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LDPE,
the first of the polyethylenes to be developed, is characterized by good
toughness and flexibility, relatively low heat resistance, low-temperature
impact resistance, and clarity in film form.
Like the medium and high-density grades, LDPE has good resistance to
chemical attack. At room
temperature, it is insoluble in most organic solvents but is attacked by strong
oxidizing acids. At higher
temperatures it becomes increasingly more susceptible to attack by aromatic,
chlorinated and aliphatic hydrocarbons.
Polyethylene
is susceptible to environmental and some chemical stress cracking.
Wetting agents such as detergents accelerate stress cracking. Some copolymers of LDPE are available with improved
stress-crack resistance.
About
half of LDPE production goes into packaging applications such as industrial
bags, shrink bundling, soft goods and produce and garment bags.
Other applications include blow-molded bottles, large industrial
containers and toys; hot-melt adhesives; injection-molded housewares;
paper-board coatings and wire insulation. LDPE
resins are rotationally molded into large agricultural tanks, chemical shipping
containers, tote boxes and battery jars.
One
of the fastest growing plastics today is linear low density polyethylene (LLDPE)
used mainly in film applications but also suitable for injection, rotational and
blow molding.
Properties
of LLDPE are different from those of conventional LDPE and HDPE Impact, tear and
heat-seal strengths and environmental stress-crack resistance of LLDPE are
significantly higher. Major uses at
present are in film products – industrial trash bags, liners and heavy-duty
shipping bags for such products as plastic resin pellets.