Microbubbles appear on the product surface (blowing agent residue)

During the rotational molding production process, the product exhibits the quality defect of 「Microbubbles appear on the product surface (blowing agent residue)」. The specific manifestation is that dense microbubbles appear on the product surface. This defect is relatively common when processing materials such as powders such as LLDPE, HDPE, PVC, PA, and its occurrence conditions are usually related to unreasonable settings of heating temperature and time, rotation speed ratio, cooling rate, mold wall thickness. When the Microbubbles appear on the product surface (blowing agent residue) situation is severe, it causes a series of cascading quality defects in the product in terms of appearance, dimensional accuracy, mechanical properties, and other aspects, not only reducing the product's functionality and safety in use, but also directly increasing the scrap rate and production costs. Therefore, this problem requires systematic diagnosis and optimization from multiple dimensions, including material selection, rotational molding machine, heating oven, rotating arm, cooling station condition, and heating temperature and time, rotation speed ratio, cooling rate, mold wall thickness.

1. Blowing agent mixed into the powder. This factor leading to the problem reflects that certain process conditions or material characteristics in rotational '2079851475616104453ing do not meet the optimal molding requirements. Such problems are often cumulative and concealed, and should be investigated and verified as key focus items during process debugging and finalization to ensure that hidden dangers are eliminated at the source. 2. The resin decomposes and generates gas during processing. The selection and handling of materials is the foundation of molding quality. The intrinsic characteristics 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, mixing of impurities, and improper proportion of recycled material can all cause various defects during processing. In addition, the insufficient overall coordination between powder melting uniformity and product wall thickness 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 Microbubbles appear on the product surface (blowing agent residue) through chain effects. In terms of equipment maintenance, the regular overhaul and precision confirmation of the rotational molding machine, heating oven, rotating arm, and cooling station are not in place, causing the actual operating parameters of the equipment to deviate from process requirements, which can also become a potential inducement of the Microbubbles appear on the product surface (blowing agent residue) problem.

1. Check the powder composition. Inspection work should establish a standardized inspection checklist, clarifying inspection items, technical standards, inspection frequency, and responsible persons. Key equipment components should be regularly disassembled to inspect the condition of hidden parts, and judgments should not be based solely on operating appearance. Inspection results should be recorded in detail and a trend analysis mechanism established to predict potential failures. 2. Reduce the heating temperature. Adjustments should follow the principle of gradual progress; each adjustment should not be too large, and it is recommended to decrease by 5%~15% of the current value. After each adjustment, observe the product quality changes for at least 5~10 molding cycles, and continue adjusting only after confirming the improvement direction is correct; avoid one-step excessive adjustment. 3. Use pure powder. 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 analysis outside production conditions, and introduce them into the formal production line only after confirming effectiveness and safety. Keep change management records for subsequent traceability and experience accumulation. In terms of material management, incoming inspection of raw materials and in-process inspection of work-in-progress should be strengthened, and the key performance indicators of powders such as LLDPE, HDPE, PVC, PA should be strictly controlled to ensure the stability of molding quality from the source.

In summary, the causes of the 「Microbubbles appear on the product surface (blowing agent residue)」 problem can be attributed to the combined action of multiple factors such as blowing agent mixed into the powder and the resin decomposing and generating gas during processing. Solving this problem requires starting from aspects such as checking the powder composition and reducing the heating temperature, and adopting systematic governance measures. In actual production, it is recommended to establish a prevention and rapid response mechanism for this problem, and achieve stable production and continuous improvement through powder melting uniformity and product wall thickness control.