Page 237 - Engineering Plastics Handbook

Polyphenylene Ether (PPE) Blends and Alloys 203

The new flexible PPE grades are candidates for a variety of consumer
electronics applications. These include plug and cord applications for desk-
top and notebook computers, personal digital assistants, faxes, portable
personal computers, printers, scanners, digital cameras, radio/cassette,
portable CDs, microdisk, MP3, DVD players, video/TV games, sound
system components, mobile phone accessories, and cordless phones.

PPE/Polyamide Alloys

Semicrystalline polyamide resins have a broad balance of engineering
properties including excellent chemical resistance and toughness [22, 23].
However, the low T of polyamides results in dimensional changes at rel-
g
atively low temperatures. The tendency of polyamides to absorb moisture
results in limited dimensional stability and limits the performance window
of unfilled polyamides. For example, upon exposure to moisture,
polyamides will absorb high levels of moisture, which acts as a plasticizer
for the polyamide and results in lower strength and rigidity. In addition,
this increase in moisture is accompanied by an increase in the dimen-
sions of molded parts.
The use of glass fiber and mineral fillers blended with the polyamide
has been employed to address moisture uptake and growth. However,
inorganic fillers increase the specific gravity and severely decrease the
ductility of polyamides.
Alloying PPE with polyamide reduces the issues of polyamide moisture
uptake and low dimensional stability. Blending PPE with polyamides
gives an immiscible blend with two discrete phases. Compatibilization
technology is used to improve the interfacial adhesion between the two
phases, enhance properties, and give a stable morphology [24, 25]. Adraw-
ing of the morphology is depicted in Fig. 9.4.
Hence PPE/PA alloys have the polyamide as the continuous phase for
good chemical resistance and processability. The discrete phase con-
sists of finely dispersed particles of PPE. The PPE acts as an “organic
filler” which lowers moisture uptake, increases properties at elevated

Polyamide

PPE
Compatibilizer

Figure 9.4 Model of morphology of compatibilized PPE/PA
alloy.