Teknor Apex: “Super-flexible” vinyls as replacement of plastisols
Breaking through the lower limit of flexibility for pelletized flexible vinyl, Teknor Apex has developed a series of ’super-flexible’ compounds that provide the softness and rubber-like traction of plastisol-based PVC products yet are processible in standard injection molding and extrusion equipment, the company announced today. To be introduced at the Teknor Apex exhibit during NPE 2003 (Booth 9755), the new Apex (R) compounds make it possible to boost the output and quality of industrial belts, rollers, step pads, appliance footers, caps, plugs, grips, and a host of other products currently manufactured by rotational, dip, or slush molding.
In contrast to paste-like plastisols, which are dispersions of PVC polymer in a liquid-plasticizer carrier, super-flexible Apex vinyl comes in the form of pellets, making it suitable for high-volume injection molding and extrusion, according to Philip Morin, industry manager for consumer and industrial products. In addition, he said, the pellet form avoids plastisol-related handling and quality problems: ‘Plastisols can vary in viscosity in accordance with temperature and mixing conditions, contain entrapped air that causes pinholes or voids in finished product, undergo separation during storage, take much longer time for color changes, and entail use of volatile organic solvents for cleanup after spills.’
Recently Teknor Apex supplied a custom formulation of Apex super-flexible vinyl for use in a commercial application where traction is a crucial property. Now the company is introducing three standard grades, clear compounds with Shore A hardnesses of 39, 45, and 50, respectively. Until now, the conventional lower hardness limit for standard flexible vinyl compounds (for example, those not based on costly ultra-high-molecular-weight PVC resin, for example) has been around 50, according to Bob Mauritz, corporate technical service associate, who led the program to develop the custom formulation.
Plasticizer Formulation Is Key to Processibility and Versatility
‘It has long been assumed that producing a standard PVC compound under 50 Shore A in pellet form would be very difficult, if not impossible, because the high level of plasticizer required would make the compound too difficult to handle and process,’ Mauritz said. ‘When a customer asked us to find a way to help them replace plastisol coating with a far more efficient extrusion coating process, we set out to break through this ‘Shore A barrier’ by developing new techniques for formulation and melt-compounding.’
Compared with plastisol manufacture, melt compounding makes it possible to build into the vinyl raw material several advantages for the molder or extrusion processor, according to Mauritz. ‘Pelletized vinyl is a completely homogeneous compound incorporating all colorants, additives, and modifying resins, including solids that normally cannot be mixed with plastisols,’ Mauritz said. ‘This makes it possible for us to disperse colors and other additives more uniformly, use advanced plasticizers to boost properties, and create whole new property profiles by blending PVC with other process aids or modifiers.’