Armin Holzner

PREVULCANIZATION OF NATURAL RUBBER LATEX BY UV TECHNIQUES: A PROCESS TOWARDS REDUCING TYPE IV CHEMICAL SENSITIVITY OF LATEX ARTICLES

Abstract The UV induced prevulcanization of natural rubber (NR) latex provides an innovative technology for an efficient cross-linking. In the photochemical process, a selected photoinitiator and a poly-functional thiol are added to the NR latex. Free radicals (bond cleavage of the photoinitiator) are generated due to UV irradiation and cross-linking of the latex particles is then achieved by a thiol-ene addition reaction. The thiol-ene addition reaction in NR films is characterized with Fourier transform infrared and Raman spectroscopy. To achieve the prevulcanization of latex, both a thin film photoreactor and a falling film photoreactor are applied. Solid latex films are then produced by conventional dipping of the precured NR latex. The NR latex films are distinguished by good skin compatibility due to the absence of sensitizing or irritating processing agents which are used in conventional sulfur vulcanization. Moreover UV cross-linked films display excellent physical properties as well as high aging...

Survey of the crack growth approach for the fatigue life estimation of application-relevant rubbers

Fatigue life prediction models for rubber based on the crack growth approach have the benefit that only crack growth measurements are needed which are considerably shorter than fatigue life measurements. The question is if these models are also applicable for industrial rubber blends under application-oriented conditions. Therefore, the model described in Gent et al. [1] and Lake & Lindley [2] was evaluated. The calculated and measured fatigue life showed differences. The reasons for this could be that other rubber blends than in the original study were used and the heat build-up of the samples.

UV-induced modulation of tribological characteristics: Elastomeric materials featuring controlled anisotropic friction properties

The design of tribologically optimized structures has gained importance in various fields of elastomeric applications ranging from the health care sector to the automotive industry. While many attempts towards improved surface characteristics have been made in recent years, this contribution highlights a new innovative two-step surface modification strategy for enhanced friction properties. Using versatile thiol-ene chemistry, tailored surface structures are architected by means of spatially controlled immobilization of micro-scaled inorganic particles onto natural rubber materials. The chemical composition of the surface was monitored prior to and after its functionalization by XPS, FTIR, zeta potential and contact angle measurements. Physical transformation was analyzed through optical, scanning electron and confocal microscopy in order to gauge surface topology and roughness whilst tribological studies were performed to characterize the friction properties in two dimensions. Upon flood UV exposure, ran...