Thermoforming solid-phase pressure

However, the forming temperature is below the melting temperature of the plastic. See thermoforming, solid-phase pressure. 

Keywords thermoforming, solid-phase pressure forming (SPPF), vacuum forming, pressure forming, processing window, viscoelasticity, residual stress, sagging, shrinkage, quality control. 

Polypropylene can be extruded into sheets and thermoformed by solid-phase pressure forming into thin-walled containers. Due to its light weight and toughness, polypropylene and its copolymers are extensively used in automobile parts. 

The major opportunities for this new barrier resin composite are in shallow solid phase pressure thermoformed containers and in melt phase thermoformed containers. These rigid containers are typically pigmented, thus eliminating the problem of the yellow tint (Table VIII). 

Formability. Materials with a broad softening range, such as PS and PC, can be thermoformed into deep-draw package shapes. Crystalline polymers, eg, HDPE and PP, are more difficult to thermoform, but solid-phase forming processes below the melting point are possible. Multilayer semirigid barrier containers are made by Shell s Solid Phase Pressure Forming Process and the patented Dow... 

In a fiber form, LCPs are used in a similar manner as aramid fibers. In solid form, as is used in molding and extrusion, or even with thermoforming, LCPs are quite unique. In the molten phase, the molecular chains are oriented and aligned, without entanglements. This means the molten material can flow easily (like a liquid), allowing for fill of very thin sections at very low pressure. They then solidify... 

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