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In this work, this study aimed to overcome the inherent disadvantage of low thermal stability and brittleness of epoxy resins. A novel modifiers containing alkynyl‐ and allyla‐ groups, (E)‐1‐(4‐(allyloxy)‐3‐methoxyphenyl)‐N‐(3‐ethynylphenyl)methanimine (MNEM) was prepared and confirmed by Fourier transform infrared spectroscopy (FTIR) and 1H‐nuclear magnetic resonance (1H NMR), and selected to improve the thermal stability and toughness of bisphenol A‐type epoxy resin (E51). The blend resins were produced by blending with different contents of MNEM into E51 resin, named E‐MNEM resins. Meanwhile, the thermal stability, mechanical properties, and micromorphology of E‐MNEM blends were analyzed in details. It was found that the thermal stability of E‐MNEM resins was improved by increasing the proportion of MNEM. Compared with E‐0MNEM resin, when the MNEM concentration reached 40 wt%, the char yield (Yc) increased from 14.95 to 29.62%, reflecting a 98.1% improvement. In addition, an appropriate concentration of MNEM could be conductive to improving the mechanical properties. An improvement of 25.5 and 7.1% in elongation and tensile strength along with the maximum value of 17.6 kJ/m2 for the impact strength was achieved by the cured E‐MNEM resins containing 20 wt% of MNEM. Finally, the fracture surface morphology of the E‐MNEM resins was analyzed by the scanning electron microscope (SEM). [ABSTRACT FROM AUTHOR]

In the current study, three different curing kinetics models were used to analyze the curing kinetics of hyperbranched benzoxazine (HB‐PED230) and monofunctional benzoxazine (P‐a) modified cyanate ester (CE) resin by non‐isothermal differential scanning calorimeter. Moreover, the effects of two benzoxazines on the copolymerization behavior, thermal stability, and mechanical properties of CE resin were studied. Compared with the P‐a modified CE resin, HB‐PED230 greatly reduces the curing temperature of the copolymer, while improving the bending strength and impact strength. The curing temperature of HB‐PED230 modified CE resin was 79°C lower than neat CE resin, while the CE/P‐a blended resin only reduce 48°C. As the amount of HB‐PED230 increased, the flexural strength and flexural modulus of the copolymers were improved. Surprisingly, when 7 wt% of HB‐PED230 was added, the impact strength of the copolymer was increased by 177.6%, implying that the toughness of CE resin had been greatly improved. Moreover, the fracture morphology of the copolymers was observed by scanning electron microscope. In summary, a small amount of HB‐PED230 blending can effectively improve the overall performance of CE resin. [ABSTRACT FROM AUTHOR]

The current research work presents a novel nonionic curing agent (AEDA) synthesized by utilizing ethylene glycol diglycidyl ether (EGDE), 3,4‐dimethoxyaniline (DI), and triethylenetetramine (TETA). Infrared spectroscopy and nuclear magnetic resonance spectroscopy were used to characterize the structure of AEDA curing agent. Non‐isothermal scanning calorimetry was used to determine the activation energy and curing conditions of epoxy resin in the curing process. An impact testing machine, a tensile testing machine and a scanning electron microscope (SEM) were used to analyze the impact strength, tensile strength, bending strength, and micromorphology of the AEDA/E‐51 system with different mass ratios. The results show that AEDA is an effective high‐temperature curing agent. For the AEDA/E‐51 system with the optimal mass ratio of 10:100, the best curing temperature is 92.15°C, and the post‐curing temperature is 135.65°C. Furthermore, the apparent activation energy (Ea) of 1670 J/mol, the pre‐exponential factor (A) of 3.7 × 10−4, and the reaction series (n) value of 0.76 are obtained for the AEDA/E‐51 system. The impact strength of AEDA/E‐51 epoxy resin polymer is 7.82 kJ/m2, tensile strength is 14.2 MPa, and bending strength is 18.92 MPa. The micromorphological results of the AEDA/E‐51 system are consistent with the results of DSC test and mechanical properties test. Hence, this study provides theoretical support for the practical applications of AEDA as curing agent. [ABSTRACT FROM AUTHOR]

In this study, it was aimed to investigate octavinyl‐polyhedral oligomeric silsesquioxane (OV‐POSS) incorporation into natural rubber (NR)/butadiene rubber (BR) elastomer blends as a potential compatibilizer. The effects of OV‐POSS loading levels on the thermal, mechanical, morphological, and dynamic‐mechanical properties of elastomer blends were explored. Fourier‐Transform Infrared Spectrometer (FTIR), Temperature Scanning Stress Relaxation (TSSR), and Differential Scanning Calorimetry (DSC) results revealed the conceivable effect of OV‐POSS nanoparticles in the vulcanization through reacting with sulfur and/or elastomers. Scanning Electron Microscope (SEM), X‐Ray Diffraction (XRD), and tensile test measurements supported the improvement of mechanical properties due to homogeneous dispersion at low loading levels. On the other hand, high amount of OV‐POSS incorporation (7 and 10 phr) resulted in a decrease in mechanical properties, owing to the agglomeration of nanoparticles. According to contact angle and Dynamic mechanical analysis (DMA) results, it could be concluded that OV‐POSS nanoparticles were localized at the interface of the elastomers and enabled the compatibilization of immiscible NR/BR blends. [ABSTRACT FROM AUTHOR]

Membranes require superior mechanical strength due to applied harsh conditions. The mechanical properties of membranes decrease with increasing hydrophilicity of its elements. In this study, mechanical properties were investigated for two special blended membranes which were made by blending polysulfone with (polysulfone‐g‐poly (n‐butylacrylate) and polysulfone‐g‐poly (tert‐butylacrylate) as components. All of the prepared membranes were characterized by differential scanning calorimeter, thermal gravimetric analysis, field emission scanning electron microscope, and atomic electron microscope and were investigated in terms of pure water flux, water contact angle, molecular weight cut off, and morphology. It was found that water contact angle decreased from 73.6° which belongs to neat membrane decreased to 46° for blended membranes containing higher amounts of copolymers; however, the pure water flux increased with increasing copolymer content considerably compared with the neat membrane. Also, molecular weight cut off increased aggressively. Furthermore, mechanical properties including tensile strength, Young modulus, and elongation at break were measured and compared with the neat polysulfone membrane. Results showed that the tensile strength and modulus decreased with an increase in the copolymers content, despite the increase in the elongation at break. The effect of applied pressure on the membrane structure and also bursting strength were studied, and it has been proved that not only the structure of the membranes but also their performance is strongly affected by the composition of the membranes. [ABSTRACT FROM AUTHOR]

Three kinds of poly(urea-formaldehyde) (PUF) microcapsules filled with epoxy resins (MCEs) were applied to bismaleimide (BMI)/ O,O′-diallyl bisphenol A (BA) system to develop novel fiber reinforced BMI/BA/MECs composites. The effects of MCEs on the mechanical properties, the hot-wet resistance, and the dynamic mechanical properties of fiber reinforced BMI/BA composites were investigated. The morphologies of fiber reinforced BMI/BA/MCEs composites were characterized by scanning electron microscope (SEM) and optical microscope (OM). Results indicate that the appropriate contents of MCEs can significantly improve the mechanical properties and the hot-wet resistance of fiber reinforced BMI/BA composites. In this study, MCEs may decrease the storage modulus of fiber reinforced BMI/BA composite but they have no significant influence on the glass transition temperature ( Tg) of the composite. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Polypropylene + low density polyethylene (PP + LDPE) blends involving 0, 25, 50, 75 and 100 wt% of PP with dialkyl peroxide (DAP) were prepared by melt blending in a single-screw extruder. The effects of adding dialkyl peroxide on mechanical and thermal properties of PP + LDPE blends have been studied. It was found that at lower concentrations of peroxide (e.g., 0-0.08 wt% of dialkyl peroxide) LDPE component is cross-linked and Polypropylene (PP) is degraded in all compositions of PP + LDPE blends. Mechanical properties (Tensile strength at break, at yield and elongation at break), Melt flow index (MFI), hardness, Scanning Electron Microscope (SEM) and thermal analyses (DSC) of these blends were examined. Because of serious degradation or cross-linking the mechanical properties and the crystallinty (%) of those products were decreased as a result of increasing peroxide content. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]