Renewable elastomers based on blends of maleated polypropylene and plasticized starch

Most recent developments in polymers from renewable resources have focused on thermoplastics, whereas there has been no comparable development of plastics with elastomeric properties. Here we evaluate the possibility of developing renewable elastomers based on starch. Potato starch plasticized with glycerol (called plasticized starch, or PLS) was melt‐blended with small quantities (5 wt % or 15 wt%) of maleated polypropylene (MAPP). The maleic anhydride groups of the polypropylene are expected to react with the hydroxy groups of starch under melt blending conditions. The resulting blends of MAPP and PLS were characterized by mechanical testing, SEM, DMA, and DSC. SEM, solubility and adhesion tests indicate that the blends are two‐phase materials, in which the continuous phase PLS is physically crosslinked by polypropylene domains. The materials showed rubbery properties as judged by a low glass transition temperature (～?50°C independent of polypropylene content), and a wide rubbery plateau in DMA experiments that extended from room temperature to as high as 170°C. The tensile properties are also characteristic of elastomers. However, slow aging due to starch crystallization, and extraction of glycerol upon water exposure remain two challenges that must be overcome before the materials can be used as practical elastomers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Physical and Tribological Properties Degradation of Silicone Rubber Using Jatropha Biolubricant

This article aims to investigate the degradation of physical and tribological properties (friction coefficients and wear resistance) of a dynamic sealing material (silicone rubber [VMQ]) exposed to Jatropha oil (JO), engine mineral oil (EMO), and a blend (B20; 80% EMO–20% JO), separately. JO has demonstrated better lubricating properties than EMO in various mechanical applications; however, the degradation of elastomers by using this oil has not been studied yet, nor have its effect on their tribological properties. The physical degradation was evaluated by conducting static immersion tests (670 h at 25 °C) based on ASTM-D471 and ASTM-D7216 methods. Hence, the changes in mass, volume, tensile and tear strengths, and hardness of VMQ were measured. In addition, creep compliance tests were conducted to determine the changes in viscoelastic properties and the changes in morphology and topography were measured by scanning electron microscopy (SEM) and optical profilometry, respectively. In addition, the compositional changes were determined by Fourier transform infrared (FTIR) analyses to complement the degradation examination. Changes in the friction coefficients were determined by ball-on-disk tests and changes in wear resistance were obtained by accelerated wear tests (microabrasion tests). Finally, VMQ exhibited no significant physical and compositional degradation due to immersion in the three lubricants. However, considerable changes in the friction coefficients and wear resistance were observed; the change in the friction coefficients was minimal using JO. In addition, the coefficients using JO were 50% lower than those for EMO and the changes in wear resistance were lowest after immersion in JO.     

DYNAMICALLY VULCANIZED THERMOPLASTIC ELASTOMER BLENDS OF NATURAL RUBBER AND POLYPROPYLENE

Dynamic vulcanization of a soft grade of thermoplastic natural rubber (TPNR) was carried out using several concentrations of Hexamethylene N, N′ bis (tert-butyl peroxy carbamate) (HBTP). The blends were melt mixed in a Brabender plasticorder. The effectiveness of dynamic vulcanization was investigated using the Brabender plastograms, swelling index measurements, rheological behavior by means of a capillary rheometer, dynamic mechanical properties, and tensile testing. It was found that varying the HBTP concentration had a great influence on the rheological behavior as well as the dynamic and tensile properties of the material. The increase of HBTP dosage resulted in an increase of the extent of crosslinking and caused an increase of the elastic modulus and a reduction of the loss modulus. The ultimate tensile strength and elongation at break also increased with increasing HBTP loading. The rheograms indicated that the blends exhibit a pseudoplastic behavior.     

碳黑对磁敏高弹体力学性能的影响

磁敏高弹体也称磁流变弹性体，是一种新型的功能材料和智能材料，其力学性能可以由外加磁场来控制。制备了不同碳黑含量的磁流变弹性体，并实验研究了其磁流变效应和热稳定性，得出了碳黑对磁流变弹性体力学性能的影响。实验结果表明，制备磁流变弹性体时，向基体中添加适量的碳黑，能够增强材料的磁流变效应、降低材料的损耗因子、提高材料的热稳定性。     

蒙脱土对硅橡胶基磁流变弹性体性能的影响

考察蒙脱土对硅橡胶基磁流变弹性的动态力学特性和磁流变性能的影响，通过调节体系中蒙脱土的含量优化硅橡胶磁流变弹性体的综合性能。研究结果表明，当弹性体中蒙脱土的含量在4．6％时，硅橡胶基磁流变弹性体／蒙脱土复合材料的模量比纯弹性体的模量提高了近345％，硅橡胶磁流变弹性体的磁致模量达到1.76MPa，磁流变效应为63．7％。     

Modification of waste silicas by silanes and titanates and their use as reinforcing fillers in elastomer composites

Results on the use of waste silica, a by-product in the production of aluminum fluoride, as an elastomer filler are presented. Modification of the purified silica surface with silane and titanate coupling agents has been carried out. The effect of the type and amount of modifying agent on the physico-mechanical properties in vulcanizates of butadiene-styrene rubber and in polyurethane elastomers has been tested. The mechanical properties of butadiene-styrene rubber vulcanizates filled with waste silica show that the most favorable modifying effect is shown by mercaptosilanes A-189 and A-1893, polysulfide Si-69, and titanate KRTTS, as indicated by increased strength parameters. However, testing of the mechanical properties in polyurethane elastomers filled with waste silica has demonstrated that silica modification with aminosilanes A-1100 and A-1120 yield polyurethane compositions of optimum strength parameters.     

Study on rubber blends: Influence of epoxidation on phase morphology and interphase

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     

Synthesis and characterization of side‐chain liquid‐crystalline elastomers containing cholesterol

A series of new smectic and cholesteric liquid‐crystalline elastomers were prepared by graft polymerization of mesogenic monomer with the chiral and nonmesogenic crosslinking agent using polymethylhydrosiloxane as backbone. The chemical structures of the monomers and polymers obtained were confirmed by Fourier transform infrared and proton nuclear magnetic resonance spectra. The mesomorphic properties were investigated by differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction measurements. M₁ showed cholesteric phase during the heating and the cooling cycle. Polymer P₁, elastomers P₂ and P₃ exhibited smectic phase, elastomers P₄? P₆ showed chiral smectic C phase, P₇ showed cholesteric phase, and P₈ displayed stress‐induced birefringence. The elastomers containing less than 15 mol % M₂ displayed elasticity and reversible phase transition with wide mesophase temperature ranges. Experimental results demonstrated that the glass transition temperatures, the isotropization temperatures, and the mesophase temperature ranges decreased with increasing content of the crosslinking unit. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 383–390, 2005     

Thermal stability of some heat-resistant elastomers

The thermal stabilities of four fluoroelastomers, a polyphosphazene elastomer and four polysiloxanes, mainly in the vulcanised state, have been compared by isothermal weight loss experiments in nitrogen, or in air. The overall activation energies for degradation as a function of percentage conversion to volatiles have also been determined. In the majority of cases there was a linear relationship between activation energy and percentage conversion but the slope may be positive, negative or zero.     

Lignin valorization by forming toughened thermally stimulated shape memory copolymeric elastomers: Evaluation of different fractionated industrial lignins

Lignin‐based thermal responsive dual shape memory copolymeric elastomers were prepared with a highly branched prepolymer (HBP, A₂B₃ type) via a simple one‐pot bulk polycondensation reaction. The effect of fractionated lignin type (with good miscibility in the HBP) on copolymer properties was investigated. The thermal and mechanical properties of the copolymers were characterized by DMA, DSC, and TGA. Tensile properties were dominated by HBP <45% lignin content while lignin dominated >45% content. The copolymers glass transition temperature (T_g) increased with lignin content and lignin type did not play a significant role. Thermally stimulated dual shape memory effects (SME) of the copolymers were quantified by cyclic thermomechanical tests. All copolymers had shape fixity rate >95% and >90% shape recovery for all compositions. The copolymer shape memory transition temperature (T_trans) increased with lignin content and T_trans was 20°C higher than T_g. Lignin, a renewable resource, can be used as a netpoint segment in polymer systems with SME behavior. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41389.