NEW GENERATIONS OF RESINS AND FILMS CUT COSTS PER PACKAGE

This paper reports on recent development in polymer technology which have brought the second generation of volume thermoplastics with improved properties and performance. Nowhere is the transformation more thoroughgoing than in polyethylene film, whose producers now have not one but three polymers for volume use. The first new-generation PE film resin was intermediate molecuar weight HDPE (IMW), which went commercial about three years ago and quickly changed HDPE film from a small specialty business into a rapidly growing industry with packaging as one of its two most vigorous markets. The second generation includes high-mol. wt (HMW) high density PE which permits downgaging of films heretofore made of LDPE by as much as two-thirds. Such remarkable material economies give HMW big potential for replacement of LDPE in applications where clarity is not essential but economy is: self-service produce bags or multiwall shipping-sack liners. The third improvement is related to the linear low-density polyethylene (LLDPE) which yields film without the paperlike traits of HMW but with considerably greater tear-, puncture-, and pinhole-resistance than LDPE. They exhibit improvements in the ″stretch″ properties of stretch film, retain more strength at low temperatures, and offer better heat-sealability. Recent advances in packaging materials based on PS and PVC are also reported.