Page 236 - Engineering Plastics Handbook

202 Engineering Plastics

Unlike polypropylene, PPE/PS resists breakage at freezer tempera-
tures, and it maintains rigidity at much thinner gauge. In addition, prac-
tical stiffness at elevated temperature is better than PP or PET.
Further, modified PPE resins can be processed on most standard PS and
PET extrusion and tooling equipment, enabling converters to extend their
portfolio without a large capital investment.
These packaging grades can be used as an additive for polystyrene to
improve material stiffness at elevated temperatures as well as increase
impact at low temperatures.
Food packaging grades have the Noryl PKN designation and they
include

Noryl PKN 4717: Transparent, foamable, 315°F (157°C) Vicat
Noryl PKN 4766: Transparent; 264°F (129°C) Vicat
Noryl PKN 4752: Transparent, 345°F (174°C) Vicat
Noryl PKN 4765: Opaque, 304°F (151°C) Vicat
Noryl PKN 4775: Opaque, 288°F (142°C) Vicat

Flexible flame-retardant grades. These are a new family of flexible modi-
fied-polyphenylene ether resins specifically developed for wire-coating
applications. They are designed as an alternative to polyvinyl chloride
(PVC), flame-retarded polyethylene (FR-PE), and thermoplastic polyurethane
(TPU) in wire-coating applications for the direct-current (dc) cord and
plug segments of the consumer electronics industry. Flexible PPE resins
meet OEM requirements for bending strength, flexural strength, dura-
bility, hydrolytic stability, and insulating properties.
Flexible PPE grades are nonhalogenated, contain no heavy-metal pig-
ments, offer broad thermal performance, and are lighter and more flexi-
ble than many competitive thermoplastics and offer lower systems costs.
For example, PVC contains chlorine, which can break down into toxic and
highly acidic gases when burned; flexible PPE exhibits a lower density than
FR-PE and TPU—weight reductions of 20 to 30% are achievable; and the
higher flow characteristics and faster extrusion rates suggest the poten-
tial for higher productivity.
The new grades Noryl WCD910 and Noryl WCP860 address several
important needs of the electronics cord/plug segment, particularly the
need for polymers of less environmental concern (ECO-label). Indeed,
Europe and Asia are moving to the use of nonhalogenated materials and
are also calling for a reduction or elimination of heavy-metal pigments,
which also raise environmental concerns. Additionally, there is strong
incentive to use polymers that can easily be recycled—both in the plant
and at the end of component life—which favors thermoplastics over ther-
mosetting polymers.