Properties and features
Plastics are organic substances formed by macrocells called polymers. These polymers are large groups of monomers linked by a chemical process called polymerization. Plastics provide the necessary balance of properties that can not be achieved with other materials such as: color, lightweight, soft touch and resistance to environmental and biological degradation.
In fact, plastic refers to a state of the material, but the material itself: synthetic polymers commonly called plastics are actually synthetic materials that can achieve the plastic state, ie when the material is viscous or fluid, and no resistance properties to mechanical stress. This state is reached when the material becomes solid plastic state usually by heating, and is ideal for different production processes and that this state is when the material can be handled in the forms that exist today. So the word plastic is a way to refer to synthetic materials capable of entering into a plastic state, but plastic is not necessarily the group of materials to which this word refers daily.
The properties and characteristics of most plastics (though not always fulfilled in certain special plastics) are these:
* Easy to work and shape,
* Have a low production cost,
* Possess low density,
* Tend to be waterproof,
* Good electrical insulators,
* Acceptable acoustic insulation,
* Good thermal insulation, but most can not withstand very high temperatures,
* Resistant to corrosion and many chemical factors;
* Some are not biodegradable or easily recyclable, and if they burn, are highly polluting.
The first part of the production of plastics is the production of polymers in the chemical industry. Today the recovery of post-consumer plastic is also essential. Part of the industry-finished plastic directly used as grain or resin. More frequently, various forms of molding (injection, compression, rotation, inflation, etc.) or profile extrusion or yarns are used. Greater part of the plastic process is performed in a horneadora machine.
Classification of plastics
This classification is considered the origin of the monomer from which part of the polymer production.
* Natural: These are polymers whose monomers are derived from natural products with certain characteristics, for example, cellulose, casein and rubber. In two of these examples there are other plastics which come:
or cellulose derivatives are: the celluloid, cellophane and Cellon.
or rubber derivatives include rubber and ebonite.
* Synthetic: Those that originate in man-made, mainly petroleum products such as polyethylene bags products
According to their behavior in heat.
A thermoplastic is a plastic that, at room temperature, is plastic or deformable, it becomes a liquid when heated and hardens to a glassy state when cooled sufficiently. Most thermoplastics are high molecular weight polymers, those with chains associated through weak Van der Waals forces (polyethylene); strong dipole-dipole interactions and hydrogen bonding; or even stacked aromatic rings (polystyrene). Thermoplastic polymers differ from thermoset polymers that after heated and molded form they can overheat and other objects, as in the case of thermosetting or thermoset, its shape after cooling does not change and the preferred fire.