Common Polymers and Additives used for Processing - Introduction to Polymeric Composites with Rice Hulls - page 48

4.5 High-density Polyethylene
HDPE is a thermoplastic polymer made from petroleum sources. This resin is used
widely in the plastics industry for applications such as corrosion-resistant pipes, geo-
membranes, plastic lumber, bottle caps, food containers, auto fuel tanks, plastic bags,
water pipes, electrical/plumbing boxes, hard hats, and industrial safety equipment.
Common and popular special applications are the use of HDPE, whereby large sheets
are employed for the prevention of pollution from soil and groundwater from solid
wastes, and also for the pyrotechnics trade. Milk jugs and other blow-moulded hollow
products are also important applications of HDPE.
4.5.1 Properties
HDPE is known for its high strength:density ratio. The mass density of HDPE is
0.93-0.97 g/cm 3 . The density of HDPE is only marginally higher than that of LDPE,
but HDPE has little or no branching, giving it stronger intermolecular forces and
a tensile strength than LDPE. The difference in strength exceeds the difference in
density, giving HDPE a higher specific strength. It is also harder and more opaque
and can withstand higher temperatures of ≈121.1 °C for short periods and ≈110 °C
for long periods of time.
4.6 Acrylonitrile-butadiene-styrene
ABS polymers are opaque thermoplastic resins formed by the polymerisation of
ABS monomers and have many diverse properties. ABS is classified as a terpolymer
(i.e., composed of three monomers). Their development as commercial polymers
resulted from research on synthetic rubber. The proportions of the three monomers
can be varied, which accounts for the great number of possible properties.
Graft polymerisation methods are, in general, used to make various grades of
ABS. They are versatile resins and can be processed easily on all thermoplastic
processing machines. Some of the applications for ABS are: appliance housings,
light luggage, pipes, tool housing, extruded lumber, automotive parts, tool boxes,
and furniture components.
4.6.1 Properties
ABS resins are hygroscopic (moisture absorbing) and pre-drying before processing is
advised. Some of the main properties of ABS are: