A discussion about phase morphology and interphase is presented taking into account the influence of the epoxidation on NR/SBR blends. Unfilled blends were examined in a broad composition range to investigate the morphology by TEM (transmission electron microscopy) and to estimate the volume fraction of the interphase by means of DMA (dynamic mechanical analysis). It was observed that the domain sizes and the volume fraction of the interphase depend on the difference in polarity of rubbers caused by the presence of the epoxidized phase and the polarizability caused by the difference on the vinyl content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2377–2384, 2007

The diffusion process of a homologous seria of phthalates (DMP, DEP, DBP, DOP and DDP) in different nitrile rubbers (NBR) and in hydrogenated nitrile rubber (HNBR) was investigated by using two methods based on FT-IR Spectroscopy, namely the macroscopical "time-lag" method and the microscopical "concentration-distance" analysis. Within the homologous seria of the phthalates the diffusion coefficient demonstrates significant structure-property relationships concerning (i) the chain length of the alkyl groups of the phthalates, (ii) the content of nitrile groups in the matrix, (iii) the unsaturation of the rubber and (iv) the crosslink density of the NBR. The activation energy of the diffusion process was derived for DOP in NBR (39% ACN) and the corresponding hydrogenated grade (36% ACN). The diffusion coefficients of DOP in NBR (34% ACN) by using the "time-lag" method are larger than those determined by the "concentration-distance" results in similar values.

Model processing aids with well-defined molecular structure (alcohols, acids and esters derived from C-12- and C-12 -hydrocarbons) were investigated in S-SBR in the concentration range between 1.5 phr to 6 phr for (i) the plasticizing efficiency at low temperatures, (ii) the solubility and (iii) the viscoelastic properties of the rubber mixes. in addition the solubility of a commercial product was investigated at processing temperatures. It was observed that the highest plasticizing efficiency was reached by esters. it has been found that the molecular weight as well as the functional group control the solubility in rubber. The solubility decreases in the sequence: ester > acid > alcohol. The viscoelastic analysis demonstrates that by incorporation of the model processing aids the plateau modulus G, is not strongly affected but the reptation time tau(rep) is significantly decreased.

The phase morphology of NR-based blends was investigated in relation to the polarity of the second blend constituents (BR, SBR with varying vinyl content, ENR and EpSBR). The polymers were thermodynamically characterized by their solubility parameter. The phase morphology was determined by employing dynamic-mechanical spectroscopy and transmission-electron-microscopy (TEM). It was shown that the domain size of the minor constituent increases linearly with interfacial tension. The degree of compatibility was classified by the solubility parameter difference and in addition using the T-g shift and the half width of the damping maxima. The phase inversion region is determined from the stepwise increase in the loss modulus. With TEM, two phases can be recorded even for blends with a high degree of compatibility, where dynamic-mechanical spectroscopy approaches its resolution limit.

Considering the performance of multilayer elastomer products like tires the distribution of crosslinking chemicals caused by diffusion following the assembly step during storage and vulcanization is an interesting aspect for covulcanization, crosslink density and influences on the adhesion systems. In this manner the diffusion behavior and the equilibrium distribution of the dithiophosphate accelerator, di-(2-ethyl)hexylphosphorylpolysulfide (SDT) between different rubber compounds used in tires was investigated by means of Fourier Transform infrared spectroscopy (FT-IR spectroscopy) and swelling. The equilibrium distribution of SDT differs as a function of the rubber matrices involved, with the consequence that the concentration decreases in the direction tread -undertread - steel cord mixture.