What is Polymers | Thermosetting and Thermoplastic plastics

What is Polymers | Thermosetting and Thermoplastic plastics

What is Polymers

  • A polymer is a compound consisting of long-chain molecules, each molecule made up of repeating units connected together.
  • There may be thousands, even millions of units in a single polymer molecule.
  • The word is derived from the Greek words poly, meaning many, and meros (reduced to mer), meaning part.
  • Most polymers are based on carbon and are therefore considered organic chemicals.
  • Polymers can be separated into plastics and rubbers.
  • As engineering materials, they are relatively new compared to metals and ceramics, dating only from around the mid-1800 s.
  • It is appropriate to divide them into the following three categories
  1. Thermoplastic polymers (thermoplastics/TP)
  2. Thermosetting polymers (thermosets/TS)
  3. Elastomers (rubbers/E)

Thermoplastic polymers (thermoplastics)

  • TP Solid materials at room temperature, but they become viscous liquids when heated to temperatures of only a few hundred degrees.
  • This characteristic allows them to be easily and economically shaped into products.
  • They can be subjected to this heating and cooling cycle repeatedly without significant degradation of the polymer.

The most important thermoplastics are:

  • Acrylics (Plexiglas) : lenses, window glazing
  • Fluorocarbons (Teflon) : nonstick coatings, bearings, seals
  • Polyamides (Nylons, Kevlar) : fibers
  • Polycarbonates (Lexan) : helmets, bullet-resistance windows, wind-shields
  • Polyesters (Dacron, Mylar, Kodel) : gears, cams, rollers
  • Polyvinyl chloride (PVC) : pipes, cable insulation, packaging, flooring, toys
  • Polyethylene : bottles, cans, packaging materials

Thermosetting polymers (Thermosets)

TS cannot tolerate repeated heating cycles as thermoplastics can. When initially heated, they soften and flow for molding, but the elevated temperatures also produce a chemical reaction.

The most important thermosets are:

  1. Epoxies : fiber-reinforced materials
  2. Phenolics (Bakelite) : knobs, handles, cases
  3. Polyesters : fiber-reinforced materials
  4. Silicones : waterproof and heat resistance materials

Sachin Thorat

Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Currently, he is working in the sheet metal industry as a designer. Additionally, he has interested in Product Design, Animation, and Project design. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos.

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