Shrinkage & Expansion of plastic parts

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SUMMARY

The discussion centers on the shrinkage and subsequent expansion of a plastic part made from Basell Pro-fax 6331 Natural after five months of observation. Participants highlight the importance of controlling for water absorption due to humidity and maintaining consistent temperature during measurements. They emphasize that plastics exhibit high thermal coefficients of expansion and caution against misinterpreting measurement accuracy, which is distinct from the precision of the measuring device. Additionally, residual molding stresses may contribute to warping in the part.

PREREQUISITES
  • Understanding of plastic material properties, specifically Basell Pro-fax 6331 Natural.
  • Knowledge of thermal expansion principles in plastics.
  • Familiarity with humidity's effects on plastic materials.
  • Experience in accurate measurement techniques for material analysis.
NEXT STEPS
  • Research the effects of humidity on plastic materials and their dimensional stability.
  • Study the thermal expansion coefficients of various plastics, including Basell Pro-fax 6331 Natural.
  • Learn about residual stresses in molded plastic parts and their impact on performance.
  • Explore advanced measurement techniques to enhance accuracy in material studies.
USEFUL FOR

Material scientists, plastic engineers, and quality control professionals involved in the analysis and optimization of plastic part performance over time.

nady_sophy
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TL;DR
Need to know upon shrinkage and expansion of plastic parts.
Hi,

I'm currently doing a shrinkage study upon this plastic part. I hv been observing how much can the part able to shrink over the time after molding, and now hv been on the 5th month observation. However, on the 5th month, the part starting to expand, compared with the data from the 4th month. Is this possible? Are there any plastic material that can behave this way?

By the way, this plastic part material is Basell Pro-fax 6331 Natural.
 
Engineering news on Phys.org
Plastics absorb water. Are you controlling for water absorption due to room humidity? Plastics have high thermal coefficients of expansion. Are you measuring at the same temperature? How accurate are you measurements? Note that accuracy is not the same as the number of significant digits on a digital measuring device. Is the part warping from residual molding stresses?
 
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