For manufacturing plastic pipes, there
is a use of a process called profile extrusion. This process is used to
generally produce plastic products with continuous cross-sections.

Typical examples include decorative molding, drinking straws, plastic
evestroughing, window trimming and numerous variety of other products
polymers that are melt into the hollow mold cavity under application of high
pressure.
A typical profile extrusion process works like this. The plastic is first
fed in a pellet form into the Extruder. The material gets conveyed forward
continuously by a rotating screw inside a heated barrel. Here it is being
softened by heat and friction. The softened plastic is subsequently forced
out via a die, directly into the cool water. The product gets solidified
here. Afterwards it is conveyed onwards into the take-off rollers. It is
actually the take-of-rollers which does the pulling act of the softened
plastic from the die.

The die is basically a metal plate that is placed at one end of the
extruder. It has a section cut out of its interior. This cutout, along with
the speed of the take-off rollers, plays a determining factor in the
cross-section of the product being manufactured.
Many grades of thermoplastic can be extruded based on the application. The
two primary categories are rigid and flexible extrusions. Flexible materials
are needed for profiles that are required to serve as seals (for example say
refrigerator gaskets) while rigid thermoplastics are needed if structural
integrity is required. Typical examples include rigid polyvinyl chloride,
guttering and siding. The next section takes a look at the materials
available.
Features of Profile Extrusion
- Low Part Cost
- Low Tool Cost
- High Production Capability
- Shorter lead times in production
- Uniform cross section of parts
- Multiple materials/durometers are possible in the same part
Materials for Profile Extrusion
Generally two classes of materials are manufactured into profiles. This of
course depends upon the application and needs of the final product. These
two classes, rigid and flexible profiles, are differentiated based on the
starting material and final properties of the profile.
Rigid profiles are typically hard and relatively inflexible, often found in
building applications. They can be manufactured using different resins.
Flexible profiles on the other hand are flexible. The parts get bent easily,
and are often soft (Typical durometer hardness range for them is from 5095
ascertained by Shore A test). They are also easily compressible and generally
used as internal components of items. The following table summarizes a
variety of resins that are used in the profile extrusion.
| Resins for flexible
applications |
Resins for rigid
applications |
| Plasticized PVC |
ABS |
| TPO (thermoplastic olefins) |
Polycarbonate |
| Thermoplastic rubbers |
Non-Plasticized PVC |
| Thermoplastic Urethanes |
Polypropylene |
| LDPE |
HDPE |
Typical examples of Profile Extrusion
The following examples illustrate clearly illustrate the broad possibilities of Profile extrusion.
- Window profiles
- Sealing sections
- Modular drawer profiles
- Decorative trims