Effect of Tie-Layer on the Bond Strength Between Thermoplastic and Borate-Treated Wood Substrate

Authors

  • Steven G. Michael
  • Vikram Yadama
  • Donald A. Bender

Keywords:

Thermoplastic, tie-layer, wood composite, peel strength, preservative treatment, Parallam, Douglas-fir, southern pine

Abstract

A challenge in using wood or wood composites for exterior applications is durability. Borate-treated wood substrates are durable if leaching of the chemical over time can be reduced to acceptable levels. The goal of this project was to encapsulate borate-treated structural wood and wood-based composites with thermoplastic to extend their durability. In this study, the efficacy of two tie-layers (maleic anhydride modified high-density polyethylene and styrene-butadiene polymer) in bonding high-density polyethylene (HDPE) to treated wood substrate was examined together with determining the ideal hot-press parameters necessary to achieve a good bond. Boric oxide treated Douglas-fir and southern pine Parallam® and untreated Douglas-fir solid wood were the substrates investigated. The optimum processing parameters were 180°C platen temperature, 1035 kPa press pressure, and 300 s press time. Bond strength was determined by conducting a 90° peel test and a block-shear test. Durability of the thermoplastic barrier layer was evaluated by subjecting specimens to an accelerated aging test and reevaluating the bond strength. Maleic anhydride-modified HDPE tie-layer yielded improved bond strength that was durable, especially when bonded to a treated southern pine substrate.

References

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Published

2010-10-11

Issue

Number 4 / October 2010

Section

Research Contributions

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