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CLASSIFICATION BY PROPERTIES
Thermosetting Polymer
Structure
Structure of Thermosetting Polymer
Formation Process (^) • A pre-polymer, or backbone, resin is reacted with a crosslinking agent under heat and pressure to form a crosslinked network. Thermoset network formation can also be achieved without heat and pressure by using radiation or room temperature initiators / promoters.
- When processed, a thermoset material undergoes a chemical change; that is, a chemical reaction occurs as the crosslinking agent chemically bonds to the polymer backbone resin.
Properties
- Material cannot be melted, reprocessed, or re-formed. The presence of a chemically bonded network imparts very desirable properties
- Have cross linked nature
1.0 CLASSIFICATION BY PROPERTIES
Advantages
- Stronger than thermoplastic materials due to the crosslinked network
- Higher in modulus, or stiffness, and have unique deformation responses when subjected to mechanical loading
- Superior temperature stability due to cross linked
- Higher loading of additives
- Cost effective
- Low-viscosity and easy to work with because they exist in liquid form at room temperature
- Carry a lower health hazard than thermoplastics, as no potentially toxic fumes such as styrene are released during the molding process.
Disadvantages
- Thermoset plastics can’t be recycled
- (^) More difficult to surface finish
- Can’t be remolded or reshaped
Examples
- Poxy
- Silicone
- Polyurethane
- Phenolic
Applications
- Used in chemical / corrosive service environments
- The thermoplastic curing process after been heated is 100% reversible as no chemical bonding takes place.
Properties
- High strength, shrink-resistance and easy bendability. Depending upon their chemistry they can be very much like rubber, or as strong as aluminum
- Easy to mold & shape when they are hot
Advantages
- Have high strength
- Lightweight and have relatively low processing costs. Sometimes engineers use thermoplastics instead of metals because of their much lighter weight.
- Easy to manufacture thermoplastic components quickly in high volumes with high precision
- Excellent thermal and heat insulator
Disadvantage
- Have poor resistance to organic solvents, hydrocarbons and highly polar solvents
- Some types of thermoplastics fracture instead of becoming deformed when exposed to high levels of stress
- Some types of low-quality thermoplastics melt when they're exposed to ultraviolet light for extended times.
Examples
- Polyvinyl chloride, or PVC
- Polyester resin
- Polymethyl methacrylate
- Nylon
Applications
- Commonly used for pipes, bottles and plastic container
- Used for car bodies and garden furniture
- Lenses and windows
2.0 CLASSIFICATION BY FUNCTION
Structure
A portion of cellulose fiber
1. Fibers
- Synthetic fibres are fibres formed from synthetic polymers (polyamides, polyesters, polyacrylonitrile, polyolefins, polyvinyl chloride, polyvinyl alcohol, etc.).
Propeties
- Long strands of molecules interwoven to form a linear, string-like structure.
- Can be classified into natural, artificial and synthetic fibers
- Synthetic fibres, are characterised by their high strength, high relative elongation, elasticity, rapid recovery and low residual strain after unloading, resistance to repeated and alternating loads.
Advantages
- Synthetic fiber are longer and long lasting
- Relatively high molecular weight
- (^) High length to diameter ratio
- High Flexibility and tenacity
- Good Spinning Quality
- High Abrasion Resistance
Disadvantages
- Fibers are usually only strong in one direction, lengthwise
- Tend to be weak if pulled otherwise, width-wise
- Synthetic fiber are poor absorbent of moisture and catch fire easily Examples
- Natural Fibers (Cotton, Wool)
- Synthetic Fibers ( Rayon, Nylon, Polyester, Acrylic)
Applications • Packaging Product : Bags , sacks, wool packs
- Medical : biodegradable micro tube for repair of blood vessels, teeth reconstructions
- Household textile : carpet, area rugs, pile fabrics, curtain
- Apparel Product : Clothes, Jacket, Raincoat, swimming wear, dresses, skirts
insulation.
- Use of a polymer coating depends on the operating temperature, wear and tear of environment and type of corrosion
Advantages • Inexpensive
- Concrete Protection
- (^) Improve wear resistance and wettability
- Polymeric coating cools down buildings
- Spin coating can be done at atmospheric pressure and is very cheap
Disadvantages
- Life cycle costing
- Repair of poor substrate conditions
- Less products for the same amount of surface preparation
- For spin coating, the whole substrate is coated , patterning must be done separately Examples
- (^) Nylon 11
- Polyurethane
- Acrylics and alkyds
Application
- Automotive : conveyor equipment, aircraft, radomes, tugboats, road- building machinery, and motorcycle parts.
- Functional : Adhesives, photographic films
- Protective : anticorrosion
- Decorative : Paint
- Surface Modification: paper coating, hydrophobic coatings
- Medical : Coatings for orthopaedic materials, cardiovascular stents, antibacterial surfaces, drug delivery, tissue engineering and biosensors
Films
Structure
Layer structure of Film Polymer
Formation Process
- Produces toxic fumes when being burned
- Low melting point
Examples • Polyethylene naphthalate
- Polystyrene
- Polypropylene
- (^) High Density Polyethylene
- Low Density Polyethylene
- Polyethylene terephthalate
- Polycarbonate
Applications • Packaging : Plastic Bag, Food Packaging, Plastic Book Wrapper, Plastic Bottle
- Medical: garbage and hazardous material bags, I.V. bags, sterile wrap
- Construction: vapor barriers in walls, moisture barriers under concrete, paint drop cloths ,drapes
Adhesives
Structure
Structure of Adhesive Joint
Formation Process
- In the formation of an adhesive bond, a transitional zone arises in the interface between adherent and adhesive. In this zone, called the interphase, the chemical and physical properties of the adhesive may be considerably different from those in the noncontact portions. It is generally believed that the interphase composition controls the durability and strength of an adhesive joint and is primarily responsible for the transference of stress from one adherent to another. The interphase region is frequently the site of environmental attack, leading to joint failure.
- Chemical bonding involves intermolecular forces between the adhesive and adherend, which forces may be covalent and van de Waals.
area
- relative weakness in bonding large objects with a small bonding surface area
- greater difficulty in separating objects during testing. Examples
- Natural Adhesive (Starch, casein, Rosin, animal glue)
- Natural Rubber Based Adhesive
- (^) Synthetic Adhesives (Styrene butadiene rubber, Btyl rubber, Polychloroprene rubber, nitrile rubber, silicon rubber)
Applications
- Construction : floor tile and continuous flooring installation, ceramic tile installation, carpet adhesives, flooring underlayment adhesives cements, drywall lamination adhesives
- Consumer adhesives : model and hobby supplies, decorative films, school and stationery products.
- Packaging : carton-side seam and closures, composite bonding of disposable products, bags, labels, cups, cigarette and filter manufacture, speciality packages (cosmetics, toiletries), composite containers and tubes.
- (^) Tapes : packaging, industrial, surgical, masking, and consumer tapes.
- Transportation : auto, truck and bus assemblies, weatherstrip and gasket bonding, aircraft and aerospace structural assemblies.
Foams
Structure
Closed Cell Foam Open Cell Foam
Formation Process
- Carried out by incorporating into the batch of material a blowing agent that, upon heating, decomposes with the liberation of a gas. Gas bubbles are generated throughout the now-fluid mass, which remain in the solid upon cooling and give rise to a spongelike structure.
- The same effect is produced by dissolving an inert gas into a molten polymer under high pressure. When the pressure is rapidly reduced, the gas comes out of solution and forms bubbles and pores that remain in the solid as it cools. Properties
- In liquid or solidified form, formed from polymers.
- Contain relatively high volume percentage of small pores and trapped gas bubbles.
- In solid closed-cell foam, the gas forms discrete pockets, each completely surrounded by the solid material. In solid open-cell foam, gas pockets connect to each other.
Applications • Packaging : Food Container, Egg Cartons, Polystyrene Cups
- Thermal Insulation : Insulation for refrigerators, freezers, insulated buildings, water heaters
- Automotive : Car seats, armrests, acoustic insulation, headrests
Ultra-High-Molecular-Weight Polyethylene (UHMWPE)
Structure
Morphological Structure of UHMWPE
Formation Process
- Synthesized from its monomer ethylene, which is bonded together to form the base polyethylene product.
- UHMWPW is processed variously by compression moulding, ram extrusion, gel spinning, and sintering.
3. Advanced Polymer
Properties
- In fiber form, UHMWPE is highly aligned and has trade name Spectra
- Linear polyethylene that has an extremely high molecular weight
- Made up of extremely long chains of polyethylene, which all align in the same direction
- (^) Odorless, tasteless, non-toxic
Advantages
- An extremely high impact resistance
- Outstanding resistance to wear and abrasion
- A very low coefficient of friction
- A self-lubricating and non-stick surface
- Very good chemical resistance to normally encountered solvents
- Excellent low temperature properties
- Outstanding sound damping and energy absorption characteristics
- Electrically insulating and excellent dielectric properties
Disadvantages
- Relatively low melting temperature, its mechanical properties deteriorate rapidly with increasing temperature
Examples • Extremely long chains of polyethylene
Applications • Body Armor : Bulletproof vests, composite military helmets,
