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1.
Polybutadiene (PB) was epoxidized to various extens withm-chloroperbenzoic acid (MCPBA) in homogeneous solution. The thermal properties of the epoxidized PBs were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). As a result of epoxidation the glass transition temperature (T g) of PB increased by approximately 0.8°C for each 1 mol% of epoxidation. The thermal decomposition of the epoxidised PBs occurred in twostep process, while that of PB exhibited apparent one-step degradation process.  相似文献   

2.
A series of copolyesters (Co-PETs) containing poly(ethylene glycol) (PEG), 5-sodiumsulfodimethyl isophthalate (DMS), and dimethyl isophthalate (DMI) were synthesized via the conventional two-step melt-polycondensation method. The synthesized Co-PETs were characterized by 1H-NMR spectroscopy, FT-IR spectroscopy, differential scanning calorimeter (DSC), and thermogravimetric analyzer (TGA). The DSC results showed that the melting temperature (T m) and the heats of fusion (ΔH m) of Co-PETs decreased with increasing the DMS content in Co-PET, while the inclusion of PEG did not affect their thermal properties significantly. The water absorption and the water contact angle of the Co-PET films were found to be significantly affected by the DMS content rather than PEG content. The moisture-related cooling properties of the fabric samples made of Co-PET 5 as well as PET were evaluated by using liquid moisture management tester (MMT) and Q max measurements. The MMT and Q max results indicated that Co-PET 5 fabric containing DMS 1.0 mol% and PEG 10.0 wt% in Co-PET seemed to be a good candidate for the fabric having durable cooling effects.  相似文献   

3.
Poly(ethylene 2,6-naphthalate) (PEN)/Poly(ethylene glycol) (PEG) copolymers were synthesized by two step reaction during the melt copolymerization process. The first step was the esterification reaction of dimethyl-2,6-naphthalenedicarboxylate (2,6-NDC) and ethylene glycol (EG). The second step was the condensation polymerization of bishydroxyethylnaphthalate (BHEN) and PEG. The copolymers contained 10 mol% of PEG units with different molecular weights. Structures and thermal properties of the copolymers were studied by using1H-NMR, DSC, TGA, etc. Especially, while the intrinsic viscosities of PEN/PEG copolymers increased with increasing molecular weights of PEG, but the glass transition temperature, the cold crystallization temperature, and the weight loss temperature of the copolymers decreased with increasing molecular weights of PEG. Consequently, the hydrophilicities by means of contact angle measurement and moisture content of the copolymer films were found to be significantly improved with increasing molecular weights of PEG.  相似文献   

4.
An investigation on the role of cupric (Cu2+) ion incorporation during the thermal stabilization of polyamide 6 fibers was carried out using a combination of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) measurements. Cupric chloride pretreated and thermally stabilized polyamide 6 (PA6) fibers was characterized by a reduction in fiber diameter and linear density values together with color changes from light brown to black with increasing stabilization time. PA6 fibers were properly stabilized after 8 h of stabilization time prior to carbonization. The results obtained from DSC and TGA measurements indicated that there was an improvement in the thermal stability when cupric (Cu2+) ions were incorporated into the polymer structure. TGA thermograms showed the relative improvement in thermal stability as indicated by increasing char yield with progressing time. Char yield reached a maximum value of 33.6 % at 1000 °C for the cupric chloride pretreated PA6 fibers stabilized for 12 h at 180 °C. Experimental results obtained from DSC and X-ray diffraction methods suggested the loss of crystallinity as a result of perturbation of hydrogen bonds with progressing time. The formation of cupric ion-amide coordination bonds improved the thermal stabilization by encouraging the development of ladder-like structures. The investigation resulted in a new method of evaluation of X-ray stabilization index specifically intended for the thermally stabilized PA6 fiber.  相似文献   

5.
Polyhydroxyamides derivatized with trifluoromethyl ether and trifluoromethyl ester groups were investigated as possible candidates for a new flame retardant polymer. Model compounds for these derivatized polyhydroxyamides were synthesized and their cyclization chemistry was investigated. The model compound study revealed that trifluoromethyl ester group containing model compounds can cyclize on heating, while trifluromethyl ether group containing model compounds cannot. The non-fluorinated ester and ether derivatives behaved similarly. The trifluoromethyl ester derivatized polyhydroxyamides were synthesized according to the procedures for the model compounds. TGA characterization revealed that the fluorinated polymers have nearly same thermal stability as the underivatized PHA after cyclization.  相似文献   

6.
The effect of boron phosphate (BPO4) nanoparticles on the mechanical, thermal, and flame retardant properties of polypropylene (PP) and polyamide 6 (PA-6) fibers are investigated by tensile testing, thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), and micro combustion calorimeter (MCC). The addition of BPO4 reduces the mechanical properties of the both PP and PA-6 fibers. According to the TGA results, the addition of BPO4 does not change the thermal behavior of PP fiber and slightly reduces the thermal stability of PA-6 fiber by about 30 °C. According to MCC results, the addition of BPO4 does not change the effective total heat evolution and heat release rate (HRR) peak for PP fibers. Although the inclusion of BPO4 does not change the total heat evolution of PA-6 fiber, it reduces the HRR peaks due to increase in barrier effect of char.  相似文献   

7.
A novel phosphorus-containing flame retardant plasticizer (PFRP) derived from castor oil acid methyl ester (COME) was synthesized to substitute dioctyl phthalate (DOP) for plasticizing polyvinyl chloride (PVC) products. The chemical structures of PFRP were confirmed by fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H NMR). Meanwhile, the plasticizing effect, flammability and thermal stability of plasticized PVC films were investigated by dynamic mechanical analyzer (DMA), limiting oxygen index (LOI) test, scanning electron microscope (SEM) and thermogravimetric analysis (TGA). As the PFRP content increasing from 0 wt% to 50 wt% amount of plasticizers, the plasticizing efficiency and the mechanical properties showed a slightly decreasing tendency compared with that of DOP, while the LOI value of plasticized PVC increased remarkably from 21.5 % to 25.2 %, showing a combined plasticizing efficiency and flame retardancy. SEM and TGA analysis indicated that PFRP had little effect on thermal stability but was effective to promote the formation of compact carbon residue.  相似文献   

8.
This study evaluates the influence of different silane coupling agents on the thermal and physical properties of epoxy-anhydride composite reinforced with basalt fiber. The silane coupling agents were selected by their functional groups so that they could have different chemical interactions with the epoxy and anhydride curing agents. The thermal and degradation behavior of the composites with different fiber contents were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Through the evaluation of T g and thermal degradation behavior of both systems, it was deduced that the silane coupling agents have a great influence on the thermal properties of the composites as well as interfacial improvement. Also, the tensile properties of the composites were systematically evaluated in order to further understand the effect of silane coupling agents on the interaction with basalt fiber and epoxy matrix.  相似文献   

9.
We report the preparation of polybenzoxazole (PBO) fiber from polyhydroxyamide (PHA) precursor fiber which is free from strong acid such as polyphosphoric acid. We prepared the PHA fibers with different spin-draw ratios (SDRs) using a wet-spinning method and the PBO fibers with an SDR of 3.5 (SDR-3.5 PBO fibers) were prepared by various heat-treatment temperatures, and investigated their morphology, crystalline structure, and mechanical properties. The simultaneous thermogravimetric analysis-mass spectrometry (STA-MS) and field-emission scanning electron microscopy (FE-SEM) results confirmed that the diameter of the SDR-3.5 PBO fiber was much smaller than that of the SDR-3.5 PHA fiber, due to the release of water during the thermal cyclization reaction which forms the PBO structure. The wide-angle Xray diffraction (WAXD) pattern of the SDR-3.5 PBO fiber heat-treated at 350 °C (SDR-3.5 PBO 350 fiber) showed two peaks, at 2θ=14.83 ° and 24.38 °, and the diffraction angles dropped with increasing heat-treatment temperature. In addition, the initial modulus and tensile strength of the SDR-3.5 PBO fiber heat-treated at 550 °C (SDR-3.5 PBO 550 fiber) were found to be 19.1 GPa and 449.2 MPa, which were much higher than those of the SDR-3.5 PHA fiber, 9.3 GPa and 227.0 MPa, respectively.  相似文献   

10.
A series of monophenyl borate (MPB) modified high-ortho phenolic copolymer fibers (BOPFs) were prepared by melt-spinning of the high-ortho phenol-formaldehyde resins with different content of MPB, and cured in a formaldehyde solution. The solution curing fibers were heated up to 240 °C at elevated temperatures in N2. The effect of MPB on the structure and properties of the BOPFs was investigated by Fourier transform infrared spectrometer (FTIR), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The results show that a B-O linkage inserts into the high-ortho phenolic copolymer molecular chain with the addition of MPB, and increases the crosslinkage and thermal stability. The peak of O/P (ortho/para) value of fiber (1.94) and elongation (5.6 %) were obtained when BOPFs-4 was heat-cured at 240 °C for 2 h.  相似文献   

11.
Poly(trimethylene 2,6-naphthalate) (PTN)/poly(ethylene glycol) (PEG) copolymers were synthesized by the two-step melt copolymerization process of dimethyl-2,6-naphthalenedicarboxylate (2,6-NDC) with 1,3-propanediol (PD) and PEG. The copolymers produced had different PEG molecular weights and contents. The structure, thermal property, and hydrophilicity of these copolymers were studied by proton nuclear magnetic resonance (1H-NMR) analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and by contact angle, moisture content, and instantaneous elastic recovery measurements. The intrinsic viscosity and the instantaneous elastic recovery of the PTN/PEG copolymers increased with increasing PEG molecular weight and content, whereas the glass transition, melting, and cold crystallization temperatures, and the heat of fusion of the PTN/PEG copolymers all decreased with increasing PEG molecular weight or content. The thermal stability of the copolymers was not affected by PEG molecular weight or content. The hydrophilicity, as determined by contact angle and moisture content measurements of the copolymer films, was significantly improved with increasing PEG molecular weight and content.  相似文献   

12.
Thermal regulating fiber has been a research hotspot worldwide recently. In this paper, the energy storage microcapsules composed of silicon dioxide (SiO2) as shell and paraffin as core were synthesized in the spinning solution of polyvinyl alcohol (PVA). This solution was used to prepare thermal regulating PVA fibers by wet spinning directly. Orthogonal experiment was conducted to optimize the synthetic conditions of the microcapsules. Chemical structure and morphology of the fibers were characterized by Fourier transform infrared-attenuated total reflectance (FTIR-ATR) and scanning electron microscope (SEM) respectively. The thermal properties of the fibers were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Results present that energy storage microcapsules are successfully synthesized in PVA spinning solution with a mean particle size of 1.39 µm. The fibers containing such microcapsules show a high latent heat storage density of 45.39 J g?1, which also achieve a relatively better thermal stability.  相似文献   

13.
Epoxidized polybutadiene (EPB) was prepared by polybutadiene (PB) withm-chloroperbenzoic acid (MCPBA) in homogeneous solution. EPB was blended with poly(3-hydroxybutyrate) (PHB) up to 30 wt% by solution-precipitation procedure. The thermal decomposition of PHB/EPB blends was studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and differential thermal analysis (DTA). The thermograms of PHB/EPB blends contained a two-step degradation process, while that of pure PHB sample exhibited only one-step degradation process. This degradation behavior of PHB/EPB blends, which have a higher thermal stability as measured by maximum decomposition temperature and residual weight, is probably due to crosslinking reactions of the epoxide groups in the EPB component with the carboxyl chain ends of PHB fragments during the degradation process, and the occurrence of such reactions can be assigned to the exothermic peaks in their DTA thermograms.  相似文献   

14.
The ultrafine composite fibers consisting of lauric acid (LA) and polyamide 6 (PA6) as form-stable phase change materials (PCMs), were prepared successfully by electrospinning. The effect of carbon nanotubes (CNTs) on the structural morphology, phase change behaviors, thermal stability, flammability and thermal conductivity properties of electrospun LA/PA6 composite fibers was investigated by field-emission scanning electron microscopy (FE-SEM), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), microscale combustion calorimeter (MCC) and melting/freezing times measurements, respectively. SEM observations indicated that the LA/PA6 and LA/PA6/CNTs composite fibers possessed flat and ribbon-shaped morphologies, but the neat PA6 fibers had cylindrical shape with smooth surface; and the average fiber diameters for LA/PA6 composite fibers decreased generally with the addition of CNTs. DSC measurements indicated that the heat enthalpies of the composite fibers were lower that that of neat LA powders, while the amounts of CNTs had no appreciable effect on the phase change temperatures and heat enthalpies of the composite fibers. TGA results showed that the addition of CNTs increased the onset thermal degradation temperature, maximum weight loss temperature and charred residue at 700 °C of the composite fibers, attributed to the improved thermal stability properties. It could be found from MCC tests that there were two-step combustion processes for composite fibers, and corresponded respectively to combustion of LA and polymer chains (PA6) in composite fibers. The addition of CNTs reduced the peak of heat release rate (PHRR) of electrospun composite fibers, contributing to the decreased flammability properties. The improved thermal conductivity performances of LA/PA6/CNTs composite fibers was also confirmed by comparing the melting/freezing times of LA/PA6 composite fibers with that of neat LA powders. The results from the SEM observation showed that the composite fibers had no appreciable variations in shape and diameter after heating/cooling processes.  相似文献   

15.
Structural transformations taking place during the thermal stabilization of polyacrylonitrile (PAN) fiber used for the production of carbon fiber were characterized using a combination of polarized infrared spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and density measurements. Direct relationship between the increasing oxygen content and the density values was confirmed with increasing stabilization time. Linear density values were found to be directly influenced by the stabilization time. Thermal stability of stabilized precursor fibers was evaluated in terms of weight loss and residual weight fraction. The results showed that a residual weight fraction of 65 % at 1000 °C can be obtained but longer stabilization time resulted in a loss of residual weight fraction due to excessive thermal degradation. SEM was used for the observation of surface morphological features of stabilized precursor fibers. Polarized infrared spectroscopy showed the loss of molecular orientation of methylene (CH2), nitrile (Ct=N), and carbonyl (C=O) groups in direct response to the effects of cyclization, dehydrogenation, and amorphization (i.e. decrystallization) processes taking place during the stabilization stage.  相似文献   

16.
A comparison study of the phase transition and structure of waxy cornstarch in DMSO and AMIMCl systems was conducted using a differential scanning calorimeter, an optical microscope, a scanning electron microscope, X-ray diffraction and thermogravimetric analysis. A full disruption and dissolution of starch granules was completed in 10 h at room temperature in pure DMSO, which was faster and more effective than that in ionic liquid 1-allyl-3-methylimidazolium chloride (AMIMCl). When dispersed in DMSO/water and AMIMCl/water at various ratios, respectively, different phase transitions were clearly exhibited, and the appearance and crystal structure of starch granules were significantly damaged with an increase in the concentration. Basing on the study of the decomposition temperature change through TGA measurements, a decreased temperature was observed in both DMSO and AMIMCl system, meaning starch degradation occurred with different levels. The huge temperature change from 357 to 328 °C were found in AMIMCl system, which most likely induced the distinct exothermic phenomenon in the DSC observation due to a significant depolymerization of starch.  相似文献   

17.
In this paper, polyester fabric was modified through synthesis and fabrication of Cu/Cu2O nanoparticles using a facile and cost-effective method at boil by chemical reduction through exhaustion route. Triethanolamine (TEA) was used for aminolysis of polyester fabric and pH adjusting, copper sulfate (CuSO4) as metal salt, sodium hypophosphite (SHP) as reducing agent and polyvinylpyrrolidone (PVP) as stabilizer. A response surface methodology was also employed to optimize the reaction conditions and study the effects of SHP, PVP and TEA concentrations in the processing. The images of field-emission scanning electron microscopy (FESEM), the patterns of energy-dispersive spectroscopy (EDX) and X-ray diffraction (XRD) patterns confirmed successfully synthesis of Cu and Cu2O nanoparticles on the polyester fabric. Further, the thermal behavior of the untreated and treated fabrics was studied by using thermogravimetric analysis (TGA) and differential scanning colorimetry (DSC). The treated fabrics indicated good properties regarding wettability and flame-retardant along with high tensile strength.  相似文献   

18.
Three low-cost types of complex solvents systems were carried out to dissolve cellulose, which were NaOH/urea/acetamide, NaOH/urea/tetraethyl ammonium chloride, and NaOH/acetamide/tetraethyl ammonium chloride. As an effective dissolution, NaOH/acetamide/tetraethyl ammonium chloride behaved as the optimum system, and the solubility was 89 % under the conditions of: NaOH 8 wt%, acetamide 10 wt%, tetraethyl ammonium chloride 6 wt%, distilled water 76 wt%, and freezing temperature ?5°C. With the analysis of Ubbelohde viscometer, infrared spectra (FTIR), wide-angle X-ray diffraction (XRD), and thermogravimetric analysis (TGA) for the original and regenerated cellulose samples, it was indicated that the viscosity-average molecular weight had no significant changes in the dissolution process, the crystalline structure of cellulose was converted to cellulose II from cellulose I in native cellulose, and the regenerated cellulose had a good thermal stability.  相似文献   

19.
Poly(ethylene terephthalate) (PET) copolymers containing fluorenylidene bis(2-phenoxyethanol) (FBPE) were prepared. The glass transition temperature of copolymers increased continuously with the composition of FBPE. The glass transition temperature of PET/FBPE copolymer at loading of 15 mol% FBPE was 107 °C, which was 35 °C higher than that of PET. The melting temperature of PET/FBPE copolymers was decreased with the composition of FBPE, and it disappeared above 6 mol% of FBPE. The heat deflection temperature of copolymers increased from 60.7 °C for PET to 89.9 °C for the copolymer containing 15 mol% of FBPE. The values of optical transmittance of copolymers were 89-90 % at 550 nm, and no significant change was observed with the FBPE composition. The impact strength value of copolymer at loading of 10 mol% FBPE was 26 J/m, which was 20 J/m higher than that of PET.  相似文献   

20.
The Allyl-heptaisobutyl-polyhedral oligomeric silsesquioxane (AHO-POSS) grafted polypropylene (PP) was prepared by reactive extrusion and by physical blending routes. The structure and properties of physically blended and reactively blended POSS/PP nanocomposites were investigated by FTIR, wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis, SEM, spherutlic growth and mechanical properties studies. Chemical bonding of POSS with PP in reactive extrusion was confirmed by FT-IR spectroscopy. DSC and TGA studies showed that the thermal stability of AHO-POSS/PP nanocomposite prepared by reactive extrusion improved significantly as compared to only physically blended nanocomposites. WAXD studies showed decrease in crystallinity of the AHO-POSS/PP nanocomposites prepared by reactive extrusion. SEM studies showed aggregation tendency in case of physically blended AHO-POSS/PP nanocomposites. Spherulite growth studies show reactive blending retards spherulite growth in PP polymer.  相似文献   

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