Acrylic styrene grades offer enhanced properties.

Four acrylic/styrene copolymers, some designed for blending with other resins, soon will be introduced by the Clear Performance Plastics group of Novacor Chemicals Inc., Leominster, Mass. The new grades are currently in the final development stages and are expected to be available by mid-1993. Though the four resins were planned to expand the company's existing NAS and Zylar lines, they may be introduced as an entirely new product line.

All four acrylic/styrene resins are designed initially for injection molding applications. Extrusion performance of the new grades will be evaluated in the future, Novacor executives say.

RESISTS CRAZING

New P-592 modified acrylic/styrene copolymer is designed for housewares. Company tests show the material is highly resistant to surface crazing caused by food and beverage contact or extensive dishwashing, out-performing competitive resins such as polycarbonate, SAN and straight acrylic.

Properties of P-592 include tensile strength of 9600 psi, flexural modulus of 431,000 psi, elongation of 3%, notched Izod impact of 0.4 ft-lb/in., specific gravity of 1.09, melt-flow index of 3 g/10 min (Condition G), and heat-distortion temperature of 206 F. It's priced slightly higher than existing NAS copolymers.

CLEARLY TOUGHER

P-605, another new modified acrylic/styrene copolymer, is developed for rigid injection molded packaging. Priced at around $1.25/lb tl, the material is designed to be blended with Phillips 66 K-Resin copolymer to provide improved rigidity and impact resistance, while maintaining clarity and a haze level of 5%. An accompanying graph shows a superior combination of low haze and high Gardner impact in a P-605/KR03 blend, compared with KR03 and either GPPS or Novacor's NAS21.

P-603 and P-610 are two new impact modifiers for medium-impact polystyrene, designed to improve impact strength while maintaining stiffness and providing uniform light transmission. Target applications for P-603 and P-610 are expected to include translucent lenses.

The accompanying graphs show that a 70:30 blend of MIPS and P-610 can have higher Izod and Gardner impact strengths than pure HIPS. A similar blend of MIPS/P-603 about doubles the Gardner impact of MIPS while maintaining almost equal Izod impact. Both modifiers maintain the high tensile strength of MIPS while raising the elongation above that of pure MIPS. P-610 provides greater elongation enhancement than P-605.

The two new impact modifiers are priced at $1.90 and $1.75/lb, respectively. Novacor says that in blends with MIPS, P-603 and P-610 provide a "cost/performance balance" that is comparable to ABS.