Ultra-low density polyethylene film, referred to as ULDPE film, has a polymerization mechanism similar to that of LLDPE, both of which are linear structures without long chain branches, so it is also called the second generation of LLDPE. The number of short chain branches of ultra-low density polyethylene (ULDPE film) is higher than that of LLDPE, and the branch branches are shorter and more regular than those of LDPE, and there are no long chain branches. Its molecular weight distribution is narrow, and its crystal phase structure and degree of entanglement are different from those of LDPE. The presence of a large number of short chain branches in ULDPE film weakens the formation of the crystalline region on the polymer main chain, and when the crystalline region is formed, the crystalline region will deform and produce defects. Under the same crystallization conditions, its crystalline structure is obviously different, which leads to completely different physical and mechanical properties of the product.

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Performance

The properties of ultra-low density polyethylene film (U/VLDPE film) are as follows:

1. Excellent tensile strength, impact strength, tear strength, and puncture resistance

2. Thermal properties. Since VLPDE and ULDPE are short-chain linear crystals, their crystal structure defects are not as obvious compared to long-chain branched LDPE, so their melting points are higher, about 20буC higher than EVA copolymers, so the use temperature of their products is also higher.

3. Modulus. The modulus of U/VLDPE is smaller, lower than that of LDPE, LLDPE, and HDPE. Its film has good toughness, softness, and good hand feel.

4. Compatibility. U/VLDPE has good compatibility when mixed with other polyolefins. This is because its crystallinity is very low, so it has the ability to accommodate inorganic fillers and organic fillers similar to EVA and plasticized PVCX. When mixed with inorganic fillers, it has higher rigidity and wear resistance, and the impact resistance will not be reduced. If suitable mixing equipment is used, fillers such as chalk and mica can be added up to 70%, and there is no problem with dispersion.

5. Other properties. U/VLDPE has excellent thinning performance (up to 10-12.7um), good insulation, good optical properties, chemical corrosion resistance, oil resistance, sealing, etc.

U/VLDPE can replace EVA copolymers to produce various food and beverage packaging films, and can also replace PVC and other PE resins to produce shrink films, stretch films and thin films. In the field of plastic packaging films, it can also be used as a softening modifier, tear strength modifier, and impact modifier to mix with other PE, PP, EVA and certain EPR. Mixing with PP and PE can improve strength, performance, softness and low-temperature heat sealing properties. Since the sealing strength can be changed by changing U/VLDPE, it can be used as a heat-sealing material for multi-layer films. It can be blended with HMW-HDPE to produce candy packaging films, which can reduce the twist recovery of the film after being kinked and enhance the tear strength.

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