No abstract

Effects of epoxy resin on various arylamine‐based benzoxazine resins, i.e., aniline (BA‐a), m‐toluidine (BA‐mt), and 3,5‐xylidine (BA‐35x), have been investigated. Processing windows of BA‐35x, BA‐mt, and BA‐a were found to be widened with the amount of the epoxy. Gel points of benzoxazine‐epoxy resin mixtures can be predicted by an Arrhenius equation, e.g., gel time of BA‐35x and epoxy mixture at 70:30 mass ratio can be estimated by tgel = 0.7012 × 10−7 exp (10.563/T). Glass transition temperature (Tg) of BA‐a and BA‐mt alloyed with epoxy exhibited a synergistic behavior with the maximum Tg value at the benzoxazine‐epoxy composition of 80:20 mass ratio. However, in the BA‐35x and epoxy mixture, the decreasing trend in Tg from 241°C to 223°C with an addition of epoxy was observed. Furthermore, flexural strength and strain‐at‐break of those alloys were found to increase with increasing amount of the epoxy while modulus increased with the polybenzoxazine mass fraction. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Highly filled graphite polybenzoxazine composites as bipolar plate material for polymer electrolyte membrane fuel cell (PEMFC) are developed. At the maximum graphite content of 80 wt % (68 vol %), storage modulus was increased from 5.9 GPa of the neat polybenzoxazine matrix to 23 GPa in the composite. Glass transition temperatures (T g ) of the composites were ranging from 176 C to 195 C and the values substantially increased with increasing the graphite contents. Thermal conductivity as high as 10.2 W/ mK and electrical conductivity of 245 S cm 21 were obtained in the graphite filled polybenzoxazine at its maximum graphite loading. The obtained properties of the graphite filled polybenzoxazine composites exhibit most values exceed the United States department of energy requirements for PEMFC applications.

A novel polymer host from carboxymethyl cellulose (cMc)/poly(N-isopropylacrylamide) (pnipAM) was developed for a high safety solid polymer electrolyte (SPE) in a zinc ion battery. Effects of the PNiPAM loading level in the range of 0-40% by weight (wt%) on the chemical, mechanical, thermal, and morphological properties of the CMC/PNiPAMx films (where x is the wt% of PNiPAM) were symmetrically investigated. The obtained CMC/PNiPAMx films showed a high compatibility between the polymers. The CMC/PNiPAM20 blend showed the greatest tensile strength and modulus at 37.9 MPa and 2.1 GPa, respectively. Moreover, the thermal degradation of CMC was retarded by the addition of PNiPAM. Scanning electron microscopy images of CMC/PNiPAM20 revealed a porous structure that likely supported Zn 2+ movement in the SPEs containing zinc triflate, resulting in the high Zn 2+ ion transference number (0.56) and ionic conductivity (1.68 × 10-4 S cm −1). interestingly, the presence of PNiPAM in the CMC/PNiPAMx blends showed a greater stability during charge-discharge cyclic tests, indicating the ability of pnipAM to suppress dendrite formation from causing a short circuit. The developed CMC/PNiPAM20 based SPE is a promising material for high ionic conductivity and stability in a Zn ion battery. With the environmental concerns and the limitation of fossil fuels as well as the growing energy demands, the rechargeable battery is one kind of renewable energy sources which is consecutively developed for a sustainable energy supply. In spite of the most promising technology of lithium-ion batteries (LIBs), the zinc ion battery is used as a compelling alternative battery chemistry to LIBs for energy storage system 1-3 owing to its low cost, abundance, inflammability, low toxicity, promising energy density and environmental friendlier 4,5. The utilization of metal-ion batteries as power sources has led to exhaustive research on electrolyte systems with high electrochemical performance. It plays a significant role in battery electrochemistry that is the medium for the movement of ions within the batteries. Recently, solid polymer electrolytes (SPEs) have interested raised attention and enhanced research efforts as a fascinating alternative electrolyte bridge to liquid polymer electrolyte (LPEs) due to a lot of benefits, i.e., high durability, high energy density, lightweight, great flexibility for cell design, inert towards the electrodes, overcome the limitation of solvent leakage and low volatility, reduce the cell assembly cost, and great electrochemical and thermal stability 6. Fundamentally, SPEs consist of a dissolution of metal salts, e. g. lithium and zinc salt, in a host polymer, which the hopping process is used to describe the metal ions movement along the amorphous phase of polymer after the salts dissociate by interaction with the polar group of polymer 7. To coordinate with ions, therefore, the host polymer must contain electron donor groups such as O, N, and S. Moreover, it should

Novel shape memory polymers (SMPs) were prepared from benzoxazine-modified epoxy resin. Specimens consisting of aromatic epoxy (E), aliphatic epoxy (N), Jeffamine D230 (D) and BA-a benzoxazine monomer (B) were evaluated. The mole ratio of D/B was used as a mixed curing agent for an epoxy system with a fixed E/N. The effects of BA-a content on the thermal, mechanical and shape memory properties of epoxy-based shape memory polymers (SMPs) were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), flexural test and shape recovery test. The results revealed that the obtained SMPs exhibited a higher flexural strength and flexural modulus than those of the unmodified epoxy-based SMP at room temperature and at 20 • C above glass transition temperature (T g ). The presence of 1 mol BA-a as a curing agent provided the specimen with the highest T g , i.e. about 72 • C higher than that of epoxy-based SMP cured by Jeffamine D230. All SMP samples needed only a few minutes to fully recover to their original shape. The samples exhibited high shape fixity (98-99%) and shape recovery ratio (90-100%). In addition, the recovery stress values increased with increasing BA-a mole ratio from 20 to 38 kPa, when BA-a up to 1 mol ratio was added. All of the SMP samples exhibited only minimum change in their flexural strength at the end of a 100 recovery cycles test.

Highly filled polymer composites based on bisphenol-A/aniline based polybenzoxazine (PBA-a) and alumina particles were investigated. A very low A-stage viscosity of benzoxazine monomer gives it excellent processability exhibiting maximum alumina content as high as 83% by weight (60% by volume) which is one of the highest maximum packing values with negligible void contents. The storage modulus (E 0 ) at room temperature was increased from 5.93 GPa of the polybenzoxazine to 45.27 GPa of the composites. The significant high microhardness of the composites up to 1124 MPa was obtained and the behavior can be well predicted by the Halpin-Tsai model. Moreover, the modulus dependence of the composites on the alumina contents is well fitted by Lewis-Nielsen equation. Glass transition temperatures, degradation temperature, and solid residue of the composites also significantly increased with increasing the alumina contents. Finally, the scanning electron microscope of the composite fracture surface indicated a good distribution of the alumina particles in the PBA-a matrix. The resulting PBA-a/alumina composites are a highly attractive for an application that requires high modulus and hardness as well as high thermal stability. POLYM. COMPOS.,

Zinc ionic conducting-based gel polymer electrolytes (GPEs) were fabricated from carboxymethyl cellulose (CMC) and three different zinc salts in a mass ratio ranging within 0–30 wt%. The effects of zinc salt and loading level on the structure, thermal, mechanical, mechanical stability, and morphological properties, as well as electrochemical properties of the GPEs films, were symmetrically investigated. The mechanical properties and mechanical stability of CMC were improved with the addition of zinc acetate, zinc sulphate, and zinc triflate, approaching the minimum requirement of a solid state membrane for battery. The maximum ionic conductivity of 2.10 mS cm−1 was achieved with the addition of 15 wt% zinc acetate (ZnA), GPEA15. The supported parameters, indicating the presence of the amorphous region that likely supported Zn2+ movement in the CMC chains, were clearly revealed with the increase in the number of mobile Zn2+ carriers in FT-IR spectra and the magnitude of ionic transference number, the decrease of the enthalpy of fusion in DSC thermogram, and the shifting to lower intensity of 2θ in XRD pattern. The developed CMC/ZnA complex-based GPEs are very promising for their high ionic conductivity as well as good mechanical properties and the ability for long-term utilization in a zinc ion battery.

Abstract.A series of polymeric alloying films were prepared from bisphenol A/aniline-based bifunctional benzoxazine resin (BA-a) with three isomeric biphenyltetracarboxylic dianhydrides, i.e., 2,3!,3,4!-biphenyltetra carboxylic dianhydride (a-BPDA), 2,2!,3,3!-biphenyltetracarboxylic dianhydride (i-BPDA), and 3,3!,4,4!-biphenyltetracarboxylic dianhydride (s-BPDA) through fully thermal curing. Chemical structure, thermomechanical property and thermal stability of bisphenol A/aniline type polybenzoxazine (PBA-a) copolymers were evaluated. Their chemical structures analyzed via Fourier transform infrared spectroscopy reveal ester carbonyl linkage formation between hydroxyl group of the PBA-a and anhydride group in the isomeric dianhydride. Glass transition temperatures (T g s) of the dianhydride-modified PBA-a increased with PBA-a"<<"i-BPDA"<"a-BPDA"<"s-BPDA. Degradation temperatures (T d ) of the PBA-a copolymers recorded to be in the range of 365-402°C were significantly higher than that of the neat PBA-a i.e. 334°C. Finally, char yield of the PBA-a copolymers was found to be about 54-57% which is about twofold increase from that of the parent PBA-a.