Percent crystallinity and stiffness of polypropylene samples are examined to assess whether these properties are altered during the thermoforming process as a result of difference in positive model temperature. Percent crystallinity is evaluated by nuclear magnetic resonance; stiffness is assessed by means of a 3-point bending test. A trend of increasing percent crystallinity with increasing positive model sur-face temperature is observed, although not significant. No significant difference in bending stiffness occurred, suggesting consistent heating and cooling experiences among the different thermoforming events.
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