The Fourier transformed infrared (FTIR) spectroscopy on the rubber‐filler gel has been used as a tool for the quantitative characterization of the phase selective silica localization in styrene butadiene rubber (SBR)/natural rubber (NR) blends. The so‐called rubber‐layer L was introduced to describe the selective wetting behavior of the rubber phases to the filler. SBR/NR blends filled with silica were the focus of the experimental investigation. NR shows a higher wetting rate than SBR. Silane addition does not affect the wetting of NR but slowdowns the wetting of SBR. With increasing chamber temperature the value of the rubber‐layer L of all mixtures increases owing to the different thermal activated rubber‐filler bonding processes. Using the wetting concept the kinetics of silica localization in the phases of heterogeneous rubber blends was characterized. Because of the higher wetting rate of the NR component, in the first stage of mixing of NR/SBR blends more silica is found in the NR phase than in the SBR phase. In the next stage, silica is transferred from the NR phase to the SBR phase until the loosely bonded components of NR rubber‐layer are fully replaced by SBR molecules. POLYM. COMPOS., 31:1701–1711, 2010. © 2010 Society of Plastics Engineers.

The present work introduces a new concept based on the analysis of the rubber–filler gel for the determination of the phase selective filler localization in ternary rubber blends. Natural rubber (NR)/styrene–butadiene rubber (SBR)/ethylene–propylene rubber (EPDM) blends filled with silica were the focus of the experimental investigations. Because of the higher wetting rate of the NR component to silica, in the first stage of the preparation of SBR/NR/EPDM blends, more silica is found in the NR phase than in the SBR and EPDM phase. In the subsequent stage, silica is transferred from the NR phase to the SBR phase until the loosely bound NR-layer at the silica surface is fully replaced by SBR molecules. An extremely low amount of silica was found in the EPDM phase because of the poor EPDM–silica interaction. After a long mixing time, a large amount of silica whose surface was not yet wetted by any rubber phase could be found in the composites that can lead to fatal effects on the mechanical performance of the composites.

The aim of this study was to investigate the p53 status in two autoimmune diseases; juvenile chronic arthritis (JCA) and rheumatoid arthritis (RA). In a PCR‐sequencing analysis of exons 4–9 of the p53 gene, no mutation was identified, except for the case of an RA synovectomy sample with two mutations of intron 7. p53 gene polymorphisms for codons 36, 47, and 213 were not detected. Codon 72 polymorphism showed an indication of an increased occurrence of the Pro/Pro allelotype in JCA. Expression of P53 protein was comparable for JCA and RA synovectomy samples. For all RA samples P53 protein was detectable, whereas one sample of a JCA patient failed to express P53 protein.

Carbonate and stearate intercalated layered double hydroxides were used as fillers to prepare polymer micro-and nano-composites respectively. The stearate modified starting material was a bilayer-intercalated clay. During melt compounding excess stearates were released and the clay reverted to a monolayer-intercalated form. The exuded stearate acted as a lubricant lowering the melt viscosity of poly(ethylene-co-vinyl acetate) and linear low density polyethylene matrices. Strong hydrogen bond interactions between the chains of poly(ethyleneco-vinyl alcohol) and the clay platelet surfaces overwhelmed the lubricant effect and caused an increase in the melt viscosity of this matrix. The notched Charpy impact strength of this composite was almost double that of the neat polymer. It appears that this can be attributed to the ability of the highly dispersed and randomly dispersed nano-sized clay platelets to promote extensive internal micro-cavitation during impact loading. This creation of a large internal surface area provided the requisite energy dissipation mechanism.

ABSTRACT:The long term mechanical behavior of thermoplastic vulcanizates (TPV) based on polypropylene (PP) and ethylene propylene diene terpolymer (EPDM) and different types and concentrations of carbon black (CB) has been characterized by means of stress relaxation experiments. Evaluation of the relaxation curves was carried out using the two-component model allowing a division of the initial stress into different stress components which are caused by different networks available in TPV. The discussion focussed on the background of the stress components, which are originated by the CB addition, the non-relaxing stress components r , as well as the relaxing stress components Dr CB(polymer-layer) and Dr CB(network) . It was found that the concentration and type of CB as well as the phase specific CB distribution strongly affect the non-relaxing and relaxing stress components. Up to a CB concentration of 9% in the EPDM phase the composite behaves as a thermo-rheologically simple material because the impact of CB addition on the a-relaxation of the crystalline PP phase is still negligible. A master curve was created by the horizontal shift of the relaxing stress curves Dr Comp (t) to a reference curve. At higher local CB loadings the additional relaxation processes induced by CB addition overlap with the arelaxation, thus, no master curve could be made in that case.