Preparation, Structure And Properties Of The Thermoplastic Elastomers Based On Polypropylene-block-ethylene Copolymer And Ethylene-propylene-dine Terpolymer

In this research, the thermoplastic elastomers (TPE) based onPolypropylene-block-ethylene copolymer (PP-B)/Waste Ground Rubber Tire(WGRT), PP-B/waste ethylene-propylene-diene terpolymer powder (WEPDMP)and thermoplastic vulcanizate (TPV) based on PP-B/EPDM were prepared. Themorphology, mechanical properties, Mullins effect, reversible recovery ofcompression set and dynamic mechanical properties of the TPVs were investigatedsystemically, especially the effect of the weight ratio, compatibilization dosage andcarbon black (CB) on the properties of the TPV. Crystallization behaviors of thePP-B/EPDM TPV were investigated primarily. The results were showed as below：(1) The TPEs based on the blends of PP-B and WGRT were prepared by meltblending while the styrene-butadiene-styrene copolymer (SBS) was used ascompatibilizer. The mechanical properties and the morphology of the fracturesurface of the blends were investigated systemically. The results showed that thetensile strength and the modulus of the PP-B/WGRT blends increased remarkablywith the increasing PP-B content. The elongation at break was below100%.However, the PP-B/SBS/WGRT blends showed the representative elastomericcharacteristic and the tensile strength and tearing strength increased remarkablycomparing with the PP-B/WGRT blends. The elongation at break could exceed120%and the tension set at break was low. The SEM images of the PP-B/WGRTblends and PP-B/SBS/WGRT TPE showed that the interface interaction betweenPP-B matrix and WGRT was improved obviously after the compatibilization. (2) The thermoplastic elastomers based on PP-B/polyolefin elastomer/WGRTwere prepared by dynamic vulcanization. Then the influence of PP-B/WGRT weightratio, the filling of POE in PP-B matrix and dynamic vulcanization on themechanical properties of PP-B/POE/WGRT were investigated systemically. Theresults showed that the PP-B/WGRT blends prepared by verifying the PP-B/WGRTweight ratio and the filling of POE in PP-B matrix could not belong to TPE.However, the PP-B/POE/WGRT TPEs with the improved mechanical propertieswere prepared successfully by dynamic vulcanization, and the comprehensiveproperties were best at3phr DCP dosage. The observation of FE-SEM showed thatthe interface interaction between PP-B matrix and WGRT was improved, which ledto the improved mechanical properties of PP-B/POE/WGRT blends.(3) TPEs based on PP-B/WEPDMP composites were prepared bymelt-compounding and SBS was used as a compatibilizer. SBS had a goodcompatibilization effect on the PP-B/WEPDMP composites and significantimprovement in mechanical properties of PP-B/WEPDMP composites compatibilizedby SBS could be achieved. Compared with that of PP-B/WEPDMP composites, theelongation at break of PP-B/SBS/WEPDMP composites with6phr SBS loading wasimproved by170.3%. PP-B/SBS/WEPDMP composites with relatively highelongation at break and low tensile set at break can be attributed to TPE. FE-SEMimages showed that the fracture surface of the PP-B/SBS/WEPDMP composites wasrelatively smooth, indicating an improved elastic recovery ability. The Mullins effectresults shows that the maximum stress decreased obviously after the first loading, andthe internal friction losses in uniaxial loading-unloading cycles ofPP-B/SBS/WEPDMP sample were lower than those of PP-B/WEPDMP composites,indicating that the elasticity of the PP-B/SBS/WEPDMP composites was improved.(4) Polypropylene-block-ethylene copolymer (PP-B)/ethylene-propylene-dieneterpolymer rubber (EPDM) thermoplastic vulcanizate (TPV) were prepared bydynamic vulcanization; the mechanical properties, reversible recovery ofcompression set, Mullins effect and microstructure of as-prepared TPV wereinvestigated systematically. Experimental results indicated that the TPV had properproperties when the PP-B/EPDM weight ratio was30/70. At room temperature,increasing the EPDM content in TPV would lead to the fast recovery of compressionset and the relatively low residual compression set; increasing temperature cansignificantly speed up the recovery of compression set. Moreover, the TPV with high EPDM content had fully reversible deformation ability. Mullins effect resultsshowed that a softening phenomenon could be observed during the uniaxialloading-unloading cycles, and internal friction and loss factor under the fixed stretchwas decreased obviously after the first loading-unloading while only decreasedslightly at the later loading-unloading cycles. Furthermore, the maximum stressdecreased slightly during loading-unloading cycles. Increasing the resin dosage inTPV, the maximum stress, residual deformation, internal friction, degree of stresssoftening effect and loss factor were increased obviously. FE-SEM observation ofthe fracture surface showed that the existence of rubber in matrix enhanced theelasticity of TPV.