G. Ramorino

Developments in dynamic testing of rubber compounds: assessment of non-linear effects

Abstract In the present work, a test method to characterize the dynamic behaviour of rubber compounds by electrodynamic shaker (ES) in the frequency range of 10–1000 Hz was developed. Data of dynamic moduli of two different rubber compounds were determined through the analysis of the transmissibility of a suitably designed test system. The results were compared with those of dynamic moduli master curves obtained through frequency–temperature reduction of data measured by a commercial dynamic mechanical thermal analyser (DMTA), by scanning temperature at various frequencies in the range 0.3–30 Hz. Very good agreement of the data obtained by the two different aproaches were found, in spite of the different range of frequency explored by the two instruments, ES and DMTA, respectively. For one of the material examined, non-linear effects at low strain amplitudes were investigated by the two experimental methods considered.

Self-repairing systems based on ionomers and epoxidized natural rubber blends.

The development of materials with the ability of intrinsic self-repairing after damage in a fashion resembling that of living tissues has important scientific and technological implications, particularly in relation to cost-effective approaches toward damage management of materials. Natural rubbers with epoxy functional groups in the macromolecular chain (ENR) and ethylene-methacrylic acid ionomers having acid groups partially neutralized with metal ions possess self-repairing behavior following high energy impacts. This research investigates the self-repairing behavior of both ENR and ionomers during ballistic puncture test on the basis of their thermal and mechanical properties. Heterogeneous blending of ionomers and ENR have also been used here as a strategy to tune the thermal and mechanical properties of the materials. Interestingly, blends of sodium ion containing ionomer exhibit complete self-repairing behavior, whereas blends of zinc ion containing ionomer show limited mending. The chemical structure studied by FTIR and thermal analysis shows that both ion content of ionomer and functionality of ENR have significant influence on the self-repairing behavior of blends. The mobility of rubbery phases along with its interaction to ionomer phase in the blends significantly changes the mending capability of materials. The healing behavior of the materials has been discussed on the basis of their thermal, mechanical, and rheological tests for each materials.

Autonomous healing materials based on epoxidized natural rubber and ethylene methacrylic acid ionomers

The development of autonomous healing material has an enormous scientific and technological interest. In this context, this research work deals with the investigation of autonomous healing behavior of epoxidized natural rubber (ENR) and its blends with ethylene methacrylic acid ionomers. The autonomous healing behavior of ENR and its blends containing two different ionomers [poly(ethylene-co-methacrylic acid sodium salt) (EMNa) and poly(ethylene-co-methacrylic acid zinc salt) (EMZn)] has been studied by ballistic puncture tests. Interestingly, EMNa/ENR blends exhibit complete healing just after the ballistic test but EMZn/ENR blends do not show full self-repairing. The healing efficiency has been evaluated by optical microscopy and a depressurized air-flow test. The healing mechanism has been investigated by characterizing thermal and mechanical properties of the blends. The chemical structure studied by FTIR and thermal analysis show that the ion content of ionomers and functionality of ENR has a significant influence on the self-healing behavior.

Damage initiated self-healing in ionomer blends

The development and understanding of self-healing mechanisms have been investigated in blends of ionomers (Poly(ethyelene-co-methacrylic acid), sodium & zinc ions) (EMNa & EMZn) containing both elastomers (Epoxidized natural rubbers (ENR) and cis-1,4-Polyisoprene (PISP)) and crystalline component (Poly(vinly alcohol-co-ethylene) [PVAcE]) as secondary phases. All the blends were prepared by melt-blending and self-healing behavior was studied in ballistic puncture tests. Self-healing behavior of each material was evaluated by observing the impact zones under a stereo-optical microscope and the micrographic results were further supported by the fluid flow test in the punctured zones. Interestingly, ENR50 blends of sodium ion containing ionomers exhibited complete self-repairing behavior while zinc ion containing ionomer showed limited mending but EMNa/ENR25 and EMNa/PISP blends did not show any self-healing behavior following the damage. On the other hand, a composition dependent healing behavior was observe...