Summary of Blow Molding Development

The modern plastic blow molding process originated in the 1930s when the initial patents were granted to Plax Corporation and Owens of Illinois for automated equipment based on glass blowing techniques . However, the high cost and poor performance of plastic materials at that time discouraged rapid development. The plastic bottles offered no advantage over glass bottles; however, the introduction of low-density polyethene in the mid-1940s (developed by ICI of England) provided the advantage of squeezability which glass could not match. In 1950 Elmer Mills was granted a patent for a continuous extrusion rotary blow molder used privately by Continental Can. In the late 1950s, high-density polyethylene and commercially available molding equipment were developed, and the industry rapidly expanded.

 

High-density polyethylene added considerable breadth to the design capabilities of plastic bottles; most importantly bottles could be lighter and stiffer. Commercial equipment broadened the opportunities for blow molding(). Until that time，blow molding was being performed by only a few companies using proprietary technology. Because of the closely held patent situation in the United States most of the equipment development was taking place in Europe, principally in Germany. What the first commercial equipment for blow molding in the United States came from Europe，and was shown at the National Plastic Exhibition in 1958- Empire Plastic, a toy company，bought a Fischer Blow Molding machine to make toy bowling pins. The engineers at Empire also converted a Reed-Prentice injection molding machine to make toy baseball bats by moving the injection cylinder up over the platen and building a head with a die and bushing. A later step was to build a twin head with a Rotec valve to operate and divert the material flow from one side to another. Midland Ross-Hartig gained permission from Empire to use this design to build six machines for making doll bodies for Ideal Toy Company. These were the first blow molding machines built by Hartig，which manufactured extrusion machines. The company later became Waldron-Hartig, then Battenfield-Hartig, and are now owned by Davis-Standard In that same period Paul Marcus designed and built twin head machines called Auto-Blow. During I960 ZARN Inc. was formed in North Carolina and made milk bottles for Borden Dairy，in conjunction with Uniloy (now Johnson Controls)，who built the machines and molds. To eliminate the freight cost of transporting empty bottles，in-line bottle blowing was started by a dairy in Burlington, North Carolina using the Uniloy machines and molds.

Of all the plastic materials that can be blown like glass, polyethylene is used in greater volume than all others combined. Although mainly still used for bottles, blow molding is increasingly used for industrial parts such as automotive rear deck air spoilers, scat backs，toy tricycles，wheels，typewriter cases, surfboards, flexible bellows, and fuel tanks