High transparent PP sheet
DATE：2021/9/7 8:38:44 / READ： / SOURCE：This station
High transparent PP sheet
1. Material selection
Special material for polypropylene transparent sheet, made by Beijing Yanshan Petrochemical Company Resin Institute.
Second, the main equipment
r-500 plastic sheet extrusion line, Italy; light transmittance haze tester, Japan Toyo Seiki.
Third, the preparation process
(1) Process flow: P special material → die → three-roll calendering → cooling → traction → trimming → rewinding.
(2) Process conditions Polypropylene is a crystalline polymer, and the main factors affecting the light transmittance are the degree of finish, crystal size and crystal uniformity. All factors that are conducive to improving crystal quality, reducing internal defects and crystal size, and improving crystal uniformity can increase the transparency of the PP sheet. Three factors affect the haze of the sheet, the primary and secondary order are: die temperature, roll time, middle roll temperature. If the temperature of the die is too high, the components with lower molecular weight in the material will be degraded, the yellow index will increase, and the haze will increase, which will affect the transparency of the sheet; The molten large ball will also affect the transparency of the sheet. Rolling time is reduced, that is, the traction speed is increased. Under the action of stress, the polymer melt has induced nucleation, which shortens the nucleation time and increases the number of crystal nuclei, reduces the size of the ball, and helps reduce the haze , Improve the transparency of the sheet. When the temperature of the middle roller is too low, the nucleation rate of the product body is higher, the growth speed is fast, the crystallinity is lower, the wafer is thinned, and there are more internal defects in the crystal, which will affect the transparency of the sheet to a certain extent; the temperature of the middle roller If it is too high, the polymer melt will slowly cool down to form larger spherulites, which is also not conducive to improving the transparency of the sheet.
After experimentation, the best process parameters for extruding and producing high-transparency P sheet are obtained: the die temperature is 250°C, the wrapping time is 15, and the middle roll temperature is 55°C. Under the process conditions, a highly transparent sheet product with a haze of only 13.2% can be obtained.
Author：admin