Journal of Elastomers & Plastics

Proton conducting solid polymer electrolyte films, which are composed of diazanium hydrogen phosphate (DAHP) and poly(vinyl alcohol) (PVA), were prepared by a solution casting method. The prepared films were characterized by ultraviolet-visible, X-ray diffraction, and differential scanning calorimetry. The optical activation energy and band gap increases with increase in DAHP content in PVA. The direct current (DC) and alternating current (AC) conductivity studies have been carried out using an impedance analyzer. The sample containing 15 wt% DAHP shows highest AC conductivity of the order of 10⁻⁴ S cm⁻¹ and DC conductivity about 4.27 × 10⁻⁷ S cm⁻¹ at ambient conditions. The crystallinity has decreased and glass transition temperature (T _g) has increased with increase in DAHP content. The Williams–Landel–Ferry and Vogel–Fulcher–Tamman equations were used to calculate dynamic fragility (m) and apparent activation energy (E _g) from T _g values. The Rice and Roth model was successfully applied to determine the transport parameters for DAHP/PVA electrolytes. This article mainly focused on understanding the contribution of different parameters to conductivity phenomenon in solid polymer electrolytes.

In this article, thermoreversible covalent cross-linking of maleated natural rubber (MNR) with glycerol was studied. Firstly, NR was grafted with maleic anhydride using a reactive processing method. The result showed that MNR was successfully obtained without the addition of initiator. The highest grafting was 1.76%. Secondly, the obtained MNR was dissolved in toluene and then mixed with glycerol, which is used in this study as the thermoreversible cross-linking agent. Fourier transform infrared spectra of the casted MNR film mixed with glycerol showed that upon heating, covalent ester cross-links were formed via the reaction of succinic anhydride ring with hydroxyl groups of glycerol. The swelling test indicated that the swelling index (%) decreased with increasing glycerol loading. This indicated that the degree of cross-linking directly depended on the amount of glycerol. The tensile strength and modulus were significantly improved upon increasing the level of cross-linking. The MNR cross-linked with glycerol can be remolded at 150°C more than three times. After remolding, the mechanical properties decreased with increasing recycling round.

In the first part of the research, rubber magnetic composites were prepared by incorporation of strontium and barium ferrite in concentration scale ranging from 0 to 200 phr into rubber matrices based on acrylonitrile–butadiene rubber and styrene–butadiene rubber. The main objective was to investigate the influence of the type and content of magnetic filler on the cross-link density, physical–mechanical and magnetic characteristics of the prepared composites. In the second part of the study, the content of magnetic fillers was kept on constant level—200 phr and the main aim was to investigate the change in mutual combination of both fillers on the cross-linking and properties of the rubber magnets. The results revealed that both fillers show reinforcement effect in the rubber matrices. The higher tensile strength of composites was achieved by application of barium ferrite. Magnetic properties of composite materials were significantly influenced by magnetic characteristics of magnetic fillers. Higher remanent magnetic induction of barium ferrite was reflected in higher remanent magnetization of the equivalent composites. On the other hand, higher coercivity of strontium ferrite resulted in higher coercivity of strontium ferrite-filled composites.

Oxidative aging of natural rubber (NR) leads to the deterioration in the physical and mechanical properties. Using various antioxidants during compounding is a common way to improve the aging resistance of NR. The most widespread used antioxidants are phenolic and amine-based synthetic antioxidants and 2,2,4-trimethyl-1,2-dihydroquinoline in rubber industry. However, synthetic antioxidants cause some environmental problems during their production and tend to be replaced by natural alternatives. In this study, henna has been evaluated as a natural antioxidant in NR-based rubber compounds for efficient and conventional sulfur vulcanization systems. Performance of henna was evaluated in terms of rheological, mechanical, aging, and temperature scanning stress-relaxation properties of the compounds. It has been concluded that henna could be used as an alternative antioxidant for sulfur vulcanization of natural rubber matrix, compensating little deteriorations in vulcanizate properties. Short- and long-term performances of henna were also found to be related to vulcanization system.

In this study, acrylonitrile butadiene rubber (NBR)–gelatin blends were prepared by conventional melt blending process at 40°C processing temperature and 50 r min⁻¹ rotor speed in a Brabender-Plasticorder. Gelatin loading was varied from 10 to 50 phr. The extent of reinforcement was more prominent at 30 phr gelatin loading without compatibilization. Up to 30 phr gelatin loading, the tensile strength, abrasion resistance, and morphological properties of blends increased. After 30 phr gelatin loading, the toughness and abrasion resistance declined for samples containing 40 and 50 phr gelatin. However, cross-link density and hardness kept on increasing beyond 30 phr loading. At optimum loading of 30 phr of gelatin, 3, 3.5, and 4 phr of nano-silanized silica was added as a compatibilizer for further improvement in properties. After compatibilization of 30 phr gelatin sample with 4 phr of nano-silanized silica, the extent of reinforcement in terms of tensile strength was improved from 8.97 to 9.92 MPa.

Nitroxide-mediated polymerization was successfully employed for well-defined graft copolymerization of styrene (St) monomer from cellulose (Cell) backbone. For this purpose, Cell was acylated by 2-bromoisobutyryl bromide, and then 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) was immobilized onto Cell backbone using a nucleophilic substitution reaction to produce Cell-TEMPO macroinitiator. Afterward, St monomer was grafted onto Cell backbone through “grafting from” technique. The successful synthesis of Cell-g-polystyrene (PSt) copolymer was confirmed using Fourier transform infrared and proton nuclear magnetic resonance spectroscopies and scanning electron microscopy analysis. Finally, Cell-g-PSt/montmorillonite nanocomposite was fabricated through solution intercalation approach. The thermal properties and structural morphology of the resultant nanocomposite were investigated using thermogravimetric analysis and differential scanning calorimetry and transmission electron microscopy, respectively.