PP, PE, POE blending modification

POE is a saturated ethylene-octene copolymer with a very narrow molecular mass distribution and a certain degree of crystallinity, which provides both elastomeric properties and ease of processing like thermoplastics. In the study of PP/PE/POE blending modification, there are three findings:

1POE toughened PP, a good comprehensive effect can be obtained;

2 The type and content of matrix resin are the same as the toughening agent, which are the key factors determining the performance of the blended material. The copolymerized PP can play the role of compatibilizer and auxiliary toughening agent in the homopolymer PP/POE blend system.

3 Adding a small amount of PE in the blend system can reduce the content of the toughening agent POE, thereby increasing the rigidity and reducing the cost.

Second, the effect of POE content on the performance of homopolymer PP

When homopolymerized PP is added to POE for toughening, the effect on the performance of homopolymerized PP is shown in the following table:

It can be seen from the table that the toughening effect of POE on homopolymerized PP conforms to the toughening theory. The melt flow rate, yield tensile strength, flexural strength and flexural modulus decrease with the increase of the toughening agent POE content, while the notched impact strength increases with the increase of the toughening agent POE content, only the elongation at break. The rate has not changed.

The brittle-tough transition point of the homopolymer PP blend has a POE content of about 25%. It is not difficult to see that as the impact strength of the system increases, the rigidity of the blended material also decreases significantly, and the relative material cost is high.

Third, the effect of copolymerized PP on the performance of homopolymer PP/POE

In order to improve the impact strength of PP and ensure the rigidity of the blended material, and fully consider the material cost and processing property of the blending system, the copolymerized PP is added to the blending system, and the mass fraction of POE is set to 16%. Then, gradually add copolymerized PP of different mass fractions, and finally select the mixing ratio of homopolymerized PP and copolymerized PP. The properties of the resulting blends are shown in the table below:

It can be seen from the above table that the blending system increases the impact strength of the system with the increase of the content of the copolymerized PP, which is several times that of the same mass fraction of POE toughened homopolymer PP. When the blending material of the same impact strength is obtained, The reduction of the amount of POE can be completely reduced, thereby achieving the purpose of reducing the cost, and the rigidity indexes such as bending strength and flexural modulus of the blended material are also guaranteed, which indicates that the copolymerized PP is a good compatibilizer. It is also a good toughening agent.

The results show that when POE toughen different PP blends, it is easy to obtain a dispersed phase with a smaller particle size and a narrower particle size distribution. The average particle size (d) is 0.34 μm, and the particle size distribution is 0.2 to 0.6 μm, the smaller the particle size, the narrower the distribution, the better the impact properties of the blend and the blend exhibits a brittle-ductile transition at a lower elastomer content. It can be seen from Table 2 that it is the effect of the copolymer of PP on the whole system, which makes the POE disperse better in PP. Under the condition of POE mass fraction of 16%, the homopolymer PP is achieved. For the matrix resin, the POE mass fraction requires more than 25%. From Table 2, it was confirmed that the mass fraction ratio of the homopolymerized PP to the copolymerized PP was approximately 1:1.

Fourth, the effect of PE on the performance of copolymerized PP / homopolymer PP / POE

In the PP blending modification study, it is often found that the ternary blend toughening system is better. Therefore, the mass fraction of POE is reduced to 10% in the blend system, and the PE with a mass fraction of 10% is added. The blending system w (PE): w (copolymer PP): w (homopoly PP): w (POE) is 10:40:40:10, the performance test is shown in the following table:

It can be seen from Table 3 that with the addition of PE, the impact strength of the blend system does not decrease with the appropriate reduction of the toughening agent POE, and the rigidity of the blend system does not change greatly, but the cost of the material is reduced. Therefore, it is confirmed that the addition of PE serves as an auxiliary toughening agent. The PP spherulites are incompletely divided into wafers, and the melting point of PE is 30-40 ° C lower than that of PP. When the melt is cooled, part of the toughening agent POE is coated on the outer layer of PE, thereby increasing the toughening agent. The effective volume fraction finally achieves the purpose of refining PP crystal, toughening modification, reducing cost and improving rigidity.

V. Conclusion

1. POE is a good thermoplastic elastomer, which is used to toughen PP and obtain a good comprehensive effect;

2. The type and content of matrix resin are the same as the toughener, which are the key factors determining the performance of the blended material. The copolymerized PP can play the role of compatibilizer and auxiliary toughening agent in the homopolymerized PPΠPOE blend system.

3. Adding a small amount of PE in the blend system can reduce the content of the toughening agent POE, thereby increasing the rigidity and reducing the cost.