CO₂ Bubbles Generated During Polyurethane Casting

Isocyanate reacts with trace amounts of water to release CO₂, forming bubbles in the product. This defect is usually discovered after the product is demolded or during cross-section inspection, and is mostly concentrated in thick-walled areas or at the end of resin flow. Internal defects reduce the mechanical strength and density of the product, and have a particularly severe impact on products with pressure-bearing and sealing requirements.

(1) In terms of material pretreatment: the moisture content of the polyol or filler exceeds the standard, moisture vaporizes at high temperatures to produce gas or participates in side reactions, causing internal defects in the product. (2) In terms of material pretreatment: high environmental humidity causes the raw materials to absorb moisture, moisture vaporizes at high temperatures to produce gas or participates in side reactions, causing internal defects in the product. (3) In terms of temperature parameters: the reaction temperature is too high, accelerating side reactions, it may cause thermal degradation of the material or loss of control of the reaction rate, destroying the internal structure of the product.

(1) Process strengthening: vacuum-dehydrate the polyol before casting, increase the vacuum degree and ensure sufficient treatment time, and proceed to the next process only after confirming that bubbles are completely eliminated. (2) Pretreatment: dry the filler, set drying temperature and time parameters, and use only after testing confirms the moisture content meets the standard before use. (3) Process control: control the workshop humidity, establish an online monitoring mechanism, set upper and lower parameter limits, and implement alarm management. (4) Design optimization: optimize the reaction temperature., combine process simulation analysis or trial mold verification to continuously iterate and improve the design plan. (5) Preventive measures: establish standardized degassing and casting operating procedures, regularly train operators, and check the first piece of each shift to confirm no bubble defects.

The essence of this problem is that gas is not effectively removed during the casting '2079851475616104453, and it needs to be solved collaboratively from three aspects: degassing process, casting method, and venting design.