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Polymer degradation has been explored on the basis of synergistic infectious and inhibitive interaction between separate materials. A dual stage chemiluminescence detection system with individually controlled hot stages was applied to probe for interaction effects during polymer degradation in an oxidizing environment. Experimental confirmation was obtained that volatile antioxidants can be transferred over a relatively large distance. The thermal degradation of a polypropylene (PP) sample receiving traces of inhibitive antioxidants from a remote source is delayed. Similarly, volatiles from two stabilized elastomers were also capable of retarding a degradation process remotely. This observation demonstrates inhibitive cross-talk as a novel interactive phenomenon between different polymers and is consequential for understanding general polymer interactions, fundamental degradation processes and long-term aging effects of multiple materials in a single environment. 相似文献
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聚合物表面的润湿性及其应用 总被引:1,自引:0,他引:1
本文论述了真实聚合物表面的润湿性,聚合物表面张力的计算,界面张力的极性理论及酸碱理论,并对近年来材料表面的改性在聚合物中的应用进行了简要的评述。 相似文献
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高分子材料火灾烟气的危害及控制 总被引:1,自引:0,他引:1
介绍了高分子材料火灾烟气的产生及主要有害成分的组成。烟气对人员逃生、火灾救援产生的影响;烟气对生态环境造成的危害;根据高分子材料燃烧机理,提出了减少烟气毒性和环境危害的措施。 相似文献
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Kinetic schemes proposed by three groups of workers for polymer pyrolysis have been critically examined, in order to resolve apparent anomalies, especially in the way in which the overall first-order rate constant for volatile evolution by depropagation mechanisms, involving different modes of initiation and termination, have been interpreted. In one scheme, the treatment of rate was found to be inappropriate for changing-volume systems, and the resulting rate expressions therefore cannot be recommended. When choice of units, conventions, and symbols was taken into account, the other schemes were found to be totally compatible. These schemes lead to identical expressions for the initial rate of evolution of a volatile product, provided the symbols are defined specifically according to the conventions chosen. These expressions are to be recommended for studies of this kind. 相似文献
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Polymer nanocomposite films containing 5 wt% single-walled carbon nanotubes (SWNT) or 5 wt% multi-walled carbon nanotubes (MWNT) with random copolymers of styrene and vinyl phenol were processed from dimethyl formamide solutions. Vinyl phenol mole ratio in the copolymer was 0, 10, 20, 30, and 40%. FTIR analysis indicates that the composites containing the copolymer with 20% vinyl phenol exhibit the maximum intermolecular interactions (hydrogen bonding) between the hydroxyl group of the vinyl phenol and the carbon nanotube functional groups. Tensile properties and electrical conductivity also are the highest in the samples containing the copolymer with 20% vinyl phenol. Thus, these results show that the optimization of the extent of intermolecular interactions between a polymer chain and a carbon nanotube results in an optimal increase in macroscopic properties. Moreover, the extent of intermolecular hydrogen bonding can be improved by optimizing the accessibility of the functional groups to participate in the non-covalent interaction. In this system, this optimization is realized by control of the amount of vinyl phenol in the copolymer, i.e. the copolymer composition. 相似文献
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The phase behavior of polystyrene (PS) degradation in toluene was investigated in a visual high‐pressure reactor. The system of PS and toluene was heated from room temperature and atmospheric pressure to 350°C and 5.0 MPa. It was observed that during this process, PS dissolved quickly, and then, the system appeared to be a homogeneous phase, and PS degradation occurred in this system. With another high‐pressure batch reactor, PS degradation was studied in the temperature range 275–360°C and the pressure ranges 4.5–10.5 MPa. The drop‐in molecular weights in the temperature ranges and the amount of PS converted into volatile products were observed. Moreover, the effects of the temperature, pressure, and ratio of toluene to PS on the rate of PS degradation are discussed. The kinetic studies showed that the rate of PS degradation in supercritical toluene increased substantially because the degradation occurred in a homogeneous phase. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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Effect of hydrogen donors on polymer degradation 总被引:1,自引:0,他引:1
The thermal decomposition of hydrocarbon macromolecules, including polymers in solution, is influenced by the presence of hydrogen donors. Depending on the particular polymer, hydrogen donors may increase, decrease, or have no effect on degradation rate. We investigated the concentration effect of the hydrogen- (H-)donor, 6-hydroxy tetralin, on degradation of polystyrene (2 g/l) dissolved in mineral oil at 275°C. The time evolution of the molecular weight distribution (MWD) was determined by gel permeation chromatography of samples from the batch reactor. The data indicated that the H-donor decreases the polystyrene degradation rate. This is in contrast to the H-donor (tetralin) enhancement of degradation for poly(styrene–allyl alcohol) dissolved in a 1-butanol solution at 150°C. Because the reaction mechanism for polymer degradation involves radicals, we have developed continuous-distribution mass balances for polymers and radicals in the elementary reactions by treating molecular weight as a continuous variable. Based on reactions for initiation–termination, propagation–depropagation and H-abstraction, the model describes the various H-donor effects through relative values of rate coefficients. 相似文献
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Outdoor degradation of isotactic polypropylene (PPI) plates was studied by means of positron annihilation lifetime spectroscopy (PALS), absorption infrared spectroscopy, differential scanning calorimetry (DSC) and density measurements. Infrared spectra reveal the presence of oxygenated species into the exposed polymer induced by external agents. Results from thermal and density analysis suggest an increase of crystallinity of the sample with exposure time. Positron data strengthen such a conclusion, showing a reduction of the amorphous zones as monitored by the corresponding decrease of positronium (Ps) formation. Furthermore, an estimation of the average sizes of the free volume holes and of the defects in the crystalline regions was obtained. 相似文献
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The important mechanism of interface layer formation in polymer composite materials is a sorption interaction between polymer fillers and binder components. The structure and properties of the interface layer will be dependent on the kinetics of the sorption. The kinetics of diffusion of some low molecular compounds including epoxies into aramide fibers are studied by the method of isothermic calorimetry. Discrepancy of the kinetics from Fickian was found. Theoretical consideration showed the cause of it could be the structural inhomogeneity of the sorbents. Experimental and theoretical data evidencing that the heterogeneous structure of the sorbent is the cause of the time dependence of the diffusion coefficient are presented in this paper. 相似文献
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砜嘧磺隆在环境中的降解行为研究进展 总被引:1,自引:0,他引:1
评述了砜嘧磺隆的理化性质、残留测定方法及其在环境中的代谢降解研究进展,归纳了砜嘧磺隆的残留分析方法如气相色谱法、高效液相色谱法和液质联用法及其在消解动态研究中的应用,总结了砜嘧磺隆在植物、水、土壤等环境中的降解产物及其途径,提出了今后需进一步研究明确的问题。 相似文献
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Thin films of poly(vinyl chloride), PVC, and carboxylated poly(vinyl chloride), C-PVC, containing 1.8% of carboxyl groups
were exposed to high energy ultraviolet radiation (λ = 254 nm) in laboratory conditions. The photochemical reactions in irradiated
samples were studied by FTIR and UV–Vis spectroscopy, gel permeation chromatography and gravimetric estimation of insoluble
gel. It was found that photodegradation and photocrosslinking in C-PVC is accelerated, whereas photodehydrochlorination is
retarded comparing to these processes in PVC. Photooxidation investigated on the base of reaction leading to formation of
hydroxyl groups is also more efficient in modified PVC. However, the total amount of carbonyl groups is much lower in UV-irradiated
C-PVC than that in PVC. It indicates that competitive reactions (destruction of carboxyl groups and formation of new carbonyls)
occur simultaneously in C-PVC chains. The influence of carbonyl groups on photochemical processes can be explained by an efficient
Norrish I and II reactions as well as by energy transfer from absorbing species to weak chemical bonds. 相似文献
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聚乳酸的热降解性能研究 总被引:1,自引:0,他引:1
研究了聚乳酸(PLA)在10-40 min和170-200℃的条件下热降解后的特性粘数和端羧基含量的变化。结果表明,在一定温度下,PLA熔体特性粘数随熔融时间的延长而下降,在一定时间下,随熔融温度升高而下降,端羧基含量随熔融温度升高而增大,在PLA成型加工中,应严格控制加工温度。 相似文献
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Epoxidation of surface-bound polynorbornene films on silicon: Preventing degradation via solvent effect 总被引:1,自引:0,他引:1
Zhiqian Song 《Polymer》2011,52(20):4456-4462
We describe a strategy to prevent the detachment of polymer chain during the epoxidation of covalently grafted polynorbornene (PNb) films. Surface-bound PNb was prepared by surface-initiated ring-opening metathesis polymerization (SIROMP) from Si/SiO2 substrates, and then epoxidized with meta-chloroperoxybenzoic acid by taking advantage of the double bonds along the polymer chains. The polymer-solvent interactions of three model solvents (dichloromethane, ether and methanol) with grafted PNb and grafted epoxidized PNb were studied by measuring the intrinsic viscosity of the free counterparts in solutions with a capillary viscometer. Oxidative degradation of the films was evaluated by ellipsometric thicknesses. The change in surface morphology was characterized with atomic force microscopy (AFM). Reactions of degradation and epoxidation of grafted PNb in three model solvents were studied. Kinetics study revealed that the surface-bound PNb is epoxidized gradiently from the surface toward the silicon substrate in ether. Through the solvent control, epoxidation of surface-bound PNb film without degradation was achieved under relatively mild condition. 相似文献
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本文针对高分子物理课程特点及高等教育改革的需要,对高分子物理教学现状和存在的问题进行了分析,同时对从事高分子物理教学的教师如何提高教学质量,在教学内容、实验教学环节及考核等方面提出了一些见解。 相似文献
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Epoxy with associative covalent adaptable networks (CANs), called vitrimer, is reported to be promising to realize the recyclable utilization. The typical epoxy vitrimers are synthesized from diglycidyl ether of bisphenol A and dicarboxylic catalyzed by triazabicyclodecene (TBD). The study on the curing and thermal degradation behavior facilitates in-depth understanding of the associative CANs. In this work, the effect of TBD on the curing and thermal degradation behavior is investigated via curing kinetics and thermal degradation performance analysis. The results reveal that the activation energy of curing reaction is increased as the amount of TBD is increased. EST-5 has an average activation energy of 70.1 kJ/mol, while EST-15 reaches as high as 75.1 kJ/mol. Especially, when the conversion is up to 50%, the activation energy shows an obvious increment. In addition, it has been demonstrated that TBD accelerates the thermal degradation of cured networks at lower temperature and increases the amount of volatiles during thermal decomposition. 相似文献
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吲哚散发粪便恶臭气味,广泛存在于焦化、染料、化工、制药和农药等工业废水中。由于其特殊的双环稠合结构,靠传统的生物水解断环提高吲哚的降解效果难以为继。本文全面介绍了吲哚的来源、毒性、危害及传统生物降解技术的缺陷,特别论述了高级氧化法(AOPs)中·OH的形成反应及降解吲哚的作用机理。传统AOPs能够高效降解吲哚,但价格昂贵,操作复杂,且使用剂量常受到其他物质的干扰,易引入新的污染物,难以在大规模的水处理工程中应用。因此,认为将AOPs预氧化与生物处理技术进行高效耦合是降解吲哚经济有效的办法。本文最后介绍了硫酸根自由基的高级氧化技术(SR-AOPs)耦合厌氧生物技术降解吲哚的研究及其优点。这些研究对丰富AOPs耦合生物处理技术理论、含氮杂环污染物高效降解及资源化利用有一定的参考价值。 相似文献