Sterling Brands’ use of amorphous PHA additive enhances performance of new PVC flooring products.

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New floor tiles from Sterling Brands are made using Metabolix’s amorphous PHA biopolymer as a PVC performance additive.

With the distinction of being the largest manufacturer of clear PVC runners for home-improvement retailers, Sterling Brands LLC in Wheeling, Ill., puts cost/performance and sustainability at the forefront of new-product development. To those ends, the processor is among the first users of a new line of amorphous PHA (a-PHA) biopolymer grades designed for use as performance additives in PVC and PLA. These grades were developed by Metabolix, Cambridge, Mass.

Sterling has applied the a-PHA additive in its new line of residential, industrial, garage, and other types of utility flooring. “We have finished with product development and are now starting the marketing phase,” says Rick Renjilian, president and owner. Sterling is developing a website specifically to sell the 36 × 36 in. extruded tiles, which come in packages of six and a broad range of colors. The firm is talking to a major hardware chain that would display the product and allow people to order it for pickup. Sterling also plans to approach carpet stores.

The a-PHA additive proved to be a critical factor in this product’s development. “What it did was to allow us to increase the mineral filler content of our formulation while maintaining or improving dimensional stability. It allowed us to produce a nice, heavy-feeling, rubber-like mat that lays very flat while maintaining flexible properties,” says Renjilian. The a-PHA is miscible in PVC, dissolving in the resin, and serves as both a lubricant and secondary plasticizer, boosting the primary plasticizer’s function, Renjilian says.

Moreover, unlike traditional utility flooring, which typically is available in black or gray, the a-PHA allows Sterling tiles to be made a in a variety of colors. “We are able to bring up the mineral filler content level for dimensional stability but without sacrificing the color vividness of the product—no chalky effect,” says Renjilian.

Sterling, is now also using a-PHA additive in production of its large-volume black PVC mats for a broad range of utility surface applications (e.g., tool tables). Renjilian stresses that the company’s entire vinyl flooring and surface-product portfolio—ranging from retail flooring, garage and workshop, factory and warehouse, to retail automotive, pets, grocery, and office, is now phthalate-free. The company uses DOTP and DOA non-phthalate plasticizers in all of its products and also incorporates significant amounts of phthalate–free post-industrial PVC recycle content. “What we like about the a-PHA additive is that it allows us to reduce the amount of the primary plasticizers we use and it adds something unique to our phthalate-free products.”

Metabolix’s proprietary a-PHA, produced by bio fermentation, is a softer and more rubbery version of PHA that has been shown to offer a fundamentally different performance profile from crystalline forms of PHA. At low loading, a-PHA acts as a process aid and performance modifier for PVC. It reportedly boosts productivity during processing. In highly-filled systems for applications such as flooring, wire and cable insulation, roofing membranes, and PVC/wood composites, a-PHA enables incorporation of higher levels of wood pulp, mineral fillers, and PVC recyclate to replace virgin PVC, thereby improving both mechanical properties and economics.

Metabolix is also seeking FDA clearance for a-PHA in food-contact applications; it already has such clearance for its semi-crystalline PHA grades