| 摘要 |
A method and apparatus are disclosed for controlling crystallization in thermoplastic materials, such as polyethylene terephthalate, which crystallize when cooled from melt temperature to below glass transition temperature after being injected into a mold cavity. When greater amounts of crystallization are desired, a very high pressure is initially imposed upon the material as it cools from the melt temperature, and then the pressure is reduced proportionally to the reduction in temperature so that a nominal pressure is imposed upon the material at glass transition temperature. When a significantly lesser amount of crystallization is desired, an initial nominal pressure is imposed upon the material as it cools from the melt temperature to a predetermined temperature, at which time the pressure is drastically increased.
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