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PP sheet roll materials are generally selected brand of PP sheet resin, usually used in vacuum molding is a total of PP sheet resin and modified PP sheet materials.The modified PP sheet material mainly focuses on improving the molding process performance, transparency and heat resistance, etc. The main modification has the following aspects.
A. Improve the molding performance of PP sheet roll
In order to improve the properties of PP sheet, the most commonly used method is to use polyethylene (PE) to modify PP sheet. Mixing a small amount of (20% ~ 30%) low density polyethylene (PE) in PP sheet, can make PP sheet melting property narrow, easy to flow when the sheet heating defects can be improved, can use the ordinary vacuum molding process.Of course, the addition of polyethylene will also bring some negative effects on the performance, such as rigidity and heat resistance to a certain degree of decline in the application of hollow to be considered.
B. Improve the transparency of PP sheet roll and its molding products
Adding nucleating agent (transparent agent) to PP sheet roll is an effective way to improve the transparency of PP sheet roll and its products.After the nucleating agent is added, a large number of fine crystals will be produced in the production of PP sheet roll, which will reduce or even avoid the production of large spherulites. The reduction or elimination of large spherulites will obviously improve the transparency of PP sheet. At the same time, due to the action of nucleating agent, the formation of a large number of fine crystals, so that the cleanliness of PP sheet.The rigidity of PP sheet was improved while the transparency of PP sheet roll was improved.
C. Improve the heat resistance and rigidity of PP sheet roll
The heat resistance and rigidity of PP sheet can be improved obviously by means of filling modification.The most widely used fillers are talc powder, calcium carbonate, etc.By adding 30% ~ 40% talc powder, the rigidity of PP sheet roll can be improved obviously, and the temperature can be raised to over 140℃. Meanwhile, the excellent sanitary performance and better oil resistance of pure PP sheet can be maintained, and the price is relatively low.Its molding products can be used for microwave heating.
PP sheet roll has excellent electrical insulation performance, especially good high-frequency insulation, high breakdown voltage strength, and low water absorption, which can be used for heat resistant insulation materials used at 120 ℃.
PP sheet vacuum molding conditions
In the vacuum blister molding process, the best molding performance of modified PP sheet roll with (20% ~ 30%) low density polyethylene (PE) is obtained.
According to the requirements of PP sheet roll to the forming conditions, the Angle of mold release: punch 2 o ~ 3 o(5 o optimally), die 1o ~ 3 o(5 o optimally);Molding temperature: sheet temperature 150 ~ 180℃, mold temperature 70℃ ~ 90℃;Molding shrinkage: punch 0.02 ~ 0.03mm/mm, die 0.03 ~ 0.04mm /mm.Because PP sheet material sheet material has the characteristics of abundant material source, low price, non-toxic, tasteless, good transparency, high mechanical strength, so PP sheet material sheet material for vacuum molding processing, made of various packaging products are widely used in food, medicine, mechanical parts, daily necessities and other packaging.At present, PP packaging products appear on the market, in addition to simple lunch box, water, spoon, bowl, pickles box, a variety of local special products packaging box, yogurt pot, tray, etc. Also widely into the market.PP sheet products can be heated in microwave oven and sterilized at 125℃, so it is widely used in ready-to-eat food packaging.In addition, PP sheet vacuum blister molding products have been gradually applied in agricultural production in recent years, such as seedling tray, breeding cup, etc.
The bonding problem is the same as PE, which can be bonded after pretreatment.Welding with heating plate and friction welding was very successful.
Post-processing: when stamping by punching die and trimming die, the cutting gap needs 5mm, the material temperature is too high, the cutting burr. There should be corresponding measures to keep the minimum deformation amount during sealing. The heat sealing with coating layer, the temperature is 150 ~ 180℃, and the sealing time is 1s.