Wood plastic composites
PRIEX® coupling agents improve properties in wood-plastic composites
Wood-plastic composites (WPCs) do not corrode, and they and are highly resistant to rot, to decay, and to attack by the marine borer. They do, however, absorb water into the wood fibers embedded within the material.
The mechanical behavior of WPCs is similar to that of unreinforced polymers: they have lower strength and stiffness than wood, and their performance is dependent on both time and temperature. Moisture absorption and freeze-thaw cycling may also reduce the strength and stiffness of the WPC.
Addcomp’s PRIEX coupling agents are used to improve many mechanical properties in WPC applications, such as impact and flexural strength, rigidity, dimensional stability, and creep resistance. PRIEX additive solutions also help to reduce the water absorption of the WPC, thereby reducing the chance of mildew growth.
PRIEX® coupling agents distinguish themselves by very high levels of grafted maleic anhydride (MAH). Levels in PRIEX products are typically more than twice the grafting level of alternative coupling agents, which benefits the end product in two ways:
- very high reactivity and good wetting of the wood fiber for the best mechanical property improvement
- cost reduction through a lower addition level
Addcomp’s proprietary processing technique means very low levels of ungrafted MAH remain in PRIEX resins. Typically less than 10% of the levels of free MAH level of alternative coupling agents, resulting in:
Very low levels of free MAH left in the PRIEX® resins after grafting (typically less than 10% of free MAH level of alternative coupling agents)
- Ultra-low odor
- Ultra-low VOC & emissions
- Less interaction between free MAH and filler, thus increasing its effectiveness
And because grafting and MFI levels are tight controlled during processing, the quality of PRIEX resins is consistantly high.
The reaction mechanism of PRIEX® coupling agents for WPC is as follows:
PRIEX coupling agents provide excellent fixation of the wood fibers to the polymer matrix:
The addition of PRIEX coupling agents leads to improvement in mechanical properties as shown in the graphs below (75% wood fiber, 23% polypropylene, and 2% PRIEX coupling agent):
PRIEX coupling agents are available for wood-fiber composites based on polyethylene (PE) or polypropylene (PP). Addcomp also offers high quality slip agents for use in WPC production.