PC/ABS & ABS grades offer enhanced processability.

The Dow Plastics unit of Dow Chemical U.S.A., Midland, Mich., is introducing four grades of resins for injection molding enclosures of business machines. The new materials are said to provide improved processability relative to competing flame-retardant resin systems.

The four grades represent new-generation extensions of Dow's Pulse polycarbonate/ABS blend and Magnum ABS product lines. The company last updated these two resin series for business machine applications in late 1989 with the introduction of Pulse 1725 and Magnum 3661.

Dow executives say the goal in developing the new grades was to offer a competitive balance of processing and mechanical/thermal properties, along with improved uv resistance and surface appearance, and greater heat-distortion resistance for thinner-walled parts.

NONHALOGEN ALTERNATIVE

New Pulse 1735 PC/ABS grade includes a totally nonhalogenated flame-retardant package as an alternative to Pulse 1725, which contains bromine. This is said to address some business-equipment manufacturers' preference to avoid halogen, but without any sacrifice of processability or performance properties. Like Pulse 1725, the 1735 grade achieves UL 94V-0 flammability at 1/16 in., and also meets UL 94-5VA at 1/8 in. The patented flame-retardant package includes phosphorus as one of its components.

Pulse 1735 offers an HDT of 195 F at 264 psi, notched Izod impact of 12 ft-lb/in., and a melt-flow rate of 28 g/10 min--values equal to or slightly better than those of Pulse 1725. Dow sources say Pulse 1735's flowability is only slightly less than 1725's in terms of real-world injection shear rates. Dow claims that Pulse 1735 offers a better balance of HDT, impact and processability than other nonhalogenated PC/ABS business-machine grades on the market, including no plateout. Pulse 1735 is priced at $2.07 lb/tl in custom colors, which is competitive with other nonhalogenated PC/ABS's and 2|cents~ less than Pulse 1725.

FLAME-RETARDANT ABSs OFFER UV CHOICE

Three new grades in the Magnum 4400 series look to overcome traditional problems associated with flame-retardant ABS, such as mold plateout and limited light-stability selection. Magnum 4410, 4420 and 4430 offer a choice from medium to high uv stability. The range allows customers to choose the most cost-effective resin based on specific light stability requirements. Prices range from $1.91 to $2.01/lb tl in custom colors. All three grades have UL 94V-0 performance at 1/16 in., due to a proprietary bromine additive package that addresses health concerns by not including brominated diphenylether, according to the company.

Dow says the Magnum 4400 series significantly reduces plateout compared with equivalent competing FR-ABS resins. Dow also cites lower melt viscosity, which permits molding at lower temperatures (around 400 F melt), potentially yielding 10-25% shorter cycle times.

Magnum 4410 has an HDT of 160 F at 264 psi, melt-flow rate of 11 g/10 min, flexural modulus of 320,000 psi, notched Izod impact of 3.5 ft-lb/in., and elongation of 30%.