Effect of PES on impact properties of blends
Different types of PE can improve the impact strength of PP at room temperature, but the difference is very obvious.
polypropylene/HDPE blends, the strength of the blends remains unchanged when the mass fraction of HDPE is less than 60%, and the impact strength of the blends increases when the mass fraction of HDPE is higher than 60%. For
polypropylene/LDPE blends, only when the mass fraction of LDPE is higher than 60%, the impact strength of
polypropylene/LDPE blends can be greatly improved.
polypropylene/LLDPE blends, when the mass fraction of LDPE is more than 40%, the impact strength of PP/LLDPE blends is obviously improved. When the mass fraction of LLDPE reached 70%, the impact strength of the blend is 37.5 kJ/m2, which is 20 times of that of pure PP, 10 times and 4 times of that of the same amount of polypropylene/HDPE and PP/LDPE blends.
At low temperature (-18 C), the trend of toughness improvement of PP by three kinds of PE is consistent with that at normal temperature, and LLDPE is the best toughening agent for PP. When the mass ratio of polypropylene/LLDPE is 30/70, the impact strength of PP/LLDPE blends is 23.2 kJ/m2, which is 20 times higher than that of pure PP. Under the same conditions, the impact strength of PP/HDPE and PP/LDPE blends is only about 5 kJ/m2. This further indicates that LLDPE is the least used when the impact strength is the same, which means that the rigidity of PP can be maintained more. At the same dosage, the impact strength of LLDPE modified PP is the best, which makes the material obtain better toughness.
Influence of mixing method on toughening effect.
The impact strength of the sample mixing with twin screw extruder is the highest, and the impact strength of the sample mixing with direct injection is the worst. Because the effective length of screw of injection machine is less than that of extruder, the shear mixing effect is small, so the effect is very poor.
The impact strength of LLDPE increases greatly with the increase of LLDPE content, which indicates that the impact properties of the blend system are affected by the mixing method, but the rule is unchanged.