Home About us Contact
|
Home About us Contact | ||
|
|
||
Dynamic Differential Scanning Calorimetry (dynamic + differential_scanning_calorimetry)
Selected AbstractsCure kinetics, phase behaviors, and fracture properties of bismaleimide resin toughened by poly(phthalazinone ether ketone)POLYMER ENGINEERING & SCIENCE, Issue 12 2009Yongjin Han Poly(phthalazinone ether ketone)s (PPEK) were used to toughen bismaleimide (BMI) resin composed of 4,4,-bismaleimidodiphenyl methane (BMDM) and O,O, -diallyl bisphenyl A (DABPA). Dynamic differential scanning calorimetry (DSC) of the blends was carried out for kinetic analysis of the curing reaction. The reaction activation energy indicated that the reaction mechanism remained the same even after the incorporation of PPEK. The reaction-induced phase separation process in BMI/PPEK blends was investigated by optical microscopy (OM). The primary phase structure of the blends was fixed at the early stage of phase separation, and a secondary phase separation was observed as a result of the high viscosity of the blends. Scanning electron microscope (SEM) graphs showed that the morphology of the cured resin changed from a dispersed structure to a phase-inverted structure with the increase of PPEK content. Compared with the neat resin, the fracture toughness of the modified resin exhibits a moderate increase when PPEK was incorporated. Several toughening mechanisms, such as local plastic deformation, crack deflection, and branches, presumably took part in improving the toughness of BMI/PPEK blends on the basis of the morphology. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Cure kinetics and conductivity of rigid rod epoxy with polyaniline as a curing agentPOLYMER COMPOSITES, Issue 10 2009Tiezhu Fu The samples of rigid rod epoxy resin (4,4,-diglycidyl (3,3,,5,5,-tetramethylbiphenyl) epoxy resin (TMBP)) with different weight contents of polyaniline (PANI) as a curing agent were prepared. The kinetics of curing reaction between TMBP and PANI was analyzed by dynamic differential scanning calorimetry in the temperature range of 25,300°C. The results showed that the heat of cure reaction of TMBP/PANI sample with 10 wt% PANI was larger than those of others. The active energies with different curing conversions of TMBP/PANI sample with 10 wt% PANI were calculated by iso-conversional method using the Coats-Redfern approximation. The results showed that the activation energy was dependent on the degree of conversion. The morphology of the cured samples was detected by scanning electron microscopy measurements. The relationship between morphology and conductivity of cured samples was researched. The conductivities increased from 2.7 × 10,4 to 9.5 × 10,4 S/cm with the increase of PANI from 5 to 20 wt% in cured samples. The thermal stabilities of cured TMBP/PANI samples were examined by thermogravimetric analysis. The results showed that the cured TMBP/PANI can be promising to use as a conducting adhesive. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] The unidirectional glass fiber reinforced furfuryl alcohol for pultrusion.POLYMER COMPOSITES, Issue 6 2008The development of unidirectional glass fiber reinforced furfuryl alcohol (FA) composites has been conducted using an in situ polymerization method. The FA prepolymer synthesized in this study was prepared from blends of FA monomer and catalyst (p -toluene sulfonic acid). The process feasibility, and kinetic analysis of the unidirectional glass fiber reinforced FA composites by pultrusion has been investigated. From the investigations of the long pot life of FA prepolymer, the high reactivity of FA and FA/glass fiber, and excellent fiber wet-out of FA resin and glass fiber, it was found that the FA resin showed excellent process feasibility for pultrusion. A kinetic autocatalytic model, d,/dt = A exp(,E/RT),m(1,,)n, was proposed to describe the curing behavior of FA/glass fiber composites. Kinetic parameters for the model were obtained from dynamic differential scanning calorimetry scans using a multiple regression technique. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Epoxy nanocomposites: Analysis and kinetics of curePOLYMER ENGINEERING & SCIENCE, Issue 6 2004M.-T. Ton-That The effect of organo-nanoclay (Nanomer I30E) on the cure mechanism and kinetics of epoxy nanocomposites based on Epon 828 and Epicure 3046 was studied by means of dynamic differential scanning calorimetry (DSC) at four heating rates (2.5, 5, 10, and 20°C·min,1) and by Fourier transform infrared (FT-IR) spectroscopy. The DSC cure data for epoxy-amine mixtures with and without nanoclay was modeled by means of different approaches; the Kissinger and isoconversional models were used to calculate the kinetics parameters while the Avrami model was utilized to compare the cure behavior of the two systems. The Nanomer I30E was shown to initiate rapid homopolymerization of the Epon 828 resin at temperatures above 180°C. For the epoxy-amine mixtures, the presence of nanoclay had little effect on the cure kinetics in the early stages (i.e., at lower temperatures), and the apparent activation energy was around 60 kJ·mol,1. However, in the later stages, the apparent activation energy increased significantly in the absence of nanoclay, but did not do so when it was present. The presence of nanoclay also lowered the final glass transition temperature by about 4°C. Polym. Eng. Sci. 44:1132,1141, 2004. © 2004 Society of Plastics Engineers. [source] Curing of diglycidyl ether of bisphenol-A epoxy resin using a poly(aryl ether ketone) bearing pendant carboxyl groups as macromolecular curing agentPOLYMER INTERNATIONAL, Issue 8 2009Fuhua Liu Abstract BACKGROUND: Reactive thermoplastics have received increasing attention in the field of epoxy resin toughening. This paper presents the first report of using a novel polyaryletherketone bearing one pendant carboxyl group per repeat unit to cure the diglycidyl ether of bisphenol-A epoxy resin (DGEBA). The curing reactions of DGEBA/PEK-L mixtures of various molar ratios and with different catalysts were investigated by means of dynamic differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy methods. RESULTS: FTIR results for the DGEBA/PEK-L system before curing and after curing at 135 °C for different times demonstrated that the carboxyl groups of PEK-L were indeed involved in the curing reaction to form a crosslinked network, as evidenced by the marked decreased peak intensities of the carboxyl group at 1705 cm,1 and the epoxy group at 915 cm,1 as well as the newly emerged strong absorptions of ester bonds at 1721 cm,1 and hydroxyl groups at 3447 cm,1. Curing kinetic analysis showed that the value of the activation energy (Ea) was the highest at the beginning of curing, followed by a decrease with increasing conversion (,), which was attributed to the autocatalytic effect of hydroxyls generated in the curing reaction. CONCLUSION: The pendant carboxyl groups in PEK-L can react with epoxy groups of DGEBA during thermal curing, and covalently participate in the crosslinking network. PEK-L is thus expected to significantly improve the fracture toughness of DGEBA epoxy resin. Copyright © 2009 Society of Chemical Industry [source] | ||||||||||