Page 229 - Engineering Plastics Handbook

Polyphenylene Ether (PPE) Blends and Alloys 197

surface opposite ribs and bosses, and increased chemical resistance when
compared to conventional injection molded parts. These grades are formu-
lated with a non-brominated, non-chlorinated flame retardant.
Uses include electrical enclosures, medical equipment enclosures, copiers
and large business machine housings and their structural bases, and light-
weight structural interior components for transportation. Structural foam
grades and key features include

Noryl FN150X: Thin-wall capability; 165°F (74°C) HDT at 264 psi
(1.82 MPa); UL-94 V-0/5VA ratings
Noryl FN170X: 173°F (78°C) HDT at 264 psi (1.82 MPa); UL-94 V-1/5VA
ratings
Noryl FN215X: 170°F (77°C) HDT at 264 psi (1.82 MPa); UL-94 V-1/
V-0/5VA ratings
Noryl FM3020: 30% glass-reinforced/mineral filler; 230°F (110°C)
HDT at 264 psi (1.82 MPa); UL-94 V-1/5VA ratings
Noryl FM4025: 40% glass-reinforced/mineral filler; 230°F (110°C)
HDT at 264 psi (1.82 MPa); UL-94 V-1/V-0/5VA ratings

Table 9.7 contains representative properties of some PPE/PS structural
foam grades. In general, properties on structural foam parts are measured
on 0.25-in- (6.4-mm-) thick foamed parts. The weight reduction of the test
parts of the various grades appears in this table. For flame ratings, the
minimum density and the minimum thickness needed to achieve a flame
rating are listed.

Expandable modified PPE grades. These are used to prepare low-density,
foamed thermoplastic parts. Unlike with structural foam, the densities are
significantly lower and are designed for applications requiring high energy
absorption, temperature resistance, and light weight. Typically a volatile
material is incorporated into modified PPE beads. When heated, the beads
soften and expand. These preexpanded beads have a fine closed-cell struc-
ture. After a short maturation period the preexpanded beads become suit-
able for molding.
In the molding process, preexpanded beads are introduced into a
closed mold and then heated, whereupon the beads soften, reexpand to
fill the interstitial volume, and typically fuse together without the need
for external pressure. Expanded foam modified PPE materials exhibit
■ Fine and homogeneous closed-cell structures
3 3
■ Low densities: 1.25 to 12.5 lb/ft (0.02 to 0.2 g/cm )
■ Outstanding thermal stability up to 248°F (120°C)