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METHOD FOR THERMOFORMING POLYOLEFIN

IP.com Disclosure Number: IPCOM000247037D
Publication Date: 2016-Jul-28
Document File: 1 page(s) / 28K

Publishing Venue

The IP.com Prior Art Database

Related People

Yushan Hu: INVENTOR [+6]

Abstract

Thermoforming is a unique process where a polymer sheet is heated to a pliable state followed by vacuum stretching it in a mold to take final shape. Final products made by thermoforming can range from ultra-thin gauge containers of 1 mm thick to heavy gauge body panels of 1-in thick or more. Materials commonly used in thermoforming include polyethylene (PE), polystyrene (PS), acrylonitrile butadiene styrene (ABS) and etc. Polypropylene, an easily accessible polyolefin material, is not as commonly used. This is because polypropylene does not possess enough elasticity in its melt state, and narrow processing temperature window. However, PP offers much needed environmental stress crack resistance (ESCR), scratch resistance, clarity, high temperature resistance and more.

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Method for Thermoforming Polyolefin

Yushan Hu, Ling Zhang-Watson, Kim Walton, Dave Schiff, Miguel Prieto, Susan Gill

Thermoforming is a unique process where a polymer sheet is heated to a pliable state followed by vacuum stretching it in a mold to take final shape.  Final products made by thermoforming can range from ultra-thin gauge containers of 1 mm thick to heavy gauge body panels of 1-in thick or more.  Materials commonly used in thermoforming include polyethylene (PE), polystyrene (PS), acrylonitrile butadiene styrene (ABS) and etc. Polypropylene, an easily accessible polyolefin material, is not as commonly used.  This is because polypropylene does not possess enough elasticity in its melt state, and narrow processing temperature window.  However, PP offers much needed environmental stress crack resistance (ESCR), scratch resistance, clarity, high temperature resistance and more.

Attempts have been made to allow PP be used in thermoforming applications. Modification of PP with comonomer, such as ethylene, alters elasticity; metallocene PP offers improved melt strength, short-chain branched PP yields sag-resistance.  All aforementioned modifications to PP or new grades of PP result in added cost and new process development yet without the guarantee of thermoformable PP.

This invention allows the use of unmodified PP or modified PP in deep draw thermoforming process, and without significant changes in processing conditions from conventional setup, e.g. similar to PE...