2024-01-08 15:48:33

The difference between polyester TPU film and polyether TPU processing process

A. Drying As we all know, polyurethane TPU film belongs to a polar polymer, when it is completely naked in the air, it will slowly absorb moisture, if the processing and molding will slowly evaporate moisture, resulting in a rough surface, will make it appear inside the bubble phenomenon, and will reduce the performance, so, polyester TPU film before processing will have a drying process this step. As polyester is easily attacked and damaged by water molecules, the acid produced by hydrolysis can catalyze the further hydrolysis of polyester. Usually, under the same conditions, the water content of polyester TPU is much higher than that of polyether TPU. Therefore, during the drying process, special attention should be paid to polyester TPU, which should be dried thoroughly and strictly. Control the drying conditions.

Second, the pressure-holding phase When injecting a polymer melt, the melt must experience a combination of internal static pressure and external dynamic pressure during the preforming phase and the injection phase.

During the filling phase, the polymer melt is subjected to high pressure. Under this pressure, the free volume between the molecular segments is compressed. As the free volume between the molecular chains is reduced, the proximity of the large molecular segments enhances the intermolecular forces and the performance viscosity is improved. In addition, since polyether TPU has a low ether bond cohesion energy and a small bonding rotation potential, the tight chain effect between the enhanced molecular chains is small, so that when compressed, the relative displacement of the molecular chains is Therefore, the viscosity seems to be able to vary over a wide range. In addition, since the molecular chains of polyether TPU are softer than those of polyester TPU, it is difficult to form permanent deformation of polyether TPU, so when processing polyether TPU, polyester is used. Compared with TPU, polyether TPU must control a longer dwell time.

Third, processing time Generally speaking, the longer the molecular chain segment, the slower the center of gravity of the molecular chain moves, and the more inter-chain segments, the more difficult it is to decouple the chain. When sliding, the greater the resistance to the flow process, the longer the time and energy required, the more viscous the chain. The sensitivity of the degree to shear. The molecular weight of polyester TPU is generally higher than that of polyether TPU, so the processing time of polyester TPU is longer.

Fourth, cooling Due to the large internal consumption of polyester TPU, molecular cohesion energy, even if the return to normal state is difficult to cool, so it requires a longer cooling time.

V. Liquidity As the cohesion energy of polyether TPU ether bond is low, the rotational potential of the bond is small, the chain is more in line with the increase in the relative molecular weight of polyether, the molecular chain has a high degree of flexibility, showing good mobility, polyester TPU is slightly smaller.

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