clay (Filler): 20 parts (cost reduction and performance enhancement)
• Tribasic lead sulfate (Stabilizer): 7.0 parts (heat and UV stability)
• Stearic acid (Lubricant): 0.5 parts (for smooth processing)
• Pigment: 2.0 parts (for color) 

Compounding of PVC-

The Compounding is a critical operation in PVC processing, where PVC resin is blended with additives to achieve the desired properties for processing and the final product. The process involves mixing ingredients, including colorants, into a nearly homogeneous mass.

    Compounding operations are classified into two categories:

• Melt blending: The mixture is fluxed or fused, where ingredients are melted and blended together.
• Dry blending: The compound remains a dry, free-flowing powder, with liquid ingredients absorbed onto the polymer particles.

Melt Compounding-

The Melt compounding involves the following steps:

1. A premix of ingredients is prepared.
2. The premixed ingredients are then fluxed (melted and blended).
3. The fluxed mixture is formed into pallets and fed into processing equipment.
4. Simple mixers, such as ribbon or tumble blenders, are used to prepare the premix.

Dry Blending-

Dry blending process involves the following steps:

1. Polymer is added to the blender and heated to 80-105°C.
2. Premixed and heated plasticizers are sprayed into the blender over 10-20 minutes.
3. Stabilizers and pigments are added.
4. Other compounding additives are included, and the mixture is allowed to dry.
5. Lubricants dissolved in the plasticizers are added, and the mixture is agitated thoroughly.
6. The mixture is then cooled to below 60°C, screened, and transported to storage.

Processing Consideration-

• PVC lacks thermal stability and degrades rapidly during processing, releasing hydrochloric acid. 
• Metal surfaces in contact with the melt must be resistant to this acid, and good ventilation is essential. 
• PVC does not absorb water, but some plasticizers may. 
• uPVC melts are viscous, with a typical flow path ratio of 60:1. 
• The viscosity of plasticized PVC depends on the plasticizer level. 
• PVC is amorphous, resulting in low shrinkage.

Processing Consideration-

    Injection Moulding:

• Melt temperatures: 180-200°C for uPVC, 150-190°C for PPVC.
• Mould temperature: 20-60°C.
• Injection pressures: 100-175 MPa for uPVC, 80-120 MPa for PPVC.

    Extrusion:

• Temperature profile: 150-180°C for uPVC, 140-175°C for PPVC.
• Screw L/D ratio: 14:1 to 17:1 for uPVC, 17:1 to 20:1 for PPVC.
• Compression ratio: 2:1.

    Blow Molding:

• uPVC has a lower specific heat between processing and room temperature compared to polyethylene, allowing for shorter cycle times.
• Blow molding for uPVC uses extrusion conditions.

    Calendaring:

• Used for making uPVC film or sheet.
• High molecular weight PVC is compounded and agglomerated in an extruder mixer.
• The mix is then fed into an L-type calendar mixer and rolled to consolidate granules into a strong film or sheet.
• The resulting films, with high mechanical properties, are used in packaging.

PVC Plastisol and Organosol-

• Plastisol and organosol are paste types where polymer particles are suspended in a plasticizer, filling the voids between particles. 
• A typical plastisol includes polymer, plasticizer, a small amount of stabilizer, and filler. 
• Organosols contain a volatile diluent to reduce paste viscosity. 
• Most PVC pastes are used in the production of leathercloth and for coating objects. 
• Processes like rotational casting and paste injection molding have been developed for creating flexible products.

Trade Name:

Name Of Company	Grade Name
IPCL, India	Indovin
Reliance, India	Relcair
Mitsubishi gas Ind, Japan	Vinylfoil
Mitsui toatsu chemical, Japan	Vinychol
B.F. Goodrich, US	Vynaloy
Goodyear, US	Vycell
ICI	Vynide
Solvay	Benvic

Applications-

• Automotive: Used in air filters, boat bumpers, mats, seat belts, headrests, armrests, spark plug covers, seat covers, and transmission covers. 
• Agriculture: Used for irrigation pipes, pipe fittings, drip irrigation systems, reservoir liners, horticultural and greenhouse irrigation systems, and sprinkler system fittings. 
• Building: Used in floor tiles, coverings, fencing, wall coverings, furniture covers, sofa seats, house sidings, windows, doors, cabinets, swimming pool liners, carpet backing, heat seal adhesives, and foil coatings. 
• Electrical/Electronics: Used for pipe and profiles, wire extrusions, cable insulation, TV backs, cable fittings, wire sacks, electrical parts, plating racks, 
• Medical: Used in blood bags, glucose bags, urine bags, syringes, infusion sets, tubing, and catheter tubes.

STYRENE BASED POLYMER

• High Impact Polystyrene (HIPS) 
• Acrylonitrile Butadiene Styrene (ABS) 
• Styrene Acrylonitrile (SAN)

POLYSTYRENE (PS)

Firstly produced commercially by Dow Chemical Company in 1937. 

Monomer Preparation- Styrene is produced from the ethyl-benzene by a process of dehydrogenation at 630°C.

• Physical State: Styrene is a liquid at room temperature with a boiling point of 145.2°C.
• Odor: Has a pleasant smell in pure form but loses it due to traces of ketones and aldehydes when oxidized by exposure to air.
• Solvent Properties: Acts as a solvent for polystyrene and many synthetic rubbers, including SBR, but has limited solubility in water.
• Polymerization: Tends to polymerize when heated or exposed to UV light. 

Polymerization Process- 

• Mass Polymerization
• Solution Polymerization
• Suspension Polymerization

Structure Property Relationship-

• Polystyrene (PS) is a linear hydrocarbon polymer. 
• The glass transition temperature (Tg) of commercial PS is between 90°C and 110°C, making it hard and transparent at room temperature due to its amorphous nature. 
• Soluble in benzene, styrene, and toluene. Reactivity: The presence of the benzene ring makes PS more reactive than polyethylene. 
• PS has limited chemical resistance due to the phenyl group.

Poperties-  

Name Of Property	Value	Unit
Specific gravity	1.05	--
Tensile Strength	32.4-56.5	MPa
Tensile modulus	3103-3276	MPa
Flexural modulus	3103-3448	MPa
Elongation at break	1.2-3.6	%
Impact Strength (Izod )	13.3-24	J/m
Hardness	M 60-84	---
HDT (under 1.82 MPa load.)	76-108	°C
Glass transition temperature	74-110	°C

• Density: 1.04–1.06 g/cm³.
• Glass transition temperature (Tg): 90°C to 110°C. 
• No defined melting temperature (PS is amorphous). 
• Low cost
• Hard, rigid, and transparent 
• High stiffness, good processability. 
• Low water absorption
• Good electrical insulation properties, 
• Very low thermal conductivity. 
• Highly inflammable,
• Excellent resistance to gamma radiation.
• FDA compliant for food contact. 
• Brittle in nature, unable to withstand boiling water. 

Trade Name- 

Name Of Company	Grade Name
Supreme, India	Supreme
Dow  Chemical, US	Pelaspan
Arco Chemical , US	Dylene
Kanegafuchi Chemical, Japan	Kanelite

Applications-

• Packaging: Used in food containers, protective packaging, and foam peanuts. 
• Consumer Goods: Found in toys, combs, cutlery, and disposable razors.
• Building & Construction: Used in insulation, wall panels, floor tiles, and decorative moldings. 
• Electrical/Electronics: Applied in electronic housings, TV backs, and appliance components. 
• Medical: Used in laboratory items, disposable syringes, and blood collection tubes.

CHAPTER - 03 

(ENGINEERING PLASTICS)

• Acrylonitrile and Styrene are grafted onto a Polybutadiene backbone. 
• The resulting product contains unreacted polybutadiene and some Acrylonitrile-Butadiene-Styrene (ABS) copolymer.

• Acrylonitrile Content: Higher acrylonitrile increases chemical resistance and stiffness but reduces impact strength and toughness. 
• Butadiene Content: Higher butadiene improves impact resistance and toughness but decreases rigidity and heat resistance. 
• Styrene Content: Higher styrene increases rigidity and thermal stability but reduces impact resistance and flexibility.

Preparation of ABS -

• Monomer Addition: Styrene and acrylonitrile are added to polybutadiene latex and the mixture is heated to 50°C for monomer absorption. 
• Polymerization: A water-soluble initiator is added to polymerize the styrene and acrylonitrile. 
• Resulting Materials: The outcome is a mixture of: Polybutadiene, Polybutadiene grafted with acrylonitrile and styrene, Styrene-acrylonitrile copolymer.

Properties- 

Name Of Property	Value	Unit
Specific gravity	1.03-1.06	--
Tensile Strength	30-52	MPa
Tensile modulus	2070-2760	MPa
Flexural modulus	2200-3030	MPa
Elongation at break	2.3-3.5	%
Impact Strength (Izod )	134-320	J/m
Hardness	R 105-112	---
HDT (under 1.82 MPa load.)	93-104	°C
Glass transition temperature	105-115	°C

• Appearance: Opaque with a glossy surface finish, low dust attraction. 
• Mechanical Properties: Rigid, good shock and fracture resistance, high dimensional accuracy and stability. 
• Chemical & Solvent Resistance: Resistant to alkalis and acids (excluding concentrated oxidizing acids); dissolves in aromatic and chlorinated hydrocarbons, esters, and ketones. 
• Heat Resistance: Up to 105°C; maximum service temperature varies (60-75°C for standard grades, up to 95°C with polycarbonate alloy). 
• Flammability: Slow burning, typically meets UL HB standards, burns with a smoky yellow flame and emits a pungent gas. 
• Electrical Properties: Good electrical insulation and flowability; readily electroplated.

Processing Consideration-

• Injection Moulding 
• Melt  temperatures 220-280 °C. 
• Mould temperature is 40–90 °C. 
• Injection pressures of 69-138 MPa. 
• L/D ratio is 20:1 and Compression ratio of 2:1 to 3:1. 
• Extrusion
• Melt  temperatures 205-250 °C.
• Temperature profile 192-250°C.
• Recommended screw L/D ratio 20:1 to 36:1.
• Recommended Compression ratio 2.5:1 to 3:1.

• Thermoforming
• ABS can be thermoformed over a temperature range of   130 to 190°C.
• The optimum conditions depend on material   grade,part   design, draw ratio, sheet thickness and forming technique 
• Electroplating
• ABS is the best material for electroplating.
• The polymer is treated by an acid etching process which    dissolves out some of the rubber particles at or near the   polymer surface.After sensitization and activation   electroless metal deposition processes are carried out .

Trade Name- 

Name Of Company	Grade Name
GE, India	Cycolac
Bhansali polymers , India	Abstron
Bayer , DE	Novodur
Polychemical co, Taiwan	Polylac

Applications -

• Automobile Industry: Radiator grills, headlight housing, seat belt fixtures, headlamp fixtures, door knobs, two-wheeler front noise panels, water panels, helmet components, electroplated parts, mirror housing, wheel covers.
• Agriculture Industry: Drinking water systems, water vent systems, irrigation systems.
• Household: Plumbing fixtures, table edging, sliding doors, window trucks, refrigerator liners, refrigerator door handles, pipe fittings, ventilator system components, picnic boxes, food processors, coffee maker lids, microwave oven tops.
• Medical: IV fluid monitoring controllers, blood glucose meters, surgical clips, emergency intravenous infusion pumps, scanner bodies, ECG/EEG body frames, cabinets for medical kits, breathing exercisers.

POLYAMIDES (PA) : NYLONS

Polyamides are primarily thermoplastic due to their linear structure, especially in aliphatic nylons like Nylon 6, 6, 10, and 11. Nylons were the first engineering thermoplastics to be recognized. These polymers are containing amide groups (CONH) in their main chain. They are classified into two main types: 

• Based on Diamines and Dibasic Acids: These include nylons like Nylon 6 (made from caprolactam) and Nylon 66 (made from hexamethylene diamine and adipic acid), produced through a condensation reaction. 
• Based on Amino Acids or Lactams: These include nylons like Nylon 7 and Nylon 11, formed via condensation of amino acids or ring-opening reactions of lactams. 

Chemical Formula of Various Polyamides-

Production of Nylon 6-

• Monomer: The initial substance for the production of polyamide 6 is caprolactam, a ring-shaped monomer with six carbon atoms.
• Polymerisation: Caprolactam is first heated to a liquid intermediate and then polymerised under pressure at an elevated temperature. In the process, the ring of the caprolactam opens and the molecules join together to form long chains that constitute the polymer structure of nylon 6.
• Processing: The nylon 6 obtained in this way can be further processed in various forms such as fibres or plastic pellets for different applications

Production of Nylon 66: 

• Monomer: Nylon 66 is made from two monomers: hexamethylene diamine and adipic acid. These two monomers react with each other to form the nylon 66 polymer chain. 
• Polymerisation: Hexamethylenediamine and adipic acid are mixed and polymerised under heat. During this process, amide bonds form between the monomers, creating the nylon 66 polymer chain. 
• Processing: The resulting nylon 66 is processed into granules, which are further processed in various industrial processes into end products such as fibres, films, injection-moulded parts, etc.

Properties-

• 1.13 - 1.16 g/cm³
• 220 - 265°C
• Hygroscopic, polar, and semi-crystalline with easy processability. 
• High rigidity, hardness, and impact strength, even at low temperatures; improved by glass fiber filling. 
• Excellent dynamic fatigue resistance and toughness enhanced by water absorption. 
• High heat resistance and good electrical properties, though affected by moisture absorption. 
• Good chemical, gas barrier, abrasion, and wear resistance, with low friction and emergency running properties. 
• Virtually no stress cracking or stress relaxation. 
• Flame retardant versions are difficult to process, and dimensions are affected by humidity and temperature under load.

Application of Nylon- 

• Automotive: Used in gears, cams, bearings, valve seats, and under-bonnet parts. 
• Electrical and Electronics: Applied in connectors, terminal blocks, and cable sheathing. Textiles: Utilized in fabrics, ropes, and industrial textiles. 
• Industrial Components: Used for bushings, bearings, washers, seals, and conveyor belts. 
• Consumer Goods: Found in hair combs, toothbrushes, and sporting equipment. 
• Optical and Communication: Employed in optical fiber sheathing (e.g., Nylon 12). Medical: Used in surgical sutures, implants, and medical devices.

POLYCARBONATE

• Polycarbonates are polyesters of carbonic acid. 
• Carbonic acid is unstable, but its derivatives (phosgene, urea, carbonates) are widely available. 
• Commercial polycarbonate is produced by reacting gaseous phosgene with bisphenol A. 

Manufacturing-

• Polycarbonates are commercially produced via 
• Interfacial polymerization
• Melt polymerization.
• The solution process was previously used but is now discontinued due to poor economic viability.

Structural Properties- 

• Symmetrical structure eliminates stereo-specificity concerns. 
• Polar carbonate groups are separated by aromatic hydrocarbon groups. 
• Benzene rings in the chain limit molecular flexibility. 
• Long repeating units in the molecule.

Properties- 

• Density-1.2 g/cm³
• Glass transition temperature (Tg) -147°C.
• Amorphous Material
• They have high rigidity, dimensional stability, and good strain resistance. 
• Excellent transparency, high optical clarity, and weathering resistance. 
• Very high impact strength, toughness, and break resistance, even at low temperatures.
• Low water absorption & sensitive to stress cracking
• High heat distortion temperature in a wide range of -50°C to 135°C. 
• Flame retardant with low combustibility.
• Good electrical insulation properties. 

POLYETHYLENE TEREPHTHALATE (PET)