Polypropylene/natural rubber thermoplastic elastomer: Effect of phenolic resin as a vulcanizing agent on mechanical properties and morphology

Abstract

The aim of this study is to characterize thermoplastic elastomers (TPEs) from polypropylene and natural rubber with and without phenolic resin as a vulcanizing agent. The blends containing 40-60 wt % of polypropylene were mixed in an internal mixer and pressed with a compression molding machine. TPEs without rubber vulcanization, named as unvulcanized thermoplastic natural rubber (uTPNR) were compared to TPEs containing dynamic vulcanized rubber, referred as vulcanized thermoplastic natural rubber (vTPNR). The uTPNRs illustrated cocontinuous phase morphology, whereas the vTPNRs displayed dispersed phase of vulcanized natural rubber. Tensile properties, tear strength, thermal ageing resistance, ozone resistance, tension set, hardness and swelling test in toluene, IRM 903 oil and engine oil were carried out according to ASTM. It was found that tensile and tear strength, hardness and tension set of the uTPNRs increased with increasing polypropylene content. Dynamic vulcanization improved tensile strength, elongation at break, tension set and degree of swelling of the TPEs, whereas hardness and tear strength did not show significant change after dynamic vulcanization. The vTPNRs exhibited higher ozone resistance and swelling resistance than the uTPNRs. Reprocessability of the vTPNRs was investigated and showed that tensile strength decreased at 20 and 30% and elongation at break decreased at 13 and 27% for the first and the third reprocessing respectively.

Cross-linking of rubber in the presence of multi-functional cross-linking aids via thermoreversible Diels-Alder chemistry

“…At constant PK-FU content the cross-link density increases with the degree of furan-functionalization of PK (and corresponding equivalent of BM). Similar behavior has been reported for rubber-based systems compounded with phenolic resins, either interpenetrating [30][31][32] or chemically bonded to the rubber matrix [33][34][35][36][37][38]. PK-BU is not able to form any DA adduct and, indeed, the reference blends with PK-BU show the lowest apparent cross-link densities, which are…”

“…Upon the addition of BM, the thermoreversible reaction within and between the phaseseparated EPM-FU and PK-FU in the blends (Scheme 1:III) was shown to significantly increase the impact strength [24]. Since PK is easily functionalized with controlled conversion of furan and forms reversible thermosets when cross-linked with BM [33,35], the resulting blend of EPM-FU and PK-FU is also fully recyclable. Scheme 1.…”

“…During the vulcanization stage, the phenolic resins are cured independently from the rubber, forming an interpenetrating polymer network [30][31][32]. Depending on the structure of the phenolic resins, covalent bonds can be formed between the two networks and, thus, phenolic resins can also be viewed as rigid cross-linking agents [33][34][35][36][37][38].…”

Morphological and Mechanical Properties of Polypropylene/Epoxidized Natural Rubber Thermoplastic Vulcanizates Treated with Maleic Anhydride-Grafted Polypropylene

“…On the other hand, PP exhibits poor impact strength, which raises limitations in several other applications (da Costa et al, 2010). Various rubbers were blended with PP to prepared TPEs such as ethylene-propylene-diene rubber (EPDM), styrenic block copolymer, ethylene propylene rubber (EPR), and rubber waste from ground tread layers of truck tires blended with polyethylene to prepared TPEs (Tanrattanakul et al, 2009).…”

Efficiency of high energy electrons to produce polypropylene/natural rubber‐based thermoplastic elastomer

“…A thorough literature survey reveals that most of the study deals with PP/NR TPOs [3, 4] and TPVs [5, 6]. Conventional crosslinking systems, like sulfur [7–10], peroxides [9–15], and phenolic resins [16, 17] have been used abundantly in comparison to high energy electrons to produce PP/NR TPVs. The use of high energy electrons for dynamic vulcanization is quite difficult and requires a special experimental setup as well as experimental data from the electron beam treatment at room temperature.…”