Moisture contained in the raw material

During the extrusion '2079851475616104457 production process, the product exhibits the quality defect of "Moisture contained in the raw material". Specifically manifested as the moisture content of the raw material exceeding the standard, causing bubbles or silver streaks in the product. This defect is relatively common when processing materials such as HDPE, PP, PVC, and PC, and its occurrence conditions are usually related to unreasonable settings of melt temperature, extrusion speed, blowing air pressure, and mold temperature. When the Moisture contained in the raw material situation is severe, it will cause a series of chain-reaction quality defects in the product in terms of appearance, dimensional accuracy, mechanical properties, etc., which not only reduces the usability and safety of the product, but also directly increases the scrap rate and production cost. Therefore, this problem requires systematic diagnosis and optimization from multiple dimensions, including material selection, the condition of the extruder, die head, die, mold clamping mechanism, and blowing system, as well as melt temperature, extrusion speed, blowing air pressure, and mold temperature.

1. Raw material not fully dried. 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 the raw material, mixing in of impurities, and improper proportion of regrind will all trigger various defects during processing. 2. Humid storage environment. Moisture is one of the variables that need to be controlled with emphasis in plastics processing. Moisture in hygroscopic resins evaporates rapidly during high-temperature melting, producing bubbles and silver streaks, and can also trigger hydrolysis reactions leading to a decrease in molecular weight. Sufficient drying treatment and strict moisture regain prevention management are the basic prerequisites for ensuring melt quality. In addition, insufficient overall coordination between parison wall thickness control and parison temperature uniformity is also a factor that cannot be ignored; there are complex interactions and coupling relationships among the various process parameters, and the deviation of any single parameter may aggravate the degree of Moisture contained in the raw material through chain effects. In terms of equipment maintenance, inadequate regular overhaul and accuracy confirmation of the extruder, die head, die, mold clamping mechanism, and blowing system cause the actual operating parameters of the equipment to deviate from the process requirements, which can also become a potential inducement of the Moisture contained in the raw material problem.

1. Use a dehumidifying dryer to dry the raw material. Before introducing new tools, new materials, or new methods, a full applicability assessment and small-batch verification should be carried out. It is recommended to first conduct offline tests or simulation analysis outside of production conditions, and introduce them into the formal production line only after confirming effectiveness and safety. Keep change management records to facilitate subsequent traceability and experience accumulation. 2. Improve storage conditions. Optimization work must be based on an accurate diagnosis of the root cause of the problem, and blind attempts must be avoided. It is recommended to first determine the key influencing factors and their interactions through the process DOE test method or historical production data analysis, and then carry out targeted parameter optimization and structural improvement to achieve twice the result with half the effort. 3. Control moisture regain. The key to process parameter control lies in establishing a reliable closed-loop feedback adjustment mechanism. Through online real-time detection and SPC statistical process monitoring, deviation trends are discovered in time, and automatic control systems or manual intervention are used to maintain key parameters within the set window, achieving a fundamental transformation from after-the-fact remediation to prior prevention. 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 HDPE, PP, PVC, and PC should be strictly controlled to ensure the stability of molding quality from the source.

In summary, the causes of the "Moisture contained in the raw material" problem can be attributed to the combined action of multiple factors such as raw material not fully dried and humid storage environment. Solving this problem requires starting from aspects such as use a dehumidifying dryer to dry the raw material and improve storage conditions, and adopting 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 parison wall thickness control and parison temperature uniformity.