Journal of Elastomers & Plastics

The graft polymerization of acrylonitrile (AN) or acrylic acid (AA) onto ethylene-propylene-diene terpolymer rubber (EPDM) was carried out in toluene, using dibenzoyl peroxide (BPO) as an initiator. The synthesized AN-g-EPDM and AA-g-EPDM were characterized by FT-IR spectroscopy and thermal gravimetric analysis (TGA). AN-g-EPDM and AA-g-EPDM were incorporated into chloroprene rubber (CR)/EPDM and butadiene acrylonitrile rubber (NBR)/EPDM blends. The compatibility of EPDM/CR and EPDM/NBR blends was examined with scanning electron microscope (SEM) and differential scanning calorimetry (DSC). The physico-mechanical properties of the vulcanizates were investigated after and before thermal aging. AN-g-EPDM and AA-g-EPDM improved the morphology of CR/EPDM and NBR/EPDM rubber blends. The mechanical properties illustrate that the compatibilized blends possessed good thermal stability.

The real and imaginary parts of the complex shear compliance (J0 and J00) of styrene-butadiene-styrene block copolymer, SBS, have been measured isothermally over the frequency range; 0.03-30 Hz, at different temperatures ranging from -70 to 130°C. SBS is taken as representative example of thermoplastic rubbers, which are not susceptible for direct construction of master curves by the usual time-temperature-superposition, tTs, technique. A method has been developed to construct master curves, which we call “step mastering technique”. The step mastering was carried out by constructing different master curves at different temperatures covering both glass transitions which were then superpositioned as whole to maintain the individual shift factors of different processes unchanged. The relaxation frequency of the low temperature glass process can be obtained at any given reference temperature by fitting and extrapolating the activation curve in order to superposition its low temperature master curve (as whole) on the high temperature master one at the correct position of frequency that corresponds the new reference temperature. Accordingly, it was possible for the first time to construct a complete master curve for J0 and J00 for SBS at 30°.

The validity of the master curves obtained by the step mastering technique were confirmed by real frequency measurements in the MHz region using the Quartz method. The analysis showed that the relaxation spectrum consists of four relaxation processes. Using a molecular (meander) model, it was possible from the plateau compliance to determine the size of the structural units of the two phases, which was estimated to be 6.5 and 19.5 nm for PB- and PS-phases, respectively. A possible geometrical packing of the different domains is suggested and compared with the literature data.

The polymerization of (D, L)-lactic acid in the absence of catalysts was studied. Azeotropic distillation using xylene, gave poly(lactic acid) with very low molecular weight, which however, was further increased by post-curing in an air oven. Moreover degradation phenomena and residual xylene were observed, with this procedure. Polycondensation of lactic acid at temperatures up to 180 C under vacuum, resulted in fast reaction with poor control and the products are still characterized by low molecular weight. When the reaction was run at 220 C in inert atmosphere, amorphous poly(lactic acid) was obtained with molecular weight exceeding 3000. The product was found pure, since it is free from solvents, catalysts and monomer. Also, no evidence of thermal degradation was observed. The above characteristics are well acceptable design aspects for biomedical uses.

This paper describes the synthesis and characterization of β-naphthalene sulfonate formaldehyde condensate (BNS) polymers grafted with pendant polyether molecules. For over 40 years, BNS have been considered as commercially useful material in the area of construction. It is added to concrete or mortar to give the concrete better properties either when fluid or plastic. It gives an adequate workability without the addition of extra water. BNS allow a large reduction of water content without affecting the workability of concrete as an example. Finally, the addition of BNS leads to simultaneous increase in both strength and workability without adding extra cost.

A new model was recently established describing the stiffness of polymers as a function of temperature. This polymer stiffness-temperature model was proven to be applicable to thermoplastics for the entire temperature range from the glassy state to the flow of the material. The present paper focuses on the potential application of the statistical stiffness-temperature model to an elastomer system. A new set of cryogenic DMA data for filled and unfilled Polybutadiene was established. The effects of molecular weight and carbon black content on the mechanical response of the elastomer were carefully studied. The polymer stiffness-temperature model was applied to the polybutadiene system and the effect of the various microstructures on the model inputs was investigated. Finally, conclusions were drawn on the applicability of the stiffness-temperature model to elastomer systems.

Zinc sulfonated natural rubbers having different sulfonate contents were synthesized by the reaction of natural rubber with acetyl sulfate, followed by the neutralization of the resultant polymeric sulfonic acid with zinc acetate. The sample notation used for the ionomer is x y M-SNR, where x y is the degree of sulfonation expressed as meq/100 gm rubber, M is the neutralizing metal ion and SNR shows sulfonated natural rubber [Weiss, R.A., Fitzgerald, J.J. and Kim, D. (1991). Macromolecules, 1064: 24]. The modified samples of natural rubber were characterized using spectroscopic techniques such as X-ray Fluorescence Spectroscopy (XRFS), Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICPAES), Fourier Transform Infrared Spectroscopy (FTIR), Fourier Transform Nuclear Magnetic Resonance Spectroscopy (FTNMR), and by the evaluation of mechanical properties. The results show that the incorporation of sulfonate groups into NR improved its physical properties drastically. At a sulfonate level of 24.6 meq/100 g rubber, the tensile strength of the modified rubber incredibly increased to 13 MPa compared to the tensile strength of 0.36 MPa shown by unvulcanized base natural rubber. The Zn-SNR thus synthesized could be reprocessed at 150 C without sacrificing much of its tensile strength.