Influence of main indexes of chlorinated polyethylene (CPE) on modification of rigid PVC(5)

Effect of CPE with different particle size (screen residue) on PVC modification:

Chlorination process, grinding and so on have a great relationship, CPE too thick or too fine have a certain impact on PVC modification effect. The suspension chlorination of CPE is a heterogeneous reaction, and the particle size of PE has a significant effect on the uniformity of chlorination. If the particle size is small, the specific surface area of the particles is large, the chlorine atoms are easy to penetrate into the particles, and the chlorination is more uniform. If the particle is too coarse, the infiltration of chlorine into the particle is difficult, and the chlorination is not uniform.

It was found through experiments that the thickness of CPE particles produced from the same PE raw material also had a certain impact on the rheological properties of CPE, which showed that the plasticizing performance of CPE with excessively fine particles was slightly worse than that of CPE with coarse particles, and the plasticizing time was delayed.

The influence of CPE particle thickness on PVC modification is also related to the change of PVC powder particle morphology during PVC/CPE hot mixing. PVC powder particle size is different at room temperature, in the extrusion molding process is easy to cause plasticization is not uniform, when the mixing temperature reaches about 120 ° C, the particles become large and uniform, small particles almost completely disappear, and in a part of the particles or edges become transparent or translucent, this phenomenon shows that PVC particles due to absorb heat and produce partial gelation, Particle homogenization and the melting of a considerable part of the auxiliaries are the main characteristics of this zone, which is also one of the purposes of hot mixing. However, if the CPE particles blended with PVC are too thick, it is difficult to disperse evenly in the pre-plasticization stage of this mixture and achieve a better pre-plasticization state. In the extrusion process, it is difficult to achieve a good plasticization state, so that it is difficult to form a network structure, and then reduce the impact modification effect of CPE on PVC. This may be related to the toughening mechanism, because CPE forms a network structure in the PVC/CPE system, and the network is easy to deform, especially the polygonal network, which causes shear slip in the 45° direction. It may also be due to the low network strength of CPE (lower than PVC), can not resist the role of external shear forces, shear slip occurs; At the same time, CPE, as a stress concentrator, also causes PVC to shear slip in the direction of 45°. The formation of shear slip dissipates part of energy and improves toughness [7]. If CPE is insufficient to form a network structure in the PVC/CPE system, the impact modification effect of CPE will be reduced. The control index of the light industry standard QB/T5079-2017 is the screen residue (0.9mm sieve hole) ≤2.0%.