HOW MUCH YOU KNOW LLDPE FILM?The melt tension of LLDPE is lower than that of LDPE, and the relaxation time of melt stress is short. It can be observed that the melted film extruded from the "T" die head has a large necking and the parison has a large vertical extension during hollow molding.
table of Contents
1 Heat sealability
2 Melting performance
3 Thermal performance
4 Physical and mechanical properties
LLDPE film has good heat-sealability, as long as it reaches the lowest starting temperature, it has good heat-seal strength and strong anti-pollution ability.
Melting performance depends on factors such as relative molecular mass, relative molecular mass distribution, and long-chain branching. Similarly, the melt flow rate LLDPE and the relationship between LDPE and shear rate: The behavior of LLDPE is similar to HDPE with a relatively narrow molecular weight distribution, and has a higher melt viscosity than LDPE, so the extrusion load during extrusion molding increases and the calorific value Also increased.
Since the melt stress relaxation time is short and the residual stress in the injection molded product is small, the shrinkage rate is small and the warpage is also small.
The melting point of polyethylene is proportional to the degree of crystallization and crystal size, so the melting point of LLDPE is 10-15 degrees Celsius higher than LDPE. Even for the same LLDPE, the more the carbon number of the copolymer monomer, the higher the melting point. This rule is also applicable to Vicat softening point. The heat sealing performance of the film corresponds to the fully fused heat sealing temperature. The heat sealing temperature of LLDPE is 10-15 degrees Celsius higher than LDPE, and the melting point range of LLDPE is narrower than that of LDPE, so the heat sealing performance of the film is good.The cold resistance of LLDPE, in terms of the relationship between the catalytic temperature and the melt flow rate, the brittleness temperature of LLDPE is lower than that of LDPE and HDPE, which indicates that it can withstand lower temperatures.
Physical and mechanical properties
The ratio of LLDPE's tensile properties to LDPE properties, the number of stretches and tensile yield strength is large, especially the tensile breaking strength and elongation at break. Generally, the energy required for breaking can be obtained from the area of the stress-strain curve. Use this as an indicator of resin rigidity. Obviously, the rigidity of LLDPE is good, which may be attributed to the large number of tethered molecules in the LLDPE molecule.
The relationship between rigidity and density: the lower the density, the worse the rigidity (ie, softer). In terms of the same density, the impact strength of LLDPE wants to hit, and the impact strength of C6 and C8 comonomer polymers with more than C4 is higher.
The physical and mechanical properties of LLDPE film are significantly better than LDPE, and its softness, toughness, cold resistance and puncture resistance are better than LDPE.
Physical property parameter table of LLDPE film
Tensile strength / Mpa
Stretching rate /%
Tear strength / (N / cm)
Vicat softening point / ℃
Brittleness temperature / ℃