Plastics Molding & Manufacturing/Plastic Charactheristic

Plastic materials are generally considered all the polymers based on chains of molecules mainly based on carbonium and hydrogen atoms. There is a very wide variety of plastics, from several points of view: mechanical, thermal, electrical, aesthetical, processing method.

The first level of distinction from the industrial point of view is the thermal behavior: thermoplastics are generally injection moulded, while thermosets are compressed and shaped.

Categorizations
The thermoplastic polymers can be categorized by several point of views:


 * Thermal behavior
 * Crystalline grade (amorphous or semi-crystalline)
 * Use (commodity polymers, technopolymers, super-polymers)
 * Origin (fossil chemical synthesis, biological chemical synthesis, recycling)
 * Homogeneity (omopolymer, copolymer)
 * Molecular family (polyolephins, poliammides, etc.)

Thermal behavior
All type of plastics are divided into three major type of materials:

Thermoplastics
A thermoplastic is a type of plastic made from polymer resins that becomes a homogenized liquid when heated and hard when cooled. When frozen, however, a thermoplastic becomes glass-like and subject to fracture. These characteristics, which lend the material its name, are reversible. That is, it can be reheated, reshaped, and frozen repeatedly. This quality also makes thermoplastics recyclable.

There are dozens of kinds of thermoplastics, with each type varying in crystalline organization and density. Some types that are commonly produced today are polypropylene, polyethylene, polyvinylchloride, polystyrene, polyethylenetheraphthalate and polycarbonate.

Categorization based on molecular family
The most common and clear way of describing a material is to use its molecular family, that describes most of the properties of it within a defined window. This is happening because most of the properties are given by the properties of the monomer and how it tends to link with the composants of the same chain and its counterparts on other chains.

For example the family of polyammides contains PA6, PA66, PA12: all of them have very good mechanical properties, similar behavior with chemical agents, etc. that can be clearly distinguished from those of the polyethylene family (LDPE, HDPE).