Woodfibre Plastic Composites: Rising to the Challenge

Primary extrusion equipment specially developed for wood- and natural-fibre plastic composite materials includes a wide range of single- and twin-screw extruders from a variety of manufacturers.

American Maplan offers a line of single-screw extruders for processing pre-compounded natural fibre composite pellets. Typically, pre-compounded natural fiber composite masterbatch pellets are blended with base materials and extruded into finished profiles. The line of single-screw extruders have output rates up to 2,300 lb./hr. The company also offers a line of low-shear, counter-roatating twin-screw extruders for direct extrusion of profiles from major and minor material streams.

Werner & Pfleiderer’s WP ZSK twin-screw extruder utilizes a “three-in-one” process to dry, compound and extrude direct woodfibre plastic composite profiles in a single continuous process. Coperion, the parent company of W&P, claims a commercial application involving the smallest version of the model, WP ZSK58MC, has consistently produced 1,400 lb./hr in a direct extrusion profile.

Milacron supplies seven different models of its conical twin-screw extruders specifically targeted for WPC production applications. Extruders incorporating 80, 86 and 92 mm diameter screws have demonstrated excellent performance in commercial production of WPC deck board and profiles, according to Tom Brown, Milacron general sales manager, extrusion systems business.

“We have the ability to design and manufacture screws that match specific applications,” says Brown. “We want to utilize our entire range of products and services to customize products for the wood-plastic composite industry.”

Scott Equipment’s AST Drying System incorporates an innovative “Air Swept Tubular” design for efficient single-pass drying of wood flour. The dryer is capable of reducing the moisture content of wood flour from 10 to 15% to less than 1% in less than one minute. The drying is enhanced by aggressive agitation to continually mix the wood flour with the heated air stream.

AccuRate’s Mechatron feeders offer manufacturers of wood-fibre composite products the ability to quickly change materials or recipes without typical time-consuming procedures characteristic of many bulk feeders. Additionally the feeders provide gravimetric accuracy of +/- 0.25% based on the material’s characteristics, which in turn helps maintain color consistency in wood-fibre plastic products.

ADDITIVES RAMP UP PERFORMANCE

Canada Colors & Chemicals Ltd. is offering a full line of lubricants, blowing agents, coupling agents, flame retardants and biocides specially targeted for the WPC industry. According to Victor Satov, product sales manager, the company is able to supply WPC manufacturers with both zinc stearate and amide wax based lubricants. Satov says the lubricants, used separately or in combination, can often improve throughput, depending on the amount and type of wood fibre. Additionally the company offers a third type of lubricant, supplied by Honeywell, compatible with coupling agents.

Crompton Corporation’s Polybond coupling agents help bind materials in composite formulations, improving physical properties such as impact strength and weatherability. Polybond 3109 consists of LLDPE grafted with 1% maleic anhydride. The product’s higher flow results in easier mixing and enhanced performance in wood-filled compounds.

A study conducted by Luzenac America Inc. found an approximate 1% increase in both the flexural modulus and modulus of rupture for each percent of wood replaced with talc. The study also found that talc reduces water absorption, thickness swell and warpage.

PJ Murphy Forest Products Corp. supplies a variety of hard- and softwood wood flour in an assortment of mesh sizes. The company will provide customers with technical advice and service to help a customer choose the proper type and mesh size of wood flour for a specific application.