Material Science - Lecture 10 (Polymers)

What is a polymer?

any of a class of natural or synthetic substances composed of very large molecules, called macromolecules, that are multiples of simpler chemical units called monomers

• mga class of mga natural or synthetic nga substance which compose of very large nga molecules called macromolecules, which kaning macromolecules are mga multiple nga mga simplier chemical units nga gitawag nga monomers

What are the categories of polymers

• Natural polymers

• Synthetic polymers

What is natural polymers?

• These polymers are derived from natural sources and include substances such as cellulose, starch, proteins, silk, wool, and natural rubber.

• They are biodegradable and renewable.

What is Synthetic Polymers?

• are man-made, non-biodegradable, and usually derived from petroleum oil

• polyethylene, polypropylene, polyvinyl chloride (PVC), nylon, and polystyrene.

What are the categories of synthetic polymers based on their structure and properties?

• Thermoplastics

• Thermosets

• Elastomers

• Fibers

What are the propertied of polymers?

• Strength and Durability

• Flexibility

• Elasticity

• Thermal Stability

• Chemical Resistance

• Electrical Insulation

What are the applications of polymers?

• Packaging

• Construction

• Textiles

• Automobiles and Aerospace

• Electrical/Electronics

Give an example of polymers being use as packaging

Polymers like polyethylene and polypropylene are widely used for bottles, bags, and films because they are lightweight, durable, and barrier potential

Give an example of polymers being use in construction

Polymers like PVC, polystyrene, and acrylics are used in pipes, insulation, flooring, adhesives, and coatings because of their strength, weather resistance, and versatility

Give an example of polymers being use as textile

Polymers like nylon, polyester, and acrylics are used in clothing, carpets, or even ropes because of their strength, elasticity, and resistance to wrinkles

Give an example of polymers being use in Automobiles and Aerospace

Polymers in this field are used to make foams and composites which are lightweight

Give an example of polymers being use in Electrical/Electronics

Polymers are used for electrical insulation, circuit boards, adhesives, and coatings because of their electrical and thermal properties

What is thermoplastics

• It can be softened and processed using injection moulding, extrusion, and thermoforming to form a desired shaped of the product

• It has good elasticity and strength

Give at least 5 advantages and disadvantages of thermoplastics

ADVATAGES

• Recyclable and re-shapable with minimal impact on material properties

• Chemical and detergent resistance

• High Resistance to impact

• Improved anti-slipped properties

• Low-cost, high-volume manufacturing

DISADVANTAGES

• Not suitable for all applications

• Degrade quickly when expose to sunlight

• Under high stress, it can fracture rather than deform

• Long term loading can cause creep to some types of thermoplastics

• More expensive than thermosets

What are the thermoplastic materials?

• Polyethylene (PE)

• Polypropylene (PP)

• Polyvinyl Chloride (PVC)

• Polystyrene (PS)

• Polyethylene Terephthalate (PET)

• Polycarbonate (PC)

What is polyethylene (PE)?

This is the most widely used thermoplastic because of its versatility and chemical resistance

What are the two types of polyethylene and its example?

• High-density polyethylene - Milk Cartoons, detergent bottles

• Low-density polyethylene - Plastic wrap, garbage bags

What is polypropylene and its example?

• Just like polyethylene, it is also known for its versatility, chemical resistance, and good fatigue resistance

• Straw and bottle caps

What is polyvinyl chloride and its example

• Known for its durability, chemical resistance, and flame retardant properties

• Pipes, electrical insulation

What is polystyrene and its example?

• transparent thermoplastics with good stiffness and impact resistance

• egg cartoons and disposable cutlery

What is polyethylene terephthalate and its example?

• known for its excellent strength and clarity

• beverages bottles and polyester clothing

What is polycarbonate and its example?

• it is transparent with high impact resistance and optical properties

• safety googles and eyeglass lenses

What are the manufacturing processes for thermoplastics?

• Injection molding

• Extrusion

• Thermoforming

What is injection molding for the manufacturing of thermoplastics?

Melting the thermoplastic resin pellets and uses pressure to inject it into a mold

What is extrusion for the manufacturing of thermoplastics?

Thermoplastic is melted and pressed into a die or steel disk in a continuous profile

What is thermoforming for the manufacturing of thermoplastics?

Heating the sheets of thermoplastics and forming them either inside or outside the mold. It then cooled down and remove excess material

What is thermosets?

• Once fully set, it cannot be melted or reshaped

• has high dimensional stability ad strength

Give at least 5 advantages and disadvantages of thermosets

ADVANTAGES:

• Allows more versatile product designs

• Less expensive than metal components

• Outstanding electrical insulation

• Resistant to corrosion

• Water repellent

DISADVANTAGES:

• Cannot be reshaped once fully set

• Good surface finishing is hard to achieve

• Thermal conductivity is poor for housing replacements

• Its rigidity ca cause product failure if used in high-vibration

What are the thermosets materials?

• Epoxy resins

• Phenol-Formaldehyde Resins

• Urea-Formaldehyde Resins

• Melamine-Formaldehyde Resins

• Polyester Resins

What is epoxy resins and its application?

• It offers excellent adhesion and chemical resistance

• Used in coatings and adhesives

What is phenol-formaldehyde resins and its application?

• It exhibits high heat resistance and electrical insulation properties

• Used i circuit boards and automotive parts

What is urea-formaldehyde resins and its application?

• known for being low cost and good heat resistance

• Used in the production of plywood

What is melamine-formaldehyde resins and its application?

• It offers heat resistance and chemical resistance

• dinnerware and decorative surfaces

What is polyester resins and its application?

• It is known as unsaturated polyester resins

• boat hulls and construction materials

What are the different manufacturing techniques used for thermosets?

• Compression Molding

• Laminating

• Reaction Injection Molding

What is Compression molding?

• This create a hard-heat resistant plastic products

• dinnerware and telephones

What is laminating?

• Its products are used as a surface finish for furniture and kitchen countertops

• Glass fibers and resin-impregnated paper

What is reaction injection molding

• liquid thermosetting resin is combined with a curing agent and injected into the mold

• Most products made by this process are made from polyurethane

What is elastomers?

• It exhibits rubber-like elasticity and can return to its original shape

• Have high degree of flexibility and resilience

What are the examples of elastomers?

• Natural Rubbers

• Polyurethanes

• Polybutadiene

• Silicone

• Neoprene

What is natural rubber?

• It is from the latex of the rubber tree and it has high elasticity and low modulus

• Used in tires and automotive components

What is polyurethanes?

used in textile industry for elastic clothing like lycra

What is polybutadiene?

used for providing wear resistance in wheels of vehicles

What is silicone?

used in manufacturing medical prosthesis and lubricants

What is neoprene?

used in wet-suits and industrial belts

What are the properties of elastomers?

• Elasticity and Flexibility

• Resilience

• Low Compression Set

• Good Tear Resistance

• Chemical Resistance

• Temperature Resistance

• Weather/Water Resistance

• Electrical Insulation

What are the applications of elastomers?

• Motor Vehicles - tires

• Consumer products - various products

• Constructions - adhesives and gaskets

• Industrial products - belts and molds

• Wire and cable - wire insulation

• Medical products - prosthetics

What are the difference between elastomers and polymers?