Water vapor condensation on the inner wall of the product

In the extrusion '2079851475616104457 production process, the product exhibits the quality defect of "Water vapor condensation on the inner wall of the product".The specific manifestation is Water droplets appear on the inner wall of the product after use.This defect is more common when processing materials such as HDPE, PP, PVC and PC, and its occurrence is usually related to unreasonable settings of melt temperature, extrusion speed, blowing pressure and mold temperature.When the Water vapor condensation on the inner wall of the product 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 extruder, head, die, mold clamping mechanism and blowing system, and melt temperature, extrusion speed, blowing pressure and mold temperature.

1. The blown-in compressed air contains water.Moisture is one of the variables that need key control in plastic processing.Moisture in hygroscopic resins evaporates rapidly during high-temperature melting, producing bubbles and silver streaks, and also triggers hydrolysis reactions leading to molecular weight reduction.Sufficient drying treatment and strict moisture regain prevention management are the basic prerequisites for ensuring melt quality. 2. Mold temperature too low.Temperature is the core factor affecting melt fluidity and viscosity.Excessively high temperature settings will cause decreased melt viscosity, insufficient melt strength and even thermal degradation; excessively low temperature results in poor melt fluidity and insufficient plasticization, making smooth filling or forming impossible.A reasonable temperature window should be optimally determined within the recommended range according to the melting characteristics and thermal stability of the material. In addition, the insufficient overall coordination of 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 process parameters, and the deviation of any parameter may aggravate the degree of Water vapor condensation on the inner wall of the product through chain effects. In terms of equipment maintenance, the regular overhaul and accuracy confirmation of the extruder, head, die, mold clamping mechanism and blowing system are not in place, causing the actual operating parameters of the equipment to deviate from process requirements, which will also become a potential inducement of the Water vapor condensation on the inner wall of the product problem.

1. Install a drying and filtering device on the compressed air line.Installation of equipment or accessories should strictly follow the installation manual; key mating surfaces must be cleaned and checked for damage before installation.Fastening bolts should be tightened evenly according to the specified torque values and diagonal sequence; after installation, use precision measuring tools to verify whether the installation accuracy meets technical requirements. 2. Appropriately raise the mold temperature.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. It is recommended to formulate a preventive checklist for the Water vapor condensation on the inner wall of the product problem, incorporate parison wall thickness control and parison temperature uniformity 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 HDPE, PP, PVC and PC should be strictly controlled to ensure the stability of forming quality from the source.

In summary, the causes of the "Water vapor condensation on the inner wall of the product" problem can be attributed to the combined action of multiple factors such as The blown-in compressed air contains water, Mold temperature too low.To solve this problem, it is necessary to start from aspects such as Install a drying and filtering device on the compressed air line, Appropriately raise the mold temperature 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 parison wall thickness control and parison temperature uniformity.