Borogard ZB and wood composite

Borate preservative for wood composites

Protect wood and wood composites from destroying organisms, rot decay fungi, and subterranean termites.

Preservative for wood composites

Maintain the Beauty and Durability of WPCs

Wood-plastic compounds (WPCs) are popular building materials thanks to their durability, low maintenance, and appearance. To protect investments and meet demands, WPC manufacturers can depend on Borogard® ZB.

For more than 15 years, Borogard ZB has successfully protected WPCs against rot and decay, inhibited mold, and enhanced UV light stabilization. Its biostatic properties, low cost, and excellent safety attributes make Borogard ZB the leading preservative treatment available.


Independent laboratory and field studies carried out by universities and government testing facilities have shown that WPCs treated with Borogard ZB resist the ravages of a range of wood-destroying organisms in above-ground uses, including:

  • Decay-resistant siding, roofing, and millwork
  • Termite-resistant sheathing and subflooring
  • Commodities for export to high-decay-hazard regions

As an additive in the manufacturing of WPCs, Borogard ZB can control the growth of white and brown rot decay fungi. As a wood preservative, it also helps to protect WPCs from damage caused by wood-destroying insects, including Formosan subterranean termites. But Borogard ZB's performance goes beyond its broad-spectrum efficacy against all wood-destroying organisms.

  • Borogard ZB is a completely reacted zinc borate and is distributed homogenously throughout the WPC. Its protection is continuous, despite any surface abrasion, end cuts, and sanding that occur during installation.
  • The product is thermally stable under WPC manufacturing conditions and is easy to introduce into existing manufacturing processes.
  • Particle size and shape are optimized to reduce solubility in water, making Borogard ZB resistant to leaching and weathering and increasing its proven effectiveness over a longer period than competing products.
  • As a synergist, Borogard ZB can boost the performance of hindered amine light stabilizers (HALS), which are used to protect WPCs against UV degradation. Slowing down the degradation of WPCs’ plastic components further minimizes exposure and degradation of the wood components.
  • Borogard ZB is the most cost-effective protection available for WPCs and other composites.
  • Although effective against insects and fungi, Borogard ZB is safe for people, pets, and the environment.

Pre-treat wood for termite

In independent tests performed in Hawaii on aspen flake composites, Borogard ZB wood preservative at a retention of 0.75% (w/w) provided protection against decay fungi and Formosan subterranean termites.


Borogard ZB Application
Borogard ZB Resources
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Borates make excellent preservatives of wood composites: Efficient in protecting against both fungi and insects, fire retardant at higher loadings, low cost, easy to handle, low acute mammalian toxicity, and minimal environmental impact.

Technical Details

Available Grades

Borogard ZB has been used in North America for years, with a broad spectrum of efficacy and low acute mammalian toxicity. However, WPCs treated with Borogard ZB are not suitable for ground contact and must be protected with a water-repellent coating when used in exterior applications (eg, joinery and siding).

Borogard ZB is leach resistant—only sparingly soluble in water at room temperature (< 0.28% w/w). It contains no organic components and does not require the use of organic solvents because it is applied as a dry powder.

By adding Borogard ZB before or during the blending process, you can achieve a thorough and uniform distribution of the chemical throughout the composite material. Efficient distribution of the preservative in the manufactured board can be confirmed by chemical assay.

Borogard ZB is chemically stable to 290°C and is not altered during normal wood composite manufacturing processes. Composites treated with appropriate levels of Borogard ZB generally retain their natural appearance and strength. Ferrous metals, plastics, rubber, putties, bituminous solutions, other sealants, primer, and finish paints are not adversely affected by wood composites treated with Borogard ZB.

WPC manufacturers should determine the Borogard ZB loadings for their treated products and end-use applications. Borogard ZB loadings should not exceed 8% (w/w), and loadings in excess of 1.5% (w/w) might require additional adhesive binder to compensate for possible effects on strength.

BoroGard ZB in Action

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U.S. Borax, part of Rio Tinto, is a global leader in the supply and science of borates—naturally-occurring minerals containing boron and other elements. We are 1,000 people serving 500 customers with more than 1,700 delivery locations globally. We supply 30% of the world’s need for refined borates from our world-class mine in Boron, California, about 100 miles northeast of Los Angeles.  Learn more about Rio Tinto.

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