Star-shaped arylacetylene resins derived from silicon

Star-shaped arylacetylene resins, tris(3-ethynyl-phenylethynyl)methylsilane, tris(3-ethynyl-phenylethynyl) phenylsilane, and tris (3-ethynyl-phenylethynyl) silane (TEPHS), were synthesized through Grignard reaction between 1,3-diethynylbenzene and three types of trichlorinated silanes. The chemical structures and properties of the resins were characterized by means of nuclear magnetic resonance, fourier-transform infrared spectroscopy, Haake torque rheomoter, differential scanning calorimetry, dynamic mechanical analysis, mechanical test, and thermogravimetric analysis. The results show that the melt viscosity at 120 °C is lower than 150 mPa⋅s, and the processing windows are as wide as 60 °C for the resins. The resins cure at the temperature as low as 150 °C. The good processabilities make the resins to be suitable for resin transfer molding. The cured resins exhibit high flexural modulus and excellent heat-resistance. The flexural modulus of the cured TEPHS at room temperature arrives at as high as 10.9 GPa. Its temperature of 5% weight loss (Td5) is up to 697 °C in nitrogen. The resins show the potential for application in fiber-reinforced composites as high-performance resin in the field of aviation and aerospace.

Fabrication of Ultrafine PPS Fibers with High Strength and Tenacity via Melt Electrospinning

Electrospinning (e-spinning) is an emerging technique to prepare ultrafine fibers. Polyphenylene sulfide (PPS) is a high-performance resin which does not dissolve in any solvent at room temperature. Commercial PPS fibers are produced mainly by meltblown or spunbonded process to give fibers ~20 μm in diameter. In this research, an in-house designed melt electrospinning device was used to fabricate ultrafine PPS fibers, and the e-spinning operation conducted under inert gas to keep PPS fibers from oxidizing. Under the optimum e-spinning conditions (3 mm of nozzle diameter, 30 kV of electrostatic voltage, and 9.5 cm of tip-to-collector distance), the as-spun fibers were less than 8.0 μm in diameter. After characterization, the resultant PPS fibers showed uniform diameter and structural stability. Compared with commercial PPS staple fibers, the obtained fibers had a cold crystallization peak and 10 times higher storage modulus, thereby offering better tensile tenacity and more than 400% elongation at break.

Curing behaviors and properties of epoxy and self-catalyzed phthalonitrile with improved processability

The curing behaviors for high-performance resin system phthalonitrile-containing benzoxazine and epoxy (BA-Ph/EP), particularly the effect of the binary system composition and processing conditions on their processabilities were investigated and discussed in this article. Results indicated that all BA-Ph/EP prepolymers exhibited low initial processing viscosity (<0.3 Pa s) and have kept stable low viscosity until gel transition. The suitable molding temperature (ranged from 150°C to 180°C) and molding time (ranged from 20 min to 80 min) could be selected for practical applications of BA-Ph/EP systems. The studies of curing behaviors and gelatinization for BA-Ph/EP systems give further understanding of the curing kinetics and guidance for the fabrication of high-performance copolymers/polymers. The introduction of EP could significantly improve the cross-linking density of BA-Ph/EP polymers, and the appropriate content of EP is the key fact for the improvement. In addition, the effects of postcuring conditions on thermal properties and the adhesive property of BA-Ph/EP polymers were monitored. The thermal stabilities and adhesive property of various polymers also showed an obvious influence with the introduction of EP. The systematic study of BA-Ph/EP system could enable a broadened industrial application, especially in the areas that require high-temperature resistance.

Composite Materials Manufacturing Processes

— Using Composite materials are growing more and more today and we have to use them in possible situation. One of the Composite materials applications is on the Airplane and aero space. Reduction of Airplane weight and more adaptability with nature are examples of benefit of using composite materials in aerospace industries. In this article process of manufacturing of composite materials and specially carbon fiber composite are explained. Advance composite materials are common today and are characterized by the use of expensive, high-performance resin systems and high-strength, high-stiffness fiber reinforcement. The aerospace industry, including military and commercial aircraft of all types, is the major customer for advanced composites. Product range now includes materials for low pressure and low temperature. Some using composite materials in aero space are as follow: Satellite Components, Thin Walled Tubing for Aircraft and Satellites, launch vehicle components and honeycomb structures.

Effects of Modified Carbon Nanotubes on Curing and Mechanical Properties of N-Phenyl Maleimide/Bismaleimide Composites

One kind of bismaleimide resin (BMI) was prepared from Michael addition reaction with modification carbon nanotubes (m-CNTs). CNTs were modified by N-phenyl maleimide (N-PMI) and ethylenediamine. The effect of modification was determined by NMR spectra and Raman Analyser. The cure kinetics, thermal behavior and mechanical property of carbon nanotubes/bismaleimide-o,o-diallyl bisphenol A resin (CNTs/BMI-BA) were studied. It was found that this kind of CNTs can be easily dispersed in high performance resin only with a slight stirring. The curing apparent activation energy (Ea) decreased with the increasing amount of m-CNTs. The maleimide-CNTs could fully express its unique mechanical properties and dramatically increase the reaction activity, the storage modulus, impact strengths and bending stress of the CNTs/BMI-BA composites while the CNTs-COOH reduce the important mechanical properties. These critical enhancements will definitely help to attract more researches in this field.

Rheological Behaviors Characterization and Modeling of a Novel Three-Branched Phenylethynyl-Terminated Imide Oligomer

To prepare novel polyimides with enhanced thermal stability and low melt viscosity, a novel three-branched phenylethynyl-terminated imide oligomer was introduced. The oligomer can be used to prepare high performance resin-based composite material via resin transfer molding (RTM) due to its low melt viscosity (<2Pa.s) between 250°C and 320°C. The cured resin exhibits excellent thermal stability and higher glass transition temperature than PETI series as a result of the introduction of star-branched units. In this research, the rheological properties of the oligomer were measured and numerically fit with the dual Arrhenius model to predict the progression of the viscosity during cure. The calculated kinetic activation energies for gelation with two different Arrhenius equations, 120.8kJ/mol and 164kJ/mol, respectively,had some differences. The numerical results were compared with the experimental measurements, and it was found that the model predicts the experimental observations quite well.

Synthesis and Cure Kinetic Studies of a New Trifunctional Imide Oligomer

A novel phenylethynyl-terminated imide oligomer was prepared from a trifunctional amine and 4-phenylethynylphthalic anhydride (PEPA). The oligomer can be used to prepare the high performance resin-based composite material via resin transfer molding (RTM) due to its low melt viscosity(<2Pa.s) between 250°C and 320°C.The cured resin exhibits excellent thermal stability than PETI series as a result of the introduction of star-branched units. The thermal analysis of the curing kinetics of resin was carried out by differential scanning calorimetry (DSC), with the rate of cure reaction and the degree of cure calculated in the dynamic mode and being tested under isothermal conditions. A reasonable agreement between the experimental data and the kinetic model has been obtained over the whole processing temperature range which was important for processing simulation and quality control of processing for high performance composite.