聚甲醛的耐沸水稳定化研究

讨论了聚甲醛的沸水老化机理、沸水老化行为及改善聚甲醛耐沸水性的方法。     

聚甲醛耐老化性能及其改进研究

以研制耐候性聚甲醛为目标，将自制高分子改性剂、其它改性剂与聚甲醛共混(POM)以提高POM的耐老化性。通过拉伸强度、断裂伸长率、冲击强度和色差的测定，比较了未改性聚甲醛和改性聚甲醛的耐紫外光老化、热氧老化和热水老化性能，结果表明：自制改性剂与其它改性剂共混用于聚甲醛，能显著改善聚甲醛的稳定性及耐老化性。     

耐候聚甲醛的制备及其性能研究

通过紫外光老化箱对聚甲醛进行了长期老化实验研究,以万能材料试验机、冲击试验机、热重分析仪、色差仪等仪器对长期老化后的聚甲醛的力学性能、热稳定性、色差等进行分析。结果表明,不同自由基捕获剂复配能达到良好的协同抗光老化效果,可明显改善聚甲醛材料的力学性能保持率、热稳定性及色差变化。     

光屏蔽剂对聚甲醛耐老化性能的影响

采用炭黑和纳米级氧化锌两种光屏蔽剂对共聚甲醛进行耐老化改性,对比了改性前后聚甲醛耐紫外光、耐热氧及耐热水老化性能的变化。结果表明,紫外光老化对聚甲醛性能影响最显著,两种光屏蔽剂均能减缓聚甲醛的光降解过程。炭黑的光屏蔽效果优于氧化锌,但会加速聚甲醛热氧降解。聚甲醛试样表面层相对分子质量的变化规律基本上与试样断裂伸长率、冲击强度以及色差变化规律保持一致。     

助剂对聚甲醛常温颜色稳定性的影响研究

在聚甲醛中添加不同助剂体系,通过室温放置20 d和140 ℃烘箱加速老化7 d处理后,测定物料的黄色指数、熔体质量流动速率、拉伸强度、冲击强度变化,对助剂体系在聚甲醛中的应用进行了评价.结果表明,抗氧剂Irganox1010对聚甲醛的颜色变化有很大影响,引入金属减活化剂后,提高了聚甲醛在常温环境中的颜色稳定性,同时也较好地保持了聚甲醛的各项性能.     

丙烯酸酯弹怀体对聚甲醛耐老化性能的影响

将自制的丙烯酸酯弹性体、抗氧剂和光稳定刺与聚甲醛熔融共混后进行紫外线老化实验．并对老化前后试样的力学性能和表面层分子量进行了测试。结果表明，改性聚甲醛的分子量得到了较好的保持，抗冲击韧性及断裂伸长率均明显优于未改性聚甲醛。     

聚甲醛热降解性能研究

通过测定聚甲醛的熔融指数、拉伸强度及断裂伸长率，分析、比较其热老化的速度；同时应用扫描电镜、X-射线光电子能谱观察和分析了聚甲醛（POM）的表面形貌、表面官能团的类型。试验结果表明：120％热老化试验条件下，随着老化时间的延长，熔融指数逐渐增大，说明发生了缓慢的热氧化降解过程；20天短期热老化对聚甲醛拉伸强度及断裂伸长率影响不是很明显，说明POM的热老化应该有一个相当长的过程；扫描电镜显示：105天热老化后，聚甲醛表面出现龟裂和粉化现象；X-射线光电子能谱显示：老化前后样品中C1s谱均含有C-C和C-02个峰，但老化后C-C含量降低，C-O含量增加，说明POM的热老化以C-C断裂降解为主，原始试样O1s／C1s为56．98％，105天老化后为72．92％。     

"仪器仪表用工程塑料老化性能的研究"通过部级鉴定

由合肥工业大学化工系金荣福副教授负责的该项研究于一九九0年十二月二十七日在合肥通过国家机电委员会仪表司主持的专家鉴定.本项研究通过热老化实验,采用数学处理方法,选取动力学函数,并计算动力学参数,阐明了改性聚甲醛系列新品级的热氧降解反应机理,为聚甲醛老化和热稳定的研究提供了理论依据.提出了从老化     

聚甲醛加速老化试验研究

对聚甲醛（POM）进行了光加速老化试验和湿热老化试验研究。利用电子显微镜，差示扫描量热仪和X光电子能谱对材料在老化过程中的物理和化学性能进行了分析。结果表明，POM在老化过程中物理力学性能下降的主要原因是表面无定形区域的光氧化。     

聚甲醛耐光稳定性研究进展

综述了聚甲醛光氧老化特性和光稳定剂研究开发现状,指出了聚甲醛光稳定剂未来发展趋势。聚甲醛对抗紫外光稳定性较差,容易发生降解与氧化,添加光稳定剂有助于提高聚甲醛耐光稳定性。常用的聚甲醛光稳定剂主要包括紫外光屏蔽剂、紫外光吸收剂和受阻胺类光稳定剂等三大类,对光稳定剂的研究方向主要包括高相对分子质量化、聚合物键合化、多功能化、受阻胺低碱性化等方面。     

PET的湿热老化性能研究

研究了PET材料在加速老化条件下性能的变化。结果表明PET在湿热老化过程中老化性能的变化受三个因素影响:结晶度、水增塑、水解,各因素自始至终都在起作用,不同的阶段不同的因素起主导作用。老化初期,结晶为主导因素,它增加杨氏模量、最大拉伸应力,但使材料变脆,降低冲击强度;然后水增塑成为主要因素,它使材料韧性增加,冲击强度增大;老化后期,水解反应上升为主要因素,它引起PET大分子链断裂,分子量下降,从而引起机械性能的破坏     

Relationship Among Thermal Ageing Degradation,Dynamic Properties,Cure Systems,and Antioxidants in Natural Rubber Vulcanisates

The present work aims to study the relationship among the thermal ageing stability, dynamic properties, cure systems, and antioxidants in natural rubber (NR) vulcanisates. Thermal degradation behavior of NR vulcanisates has been investigated and correlated to the changes in cross-link density, tensile and dynamic mechanical properties. The results obtained show that thermal ageing properties of NR vulcanisates depend strongly on cross-link density, which changes during thermal oxidative ageing or the so-called postcuring effect. In addition, the increases in ageing temperature and time lead dominantly to the postcuring and linkages scission phenomena in vulcanisates cured with CV and EV systems, respectively. With increasing ageing temperature, the tensile strength shows sharp drop at ageing temperature higher than 70°C and 100°C for the specimens cured with CV and EV systems, respectively. The sharp drop of tensile strength of vulcanisates cured with CV system is attributed to the too high cross-link density, which is caused by the postcuring effect. In the case of the vulcanisates cured with EV system, the linkage scission causes the sharp drop of tensile strength. The addition of amine-based antioxidant appears to improve ageing properties. However, the excessive antioxidant reduces tensile properties via a decrease in cross-link density.     

新型ACS树脂综合性能的研究

本文主要研究了新型ACS树脂的流动性、力学性能、热性能、耐老化性能以及阻燃性能,并与ABS、AAS树脂进行了性能对比。结果表明：随着CPE含量的增加,ACS树脂的抗冲击性和阻燃性提高,熔体流动速率、拉伸强度、断裂强度和热变形温度都下降;并且ACS的抗冲击性能、耐候性和阻燃性远远高于ABS和AAS树脂。     

Influence of ultraviolet radiation and aggressive media on epoxy coating degradation

The influence of ultraviolet radiation and of 5% water solutions of sulphuric acid, potassium hydroxide and sodium chloride on an epoxy coating was investigated. It was found that those factors cause generation of characteristic (for a given ageing kind) cracks on the coating surface. UV radiation, for example, gave rise to cracks called silver cracks. It was found as well that ageing changes in the coating influence the mechanical properties such as hardness, statical and dynamical strength.     

Microconcrete ageing ultrasonic identification

In this paper, a global identification of the Voigt stiffness matrix is provided for different aged microconcrete. The approach is a part of the research that develops actively the field of cement-based materials ageing assessment. It investigates the ability of the ultrasonic and laser impact tests to classify the ageing level of the altered specimen and to obtain an evaluation of elasticity coefficients. Three different specimens are tested: the first one with no degradation is used as the reference and the other two are damaged by using freeze/thaw cycles or a chemical attack. The ageing provides a heterogeneous structure, which is approximated like an equivalent weakly transversely isotropic medium in the long wave length limit hypothesis. To validate qualitatively the porosity and water content influences on the elasticity moduli, the experimental results are compared with the prediction of the Hudson's homogenized scattering medium. This model is extended to a smooth phenomenological law in the domain of high porosity. The interest of modelling a continuously altered medium is finally outlined and opens a field of investigation in the future, which accounts for the local properties of heterogeneous materials, improving the ultrasonic inspection.     

Investigation on Physico-Mechanical Properties,Water, Thermal and Chemical Ageing of Unsaturated Polyester/Turmeric Spent Composites

Nutraceutical industrial residues are potential fillers to fabricate green or eco-friendly polymeric composite materials as they are, less costly and easily available. Attempts have been made to use turmeric spent (TS)—a nutraceutical industry waste with a high E-factor to improve need-based properties of plastics. A series of unsaturated polyester resin composites have been fabricated with different turmeric spent content viz., 5, 10, 15 and 20% w/w. The effect of amount of filler content on tensile strength, physical properties including density and surface hardness and chemical resistance of the composites were determined. The influence of water and thermal ageing on the tensile strength of turmeric filler loaded unsaturated polyester composites has been studied.     

Thermo-oxidative ageing and its effect on the network structure and fracture mode of natural rubber vulcanizates

The changes in network structure and fracture mode of unfilled and filled natural rubber vulcanizates, during ageing at 100°C have been studied by chemical analyses and scanning electron microscopy. The fall in properties during ageing is caused mainly by chain scission. The increase in crosslink density during the initial periods of ageing causes an increase in modulus and tensile strength. Carbon black accelerates ageing, probably by surface catalysis. The simple network structure of efficiently vulcanized rubber results in better retention of properties during ageing. Antioxidant retards ageing. The extent of degradation of vulcanizates is reflected in the nature of the fracture surfaces. The roughness of the tensile fracture surface is affected to varying degrees depending upon the ageing resistance of the vulcanizates. However, in tear, the mode of fracture propagation is affected by ageing.     

POM／PU共混物增容剂的合成与应用

本文以酸为催化剂，将甲醛与一缩乙二醇缩合聚合，缩合物经ＴＤＩ封端，１，４－丁二醇扩链合成了ＰＯＭ／ＰＵ共混物的增容剂ＰＯＵ。利用化学分析法、红外光谱法对合成的ＰＯＵ增容剂进行了表征；借助扫描电子显微镜，差分析仪分析了共混物的微观结构形热行为，并对共混物的力学性能进行了系统研究。研究发现ＰＯＵ的加入使分散相颗粒尺寸明显减小，使三元共混物中ＰＯＭ的烷点降低，并使三元共混物的拉伸强度、缺口冲击强度、断裂     

Bleeding of concrete as an ageing consolidation process

Bleeding of concrete results mainly from the self-weight consolidation of the granular skeleton. Simultaneous physical and chemical structural effects provoke the ageing of the skeleton. In addition, the displacements are large and the hydromechanical properties evolve locally with the porosity. All these phenomena are here addressed through an ageing nonlinear model accounting for the sample size effect experimentally observed on the bleeding capacity. The characteristic time scaling of the ageing effect is found to be dependent mainly upon the amount of cement in the mix-design and the temperature. It appears to be a key indicator for assessing the properties of fresh concretes and their evolution in time.