| The goal of this paper was to study the mechanism of phase dispersion-crosslinking synergism in the incompatible polymer blends composed of polyvinyl chloride (PVC) and low density polyethylene (LDPE). It contributes to the development of phase dispersion-crosslinking synergism technique which is efficient on improving the mechanical properties of immiscible polymer blends.Phase dispersants NBR, SBR, BR and EPDM could promote the dispersion of PVC and LDPE. NBR is a compatibilizer for PVC and LDPE, which could reduce the interfacial tension of two incompatible polymers and improve the dispersion under the shear stress. SBR, BR or EPDM could increase the melt viscosity of LDPE phase; hence decrease the viscosity ratio between PVC phase and LDPE phase. Morphology of the blends was improved inevitably. The results were obtained by studying both the influence of viscosity ratio on the morphology and mechanical properties of PVC/PE blends and the influence of phase dispersant on the rheology of two polymers and their blends.In Haake mixer, it was found that morphology evolution of PVC/PE blends was sensitive to not only processing conditions (shear strength and mixing time) but also the added compatibilizer or phase dispersant. In our conditions, the stable phase morphology of each blends was obtained after mixing 15 minutes~25 minutes. And the dispersed PVC phase in blends was easy to aggregate when the mixing rotor speed transferred from high speed to low speed for the binary blends. As a compatibilizer, CPE (or NBR) could stabilize the morphology and hinder the coalescence of dispersed PVC phase when added to the blends. However, the phase dispersant BR (or SBR) could not stabilize the phase structure, though it could accelerate phase dispersion. Though less dispersed domain could be aggregated, the blends added of EPDM has a tendency of aggregating.It is well known that CPE or NBR can act as compatibilizer of LDPE/PVC blends. The function of the compatibilizer is to increase the interfacial adhesion between thetwo phases and to keep the finer morphology during processing. BR or SBR, which was suggested to be phase dispersant, could accelerate the phase dispersion of the blends by modifying the viscosity ratio of blends; it could not increase the interfacial adhesion. Such a phase dispersed structure was thermodynamic unstable. Consequently, a fine phase structure formed in high rotor speed (equivalent to high shear strength) will become coarser when the rotor speed decreases. When it to EPDM, the phase dispersed structure was also unstable. The reason that PVC/LDPE/EPDM blends were difficult to aggregate could be resort to that EPDM was compatible with LDPE and made the LDPE matrix more viscous.Monitoring by -like solvent analysis, X-ray energy analysis and OsO4 or CrO3 staining, we have found that NBR was distributed in PVC and the interphase of PVC and LDPE, SBR, BR and EPDM were in LDPE matrix. The distribution of phase dispersants in the blends contributes to the understanding the mechanism of dispersion of immiscible polymer blends. And these phase dispersants could be separated three sorts: SBR or BR is an ordinary phase dispersant; NBR and EPDM are the other two special phase dispersants.From the results of selective solvent extraction, FTIR spectra and dynamic rheological analysis, it was concluded when the crosslinking agent alone was added to PVC or PVC blends, PVC could not to be crosslinked or to be co-crosslinked with LDPE, SBR, BR or EPDM, but it could be crosslinked with the help of NBR. However, when it came to the composite crosslinking agent (DCP/TAIC/MgO), PVC, PVC/LDPE blends, PVC/NBR blends and PVC/EPDM could be crosslinked or be co-crosslinked except for PVC/SBR blends and PVC/BR blends. In PVC/LDPE/DCP blends, the promotion of the tensile properties and PVC cannot be extracted completely by THF solvent could resort to the formation of the effective crosslinking network of LDPE with the assistance of DCP. The crosslinking network of LDPE firmly entrapped PVC chains. It...
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