(1) Raw material selection
The raw materials for extrusion molding of polyethylene sheets should be selected as much as possible using specialized resin for sheet forming. For example, 5000H high-density polyethylene produced by Sinopec Beijing Yanshan Petrochemical Co., Ltd. and DGDS-6097 (MFR=0.4g/10min, density 0.948g/cm) PE resin produced by Sinopec Guangzhou Petrochemical Branch. Select LDPE resin, MFR=0.4~0.6g/10min; HDPE resin, MFR=0.1~0.4g/10min, can also be used for extruded board (sheet) materials.
(2) A single screw universal extruder is used for production, and the rod structure mostly adopts equidistant gradient universal screws. The length to diameter ratio L/D is greater than 25:1, and the compression ratio is (3-4): 1
(3) Forming process
① Temperature control of extrusion PE material process, temperature of each section of the machine barrel: when the raw material is LDPE, the feeding section is 150-160 ℃, the plasticizing section is 160-170 ℃, and the homogenizing section is 170-180 ℃; When the raw material is HDPE, the feeding section is 120-140 ℃, the plasticizing section is 140-160 ℃, and the homogenizing section is 160-180 ℃.
Mold temperature: When using LDPE material, the middle section of the mold is 160-170 ℃, and the two ends of the mold are 180-190 ℃; When using HDPE material, the middle section of the mold is 155-165 ℃, and the two ends of the mold are 175-180 ℃.
Three roll temperature: the upper roll temperature is. 60~70 ℃, the middle roll temperature is 80~90 ℃, and the lower roll temperature is 70~80 ℃. The slab should gradually cool down when passing through the three rolls to prevent the product from generating significant internal stress and warping deformation.
② The distance between the three rollers and the mold mouth should be controlled within the range of 50-100mm to prevent the slab extruded from the mold mouth from sagging.
③ The speed of pulling the product can be similar to or slightly faster than the speed of the product extruded from the mold mouth, but it cannot be too fast. Excessive pulling speed will cause a large shrinkage in the width and size of the product.
(4) The quality requirements of polyethylene glycol board should comply with the provisions of QB/T group 2490-2000 standard.
The appearance quality requirement of polyethylene sheet is that the surface of the sheet should be smooth and flat, without bubbles, cracks, obvious impurities, dents, and color marks.
The hygiene indicators of polyethylene sheets used for food containers and utensils should comply with the provisions of GB9687 standard.
High density polyethylene calcium plastic corrugated board is a product formed by the hot bonding method of three-layer calcium plastic board. The upper and lower parts of this calcium plastic corrugated board are flat calcium plastic sheets, and the middle layer is corrugated calcium plastic sheets. High density polyethylene calcium plastic corrugated board has high strength, good resistance to vibration and impact, and a certain degree of rigidity. It can be waterproof and insect resistant, and the price is also relatively low. This calcium plastic corrugated board can be manufactured into various shapes of packaging containers.
