Dramatically new PP alloys, copolymers.

Dramatically New PP Alloys, Copolymers

When Himont R&D research scientist Gordon Brewer gave a technical paper at NPE on Himont's new Hivalloy polymer grafting technology, he couldn't even use the name Hivalloy. It was one of the quieter introductions of a major new alloying technology, made possible in part by grafting polypropylene with non-olefinic monomers (see PT, Aug. '91, p. 70-71). Nor were press releases or copies of his talk given out, though he did show slides of three sample parts: a small toy truck previously molded of ABS, a 20-in. tape cartridge holder with slots said to show none of the visual flaws sometimes associated with differential flow rates in an alloy; and a computer keyboard frame, which he said showed none of the warping often associated with PP.

The reason Wilmington, Del.-based Himont Incorporated, part of the Montecatini/Montedison group in Italy, kept its new PP alloys under a bushel was that several joint ventures which included the Hivalloy technology weren't yet in place at the time of NPE. Only in July, for instance, did Himont announce its joint venture with Mitsubishi Gas Chemical Co. in Tokyo to produce alloys based on Mitsubishi's PPE (polyphenylene ether) and Himont's propylene-based olefinic compositions. PPE is blended with PP in several types of Hivalloy.

Hivalloy is patended two-step alloying technology that bonds vinyl monomers, like styrene, to the backbone of the PP polymer chain. These pendent monomers allow the PP to be compounded with previously incompatible materials like PPE in order to create new high-performance engineering resins. PP has been compounded with crystalline materials like nylon and HDPE before. But the Hivalloy compounds are said to be the first stable alloys combining PP with PPE. These high-performance compounds are also a new line for Himont.

Himont's catalysts and polyolefin technology creates a wide range of these alloys. The polymeric feedstocks that are the starting point for all the alloys have catalytically controlled morphology. The process starts by tailor-making a porous spherule of PP in a reaction process similar to Himont's Catalloy technology, then grafting various monomers. Control of the porosity and surface area of the PP spherules is provided by the catalyst technology. Each alloy requires a unique spherule. The resulting spherules can be used as is, or as compatibilizers to alloy PP with other resins like PPE in a second reactor stage.

This two-step Hivalloy process makes compounds that can rival the toughness, surface hardness and heat-deflection temperature of engineering resins like ABS - at a fraction of the cost, Himont says. These alloys also retain some property advantages of PP, like chemical and impact resistance. They target such applications as appliances and auto bumper fascias.

NOT READY FOR PRIME TIME 

Developmental quantities of some of the new alloys (see table) are being made at Himont's new pilot plant at Lake Charles, La., with capacity of 10 million lb/yr, where much of the advanced materials development work is going on. Himont director of product development Ken Dargis says Hivalloy is "only in the earliest predevelopment stages," and a commercial Hivalloy plant could be three years away.

Brewer's paper cites properties of four alloys of PP with amorphous polymers (see Table). All the alloys begin with a polyolefin base. When the polyolefin is combined with a styrenic (as in Alloy A) it makes a resin halfway between a typical PP copolymer and between-purpose ABS. Alloy B blends different amounts of PPE, which attaches to the styrenic in Alloy A to achieve higher HDT. And Alloys C1 and C2 combine the polyolefin base with differing amounts of polycarbonate. Applications development work is said to be under way with these and other alloys.

[Tabular Data Omitted]

Initial alloys will focus on PP, but the Hivalloy process isn't limited to PP. In fact, Himont has pointedly staffed its advanced materials group responsible for Hivalloy applications development with non-PP polymer scientists. Theoretically Hivalloy could produce both specific performance alloys and blends of dissimilar waste materials for mixed-plastics recycling. "It's early to say, but this could be the basis for a mixed-plastics recycling program for Himont," says Dargis. (CIRCLE 27)