New environmentally friendly plastic Mo Yuan made EVA foam from design to processing steps

    EVA processed products are new environmentally friendly plastic foam materials, which have the advantages of good cushioning, shock resistance, heat insulation, moisture resistance, chemical corrosion resistance, etc., and are non-toxic and non-absorbent. EVA rubber and plastic products are designed to be processed and shaped, and their shock resistance is better than traditional foam materials such as polystyrene (foam), and they meet environmental protection requirements, making them an ideal choice for export products. Compared with shock-proof packaging, it can be cut and formed; due to the large difference in density, it can also have a wider range of uses.

    EVA foam foaming process: The foaming agent releases a large amount of gas at the decomposition temperature to form a foam core. After the pressure is released suddenly, the release of the foam core causes the expansion of EVA and other materials to form a foamed material.

    Features of EVA foam: Water resistance: closed cell structure, non-absorbent, moisture-proof, and good water resistance. Corrosion resistance: resistance to sea water, grease, acid, alkali and other chemicals, antibacterial, non-toxic, odorless, and pollution-free Processability: It is easy to process such as hot pressing, cutting, gluing and laminating. Anti-vibration: high resilience and resistance to tension, strong toughness, and good shock/cushioning performance. Thermal insulation: excellent thermal insulation, cold-preservation and low-temperature performance, and can withstand severe cold and exposure. Sound insulation: airtight cell, good sound insulation effect.

    The foaming process of EVA foam has a complicated mechanism and many influencing factors. It is difficult to control the foam quality. In foaming, it is necessary to observe various phenomena in real time and adjust the formula in time to produce foam with fine and uniform cells, good resilience and high tensile strength.

    In this paper, based on the foam foaming practice experience, Moyuan Company has on-site quality control and defect correction for foaming. In addition, the polymerization degree distribution will also affect the processing performance and product performance. It is better to choose the narrow molecular weight distribution of PVC resin. This processing performance and product performance are better. All are more uniform, which helps to control processing conditions and product quality. Low molecular weight will reduce the thermal stability, aging performance, mechanical properties, etc. of the product, but the high molecular weight will make it difficult to uniformly plasticize during processing, causing particles or "fish eyes" to appear when the internal and external quality of the product decreases severely. PVC resin The plasticizing time is also an important selection indicator.

    Too small particle size also has a certain effect on plasticization. The friction between particles is reduced and the plasticization time is prolonged. Therefore, the resin is required to have good fluidity and a larger particle size and a narrow particle size distribution. Both the higher viscosity PVC powder and compact PVC powder are not conducive to the full foaming of the foam.

    Generally, the loose suspension PVC resin with an average degree of polymerization of 750-650K and a value of 59-55 is selected for foam. Its processing performance is easy to be plasticized. It is used to produce large-scale sheet foaming ratio and sheet thickness is easy to control. The product qualification rate is high.

    Three issues are explained: regular foam formula adjustment, special foam formula adjustment, and cause analysis and corrective measures for common defects. 1 Conventional foam formula adjustment. Under the reference conditions of material temperature 18~20"C and air temperature 20℃, the formula of foaming cylindrical foam with a diameter of 2 meters and a height of 1 meter is called the standard formula. The commonly used standard formula is shown in Table 1.0 Table 1.0 Commonly used benchmark formula.