Effects Of Viscosities On The Morphology Development In Compatibilized Polymer Blends With Complex Interfaces

The purpose of this paper is to study the effects of viscosity ratio on the morphology in compatibilized polymer blends with complex compatible interfaces. In this work, low molecular weight maleic anhydride functionalized polybutadiene (PB-g-MAH) was added into modified polyolefin/PA6blends. The complex interface could be obtained without much varying the viscosity of polyolefin matrix. In this circumstance, both the maleic anhydride in PP-g-MAH (or PE-g-MAH) and PB-g-MAH molecule chains would react with the end amino group in PA6molecules and in situ form graft copolymers located at the interface. The graft copolymers with high molecular weight polyolefin main chain (PP-g-PA6or PE-g-PA6) would enhance the strength of the interface and benefit the shear stress transfer between two phases, which would result in the break up of dispersed PA6particles and good dispersion with small particle size; while the grafted copolymer with low molecular weight PB main chain (PB-g-PA6) would enlarge the radius of the interface, which would benefit to prolong the life-time of the elongated PA6droplets and finally result in an elongated dispersed phase with different aspect ratios. The aim of this paper is to study the effect of viscosity ratio on the dispersed particle size (for spherical domain) and aspect ratio (for elongated domain) with a certain content of low molecular weight PB-g-MAH in the matrix.The results of our study indicated that when the content of PB-g-MAH in the polyolefin matrix was too high (10wt%), no spherical PA6domains could be obtained neither in the thinnest matrix (PP-g-MAH) nor the thickest matrix (PE-g-MAH). In order to study not only the change of the domain size but also the domain shape,5wt%of PB-g-MAH was chosen. It is found that if the viscosity ratio of PA6and polyolefin matrix (P=ηPA6/ηpolyolefin) was between2.0-5.2, the dispersed PA6particles was in spherical form and the particle size decreased along with the decreasing of viscosity ratio. When PA6content was30wt%, the dispersed particle size would decrease from0.85μm (P=5.2) to0.65μm (P=2.0). The reason for this phenomenon should be ascribed to the relatively weak stress transfer in the system when the matrix viscosity was too low. Along with the increasing of the viscosity (decrease the P value), the shear stress applied on the dispersed PA6phase would increase and droplet size decrease. When the viscosity ratio decreased to1.65or lower, the dispersed PA6particles size would reach a limited size and these particles would be very difficult to be further broken up. Those particles were elongated and the aspect ratio increased with increasing the matrix viscosity (decreasing P).The formic acid extraction weight loss for polymer blends with elongated PA6phase was higher than those with spherical PA6domains. This result indicated that the blending systems with elongated PA6phase might form local co-continuous morphology and part of the PA6under the fracture surface might also be extracted out.