As discussed in our previous article on Polymer Testing Equipment, plastic is fast becoming the most popular choice of material in manufacturing industries. As many readers have been asking me to give some details about Plastic Processing Equipment and methods, I took out time to inform our readers about the various methods involved in procuring finished plastic parts.
The family of polymers is extraordinarily large and varied. There are,China Carbon Plate 160g/㎡, T300 3K, Unidirectional Manufacturers
however, some fairly broad and basic approaches that can be followed
when designing or fabricating a product out of polymers or, more
commonly, polymers compounded with other ingredients. The type of
fabrication process to be adopted depends on the properties and
characteristics of the polymer and on the shape and form of the final
In the broad classification of plastics there are two generally accepted
categories: thermoplastic resins and thermosetting resins.
Thermoplastic resins consist of long polymer molecules, each of which
may or may not have side chains or groups. The side chains or groups,
if present, are not linked to other polymer molecules (i.e., are not
cross-linked).China Carbon Plate 200g/㎡, T300 3K, Plain Weave Manufacturers
Thermoplastic resins, usually obtained as a granular polymer, can
therefore be repeatedly melted or solidified by heating or cooling. Heat
softens or melts the material so that it can be formed; subsequent
cooling then hardens or solidifies the material in the given shape. No
chemical change usually takes place during this shaping process.
In thermosetting resins the reactive groups of the molecules from
cross-links between the molecules during the fabrication process. The
cross-linked or “cured” material cannot be softened by heating.China Carbon Plate 200g/㎡, T300 3K, Twill Manufacturers
Thermoset materials are usually supplied as a partially polymerized
molding compound or as a liquid monomer–polymer mixture. In this uncured
condition they can be shaped with or without pressure and polymerized
to the cured state with chemicals or heat.
With the progress of technology the demarcation between thermoplastic
and thermoset processing has become less distinct. For thermosets
processes have been developed which make use of the economic processing
characteristics or thermoplastics. For example, cross-linked
polyethylene wire coating is made by extruding the thermoplastic
polyethylene, which is then cross-linked (either chemically or by
irradiation) to form what is actually a thermoset material that cannot
be melted again by heating.
More recently, modified machinery and molding compositions have become
available to provide the economics of thermoplastic processing to
thermosetting materials.China Carbon Plate Carbon Laminate 280g/㎡, T300 3K, Twill Manufacturers
Injection molding of phenolics and other thermosetting materials are
such examples. Nevertheless, it is still a widespread practice in
industry to distinguish between thermoplastic and thermosetting resins.
Compression and transfer molding are the most common methods of
processing thermosetting plastics. For thermoplastics, the more
important processing techniques are extrusion, injection, blow molding,
and calendaring; other processes are thermoforming, slush molding, and
Tooling for plastics processing defines the shape of the part. It falls into two major categories, China Carbon Plate 200g/㎡, T700 12K, Unidirectional Manufacturersmolds
and dies. A mold is used to form a complete three-dimensional plastic
part. The plastics processes that use molds are compression molding,
injection molding, blow molding, thermoforming, and reaction injection
molding (RIM). A die, on the other hand, is used to form two of the
three dimensions of a plastic part. The third dimension, usually
thickness or length, is controlled by other process variables.
The plastics processes that use dies are extrusion and thermoforming.
Many plastics processes do not differentiate between the terms mold and
die. Molds, however, are the most predominant form of plastics tooling.