Biaxial film orientation greatly improves film’s tensile strength, flexibility, and toughness. Without orientation, PS is too brittle to be used as film, and PP loses flexibility in the cold. Orientation also imparts heat-shrinkability to PS, PVC, and PVDC.
The earliest biaxially oriented film was OPS, developed in Germany during World War II for capacitors and coaxial cable insulation. Dow Chemical launched biax PVDC (Saran) film in the late 1940s. But the mid-’50 s was the heyday, when resin companies’ R&D labs were orienting everything they could find to see what would happen.
DuPont’s Mylar biaxial PET film was developed in 1952 and went into production in ’55 in Circleville, Ohio, using tenter frames developed by Marshall and Williams, then a supplier of textile machinery. M&W (now a division of Parkinson Technologies) also built the first known TD orienter for plastic film as a prototype for DuPont in 1953. Mylar targeted specialty durable applications like capacitors, recording tape, and unbreakable storm windows. Meanwhile, Dow’s Trycite OPS went into commercial production in 1958 after 15 years of development.
After the commercialization of PP in 1957, resin companies vied to find ways to orient it. Dow and DuPont both had developmental OPP film programs in the ’60s, but dropped them.
Bruckner Maschinenbau in Germany delivered its first commercial biax tenter-frame line to run monolayer OPP in 1965 at Showa Polymers in Japan. Bruckner was founded five years earlier, when it developed the first tenter-frame process developed just for plastics.
In the late ’60s, Hercules became the first U.S. company to succeed with OPP film, using a bubble process. It was followed shortly by Mobil’s Film Div. (originally National Distillers) with a tenter process. Mobil had initially tried a monoaxial TDO process with tenters in 1959, then added a proprietary MDO process involving edge pinning.
The latest biaxial film is made of biodegradable polylactic acid (PLA). It was launched in 2002 by DSK GmbH in Germany.
Very few readers of this issue can remember, or even imagine, what it was like when an injection mol...