稀土有机化合物催化LDPE光降解研究

文章研究了低密度聚乙烯(LDPE)加入不同用量的硬脂酸混合稀土(ReSt3)、硬脂酸铈(CeSt4)、硬脂酸铁(FeSt3)的力学性能和光降解性能的变化。经过研究找出效果较好的光降解剂及用量,以求在保证其使用性能的基础上加快降解速度,减少白色污染。研究结果表明,加入光敏剂后对LDPE的力学性能影响不大,能保证其使用性能;在光照初期,发生了交联反应,使得LDPE的力学性能有所提高,随着光照时间的延长,力学性能开始下降。在光照过程中,LDPE表面氧化随辐照时间变长而加剧。三种光降解剂对LDPE的降解效果为硬脂酸铁优于硬脂酸铈优于硬脂酸稀土。     

光降解聚乙烯薄膜的研究

合成并用FT-IR表征了硬脂酸铁(FeSt3)光敏剂。采用自制光敏剂与纳米二氧化钛(TiO2)制备出可光催化降解薄膜,通过人工加速紫外老化降解试验,测定了含有光敏剂的低密度聚乙烯(LDPE)薄膜的力学性能、FT-IR谱图和黏均相对分子量的变化。结果表明:硬脂酸铁(FeSt3)对LDPE具有很强的光催化降解作用,并且含量越高,光催化作用越强;纳米TiO2可以延缓LDPE的降解诱导期,且随着其含量增大,效果越明显。     

硬脂酸铁加速LDPE膜光降解作用的研究

本文合成了硬脂酸铁(FeSt_s),用等离子体发射光谱、热分析仪、紫外光谱、红外光谱等分析手段进行了表征,研究了它对光氧化低密度聚乙烯(LDPE)薄膜羰基指数和粘均分子量的影响,并探讨了它的作用机理.结果表明:在LDPE膜中加入0.1%～0.3?St_s,即可控制可分解LDPE膜的使用寿命;羧酸铁在光解LDPE膜中的敏化活性依次递减如下:硬脂酸铁>月桂酸铁>辛酸铁;月桂酸铁和辛酸铁的光敏催化活性较低;二苯甲酮不是LDPE的有效光敏剂,能阻滞LDPE的光降解作用;高温下UV光降解LDPE膜的光降解速率高于低温下的光降解速率.     

添加硬脂酸锌改善LDPE薄膜的开口性

研究了用硬脂酸锌(ZnSt)为润滑剂改善LDPE薄膜开口性差的生产技术条件,并对产品的外观、物理力学性能进行了分析研究。     

含铁络合物类光敏剂降解塑料性能的研究

合成了以二硫代氨基甲酸为配体的一系列铁络合物以及硬脂酸铁光敏剂。通过人工加速紫外光降解试验和自然暴露试验,研究了含光敏剂的LDPE膜的力学性能、粘均分子量、红外线吸收及羰基指数的变化,比较讨论含上述铁盐光敏剂的LDPE的光降解性能     

低密度聚乙烯/改性水滑石纳米复合材料的制备、结构与性能

采用共沉淀法制备了镁铝水滑石(Mg-Al-LDHs),并以之为原料通过柱撑法制备了Zn O柱撑Mg-Al-LDHs。采用硬脂酸(SA)对其进行有机改性,得到改性水滑石(LDHs-SA),然后通过熔融插层法制备了低密度聚乙烯(LDPE)/LDHs-SA纳米复合材料。通过红外光谱分析、热分析、流变学分析、力学性能分析等对LDPE/LDHs-SA纳米复合材料的结构、性能进行了表征与分析。结果表明:当LDHs-SA的添加量为3%时,LDPE/LDHs-SA纳米复合材料的力学性能达到最优,其拉伸强度、断裂伸长率和冲击强度较之LDPE分别提高了4.4%、30.2%和13.1%。此外,LDHs-SA的加入改善了LDPE材料的热稳定性和流变性能。     

注塑用聚丙烯化学发泡专用料的研制与性能

将PP/LDPE共混物、硬脂酸改性碳酸氢钠(Na HCO3)与纳米碳酸钙(纳米Ca CO3)作为原料,采用闭模发泡注塑工艺制备了聚丙烯(PP)化学发泡专用材料。通过熔体流动速率(MFR)、热重分析(TG)与扫描电镜(SEM)对其进行了表征,研究了硬脂酸对碳酸氢钠分解温度的影响,熔体强度、改性碳酸氢钠与成核剂对减重率与力学性能的影响。结果表明,硬脂酸与碳酸氢钠按照1∶2的比例加入,使初始分解温度提高到184℃,分解区间为184～199℃,熔体强度与改性碳酸氢钠用量的提高均可使发泡试样的减重率增大,成核剂的加入提高了发泡试样的冲击强度。当加入改性Na HCO32. 5份,成核剂Ca CO32份,LDPE 20份时,减重率为9. 25%,冲击强度为32. 7 k J/m2,与未发泡材料的冲击强度(23. 8 k J/m2)相比,提高了37. 4%。     

POE对LDPE发泡行为的影响

用化学发泡注射成型技术,在低密度聚乙烯(LDPE)中加入不同牌号聚烯烃弹性体(POE),于二次开模时制备微发泡LDPE复合材料,分析材料本征特性对发泡LDPE复合材料发泡行为的影响。结果表明:LDPE中加入不同牌号POE后,表现出不同黏度;加入8100,8440,8450POE的LDPE复合材料发泡后,泡孔平均直径较大,泡孔尺寸不均匀,有并泡现象存在;而加入8180POE的发泡LDPE复合材料,泡孔直径较小,泡孔尺寸均匀,发泡质量理想,适用于发泡LDPE制品的开发。     

可控光降解聚乙烯薄膜的研究

制备了硬脂酸铈（CeSt4）光敏剂。采用自制的CeSt4与硬脂酸锌（ZnSt2）、硬脂酸钙（CaSt2）、纳米二氧化钛（TiO2）等配合剂,制备出一种添加型的可控光降解聚乙烯（LDPE）薄膜。用红外光谱、粘均法测分子量和DSC等方法,对老化后的LDPE薄膜样品进行了表征。试验结果表明：CeSt4是一种很好的光敏剂;ZnSt2和CaSt2是有效的光降解促进剂,可缩短LDPE薄膜的光降解诱导期;改性纳米TiO2可延长LDPE薄膜光降解诱导期。     

淀粉粒径对微细化淀粉/LDPE共混体系降解性能影响

采用光降解、土埋降解和环境降解法，研究了不同粒径微细化淀粉／LDPE共混膜的降解性能。结果表明，淀粉粒径的降低促进LDPE的环境降解基体的形成，加速淀粉和LDPE的环境降解速度。微细化淀粉／LDPE共混体系的降解是环境促降解因子共同作用的结果。     

Simulated evaluation of the degradation of hydrophobically associative polymers in the formation

In this work, indoor physical simulation experiments were used to examine the effects of shear, thermal, chemical, and microbial degradation on the properties of the hydrophobic associative polymer AP-P4. It was discovered that the viscosity of the polymer solution generally decreased as the shear time was extended. The larger the shear strength, the lower the solution viscosity. Fitting of the nonlinear equation of solution viscosity with shear time, η = 12,988 t^−1.08. When thermal degradation started, the solution viscosity first started to rise, however, this phase was just a short one. The viscosity of the solution gradually started to decrease as the thermal degradation period grew. In addition, the trends of properties like hydrokinetic radius, hydrophobic connectivity, and hydrolysis essentially followed the same patterns as those of solution viscosity. At the beginning of the degradation process, the viscosity retention of the polymer solution without oxygen is significantly higher than that of the aerobic environment. However, the difference between the two becomes smaller as the degradation time increases. In addition, the AP-P4 had good temperature resistance and aging resistance capabilities when iron ions were present. Finally, it was discovered that AP-P4 had a strong antibacterial effect, which decreased the viscosity brought on by microbial action.     

Thermal Degradation of Polystyrene

The thermal degradation of polystyrene in the absence of oxygen is examined, at temperatures above or below 300°C. The decrease in degree of polymerisation occurring either with negligible volatilisation at lower temperatures, or with evolution of low molecular weight products at higher temperatures, is simulated by Monte-Carlo procedures. The results suggest that below 300°C, scission of the polymer chains is random, and involves also a minor fraction of some abnormal, as yet unidentified, structures. Above 300°C, an extensive intermolecular transfer process seems to be the main cause of the decrease in degree of polymerisation, whereas an overall depolymerisation of 100 structural units at each chain scission is the source of volatilisation.     

用热分析方法研究络合物Pd（NH3）4Cl2.H2O的热氧降解过程与动力学

用差热分析法、热重分析法和微分热重分析法研究经各合物Ｐｄ（ＮＨ３）４Ｃｌ２．Ｈ２Ｏ在空气流中的热氧解过程和动力学，发现Ｐｄ（ＮＨ３）４Ｃｌ２Ｈ２Ｏ热氧降解过程由４个紧连步骤组成。     

Polymer pyrolysis: A resolution of anomalies in kinetic schemes for the rate of evolution of volatile products

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.     

甲氰菊酯的酶促降解

阴沟肠杆菌w10j15中提取到甲氰菊酯降解酶,测定了其对甲氰菊酯的降解特性。研究结果表明,降解酶在40℃、pH7 5时对甲氰菊酯显示最大的降解活性,对甲氰菊酯的降解率为65%。经实验测定,其每毫克酶蛋白质最大降解速率Vmax为48 08 nmol·mL-1·min-1,米氏常数(Km)为332 23 nmol·mL-1。     

气氛对低氮天然橡胶热降解的影响

采用热重分析(TG),研究了恒定升温速率下,低蛋白橡胶在氮气和空气气氛中的热降解行为,考察了反应气氛对降解速率、降解率和动力学参数的影响,分析了两者降解机理的可能差别。发现降解温度和降解率,氮气中均高于空气中;表观反应级数氮气中为2.0级,空气中为1.9级。     

有机氯农药的微生物降解研究进展

由于有机氯农药具有生物积蓄性、持久性、高毒性等特征,给环境带来了巨大的危害,微生物降解是目前主要的降解手段之一。综述了国内外有机氯农药的种类、多介质的迁移、降解有机氯农药的微生物及其降解的机理,并对有机氯农药微生物降解的发展前景进行了展望。     

Moisture and temperature degradation of double cantilever beam adhesive joints

In this work, the double cantilever beam (DCB) test is analysed in order to evaluate the combined effect of temperature and moisture on the mode I fracture toughness of adhesives used in the automotive industry. Very few studies focus on the combined effect of temperature and moisture on the mechanical behaviour of adhesive joints. To the authors’ knowledge, the simultaneous effect of these conditions on the fracture toughness of adhesive joints has never been determined. Specimens using two different adhesives for the automotive industry were subjected to two different ageing environments (immersion in distilled water and under 75% of relative humidity). Once they were fully degraded, they were tested at three different temperatures (?40, 23 and 80 °C), which covers the range of temperature an adhesive for the automotive industry is required to withstand. The aim is to improve the long term mechanical behaviour prediction of adhesive joints. The DCB substrates were made of a high strength aluminium alloy to avoid plastic deformation during test. The substrates received a phosphoric acid anodisation to improve their long term adhesion to the adhesive. Results show that even though a phosphoric acid anodization was applied to the adherends, when the aged specimens were tested at room temperature and at 80 °C, they suffered interfacial rupture. At ?40 °C, however, cohesive rupture was observed and the fracture toughness of the aged specimens was higher.     

线性PBS基脂肪族聚酯的合成和降解研究

为了探讨线性PBS基脂肪族共聚酯的结构和降解之间的关系,首先合成了线性PBS基脂肪族共聚酯,即聚丁二酸丁二醇酯-共-聚己二酸丁二醇酯P(BS-co-BA),聚丁二酸丁二醇酯-共-癸二酸丁二醇酯P(BS-co-BSe),并将线性PBS基脂肪族共聚酯及PBS在土壤悬浮液中进行降解,通过GPC、熔点测定仪对线性PBS基脂肪族共聚酯的分子量和熔点进行了测定;通过测定降解过程中失重率和降解前后聚酯薄膜表面形貌来对共聚酯降解程度进行表征。结果表明:随着二元酸碳链的增长,分子对称性降低,降解性能增大。通过观察分子量,熔点及降解失重率的测定结果,得出分子量越大,降解越不容易进行;熔点越小,降解性能越好。     

Degradation of low density polyethylene during extrusion. III. Volatile compounds in extruded films creating off‐flavor

This study was aimed at finding a correlation between the experienced off‐flavor in packaged foods and the presence of specific degradation products in PE packaging films. The possibility to trap degradation products by chemical reactions with scavengers, that is, zeolites and maleic anhydride grafted LLDPE, were investigated. This trapping would prevent the degradation products from migrating to the polymer film surface and further into food in contact with the film. This work concludes that off‐flavor in water packed in LDPE‐films depends on extrusion temperature and the content of oxidation products in the polymer film. At lower extrusion temperatures, reactive additives to the LDPE material could control the release of off‐flavor giving components. Adsorbents, such as zeolites, which are able to adsorb degradation products, are effective also at higher extrusion temperatures. The amount of oxidized degradation products in the films correlated well to the perceived off‐flavor in the packed water. The presence of aldehydes and ketones have a clear impact on the off‐flavor. The best correlation between off‐flavor and oxidized components were found for C₇? C₉ ketones, and aldehydes in the range of C₅ to C₈. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 847–858, 2005