The development of polymers that can repair damage autonomously would be useful to improve the lifetime of polymeric materials. To date, limited attention has been dedicated to developing elastomers with autonomic self-healing ability, which can recover damages without need for an external or internal source of healing agents. This work investigates the self-healing behavior of epoxidized natural rubber (ENR) with two different epoxidation levels (25 and 50 mol % epoxidation) and of the corresponding unfunctionalized rubber, cis-1,4-polyisoprene (PISP). A self-adhesion assisted self-healing behavior was revealed by T-peel tests on slightly vulcanized rubbers. A higher epoxidation level was found to enhance self-healing. Self-healing of rubbers following ballistic damages was also investigated. A pressurized air flow test setup was used to evaluate the self-healing of ballistic damages in rubbers. Microscope (OM, SEM, and TEM) analyses were carried out to provide further evidence of healing in the impact zones. Self-healing of ballistic damages was observed only in ENR with 50 mol % epoxidation and it was found to be influenced significantly by the cross-link density. Finally, self-healing of ballistic damages was also observed in ENR50/PISP blends only when the content of the healing component (i.e., ENR50) was at least 25 wt %. From an analysis of the results, it was concluded that a synergistic effect between interdiffusion and interaction among polar groups leads to self-healing in ENR.

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Polypropylene blends with polyhedral oligomeric silsesquioxanes (POSS) bearing different alkyl groups were investigated to elucidate the effect of the alkyl group length on the mechanical behavior of the blends. In particular, blends of polypropylene (PP) with either octamethyl-POSS, octaisobutyl-POSS, or isooctyl-POSS were studied. Differential scanning calorimetry evidenced only minor changes in the degree of crystallinity compared to neat PP. Uniaxial tensile tests showed that the incorporation of octamethyl-POSS induces an increase in Young’s modulus and a reduction of the yield strength in comparison with unfilled PP. By contrast, upon the incorporation of octaisobutyl-POSS and isooctyl-POSS, both Young’s modulus and the yield strength were found to decrease by increasing the POSS content. It is suggested that POSS behave as particles having a siliceous hard-core surrounded by a hydrocarbon soft-shell, which limits the stress transfer from the matrix to the core in dependence on the length of the alkyl groups. Finally, the essential work of fracture method was employed to study the fracture behavior of octamethyl-POSS/PP blends, with different POSS contents (0, 3, and 10 wt %)

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New oligomers of N-vinyl-2-pyrrolidone, functionalized at one end with hydroxy functions, were obtained by radical polymerization in the presence of a hydroxylated compound, namely 2-isopropoxyethanol, acting as chain-transfer agent. The oligomeric samples obtained were characterized in terms of molecular weight and molecular weight distribution by means of analytical size exclusion chromatography (SEC). To this purpose, a calibration curve for a set of SEC columns had been determined, making use of poly(N-vinyl-2-pyrrolidone) standards purposely prepared. The chain transfer constant CT of 2-isopropoxyethanol towards N-vinyl-2-pyrrolidone was determined from the knowledge of the cumulated number-average degree of polymerization X̄n and monomer conversion Yt of the samples during the reaction

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