Enabling wood-plastic composites: Additives, aids & agents

As anyone who has ever spent a long afternoon power washing their deck knows, the rapid expansion of thewood-plastic composites (WPC) industry over the past several years is largely due to the performance advantages these products provide over competing wood materials.

Found in decking and railing, windows and doors, decorative trim and moldings, docks and boardwalks, and in automobile door panels and truck flooring, WPCs increasingly offer better flexural and impact strength, better moisture resistance, less shrinkage, and improved weatherability than natural wood.

The key to these characteristics lies in the increasing number of additives and processing aids designed for WPC products, as well as the coupling agents used in combination with additives to help transfer the inherent strength of cellulosic wood fibers to the surrounding plastic.

Here, Canadian Plastics spotlights some of the latest in WPC additives, coupling agents, and processing aids on offer from suppliers.

Struktol Company of America

WPC manufacturers can select from a number of recent processing aids for WPCs developed by Struktol.

STRUKTOL TPW 104 is designed primarily for polyethylene (PE) and polypropylene (PP) composites to compatabilize, improve homogeneity, processability, output rates and surface quality. TPW 104 has also been used in other polymers. STRUKTOL TPW 113 is designed for filled olefin compounds as a processing aid and acts as a synergist to enhance properties where coupling agents are employed. The company’s STRUKTOL TPW 709 is intended as lubricant used when a broad range of composites are in the mix and can be used with or without coupling agents. And STRUKTOL TPW 012 is designed for polyvinyl chloride (PVC) compounds, especially for composite formulations. It is a blend of internal and external lubricants as well as compatabilizers and processing aids for optimum processing and output rates. Struktol describes this unique system as a “one pack” that eliminates the need for any other lubes including calcium stearate.

Struktol Canada Ltd. (Uxbridge, Ont.); www.struktol.com; 416-286-4040

Dupont

Resins in the Fusabond product line from DuPont are modified polymers functionalized (typically by maleic anhydride grafting) to help bond together polymers used in toughened, filled and blended WPCs.

The product line includes modified ethylene acrylate carbon monoxide terpolymers, ethylene vinyl acetates (EVAs), PE, metallocene polyethylenes, ethylene propylene rubbers and PP.

Recently, the company launched Fusabond E EC-603D, a compatibilizer for users of recycled PE. DuPont is marketing the material to manufacturers of industrial packaging and plastic lumber, as well as blow molders, injection molders and compounders.

Also, the new Fusabond W PC-576D is a grade specifically designed for use in wood alternatives. According to DuPont, Fusabond W PC-576D is a random ethylene copolymer, incorporating a monomer which is classified as being a maleic anhydride equivalent for application uses.

E. I. du Pont Canada Company (Mississauga, Ont.); www.plastics.dupont.com; 1-800-387-2122

Eastman Chemical Company

The Epolene MA-grafted series of coupling agents from Eastman Chemical include the PE-based Epolene G-2608, as well as the newer PP-based E-43, G-3003, and G-3015 grades.

“Customers using these grades have seen a 70 per cent increase in overall tensile properties, a 30 per cent to 35 per cent increase in modulus of rupture (MOR), over 200 per cent in unnotched Izod impact, about 20 per cent improvement in heat-distortion temperature (HDT), and dramatic increases in moisture resistance,” said business development manager Damon Hollis.

With its Licocene product, Clariant offers “designer waxes” for different applications. Licocene are a new class of high-performance materials manufactured in a special process developed by Clariant that uses metallocene catalysts, making it possible to tailor properties of the Licocene, such as melt temperature, viscosity, or hardness for special applications.

Clariant

The Licocene PE MA and Licocene PP MA series were specially developed as coupling agents and compatibilizers for natural fiber-filled composites. In WPC with polyethylene as the polymer ingredient, Licocene PE MA 4351 TP is used. In WPC in which polypropylene is used as a polymer, meanwhile, Clariant recommends Licocene PP MA 6452 TP. Both additives are waxes based on polyethylene, or polypropylene, respectively, which were polar-modified with maleic anhydride.

According to Clariant, the addition of Licocene increases the hardness of the composite in both cases, thus improving its impact resistance and increasing its e-module. Also, with its reduced water absorption, the material features increased dimensional stability, while its higher elasticity reduces the risk of splintering and breaking. “Licocene significantly improves the quality of WPC both indoors and in outdoor flooring and fences,” the company said.

Clariant (Canada) Inc. (Montreal); www.clariant.ca; 514-334-1117

Reedy InteRnatIonal CoRpoRatIon

New from Reedy is a series of additive packages for WPCs based on high-density polyethylene (HDPE), PP and PVC. Among these is Saftec AS, a heat stabilizer that is applied to the wood fiber prior to processing, which facilitates processing of highly filled composites at higher temperatures without oxidation or charring. According to Reedy, Saftec AS provides enhanced colour stability, reduced water absorption, and prevention of mold growth. The product also acts as a processing aid, allowing for higher extrusion rates with improved tensile and flexural strength and surface characteristics.

The company’s Safoam RIC/FP, meanwhile, is a new active powder form of the company’s low-temperature endothermic chemical nucleating and blowing agent. It is also available as RIC50/FP masterbatch with 50 per cent active ingredient.

Reedy International Corporation (Keyport, N. J.); www.reedyintl.com; 732-264-1777

Boeealis Compounds

In partnership with AMI Agrolinz Melamine International, Borealis has introduced a new generation of modified, extrudable melamine resins — the first such resin, according to Borealis, available for use on conventional extrusion equipment.

The company’s HIPERESIN MPER is designed for the extrusion of WPCs with up to 70 per cent of wood fibres or wood flour. Trademarked as HIPERWOOD, the thermosetting HIPERESIN MPER helps to overcome known shortcomings of conventional, thermoplastic-based WPCs such as low thermal stability by combining unique thermoplastic processing behaviour with thermo-setting product performance.

HIPERWOOD is processed on commercial WPC extrusion lines such as conical counter-rotating twin-screw extruders, but with an inverse temperature profile. The extruded profiles cure and crosslink by passing through the heated die. According to Borealis, HIPERWOOD provides high scratch resistance, high mechanical properties and dimensional stability — particularly at higher temperatures — as well as adhesion to various substrates.

Borealis Compounds (Port Murray, N. J.); www.borealisgroup.com; 908-850-6200

EquistaR Chemicals

Equistar Chemicals, a subsidiary of Lyondell Chemical Company, offers the Integrate series of maleated PE coupling agents for PE-based composites, plus new maleated PPs for wood-PP.

“WPC lumber typically shows at least 50 per cent higher MOR and 20 per cent higher modulus of elasticity (MOE) with the incorporation of these additives,” said James Krohn, business development manager.

Equistar Chemicals (Houston, Tex.);
www.lyondell.com; 979-245-1225

Eastman Chemical Company (Kingsport, Tenn.); www.eastman.com; 423-229-2000