Mark Stewart

The Munson blenders have a working volumetric capacity of 225 cubic feet (6.37 cubic meters). Carmichael says paddles were specified because they can be easily cleaned, since their design yields less surface area than other mixing elements. Fast cleaning reduces downtime during product changeover. It also means workers usually have no need to enter the blenders when cleaning them, which reduces the regulatory liability of the company.

Melsur Corporation, the world’s leading supplier of hard plastic melamine school furniture, molds components from a mixture of resin, wood flour and pigments. Each of the 32 color variations, 30 products and custom designs must be blended individually, a process that can take up to four hours, depending on product. Anything less than empirically defined cycle times alters the final color and produces blemishes in the finished product.

The basic mixing process stimulates the absorption of peroxides by pelletized, thermoplastic polymers one-eighth of an inch (3.175 mm) in size. The peroxides act as curatives that give the polymers the ability to crosslink and become thermosetting. “As for the polymers, we use elastomers, polyolefins, and silicones, but mainly polyolefin-based materials,” Johnston says. “Generally the resin must absorb from one to about three percent of its weight in peroxide, which sometimes requires pre-heating of the pellets. In addition,” he continues, “the R&D department is looking at antioxidants that are liquid at room temperature.” Antioxidants can extend the lifetimes of the final materials and improve their electrical properties.