Dynamically vulcanized blends of polypropylene and ethylene octene copolymer: Influence of various coagents on mechanical and morphological characteristics

Abstract

Dynamically cured blends of polypropylene (PP) and ethylene octene copolymer (EOC) with coagentassisted peroxide curative system were prepared by meltmixing method. It was well established that PP exhibits b-chain scission in the presence of peroxide. Principally, incorporation of a coagent increases the crosslinking efficiency in the EOC phase and decreases the extent of degradation in the PP phase. The present study mainly focused on the influence of three structurally different coagents, namely, triallyl cyanurate (TAC), trimethylol propane triacrylate (TMPTA), and N,N 0 -m-phenylene dimaleimide (MPDM), on the mechanical properties of the PP/EOC thermoplastic vulcanizates (TPVs). The reactivity and efficiency of different coagents were characterized by cure study on EOC gum vulcanizate. TAC showed the highest torque values followed by MPDM and TMPTA. Significant improvements in the physical properties of the TPVs were inferred with the addition of coagents. Among the three coagents used, MPDM showed the best balance of mechanical properties in these TPVs. The results indicated that torque values obtained during mixing and the final mechanical properties can be correlated. Different aspects were explained for the selection of a coagent that forms a product with desired properties. The phase morphologies of the TPVs prepared were studied by scanning electron microscopy. Tensile fracture patterns were also analyzed to study the failure mechanism of the samples.

Blends of ground tire rubber devulcanized by microwaves/HDPE - Part A: influence of devulcanization process

“…Some researchers use this advantage to examine different phenomena such as dynamic vulcanization [21][22][23][24][25][26][27][28][29] , as performed in this work. During the mixing, just after the addition of the matrix phase and as soon as the torque measured by the equipment was stabilized, GTR (containing or not vulcanization additives) was added into the mixer, what permitted the analysis of the dynamic revulcanization behavior of the blends, which is shown in Table 3.…”

Blends of ground tire rubber devulcanized by microwaves/HDPE - Part B: influence of clay addition

“…The literature presents some works in which dynamic vulcanization is analyzed during processing into internal mixer [22,[37][38][39][40][41][42][43][44] , as performed on this work. In this particular case, the influence of a clay addition in the dynamic revulcanization reaction is analyzed.…”

“…G' values could be influenced by cross-linking density [52] and/or blend morphology [42,43] , being that the morphology refinement and compatibility between the phases tend to increase the G' values. According to SEM micrographs, no conclusion about the morphology refinement of the blends can be made, but the mechanical properties results depict the poor adhesion between the phases, being that a possible particle detachment from the matrix occurs when applied an external stress.…”

Interrelationships of morphology, thermal and mechanical properties in uncrosslinked and dynamically crosslinked PP/EOC and PP/EPDM blends

“…The samples of about 6 mg sealed in aluminum pans were heated from -80 to 200°C at a scanning rate of 10°C/min under nitrogen atmosphere. The degree of crystallinity of PP was determined from the heating curve by using standard formula which was discussed earlier by the authors [17,18]. Mechanical Testing -The dumb-bell shaped specimens of the TPV used for testing were die cut from the compression molded sheet and the testing was done after 24 hours of maturation at room temperature.…”

“…Lai et al [16] investigated the fracture behavior and physicomechanical properties of peroxide cured PP/EOC TPVs. As a part of the extensive research work on the peroxide cured PP/EOC TPVs, our earlier report deals with the influence of different peroxides [17], different coagents [18] and different mixing sequences [19,20] on the solid and melt state viscoelastic properties of PP/EOC TPVs. The present study primarily aims to evaluate the performance of the coagent assisted peroxide cured PP/EOC TPVs as a potential alternative to the conventional PP/EPDM TPVs.…”