聚苯乙烯海南自然气候暴露后的老化现象

采用直接气候暴露、玻璃板下暴露和百页窗下暴露三种自然老化方法研究了聚苯乙烯(PS)外观、力学性能和熔体流动速率在海南自然老化过程中的变化,考察了光、热、氧、水对PS老化的影响。结果表明,PS在海南的自然老化以断链反应为主,分子量的下降与太阳辐照强度密切相关;老化过程中,由于试样温度变化所产生的内应力是影响PS力学性能的重要因素;水对PS的各项性能不产生大的影响。     

高密度聚乙烯土工格栅光氧老化研究进展

对高密度聚乙烯(HDPE)土工格栅的光氧老化机理进行系统性的介绍;分析影响土工格栅光氧老化的外界因素,包括环境因素、安装损耗和加工方式等;同时介绍高密度聚乙烯土工格栅降解后性能的变化,从力学性能、外观变化及微观指标三方面总结其老化后的表征指标,并指出HDPE土工格栅光氧老化研究方面的不足。     

191～#不饱和聚酯树脂西部曝晒和人工加速老化的研究

对191#不饱和聚酯树脂进行了自然曝晒老化、人工热氧加速老化及人工氙灯加速老化试验,并对老化前后试样的外观形貌、光泽度、黄色指数、拉伸强度和弯曲强度进行了研究。实验结果表明,随着加速老化的不断进行,试样表面会出现泛黄、失光率增大和裂纹等现象,强度呈先增后降的趋势,弯曲强度由20 MPa(未老化时)增至最大值40 MPa(热氧老化60 d或氙灯老化45 d),拉伸强度由113 MPa(未老化时)增至最大值125 MPa(氙灯老化30 d)和128 MPa(热氧老化60 d);老化方式不同,老化前后试样的性能变化也不相同,即失光率对热氧老化更敏感、强度对紫外光老化更敏感;西部曝晒180 d,不饱和聚酯树脂仍处于后固化阶段,但强度已开始下降,下降程度与曝晒地区有关,变化最明显的是新疆尉犁地区,弯曲强度由最大值40 MPa(自然曝晒120 d)降低至35 MPa(自然曝晒180 d)。     

耐候型聚甲醛复合物的制备与性能研究

将二甲基硅氧烷、紫外线吸收剂、光稳定剂、抗氧化剂、紫外线屏蔽剂、甲醛吸收剂与聚甲醛（POM）共混制备了耐候型POM,分析了光老化、热氧老化、水热老化实验后耐候型POM的性能、结构变化及助剂的分布情况。结果表明,耐候助剂提高了POM的力学性能保持率;POM的老化过程主要发生在无定形区域,且对光尤为敏感、热氧次之,对水热的影响较小;耐候助剂主要分布于无定型区域,在发挥耐候效果的同时,由于紫外线照射,本身会被消耗。     

ABS/BaSO4体系老化性能的研究

利用自然曝露和热烘箱老化实验，通过考察老化过程中力学性能及红外光谱中Ｃ＝Ｃ双键吸收峰强度的变化，研究了ＡＢＣ／ＳａＳＯ４体系的老化性能及硬脂酸、钛酸酯偶联剂、稀土偶联剂等处理剂对该体系老化性能的影响。加入ＢａＳＯ４可提高ＡＢＳ的耐老化性能；硬脂酝 及稀土偶联剂对填充体系光氧老化有微弱的促进作用，而对热氧老化过程无明显影响；钛酸酯偶联剂对体系的光氧、热氧老化过程均有加速作用，能降低绵耐老化性能。     

高分子材料的老化研究

本文介绍了由高分子材料老化引起的外观、物理性能、力学性能、电性能的变化;分析了引起高分子材料老化的内在因素和外在因素,例如化学结构、物理形态、立体规整性、分子量及其分布情况、金属杂质、温度、湿度、氧气、光照、化学介质、生物等;阐述了自然环境老化实验、人工加速老化实验、耐候性实验、热老化实验、湿热老化实验、臭氧老化实验、盐雾腐蚀实验、耐寒性实验、抗霉实验等老化评价方法和物理性能、力学性能、微观分析、耐久性能以及系统分析技术等老化性能评价指标;并对热老化预防措施、湿热老化预防措施、氧老化预防措施、光老化预防措施以及生物老化预防措施进行了展望。     

不同老化条件对轮胎耐久性能及损坏形式的影响

研究氮氧老化、热氧老化和臭氧老化3种老化条件对轮胎耐久性能及损坏形式的影响。结果表明：热氧老化后轮胎耐久性能明显下降,氮氧老化后轮胎耐久性能略有下降,臭氧老化后轮胎耐久性能变化不大;氮氧老化和热氧老化后轮胎耐久损坏形式均为胎侧鼓包脱层,其中热氧老化后轮胎损坏更严重,而臭氧老化后轮胎耐久损坏形式为胎肩出现裂口;氮氧老化和热氧老化后剖析胎面胶的硬度和定伸应力增大,拉断伸长率减小,生热变化不大;臭氧老化对剖析胎面胶性能的影响不大。     

各类稳定剂对聚乙烯薄膜光氧老化的稳定作用

研究了不同光稳定剂和抗氧剂及其配合使用、光稳定剂含量对聚乙烯薄膜耐光氧老化性的影响。结果表明：在各类光稳定剂中、受阻胺类稳定剂的效果最好;紫外线吸收剂与受阻胺配合使用可使膜的耐老化性有所提高;各类抗氧剂对聚乙烯膜的耐光氧老化性没有不利影响;光稳定剂含量增加,薄膜耐老化寿命提高。     

聚氨酯老化机理与研究方法进展

热、氧、光等环境因素对聚氨酯材料的老化起到了加速作用,介绍了近年来聚氨酯老化机理的研究以及聚氨酯老化研究的实验方法和仪器分析方法。     

耐候ABS加速老化性能研究

本文通过对耐候改性ABS材料进行热氧加速老化、氙灯加速老化和紫外光加速老化,观测热氧、氙灯、紫外光对耐候改性ABS材料的老化后外观变化和老化后性能变化,初步得出三种常见的加速老化对耐候ABS性能影响及其具体影响因素。     

Dye-Mediated Photo-Oxidation Biomaterial Fixation: Analysis of Bioinductivity and Mechanical Properties of Bovine Pericardium for Use in Cardiac Surgery

Extracellular matrix bioscaffolds can influence the cardiac microenvironment and modulate endogenous cellular mechanisms. These materials can optimize cardiac surgery for repair and reconstruction. We investigated the biocompatibility and bioinductivity of bovine pericardium fixed via dye-mediated photo-oxidation on human cardiac fibroblast activity. We compared a dye-mediated photo-oxidation fixed bioscaffold to glutaraldehyde-fixed and non-fixed bioscaffolds reported in contemporary literature in cardiac surgery. Human cardiac fibroblasts from consenting patients were seeded on to bioscaffold materials to assess the biocompatibility and bioinductivity. Human cardiac fibroblast gene expression, secretome, morphology and viability were studied. Dye-mediated photo-oxidation fixed acellular bovine pericardium preserves human cardiac fibroblast phenotype and viability; and potentiates a pro-vasculogenic paracrine response. Material tensile properties were compared with biomechanical testing. Dye-mediated photo-oxidation fixed acellular bovine pericardium had higher compliance compared to glutaraldehyde-fixed bioscaffold in response to tensile force. The biocompatibility, bioinductivity, and biomechanical properties of dye-mediated photo-oxidation fixed bovine pericardium demonstrate its feasibility as a bioscaffold for use in cardiac surgery. As a fixed yet bioinductive solution, this bioscaffold demonstrates enhanced compliance and retains bioinductive properties that may leverage endogenous reparative pathways. Dye-mediated photo-oxidation fixed bioscaffold warrants further investigation as a viable tool for cardiac repair and reconstruction.     

几种萘酞菁硅配合物的光动力效应的研究

研究了7种轴向配位的萘酞菁硅配合物的激发态性质、产生单重态氧的能力及对几种氨基酸的光敏氧化能力.研究表明,对于相同浓度的不同配合物来说,随着轴向配位基团推电子能力的逐渐增强,激发三重态寿命降低,产生单重态氧的能力逐渐下降,而产生单重态氧的能力是光敏氧化氨基酸反应速率的决定因素,因此,其光敏氧化氨基酸的一级反应速率常数逐渐减小.     

光氧稳定剂对塑木复合材料性能的影响

以紫外光稳定剂531和抗氧剂2246为光氧稳定剂,研究了塑木复合材料受光氧影响时的弯曲性能、色泽变化、氧化诱导期和外观变化.研究表明,经紫外光照射后,光氧稳定剂对材料的弯曲性能影响不大,但添加有光氧稳定剂的材料的表面色泽变化小,发白不明显.在紫外光稳定剂531和抗氧剂2246的添加量分别为0.3%时,材料经300h紫外...     

Weathering of fiber-reinforced epoxy composites

Unless suitably stabilized and coated, fiber-reinforced composites are subject to photoinitiated oxidation which results in a degradation of the resin surface and an eventual reduction in the composite's mechanical properties. The photo-oxidation, which is initiated by UV-absorbing oxidation products created during cure, is relatively amenable to detection by techniques of analytical chemistry. Mechanical test results, which reflect a wide range of material properties, are more subject to variability and misinterpretation.     

加工抗氧剂对聚乙烯光氧化和敏化光氧化的影响

研究了抗氧剂残留对线性低密度聚乙烯(LLDPE)的光氧化和添加了光敏剂的敏化光氧化的影响,结果表明,抗氧剂残留明显地降低了LLDPE的光氧化和敏化光氧化反应速率。添加了光敏化剂的不含抗氧剂LLDPE样品在暗处同样会发生氧化反应,而抗氧剂残留可以有效地阻止氧化反应的发生。因此,LLDPE粉料不适于添加光敏化剂加工成可控降解塑料。     

神府镜煤光氧化产物的组成和结构研究

在紫外光照射下,用氧气对神府镜煤进行了光催化氧化研究。探讨了氧化时间对氧化煤中腐植酸含量的影响。通过溶剂抽提,FTIR分析及GC/MS分析对神府镜煤光氧化产物进行了组成和结构分析。研究表明:控制光氧化时间,可以获得不同腐植酸含量的光氧化产物,在光氧化4 h时,镜煤中腐植酸含量最高;镜煤在光氧化产物过程中,芳香结构较难打开,主要是醚键等含氧官能团发生反应,生成羧基和甲基等。     

铕配合物对线形低密度聚乙烯老化性能的影响

合成了组成为Eu2·(BA)3·(PhEN)2·nH2O的铕、苯甲酰丙酮和1,10-二氮杂菲三元配合物。利用热重分析仪、热氧老化箱以及自然曝晒、氙灯加速老化实验,并通过考察不同氧化过程中材料力学性能和红外光谱的变化, 研究了此配合物加入线形低密度聚乙烯(PE-LLD)后对其热氧老化、光氧老化及总的老化性能的影响。研究表明,该铕配合物对PE-LLD的光氧化过程有明显的阻滞作用,而对其热氧化过程则有加速作用,对材料老化性能总的影响取决于二者的综合。     

The kinetics and mechanism of polyethylene photo-oxidation

The kinetics of the natural and accelerated photo-oxidation of low-denisty polyethylene (LDPE) films have been studied; different geographical locations have been selected for the natural tests, and a range of temperatures used in the accelerated experiments in a specially built temperature-controlled ultraviolet radiation enclosure. A meaningful correlation between natural and accelerated weathering results was established, by means of an adequate superposition of the effects of UV radiation exposure and temperature. Reasonably detailed and accurate, lumped-parameter, kinetic models of the photo-oxidation process have also been developed, to interpret and predict the results of measurements of carbonyl, hydroperoxide and vinyl absorbances as functions of time and temperature; the models predict the general experimental behaviour, and also that both the formation of hydroperoxides and carbonyl Norrish-I reactions are important initiation steps. More complex models have the potential of interpreting other fine details of the degradation behaviour, namely the generation of other chemical species, and the chain scission and cross-linking process which are directly related to changes in the mechanical properties.     

The photochemistry of 1-benzoyl-2-naphthol and 6-hydroxybenzanthrone and their effect on the rate of photo-oxidation of polypropylene

A comparison of the effect of two structurally similar additives, 1-benzoyl-2-naphthol and 6-hydroxybenzanthrone, on the rate of photo-oxidation of polypropylene under conditions of simulated daylight shows that while 6-hydroxybenzanthrone acts as a prodegradant, 1-benzoyl-2-naphthol is a light stabilizer. Examination of the spectroscopic and photochemical properties of 1-benzoyl-2-naphthol indicates that in fluid solution the photoexcited stabilizer is probably deactivated within the singlet manifold. In glassy solvents at 77°K, on the other hand, triplet formation does occur, but only in molecules in which the intermolecular hydrogen bond of the 1-benzoyl-2-naphthol is disrupted.