Bag packaging material has characteristics of amorphous structure or low crystallinity polymer resin film, heated quickly melt, this kind of polymer resin generally has a hot sealing performance;And crystallinity of high polymer resin, when heated, crystallization zone melting rate is slower, so highly crystalline polymer resin film heat sealing performance generally cannot meet the requirements of bag production line.Heat sealing performance of thin film, of course, also depends on the resin softening temperature, thermal conductivity, such as heating mode:
Amorphous region higher percentage of LDPE film with lower T, within 0.5-2 sde world can be melted the adjacent two layers of LDPE film, due to the thermal motion of molecular chain and fusion of each other: HDPE is due to a high degree of crystallinity, to make it hot sealing, need to heat it crystallization of d m, the lattice damage, and then to heat sealing, the destruction process of within 0.5-2 s can be difficult to achieve.
CPP amorphous structure generally account for around 40 ℃, which has excellent heat sealing performance: but the BOPP hot sealing property is poor, this is because the crystallinity of BOPP CPP is high, and the molecular chain orientation have occurred, orientation and Rachel chang structure destruction need longer relaxation time c similar to BOPP, BOPET T too high (265 ℃), the crystallinity is bigger, so it generally do not have heat sealing performance;If in to PET monomer polymerization stage step by step to add a small amount of the third monomer butyl glycol, or phthalate) is generated by copolycondensation of polyester molecular chain regularity was damaged, the amorphous polyester is prepared area ratio increases, the PET copolymerization product is the heat sealing.
LDPE and commonly used in the preparation of flexible packaging materials, CPP as the lining of the composite membrane, because they have good heat sealing performance.
