Deformation of the product after use in high-temperature environments (post-crystallization effect)

In the '2079851475616104458 (vacuum forming) production process, the product exhibits the quality defect of "Deformation of the product after use in high-temperature environments (post-crystallization effect)".The specific manifestation is The product deforms after use at relatively high temperature.This defect is more common when processing materials such as PP, PS, PET, PVC and ABS sheets, and its occurrence is usually related to unreasonable settings of sheet heating temperature, forming pressure/vacuum, mold temperature and cooling time.When the Deformation of the product after use in high-temperature environments (post-crystallization effect) situation is severe, it will cause a series of chain quality defects in the product's appearance, dimensional accuracy, mechanical properties and other aspects, which not only reduces the product's functionality and safety in use, but also directly increases the scrap rate and production cost.Therefore, this problem requires systematic diagnosis and optimization from multiple dimensions such as material selection, the status of the '2079851475616104458 machine, heating oven, mold and vacuum/air pressure system, and sheet heating temperature, forming pressure/vacuum, mold temperature and cooling time.

1. Post-crystallization of crystalline resins such as PP proceeds slowly.Material selection and handling are the foundation of forming quality.The intrinsic properties of the resin such as molecular weight, molecular weight distribution and melt index determine its processing window and final performance.Factors such as excessive moisture content of raw materials, mixed impurities and improper regrind ratios will all cause various defects during processing. In addition, the insufficient overall coordination of sheet heating uniformity and stretch ratio control is also a factor that cannot be ignored; there are complex interactions and coupling relationships among the process parameters, and the deviation of any parameter may aggravate the degree of Deformation of the product after use in high-temperature environments (post-crystallization effect) through chain effects.

1. Increase the cooling rate to make crystallization sufficient.When implementing adjustments, it is recommended to use the single-factor variable method, adjusting only one parameter at a time and fully evaluating the effect, to avoid simultaneous changes of multiple parameters making the cause of the problem untraceable.The adjustment amplitude should be small rather than large; each adjustment is recommended to be controlled within 5%~10% of the original value, and after adjustment run stably for at least 3~5 mold cycles to observe the effect. 2. Use a nucleating agent.Before introducing new tools, new materials or new methods, sufficient applicability evaluation and small-batch verification should be carried out.It is recommended to first conduct offline tests or simulation analyses outside production conditions, and introduce them into the formal production line only after confirming effectiveness and safety.Keep proper change management records to facilitate subsequent traceability and experience accumulation. It is recommended to formulate a preventive checklist for the Deformation of the product after use in high-temperature environments (post-crystallization effect) problem, incorporate sheet heating uniformity and stretch ratio control into the daily inspection scope, and conduct online monitoring of key parameters through the SPC statistical process control method to achieve early warning and rapid response to problems. In terms of material management, incoming inspection of raw materials and in-process testing of work-in-progress should be strengthened, and key performance indicators of PP, PS, PET, PVC and ABS sheets should be strictly controlled to ensure the stability of forming quality from the source.

In summary, the causes of the "Deformation of the product after use in high-temperature environments (post-crystallization effect)" problem can be attributed to the combined action of multiple factors such as Post-crystallization of crystalline resins such as PP proceeds slowly.To solve this problem, it is necessary to start from aspects such as Increase the cooling rate to make crystallization sufficient, Use a nucleating agent and take systematic governance measures.In actual production, it is recommended to establish a prevention and rapid response mechanism for this problem, achieving stable production and continuous improvement through sheet heating uniformity and stretch ratio control.