THE IMPORTANCE OF USING THE RIGHT PAPER IN YOUR ABRASIVES

By Mike Lindquist, Ph.D. (retired)
Research and Development Product Technical Leader, Abrasives
Neenah Paper, Inc.
Technical Products
Alpharetta, GA
www.technicalpaper.com 

Behind every good abrasive, is a good backing material. Selecting the right one affects the performance of the abrasive composite and, ultimately, the end product. Therefore, it pays to opt for high quality and consistency of product. In particular, latex-saturated and coated backing systems offer the best combination of flexibility, durability and toughness. Since the introduction of the first latex-saturated paper in the 1940s, advances in this complex science have led to the development of products that have replaced those made from wood, plastic, cloth and leather. In this article, we will look at some of the benefits of using latex*-saturated and coated backings and provide some tips on qualities to look for when choosing a backing material.

For Wet or Dry Applications
Latex-saturated and coated backing systems are waterproof and designed for traditional wet sanding applications such as automotive repair, general metal sanding and oil sanding of wood. A unique balance of properties helps assure that the backing life exceeds that of the grit, even after prolonged periods of immersion in water. In addition to wet durability, these backings provide superior holdout and adhesion to the make and size coatings.

Waterproof backings may also contain backsize coatings to enhance the performance of the finished coated abrasive. These specialty coatings provide added curl resistance, increased water resistance and improved grip during hand sanding applications.

Abrasive backings for dry sanding applications such as wood, automotive, marine, furniture and metal sanding also need the right balance of strength, flexibility and tear resistance. Latex helps provide these qualities and is important in preventing delamination of the paper in pressure-sensitive adhesive or hook-and-loop attachment systems.

Here are some qualities to look for when choosing a backing material for your abrasives:

• A smooth, flexible barrier coating. Abrasives made with flexible coatings are less likely to crack. They can also be used in places that more inflexible abrasives cannot go, such as tight corners. Smoother barrier coatings allow greater variety of grain sizes. The smoother the surface, the finer a grit it can handle. This enhances cut performance of the abrasive and the appearance of the sanded surface. When used in dry sanding applications, latex-saturated and coated backing materials tend to be more flexible and fold without cracking.
• Random fiber orientation allows the backing to be more dimensionally stable and less likely to curl in different levels of humidity. In some cases, synthetic fibers can be added to the wood pulp furnish, which provides even greater dimensional stability whether the abrasive paper is used wet or dry (in humid or non-humid environments
• High internal bond strength allows composites to hold together well and prevents delamination of the paper.
• Wet tensile strength is particularly important in backing materials that will be used in wet sanding. Good “wet body,” the stiffness of the material when wet, is also important. The backing should not feel limp but instead have a leathery feel, which allows the user more control when sanding.

When used in dry applications such as disc sanding or hand sanding, papers that contain latex not only help improve curl resistance in the abrasive but they also significantly enhance tear strength and the balance of tear strength in machine and cross directions (length and width of the paper).

Conclusion
All backing materials are not the same. No matter which one you choose, make sure the backing offers the right combination of qualities that best suits your abrasive composites and the end products. By choosing wisely, you will help ensure that your backing and composite are a match made in heaven.

* Refers to synthetic latex, not natural rubber latex.