Question

Explain the relationship between STRUCTURE/ PROPERTIES/ PROCESSING/ PERFORMANCE of a polymer which is a drawn fiber thermoplastic.

Answer 1

A polymeris a large molecule, or macromolecule, composed of many repeated subunits. Because of their broad range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life.Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass relative to small molecule compounds produces unique physical properties, including toughness, viscoelasticity, and a tendency to form glasses and semicrystalline structures rather than crystals.

Fiber thermo plastic:

A thermoplastic is a material, usually a plastic polymer, which becomes soft when heated and hard when cooled.Thermoplastic materials can be cooled and heated several times. They can be recycled. When thermoplastics are heated, they melt to a liquid.

Most thermoplastics have a high molecular weight. The polymer chains associate through intermolecular forces, which weaken rapidly with increased temperature, yielding a viscous liquid. Thus, thermoplastics may be reshaped by heating and are typically used to produce parts by various polymer processing techniques.

processing techniques:

Injection molding, compression molding, calendering, and extrusion.

performance:

Thermoplastics differ from thermosetting polymers, which form Fische chemical bonds during the curing process. Thermosets do not melt, but decompose and do not reform upon cooling.

Above its glass transition temperature, T_g, and below its melting point, T_m, the physical properties of a thermoplastic change drastically without an associated phase change.

Some thermoplastics do not fully crystallize below the glass transition temperature T_g, retaining some or all of their amorphous strands. Amorphous and semi-amorphous plastics are used when high optical clarity is necessary, as light is scattered strongly by crystallites larger than its wavelength. Amorphous and semi-amorphous plastics are less resistant to chemical attack and environmental stress cracking because they lack a crystalline structure.

Brittleness can be decreased with the addition of plasticizers, which increases the mobility of amorphous chain segments to effectively lower T_g. Modification of the polymer through copolymerization or through the addition of non-reactive side chains to monomers before polymerization can also lower T_g. Before these techniques were employed, plastic automobile parts would often crack when exposed to cold temperatures.

some examples:

Acrylic:

Polymer called poly(methyl methacrylate) (PMMA), is also known by trade names such as Lucite, Perspex and Plexiglas. It serves as a sturdy substitute for glass for items such as aquariums, motorcycle helmet visors, aircraft windows, viewing ports of submersibles, and lenses of exterior lights of automobiles. It is extensively used to make signs, including lettering and logos. In medicine, it is used in bone cement and to replace eye lenses. Acrylic paint consists of PMMA particles suspended in water.

ABS:

Acrylonitrile butadiene styrene (ABS) is a terpolymer synthesized from styrene and acrylonitrile in the presence of polybutadiene. ABS is a light-weight material that exhibits high impact resistance and mechanical toughness.

It is used in many consumer products, such as toys, appliances, and telephones.

Nylon:

Is belongs to a class of polymers called polyamides. It has served as a substitute for silk in products such as parachutes, flak vests and women's stockings. Nylon fibers are useful in making fabrics, rope, carpets and musical strings, where as in bulk form, nylon is used for mechanical parts including machine screws, gear wheels and power tool casings. In addition, nylon is used in the manufacture of heat-resistant composite materials.

PLA:

Polylactic acid (polylactide) is a biodegradable thermoplastic.

It is one of the materials used for 3D printing with fused deposition modeling (FDM) techniques.

Polybenzimidazole:

Polybenzimidazole(PBI,short for Poly-[2,2’-(m-phenylen)-5,5’-bisbenzimidazole]) fiber is a synthetic fiber with a very high melting point. It has exceptional thermal and chemical stability and does not readily ignite

superior stability, retention of stiffness, toughness at elevated temperature. Due to its high stability, Polybenzimidazole is used to fabricate high-performance protective apparel such as firefighter’s gear, astronaut space suits, high temperature protective gloves.

Polycarbonate:

Uses in electronic components, construction materials, data storage devices, automotive and aircraft parts, check sockets in prosthetics, and security glazing.

Teflon:

Teflon is a brand name of DuPont for a variety of the polymer polytetrafluoroethylene (PTFE), which belongs to a class of thermoplastics known as fluoropolymers. It is known as a coating for non-stick cookware. Being chemically inert, it is used in making containers and pipes that come in contact with reactive compounds. It is also used as a lubricant to reduce wear from friction between sliding parts, such as gears, bearings, and bushings