Long-glass properties for less cash

New York -A recent technology agreement promises to change the price-performance balance of long-glass-fiber-reinforced polypropylene, driving down its cost in high-volume applications and potentially opening the door for automotive, appliance, and other large-part structural applications. The deal, announced here in August, allows LNP Engineering Thermoplastics (Exton, PA) to market Twintex long-glass-fiber pellets produced by Vetrotex America (Wichita Falls, TX).

LNP will market the pellets as Verton MTX. Unlike LNP's previous Verton products, which are produced in a pultrusion process, Twintex's technology combines glass and thermoplastic in one continuous roving during fiber manufacturing. The resulting pellets can support extremely high glass-loadings-in excess of 75%, according to William Magill, Twintex business manager. In LNP's case, the pellets will contain 75% glass by volume.

Intended for use as a glass concentrate, the pellets can be blended with a variety of polypropylene base resins right at the molding machine. Verton product manager Matthew Miklos estimates that machine side blending will produce cost savings in the 20-30% range at volumes around one million lbs/year-by enabling users to start with ordinary low-cost polypropylene and achieve their final glass loadings with a relatively small amount of costly concentrate. "The savings is in the final blend," he says, noting that LNP needs to drive prices into the range of $1.00 to $1.20/lb to compete with other structural thermoplastics in typical automotive applications.

The marketing agreement, which is limited to injection molding and extrusion-compression applications, could free long-glass-fiber-reinforced poly-propylene from a longstanding vicious circle: While its mechanical and physical properties make it a good choice for large-piece structural parts, these parts tend to use so much plastic that they have the greatest sensitivity to long-glass-reinforced polypropylene prices. "It's been a problem," concedes Miklos.

Though Verton MTX primarily targets cost reduction at high volumes, this blend-to-order family of materials will offer mechanical-property advantages, too, Miklos reports. Take impact strength, for instance. Rather than blending the glass concentrate with an ordinary polypropylene homopolymer, users might instead blend it with impact grades of polypropylene. Miklos cites early data that show falling-dart impact improvements in the 15-20% range compared to earlier Verton grades that use an unmodified polypropylene. "You can basically dial in the properties at the molding machine," he says.