Long-Life Straw and Other Benefits of Borates

:: Tuesday, November 27, 2018 :: Posted By Jenny Qi Huang

In 1865, when Joseph Lister pioneered the use of antiseptics in surgery, he started by employing carbolic acid. Later he announced the discovery of a new antiseptic, boracic acid (aka boric acid), which he described as "highly effective and much less irritating." In doing so, he unwittingly paved the way for significant developments in the green exploitation of renewable resources at the end of the following century.

The bacteriostatic properties of boric acid led to its worldwide medical adoption—as a powder, in solution, and in wound dressings—for some 70 years. Later, those properties were recruited to protect wood from the infections to which cellulose is prone. And today, borates are used to transform natural fibers that have been under-used or wasted into long-lasting, high-performance modern materials.

Borates are effective for antifungal and antipest uses

Borates were eventually superseded in hospitals and medicine by more specific antiseptics. But their ability to prevent the growth of microorganisms remains highly relevant to a world that needs resource conservation and waste prevention.

Borates control the biodeterioration caused by bacteria, fungi, and insects by combining in solution with groups of biochemicals, such as co-enzymes, that are vital to metabolic processes at the cellular level. These combinations subsequently become unable to take part in the metabolic pathway, and so the cells of the organisms starve and become moribund.

Borates are highly effective broad-spectrum preservatives, giving full control over the fungi and insects responsible for the biodeterioration of natural-fiber products. However, borates simultaneously possess very low acute mammalian toxicity, so they pose virtually no risk to people or pets.

The reasons behind this are twofold. First, mammals are unaffected by borates in the amounts used because their vast size relative to the fungi or insects means they are not subjected to the same levels of physical exposure. Second, mammals are safeguarded by efficient kidneys, which excrete borates and so prevent bioaccumulation.

Borates in industry provide environmental benefits and improve safety

Borates are generally considered to have a low environmental impact. In the natural environment and in agriculture, boron is one of the seven essential plant micronutrients—not only benign, but necessary for healthy plants and improved crop yields. The benefits of borates extend into a variety of global industries.

When used for wood protection, the efficacy of borate treatment has been recognized around the world for many decades. Special products, notably Tim-bor® wood preservative, have been developed to optimize this effectiveness. Other natural fibers that are susceptible to biodeterioration can now be given similar protection.

These benefits mean that certain fibers—previously considered low value or even waste products—can now be used as economical, efficient, and environmentally sustainable materials that meet the high standards of today's manufacturing and construction industries. Many fibers were previously rejected because they are vulnerable to insect infestation and rot also because they are flammable. In short, while they might enhance the comfort of a home, they might also be safety hazards and offer a ready meal for bacteria, fungi, and insects.

Borate treatment effectively rules out the bug problem, and a somewhat higher concentration also protects against fire risks.

  • Old newspapers, for example, are hardly worth recycling as even low-grade paper pulp once they are de-inked. But shredded, they become an excellent insulation material and are processed in huge quantities for this purpose. Unfortunately, the cellulosic insulation is also highly flammable and attractive to nesting insects—two problems solved by the addition of boric acid.
  • Almost unlimited quantities of straw are produced every harvest, and in most countries, it is more or less wasted. Yet compressed into strawboard, it is an excellent material for interior panels in buildings—light, strong, versatile, easy to handle, and cheap. In service, it performs well and as it is compressed, it is remarkably fire-resistant—until it is infested by colonies of the Psocopteran book louse. Treatment with Polybor® disodium octaborate tetrahydrate is very effective against book lice and other insects—the British Standard No. 4046 for strawboard specifies a 0.1% mean boron content.
  • The use of sheep's wool, effective though it might be as an insulator in the construction industry, had previously been discounted on grounds of its relatively high cost and its susceptibility to attack from carpet beetle and clothes moth larvae. A mixture of low-cost short or colored wool fibers treated with Polybor is now a cost-effective option in many markets. A 5% borate retention ensures the insulation will not come under carpet beetle or moth attack, and although the material is still relatively expensive it is becoming a viable alternative where there are concerns about safety or environmental impact.
  • A relatively recent development in the use of natural fibers is to take Polybor-treated flax or hemp, and hot press the vegetable fiber with 5% polypropylene filaments to bind the mixture together under high pressure. The result? A cost-effective, robust, lightweight, rot- and mold-proof board that is useful in manufacturing industries the world over. Already it is being tested as an interior panel material for automobiles as total recyclability (which the new board has) is mandatory in some European markets.

Other chemicals have been suggested and tried in the effort to bring renewable resources into play but most fall short on the very safety or environmental grounds they seek to alleviate. Borates, some traditional and some specially developed, are helping to reduce dependence on finite materials, optimize usage of renewable resources, and find applications for waste materials. They are advancing the cause of genuinely sustainable technologies and living standards for us all.

Related Resources

Wood Protection and Biocides

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 east of Los Angeles.  Learn more about Rio Tinto

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