In general, polymers are divided into three categories in terms of application: thermoplastic, thermostatic and elastomer. Among these are materials such as fiberglass, which is actually a silica polymer.
1. Thermoplastics
In thermoplastics, there is a simple structure of polyethylene in polypropylene, polystyrene, polyvinyl chloride and Teflon, which changes the nature of the molecule by replacing the hydrogen atom in the sides of the main structure, for example in Teflon. The chain tightens as more molecules are added to the skeleton. In nylons, acrylics, steels, cellulosics and polycarbonates, the addition of polar groups, ie hydrogen bonding, increases the strength. Finally, by using side connections, for example in polyester and rubber, the thermostatic plastic group is brought to strength.
Material Density (grams per cubic centimeter) Tensile strength (Newton per square millimeter) Elastic modulus (Newton per square millimeter) Relative length to failure change (percentage)
PE 0.96 to 0.92 30 to 10 1200 to 200 1000 to 100
PS 1.08 to 1.05 75 to 50 3600 to 3200 5 to 3
PP 0.896 35 to 21 1300 700 to 250
PVC 1.38 60 to 50 3000 100 to 20
PA 1.15 to 1.1 85 to 65 3400 to 1300 250 to 40
PTFE 2.3 to 2.1 26 to 18 4000 250 to 200
UP, EP 1.2 70 to 60 5000 to 3000 2
Table 1- Properties and applications of a number of thermoplastics
Applications of thermoplastics
Polyethylene (PE) is used in the manufacture of kitchen utensils, toys and sports equipment.
Polypropylene (PP) is used to make the body of pumps, toilets, carpet fibers, tanks and suitcases.
Polyvinyl chloride (PVC), which itself becomes soft and hard.
Polytetrafluoroethylene (PTFE) or Teflon is used in the manufacture of washers and non-stick coatings.
Polyetherimides (PI) used in the aerospace, fuse box and electronics industries.
Polyamides (nylons) are used in the manufacture of non-lubricating bearings, anti-wear components, windshield wipers and accelerometer gears.
Polyoxymethyl is used in the manufacture of gearboxes, gears and pump components.
Polymethyl acrylate is used to make magnifying glasses, lenses, watch glasses and sunglasses.
Steel is used to make parts of the car in the fuel system, seat belts, car lift handles and pens (automatic).
2. Thermostats
Polymers with lattice molecular structure and predominantly covalent bonds are formed. That is why thermostats have high strength, rigidity and hardness, so they are brittle. The lattice structure that makes up a very large molecule has a decisive effect on the properties of the thermostat. Table 2 describes the properties of some thermostats.
Material Density (grams per cubic centimeter) Tensile strength (Newton per square millimeter) Elastic modulus (Newton per square millimeter) Relative length change (percent)
Phenolics 1.27 60 9 2
Amino resins 1.5 67 11 1
Unsaturated polyesters 1.28 87 4 3
Epoxy resins 1.25 100 3 6
Silicones 1.55 27 8 0
Table 2 – Properties and applications of a number of thermostats
Applications of thermostats
Phenols: electrical switches, small clamps and handles, adhesives
Amino resins: small clamps and knobs, buttons, resistant adhesives, melamine-filled cellulose parts
Unsaturated polyesters: Glass-reinforced for car and aircraft dashboards, small boat hulls, seats, kitchen and bathroom parts
Epoxy resins: protective and decorative coatings, high voltage insulators, switches and transistors
Silicones: Adhesives, Washers, Adhesives, Putties and Seals
3.Elastometer
It is composed of synthetic and natural polymer materials (such as raw rubber). Therefore, it is a heavy polymer with a complex structure that has the same behavior and characteristics as rubber. Tires are flexible. Generally used in the manufacture of belts, car tires, O-rings, hoses and electrical wiring. In terms of hardness, tires are divided into three categories: soft, semi-hard and hard. The higher the sulfur content, the harder the rubber. Tires have five components, including sulfur, accelerator, polymer (about 45 to 65%), preservatives (such as antisenate), and additives. As the amount of sulfur increases, the elastometer becomes harder and is used as a shock absorber base to install the engine. The table below shows the properties of different tires.
Material Density (grams per cubic centimeter) Tensile strength (Newton per square millimeter) Relative elongation (percentage)
Reinforced Unreinforced
Polyisoprene (natural rubber) 0.93 27 17 850 to 750
Butadiene styrene 0.94 24 1.2 600 to 400
Acrylonitrile butadiene 1.0 6 3.4 700 to 450
Polychloroprene (neoprene) 1.25 27 20 900 to 800
Silicon 1.6 to 1.1 8 2 600 to 100
Table 3 – Properties and applications of a number of tires
