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1.
Three different boron containing materials, zinc borate (ZnB), borophosphate (BPO4), and boron and silicon containing oligomer (BSi), were used to improve the flame retardancy of melamine cyanurate (MC) in a polyamide‐6 (PA‐6) matrix. The combustion and thermal degradation characteristics were investigated using limiting oxygen index (LOI), UL‐94 standard, thermogravimetric analysis‐Fourier transform infrared spectroscopy (TGA‐FTIR), differential scanning calorimeter (DSC), and scanning electron microscopy (SEM). All the three boron compounds showed no synergistic effect with MC, and only BPO4 at high loadings showed comparable LOI values by increasing the dripping rate. For ZnB and BSi glassy film and char formation decreases the dripping rate and sublimation of melamine and give rise to low LOI. According to TGA‐FTIR results, addition of boron compounds does not alter the gaseous product distribution of both MC and PA‐6. The addition of boron compounds affects flame retardancy through physical means. It was noted from the TGA data that boron compounds reduced the decomposition temperature of both MC and PA‐6, also affecting the flame retardancy negatively by premature degradation of MC at low temperatures. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
2.
Gregory Von White II Roger L. Clough James M. Hochrein Robert Bernstein 《Polymer Degradation and Stability》2013
Nylon 6.6 containing 13C isotopic labels at specific positions along the macromolecular backbone has been subjected to extensive thermal-oxidative aging at 138 °C for time periods up to 243 days. In complementary experiments, unlabeled Nylon 6.6 was subjected to the same aging conditions under an atmosphere of 18O2. Volatile organic degradation products were analyzed by cryofocusing gas chromatography mass spectrometry (cryo-GC/MS) to identify the isotopic labeling. The labeling results, combined with basic considerations of free radical reaction chemistry, provided insights to the origin of degradation species, with respect to the macromolecular structure. A number of inferences on chemical mechanisms were drawn, based on 1) the presence (or absence) of the isotopic labels in the various products, 2) the location of the isotope within the product molecule, and 3) the relative abundance of products as indicated by large differences in peak intensities in the gas chromatogram. The overall degradation results can be understood in terms of free radical pathways originating from initial attacks on three different positions along the nylon chain which include hydrogen abstraction from: the (CH2) group adjacent to the nitrogen atom, at the (CH2) adjacent the carbonyl group, and direct radical attack on the carbonyl. Understanding the pathways which lead to Nylon 6.6 degradation ultimately provides new insight into changes that can be leveraged to detect and reduce early aging and minimize problems associated with material degradation. 相似文献
3.
The degradation of poly(3-hydroxybutyrate), P(3HB), was determined in two conditions namely, a non-aqueous condition of chloroform-methanol mixture in the presence of either one of the two following catalysts, 4-toluenesulphonic acid and imidazole, and secondly in an aqueous condition of increasing pH. From our study, a random chain scission of PHB occurred in the non-aqueous condition while the degradation of PHB in the presence of water occurred through surface hydrolysis with no change in the molecular weight. In the surface hydrolysis of the polymer, the rate was increased with higher pH values. 相似文献
4.
Meifang Zhu Qiang Xing Houkang He Yu Zhang Yanmo Chen Petra Pötschke Hans-Jürgen Adler 《Macromolecular Symposia》2004,210(1):251-261
In this work, surface modification technique with coupling agents and anchoring polymerization was adopted to tailor the surface properties of nanoscaled titanium dioxide (TiO2). Ethyl glycol sols with TiO2 were prepared in order to simulate the dispersibility of differently modified TiO2 in a molten polyamide 6 (PA6) matrix. The modified TiO2 were melt compounded with PA6 and composites and fibers were prepared. The average filler diameter of 47 nm (in composites) and 44 nm (in fibers) indicated homogeneous dispersion of TiO2 in the matrix, whereas unmodified TiO2 showed agglomerated structures in the PA6 matrix. The mechanical properties of the composite fibers were improved as compared to pure PA6 fibers and composite fibers with unmodified TiO2. 相似文献
5.
Yuhua Zhong Luchong Zhang Andreas Fischer Liang Wang Dietmar Drummer 《高分子科学杂志,A辑:纯化学与应用化学》2018,55(1):17-23
A novel thermally conductive Polyamide 6 (PA6) with good fire resistance was prepared by introducing a phosphorous-nitrogen flame retardant (FR) and platelet-shaped hexagonal boron nitride (hBN) into the matrix. With high thermal conductivity and good flame retardancy, the material is suitable for applications in electronic and electrical devices. The limiting oxygen index (LOI) changes for various loadings content of FR. However this formulation still does not show an ideal fire resistance, due to the appearance of melt dripping behavior during the UL 94 test. With the extra introduction of 3 vol% and 5 vol% hBN, the melt dripping behavior during the burning process completely disappeared. The hBN also increased the thermal conductivity. Furthermore PA6 compounded with FR and hBN showed a better thermal stability than neat PA6. The morphology of the char residues was investigated by scanning electron microscopy (SEM). The flaky hBN acted as the framework in the char structure and the rigid hBN could effectively break the bubble-shaped char on the surface of the residues which resulted in the enhancement of the strength and compactness of the char. 相似文献
6.
Hai‐Juan Lin Li‐Jing Han Xue‐Mei Wang Yi‐Jie Bian Yue‐Sheng Li Li‐Song Dong 《先进技术聚合物》2013,24(6):576-583
A phosphorus‐containing polyester, poly (ethylene diglycol phenylphosphinate) (PEDPP) was synthesized from phenylphosphonic dichloride and ethylene diglycol. The structure of PEDPP has been determined by Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance and matrix assisted laser desorption ionization‐time of flight‐mass spectrometer. A series of polylactide (PLA) blends with various content of PEDPP as flame retardant was prepared by direct melt compounding; the PLA/PEDPP blend is partially miscible. PEDPP is an effective flame retardant for PLA. The limiting oxygen index values increased from 19.7% for pure PLA to 29.0% for the blend containing 10wt% PEDPP. Thermogravimetric analysis‐FTIR analysis indicated that the PEDPP affected the pyrolytic decomposition process of PLA, which is established by the change of the pyrolytic decomposition rate and the gross mass of gaseous fuel formation. The pyrolytic decomposition activation energies of PLA and PLA/10%PEDPP were estimated via Flynn–Wall–Ozawa method. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
Thallada Bhaskar Kazuya Murai Toshiki Matsui Mihai Adrian Brebu Md. Azhar Uddin Akinori Muto Yusaku Sakata Katsuhide Murata 《Journal of Analytical and Applied Pyrolysis》2003,70(2):369-381
The thermal degradation of acrylonitrile-butadiene-styrene copolymer (ABS-Br; 10 g) containing brominated flame retardant (Br: 9.59 wt.%) was carried out at 450 °C using a semi batch operation using two different temperature programs. The heating rate was found to affect the quality of the degradation oil and yield of products (liquid, gas and residue). Data on the effect of the temperature program on the accumulation of liquid products was presented. It was found that the majority of the bromine was concentrated in the carbon residue and while majority of the nitrogen accumulates in the liquid products irrespective of degradation mode. The use of a one step constant heating rate process (I) produced a higher liquid yield (39%), than a two step process (29%). Differences were also noted in the Br and N contained in the liquids produced by the two processes. 相似文献
8.
Influence of compatibilizer degradation on formation and properties of PA6/organoclay nanocomposites 总被引:1,自引:0,他引:1
Orietta Monticelli Zenfira Musina Federica Bellucci Saverio Russo 《Polymer Degradation and Stability》2007,92(3):370-378
Nanocomposites based on polyamide 6 (PA6) and commercial layered silicates have been prepared by both in situ polymerization and melt compounding. The main aim of the present work has been centred on compatibilizer degradation, caused by the preparation conditions, in terms of nanocomposite end features. Two montmorillonite (MMT)-type, organically-modified clays (OMLS), namely Cloisite 30B® and Nanofil 784®, and a sodium MMT (Cloisite Na®) have been studied. Thermal properties of the layered silicates have been evaluated by TGA, IR, WAXD and pyrolysis-gas-mass. In order to better assess the influence of high temperature processes on clay modifications, a thermal treatment which mimics the conditions used during the in situ polymerization (4 h at 250 °C) has been applied on layered silicates. The above treatment, besides the elimination of absorbed water from all the clays, turned out to prove noteworthy differences in compatibilizer modification for the two organoclays. Indeed, in the case of Closite 30B® only a removal of organic molecules outside the silicate galleries and a likely reorganization of those present inside the galleries have been detected, while a relevant chemical modification of Nanofil 784® compatibilizer has been conversely found.As far as nanocomposite characteristics are concerned, the latter have been found to depend on both the preparation method and clay type. In the case of in situ polymerization, also thermally-treated layered silicates, coded (T), have been used, in order to put more clearly in evidence the role of compatibilizer decomposition on nanocomposite formation and properties. Indeed, nanocomposite samples containing Closite 30B®(T) have been found to be completely exfoliated, while the same thermal treatment seems to make worse the properties of those based on Nanofil 784®(T). Furthermore, with respect to nanocomposites based on pristine clays, samples containing thermally-treated silicates turned out to be different in terms of both molecular mass and crystal structure of the polymer matrix. Namely, PA6 γ-form seems to be promoted for all nanocomposites prepared in such a way, probably because of water removal at high temperature, which makes -OH groups of the layered silicate more free to interact with polyamide chains, thus causing a restriction of their mobility. 相似文献
9.
The effects of wood-flour on combustion and thermal degradation behaviors of PVC in wood-flour/poly(vinyl chloride) composites 总被引:2,自引:0,他引:2
Xiao-yan Bai Qing-wen Wang Shu-juan Sui Chun-sheng Zhang 《Journal of Analytical and Applied Pyrolysis》2011,91(1):34-39
The effects of wood-flour on combustion and thermal degradation behaviors of PVC in wood-flour/poly (vinyl chloride) composites (WF-PVC) were investigated by using cone calorimeter (CONE) and TGA. The results show that thermal degradation behavior of WF-PVC composites has obvious characteristics of that of PVC. Interactions occur between wood-flour and PVC during the combustion and thermal degradation of WF-PVC composites. The thermal degradation of wood-flour can be accelerated by pure PVC. Moreover, the char formation can be raised by adding wood-flour to PVC. Compared with PVC at all flaming stage, when heat flux is kept at 50 kW m−2, the average heat release rate (av-HRR), the total heat release (THR), the total smoke production (TSP) and the average specific extinction area (av-SEA) of WF-PVC composites are respectively reduced by 44%, 9.2%, 25.8% and 29.9%. In WF-PVC composites, the wood-flour has remarkable effects on the properties of heat release and smoke release of PVC. 相似文献
10.
By introducing binary hydroxyl groups into poly(p‐phenylene benzoxazole) (PBO) macromolecular chains, we synthesized dihydroxy poly(p‐phenylene benzobisoxazole) (DHPBO) polymers and then prepared DHPBO fibers by dry‐jet wet‐spinning. Comparative studies were performed between intrinsic PBO fibers and DHPBO fibers. The effects of hydroxyl polar groups on improving the UV aging resistance of PBO fibers were investigated. With the introduction of hydroxyl groups, substantial changes in the chemical structures and surface morphologies of DHPBO fibers were observed. As proved by tensile testing and intrinsic viscosity measurement, the UV resistance of DHPBO fibers is obviously improved compared to that of intrinsic PBO fibers. XRD results indicate that the UV aging of these fibers occurs mainly on the surfaces of fibers. Based on these results, the mechanism of UV aging of PBO fibers was discussed. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
11.
Hua Cai Vipul Dave Richard A. Gross Stephen P. McCarthy 《Journal of Polymer Science.Polymer Physics》1996,34(16):2701-2708
The effects of physical aging, degree of crystallinity, and orientation of poly(lactic acid) (PLA) were studied using differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS). The samples of PLA with 96% [L] and 4% [D] contents were prepared by injection molding. The physical aging of PLA strongly depended on time and temperature. The change of rate of physical aging was very fast initially and slowed down as time increased. The enzymatic degradation of PLA was carried out with proteinase K at 37°C at a pH value of 8.6 in a Tris/HCl buffer solution. The enzymatic degradation rate was found to decrease as a function of physical aging (i.e., excess enthalpy relaxation). The rate of enzymatic degradation of PLA decreased with the increase in crystallinity. A threshold was observed when the heat of fusion was less than 20 J/g. The weight loss of PLA with a low level of crystallinity had no apparent change during any period of testing time. The rates of enzymatic degradation of stretched and injection-molded specimens were comparable. © 1996 John Wiley & Sons, Inc. 相似文献
12.
Transcrystallization of polypropylene (PP) on the polytetrafluoroethylene (PTFE) fiber was investigated. Both nucleation rate and crystal growth rate were determined by a polarized optical microscope. Based on the theory of heterogeneous nucleation, it has been found that the induction time can correlate well with the nucleation rate in determining the interfacial free energy difference function Δσ. The ratio of Δσ in the bulk matrix to that at the interface is 1.63 which implies the transcrystalline growth is favorable from a thermodynamic point of view. No difference in crystal growth rate of PP has been found in either spherulites or transcrystalline layers. On the basis of regime theory, a transition between regimes II and III was observed at ΔT = 48K. From the morphology studies, it has been found that the thickness of the transcrystalline layer increases with crystallization temperature, from 30 to 120 μm in the temperature range of 110–140°C. The growth of transcrystalline layer is hindered by the spherulites nucleated in the bulk. Moreover, the radius of spherulites adjacent to the transcrystalline layer is much smaller than that distant to the fiber. No significant increase in nucleation density at fiber ends is observed. Effect of internal stresses of fibers on the fiber's nucleating ability is not pronounced. © 1996 John Wiley & Sons, Inc. 相似文献
13.
Poly(lactic acid) (PLA) composites containing 5 wt% synthetic (type 4A) and natural (chabazite) zeolites were prepared using extrusion/injection molding. Morphological, structural, and thermal properties of composites were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). DSC results revealed that the glass transition and melting temperatures were not significantly changed; however, the incorporation of both type 4A and chabazite zeolites enhanced the nucleation of PLA crystallites as well as increased the percent crystallinity. Thermal degradation properties of PLA and PLA/zeolite composites were studied by non-isothermal thermogravimetric analysis (TGA) in nitrogen atmosphere. TGA results showed that at temperatures above 300 °C, PLA/type 4A synthetic zeolite composites were thermally decomposed more easily than the PLA and PLA/chabazite natural zeolite composites. The apparent activation energies of thermal degradation of PLA and PLA/zeolites composites estimated using both the Flynn-Wall-Ozawa and Kissinger methods followed the same order: PLA/type 4A < PLA/chabazite < PLA. 相似文献
14.
María Angeles CorresManoli Zubitur Milagros CortazarAgurtzane Múgica 《Journal of Analytical and Applied Pyrolysis》2011,92(2):407-416
The nature and the extent of degradation of poly(hydroxy ether of bisphenol-A) phenoxy resin were analysed by thermogravimetry (TGA/DTGA) under nitrogen and air atmosphere. Decomposition kinetics were elucidated according to Flynn-Wall-Ozawa, Friedman and Kissinger methods. The evolved gases during degradation were inspected by a thermogravimetry analyser coupled with Fourier Transform Infrared Spectrometer (TGA/FTIR) and also with a TGA coupled to a Mass Spectrometer (TGA/MS). Mass spectra showed that chemical species evolved in phenoxy decomposition in air were very similar to those assigned from degradation in nitrogen (water, methane, CO, CO2, phenol, acetone, etc.). However, these species appear in different amount and at different temperatures in both atmospheres. FTIR analysis of the evolved products showed that water and methane were the beginning decomposition products, indicating that decomposition is initiated by dehydration and cleavage of C-CH3 bond in the bisphenol-A unit of phenoxy resin. After this initial stage, random chain scission is the main degradation pathway. Nevertheless, in air atmosphere, previously the complete decomposition of the phenoxy obtaining fundamentally CO2, and water, the formation of an insulated surface layer of crosslinked structures has been proposed. 相似文献
15.
Wind blades, an important application of polymeric composite materials, are subject to natural weathering. This study aims to evaluate mechanical, thermal and morphological behavior during accelerated aging in three thicknesses of epoxy and fiberglass polyurethane-coated composite plates used in wind turbines, in addition to testing with two acoustic emission techniques. An accelerated aging chamber simulated natural weathering mechanisms for 45, 90, 135 and 180 days. This degradation primarily reduced the mechanical properties of the thinner composites, with some damaged specimens exhibiting fiber-matrix debonding. Thermal properties deteriorated. There were no morphological changes on the polyurethane–epoxy interface; however, degradation occurred in the fiber-matrix interface on the surface exposed to radiation. The degree of chalking indicated coating deterioration on the external surface of the polyurethane. The acoustic wave propagation speed and attenuation coefficient measured prior to mechanical testing indicated the presence of damage areas. 相似文献
16.
Grace Olufunmilayo Ogunlusi Olayinka A Oyetunji Olanrewaju Owoyomi Jide Ige 《Journal of Dispersion Science and Technology》2017,38(8):1129-1134
The redox reaction between tris(1,10-phenanthroline)iron(II), [Fe(phen)3]2+, and azido-pentacyanocobaltate(III), [Co(CN)5N3]3? was investigated in three cationic surfactants: dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB) in the presence of 0.1?M NaCl at 35°C. Second-order rate constant in the absence and presence of surfactant, kw and kψ, respectively, were obtained in the concentration ranges DTAB?=?0???4.667?×?10?4?mol?dm?3, TTAB?=?0–9.364?×?10?5?mol?dm?3, CTAB?=?0???6.220?×?10?5?mol?dm?3. Electron transfer rate was inhibited by the surfactants with premicelllar activity. Inhibition factors, kw/kψ followed the trend CTAB?>?TTAB?>?DTAB with respect to the surfactant concentrations used. The magnitudes of the binding constants obtained suggest significant electrostatic and hydrophobic interactions. Activation parameters ΔH≠, ΔS≠, and Ea have larger positive values in the presence of surfactants than in surfactant-free medium. The electron transfer is proposed to proceed via outer-sphere mechanism in the presence of the surfactants. 相似文献
17.
18.
The kinetics of the thermal degradation and thermal oxidative degradation of poly(p-dioxanone) (PPDO) were investigated by thermogravimetric analysis. Kissinger method, Friedman method, Flynn-Wall-Ozawa method and Coats-Redfern method have been used to determine the activation energies of PPDO degradation. The results showed that the thermal stability of PPDO in pure nitrogen is higher than that in air atmosphere. The analyses of the solid-state processes mechanism of PPDO by Coats-Redfern method and Criado et al. method showed: the thermal degradation process of PPDO goes to a mechanism involving random nucleation with one nucleus on the individual particle (F1 mechanism); otherwise, the thermal oxidative degradation process of PPDO is corresponding to a nucleation and growth mechanism (A2 mechanism). 相似文献
19.
Poly(vinyl
chloride) (PVC), plasticized by di(2-ethylhexyl) phthalate (DEHP), medium
molecular mass polyesterurethane (PU) or by both plasticizers, was thermally
degraded under dynamic thermogravimetric conditions and the kinetics of decomposition
was studied by isoconversional methods and by non-linear regression. It has
been found that the initial decomposition temperature is higher for PVC plasticized
with PU, as compared with PVC plasticized with di(2-ethylhexyl) phthalate
(DEHP) or plasticized with PU/DEHP, and thermal degradation shows features
of a multi-step complex process. Application of polymeric plasticizer leads
to the increase and a 'smoothing' effect in the course of energy
of activation and pre-exponential factor at the initial stage of decomposition
indicating thus the hindered migration of medium molecular mass compound from
PVC matrix (in comparison with PVC containing monomeric DEHP) due to steric
hindrances as well as due to specific interactions between C=O and Cl groups
along the macrochains. Kinetic model function of the decomposition process
of PVC/DEHP and PVC/DEHP/PU blends was found to be a two-stage autocatalyzed
reaction of nth
order; autocatalytic effect is associated most likely with the role of HCl
formed during PVC decomposition. For PVC/PU blend best fit was found by non-linear
regression for a two-stage scheme in which first stage was Prout-Tompkins
model and the second was autocatalytical model of nth
order - the first one involves particle disintegration, which was promoted
by product generation at branching PVC 'pseudo-crystals' nuclei,
thus exposing more surface on which decomposition reaction proceeds. 相似文献
20.
Mitsuyuki Morita 《Journal of Polymer Science.Polymer Physics》1994,32(2):231-242
Effects of solvent and electrolyte on the electrochromic behavior and degradation of polyaniline in nonaqueous aprotic media, as well as its electrochemical redox and degradation mechanisms, were investigated with chemically prepared polyaniline-poly (vinyl alcohol) composite films and polyaniline homogeneous films. Visible and FT-IR absorption spectra of the polyaniline films, oxidized electrochemically at various polarization potentials, showed that the mechanisms in aprotic media involved two successive oxidation processes. In contrast to aqueous systems, the higher oxidation process involved further anion insertion without deprotonation, and the degradation was due to partial formation of the electrochemically inactive quinonediimine structure at excessive polarization potentials. From investigations of solvent and electrolyte effects, it is suggested that the electrochromic behavior and degradation of polyaniline are influenced by the electron-donating and accepting ability of solvents, acceptor strength of electrolyte cations, and the nucleophilic character of electrolyte anions. It was also suggested that some anions like as well as protons, are constrained in the PVA matrix by specific electrostatic interactions and steric effects to improve the stability of polyaniline in the highly oxidized state. © 1994 John Wiley & Sons, Inc. 相似文献