Stretching Temperature For Heat Shrinkage Production
DATE：2019/9/17 8:56:39 / READ： / SOURCE：This station
Stretching temperature for heat shrinkage production
Stretching temperature
The stretching temperature, also referred to as the orientation temperature, refers to a temperature range in which the film blank (film tube blank) is stretched to align the polymer macromolecules to obtain an optimum heat shrinkage rate and mechanical properties. This temperature range is below the melting temperature of the polymer and at a high elastic temperature above the softening temperature. Therefore, different polymers have their optimum stretching temperature range.
In general, crystalline plastics (such as PE) have a lower stretching temperature than their melting point; amorphous plastics (such as PVC) and plastics (such as PET) that block crystal formation due to rapid cooling, stretching The temperature is 10-15 ° C higher than the glass transition temperature of the polymer. In the case where the stretching orientation can be performed, the stretching temperature is low, and a good orientation effect can be obtained. Further, when the shrink film is packaged using the heat shrinkable film, the heat shrinkage temperature is relatively low.
PP is a crystalline plastic having a crystal melting temperature of about 160 °C. The characteristic of stretching is that it is necessary to form a crystal in a high polymer before the stretching orientation can be effectively performed. Otherwise, even if the PP reaches the stretching temperature, it is difficult to obtain an orientation effect by stretching it. The crystallization rate of PP is greatly affected by temperature. The higher the temperature, the more difficult it is to form crystal nuclei, and the slower the crystallization rate, so that the crystallization of PP at the stretching temperature needs to be long. To shorten the growth time of the PP crystal, it is necessary to quench the tube blank (film blank) and then reheat it. The PE, which is also a crystalline plastic, is not obvious. Therefore, the non-crosslinked LDPE shrink film can be inflated and stretched at the time of forming the film tube blank to a stretching temperature.
PVC is an amorphous polymer with obvious high elastic state. Its stretching temperature ranges from 90 to 110 °C, but it can achieve large heat shrinkage and orientation when stretched at 85-90 °C. .
The glass transition temperature of PET is 69 ° C, and the softening temperature is 10-15 ° C higher than the glass transition temperature. The temperature at which the PET is at the maximum crystallization rate is 175 °C. PET has a wide stretching temperature range (about 85-170 ° C), but actual experience tells that when the PET heating temperature is higher than 105 ° C, crystal turbidity and unstretching will occur. Therefore, in order to obtain a PET heat-shrinkable film having a high transparency, the stretching temperature is preferably controlled within a narrow temperature range of 85 to 105 °C.
Stretching temperature
The stretching temperature, also referred to as the orientation temperature, refers to a temperature range in which the film blank (film tube blank) is stretched to align the polymer macromolecules to obtain an optimum heat shrinkage rate and mechanical properties. This temperature range is below the melting temperature of the polymer and at a high elastic temperature above the softening temperature. Therefore, different polymers have their optimum stretching temperature range.
In general, crystalline plastics (such as PE) have a lower stretching temperature than their melting point; amorphous plastics (such as PVC) and plastics (such as PET) that block crystal formation due to rapid cooling, stretching The temperature is 10-15 ° C higher than the glass transition temperature of the polymer. In the case where the stretching orientation can be performed, the stretching temperature is low, and a good orientation effect can be obtained. Further, when the shrink film is packaged using the heat shrinkable film, the heat shrinkage temperature is relatively low.
PP is a crystalline plastic having a crystal melting temperature of about 160 °C. The characteristic of stretching is that it is necessary to form a crystal in a high polymer before the stretching orientation can be effectively performed. Otherwise, even if the PP reaches the stretching temperature, it is difficult to obtain an orientation effect by stretching it. The crystallization rate of PP is greatly affected by temperature. The higher the temperature, the more difficult it is to form crystal nuclei, and the slower the crystallization rate, so that the crystallization of PP at the stretching temperature needs to be long. To shorten the growth time of the PP crystal, it is necessary to quench the tube blank (film blank) and then reheat it. The PE, which is also a crystalline plastic, is not obvious. Therefore, the non-crosslinked LDPE shrink film can be inflated and stretched at the time of forming the film tube blank to a stretching temperature.
PVC is an amorphous polymer with obvious high elastic state. Its stretching temperature ranges from 90 to 110 °C, but it can achieve large heat shrinkage and orientation when stretched at 85-90 °C. .
The glass transition temperature of PET is 69 ° C, and the softening temperature is 10-15 ° C higher than the glass transition temperature. The temperature at which the PET is at the maximum crystallization rate is 175 °C. PET has a wide stretching temperature range (about 85-170 ° C), but actual experience tells that when the PET heating temperature is higher than 105 ° C, crystal turbidity and unstretching will occur. Therefore, in order to obtain a PET heat-shrinkable film having a high transparency, the stretching temperature is preferably controlled within a narrow temperature range of 85 to 105 °C.
Author：admin