Aristech Chemical Corp. of Pittsburgh is commercializing a medium-impact copolymer polypropylene, initially for thermoforming dairy containers.
The single-component material, TI4020T, is ``designed to simulate performance you might get from a blend of homopolymer and copolymer PP,'' Tim Roberts, senior development engineer, said in a telephone interview. The material balances the needs for stiffness and drop-impact resistance.
Separately, Aristech's technical center in Pittsburgh is developing a polypropylene for use in thermoforming clear lids with shallow draws. Slated for a March introduction, the material addresses clarity and processing issues. ``Sometimes those two goals fight with each other,'' Roberts said.
The 85,000-square-foot center, which opened in November 1997, uses an extrusion thermoforming line from Isap/OMV Group SpA of Verona, Italy, to develop PP materials.
``Capabilities in utilizing the OMV equipment has progressed in the last six months,'' Roberts said, with many of the lessons applicable to other manufacturers' thermoforming lines. ``We can evaluate different plug-assist materials for PP, tooling issues and mold polish for the industry at large.''
The center also operates a Husky thin-wall injection molding machine for comparison and evaluation studies of cycle times, material thickness and processing costs between thermoforming and injection molding.
Last year, Aristech added a homopolymer PP to make delicatessen containers at lower thermoforming temperatures. The material, FT021N, has ``good clarity and processability,'' and low taste and odor characteristics, Roberts said. ``We improved the formability window.''
In addition, Aristech has a high-impact copolymer, T14020N, for blending with the homopolymer when a processor needs impact resistance at refrigeration temperatures, Roberts said.
Aristech employs 1,200 and produces PP at plants in Neal, W.Va., and La Porte, Texas.
In the future, Aristech expects to have coextrusion thermoforming capabilities to develop packaging applications that cannot be done with injection molding, said Vic DiNardo, division manager of the plastics processing laboratory. ``The future of thermoforming and PP is exciting and exponential as to the possibilities,'' he said.