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US 11,203,145 B2Granted
Photoelastic characterization of residual stresses and stress distributions in injection molded preforms and stretch blow-molded bottle
AssigneeThe Coca-Cola Company
InventorsRonald D. Moffitt, Yu Shi
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Abstract
This disclosure provides new methods to characterize and relate residual stress and orientation imparted to the injection molded polymeric preform with orientation and residual stress in the resulting blow molded bottle. The method developed allows one to define and map the coupled thermal stress histories of both processes to define applicable preferred mutual processing windows for both preform and bottle molding processes. Stretch blow-molding parameters are developed using the disclosed method.
Claims17
A method of fabricating a polymer container having reduced residual stress, the method comprising:
- a) providing a preform for a polymer container;
- b) measuring the photoelasticity (stress-induced birefringence) of at least one selected section of the preform using circularly polarized light to determine residual stress patterns in the preform;
- c) using the residual stress patterns in the preform to determine an axial stretch ratio and a hoop stretch ratio for stretch blow-molding the preform which reduce residual stress in the polymer container;
- d) stretch blow-molding the preform to form the polymer container using the determined axial stretch ratio and a hoop stretch ratio;
- e) measuring the photoelasticity (stress-induced birefringence) of at least one selected section of the polymer container using circularly polarized light to determine residual stress patterns in the polymer container;
- and
- f) using the residual stress patterns in the polymer container to adjust preform dimensions for a size-adjusted perform, further reducing residual stress in the size-adjusted perform compared to the preform of step a).
4 more elements
Dependencies are inferred from the claim text.