光/生物降解聚乙烯薄膜的光降解性能

光/生物降解聚乙烯薄膜的光降解性能;淀粉;聚乙烯;塑料薄膜;降解性能     

含羧酸共生稀土光敏剂的低密度聚乙烯膜紫外光氧化降解

含羧酸共生稀土光敏剂的低密度聚乙烯膜紫外光氧化降解林宜超（福建省测试技术研究所福州３５０００３）近年来，许多作者先后研究并开发出含硬脂酸铈（ＣｅＳｔ３）光敏剂的可控光降解低密度聚乙烯（ＬＤＰＥ）［１，２］、高密度聚乙烯［３］、聚丙烯［４］、聚苯乙烯...     

煤改性聚乙烯塑料的降解性能及其机理探讨

通过对力学性能、红外光谱、粘均分子量及扫描电镜的分析,研究了煤/聚乙烯塑料在室内加速老化实验中的降解性能,并运用降解机理对实验过程进行解析及验证。结果表明,煤降解剂引发的交联和降解反应控制了薄膜的强度,使其柔韧性一直降低,且在整个120h光照过程中,断裂伸长率一直呈下降趋势;72h前是聚合物的氧化诱导期及衰变期,之后进入完全降解期。煤在改性塑料光照过程中引发自由基反应,引入羰基,导致聚乙烯大分子断链降解;共聚物的粘均分子量整体呈降低趋势,说明光照促进聚合物的降解,降解和交联交替控制着反应。煤/聚乙烯的光降解过程遵循链引发、链增长、链终止反应机理,在煤大分子光催化作用下,改变了聚乙烯常规光降解过程,加速了聚乙烯大分子断链和分子量降低。运用煤/聚乙烯塑料降解机理,能够解释样品力学性能变化、化学结构中羰基指数变化、分子量降低及降解过程中的现象和规律。     

红外光谱法研究含CeSt3的LDPE膜紫外光氧降解

报道了硬脂酸铈（ＣｅＳｔ_３）、及其在各种浓度、或不同温度、或延长贮放时间下含ＣｅＳｔ_３的低密度聚乙烯（ＬＤＰＥ）膜紫外光氧化降解过程的红外光谱。结果表明，只要在ＬＤＰＥ膜中加入０．１ｗｔ＋％～０．３ｗｔ＋％ＣｅＳｔ_３光敏剂，即可控光降解ＬＤＰＥ膜的寿命。     

铝材表面状态对TiO2薄膜光催化性能和光致亲水性的影响

在纯铝片和具有氧化铝层的铝片上用提拉法制备TiO2/Al和TiO2/Al2O3/Al样片,通过FTIRATR技术和密闭间歇式反应装置分别考察了TiO2薄膜对油酸和乙烯的光催化降解性能,通过测试接触角考察TiO2薄膜的光致亲水性.结果表明,TiO2/Al2O3/Al对油酸的光降解性能比TiO2/Al的好,但其光催化氧化乙烯性能和光致亲水性能较差.这种差别可通过不同过程的作用机理和Al与TiO2表面的电子转移作用得到较好解释,由此得出TiO2薄膜的光催化性能与光致亲水性可能是两种既有联系又相互独立的性质     

硝酸镧辅助细菌对聚乙烯的降解研究

研究了硝酸镧存在下细菌对聚乙烯的降解。主要通过FTIR和TG-DTA表征聚乙烯结构,扫描电镜以及X射线能谱仪展示了聚乙烯表面形态和元素含量变化。同时,使用分光光度计检测了降解液中细菌的数量,并与未降解的聚乙烯进行对照。FTIR显示与对照相比降解后出现了C=O吸收峰,能谱显示降解后有氧原子掺入,表明细菌主要是通过生物氧化作用对聚乙烯进行降解;TG-DTA分析和扫描电镜表明硝酸镧的添加对聚乙烯降解具有影响,分光光度计检测也显示硝酸镧有助于细菌在降解聚乙烯过程中更快的繁殖。硝酸镧可以通过加快细菌繁殖的方式提高对聚乙烯的生物降解速度。     

溶液pH值对二嗪磷紫外光降解产物及降解途径的影响

在低压汞灯(253.7 nm)光照条件下, 研究了溶液pH值对农药二嗪磷光降解产物及降解途径的影响. 结果表明: 不同溶液pH值条件下二嗪磷的光降解均符合一级反应动力学, 其在中性(pH=7.0, k=0.0234 min^-1)和碱性(pH=10.0, k=0.0236 min^-1)条件下的光降解速率基本相同, 且略高于酸性(pH=4.0, k=0.0193 min^-1)时的光降解速率. 通过UPLC-ESI-MS/MS对降解产物测定分析发现: 溶液pH值显著地影响了二嗪磷光降解产物的种类及生成量. 溶液pH=4.0、7.0和10.0的二嗪磷溶液分别UV光照60 min时分别检出了五种、八种和六种主要的光降解产物, 且同一产物在不同pH值条件下的生成量存在显著差异. 结合MS和MS/MS质谱图信息, 推导出了二嗪磷主要光降解产物的分子结构, 并根据光降解产物种类及生成量随光照时间的变化关系提出了不同溶液pH值时二嗪磷的可能降解途径.     

TiO2光催化降解胸腺嘧啶的动力学和机理

考察了用于降解来自嘧啶家族的一种核酸—胸腺嘧啶(C5H6N2O2)的高级氧化过程。结果发现,在光催化剂TiO2作用下,胸腺嘧啶的光降解进行得很快,且在紫外光照射和水溶液中时更为明显。研究了胸腺嘧啶在TiO2催化剂上的吸附、降解动力学、以及pH值对光催化降解胸腺嘧啶性能的影响。另外,考察了胸腺嘧啶降解产物的矿化;比较和讨论了在光催化过程中胸腺嘧啶的消失和矿化速率。同时还研究了氮的矿化,确立了中间产物的识别方法。最后,采用电子密度计算提出了在紫外光照射下TiO2催化剂上胸腺嘧啶降解的可能化学途径。     

TiO_2光催化降解胸腺嘧啶的动力学和机理（英文）

考察了用于降解来自嘧啶家族的一种核酸—胸腺嘧啶(C5H6N2O2)的高级氧化过程.结果发现,在光催化剂TiO2作用下,胸腺嘧啶的光降解进行得很快,且在紫外光照射和水溶液中时更为明显.研究了胸腺嘧啶在TiO2催化剂上的吸附、降解动力学、以及pH值对光催化降解胸腺嘧啶性能的影响.另外,考察了胸腺嘧啶降解产物的矿化;比较和讨论了在光催化过程中胸腺嘧啶的消失和矿化速率.同时还研究了氮的矿化,确立了中间产物的识别方法.最后,采用电子密度计算提出了在紫外光照射下TiO2催化剂上胸腺嘧啶降解的可能化学途径.     

玫瑰红作用下γ-六氯环己烷在冰相中的光敏化降解

考察了在玫瑰红(RB)存在下γ-六氯环己烷(γ-HCH)在冰中的光降解.结果表明,光敏剂RB通过其激发态[RB]~*及其产生的~1O_2~*加速了γ-HCH的光降解,RB浓度是影响光降解率最显著的因素;γ-HCH在较低初始浓度下的光敏化降解更快;无机盐离子的种类和浓度可以改变冰表面上类液层(LLL)的比例从而影响γ-HCH的光解.通过分析γ-HCH光降解产物提出了RB存在时冰中γ-HCH的光降解作用机理.     

Studies on the photo-oxidative degradation of LDPE films in the presence of oxidised polyethylene

This paper reports the results of photo-oxidative degradation studies of LDPE in the presence of varying amounts of oxidised polyethylene (OPE), which was prepared by heating LDPE films containing 0.1% cobalt stearate in oxygen atmosphere at 100 °C. OPE, with a CI of 12 was used as an additive for LDPE. Varying amounts of OPE (0.5-5%) were blended with polyethylene in an extruder and films of 70 μm thickness were prepared by film blowing process. The physico-chemical properties of the films were evaluated and these were found to be proportional to the amount of OPE. The films thus obtained were subjected to UV-B exposure at 30 °C for extended time periods. The chemical and physical changes induced by UV exposure were followed by monitoring the changes in mechanical properties (tensile strength and elongation at break), carbonyl index (CI), morphology, molecular weight, MFI and DSC crystallinity. Incorporation of OPE was found to be effective in initiating the photo-degradation of LDPE in relatively short span of time and the degradation was found to be proportional to the amount of OPE in the formulation.     

Surface ozonation and photooxidation of polyethylene film

High-density polyethylene (HDPE) and low-density polyethylene (LDPE) films were oxidized by treatment with ozone and by photooxidation with a low-pressure mercury lamp. The changes that resulted in the surfaces of the films were followed by ESCA. On ozonation, the surface of LDPE initially is oxidized more rapidly than that of HDPE; however, extended ozonation produces a surface composition that corresponds to C₈O for HDPE and to C₁₈O for LDPE. The surface oxidation products are mainly carboxyl groups, with lower levels of carbonyl and C? O groups. For both polymers photooxidation provides more extensively oxidized surfaces than ozonation, although the surface of HDPE oxidizes slightly faster than that of LDPE treated under identical conditions. In both cases the surface stoichiometry after extensive photoxidation is C₆O. The functional groups formed are mainly carboxyl and C? O. The effects of ozonation and photooxidation on the polyethylene surfaces are compared with those produced by several other means of surface oxidation.     

Model for the photooxidation of parylenes

Parylenes belong to a family of polymers that have been investigated for use in electronic and medical applications. The photooxidation of these materials is of interest both to prevent degradation and to induce targeted chemical changes. This article describes a transport and reaction model for the photooxidation of parylenes. This model is based on existing polymer photooxidation mechanisms that have been adapted to this system. The model has been compared with existing parylene photooxidation data for this system and shows qualitative agreement with surface oxidation profiles and oxidation depth profiles. On the basis of the results of the model comparison, it has been determined that the key parameters that appear to affect the photooxidation of parylenes are the diffusion coefficient of oxygen in these films and the concentration of oxygen initially present in these films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2666–2677, 2004     

High photocatalytic degradation activity of polyethylene containing polyacrylamide grafted TiO2

A novel photocatalytic polyacrylamide grafted TiO₂ (PAM-g-TiO₂) nanocomposite was prepared and embedded into a low density polyethylene (LDPE) plastic. Photocatalytic degradation of the LDPE/PAM-g-TiO₂ composite film was carried out under ambient conditions under ultraviolet light irradiation. The properties of composite film were compared with those of the pure LDPE film by measuring the changes in weight loss, carbonyl index, molecular weight, tensile strength and elongation at break. PAM-g-TiO₂ embedded LDPE showed highly enhanced photocatalytic degradation. Irradiating the LDPE/PAM-g-TiO₂ composite film for 520 h under UV light reduced its weight by 39.85% and average molecular weight (M_w) by 94.60%, while that of pure LDPE film was only 1.03% and 69.59%, respectively. The addition of PAM-g-TiO₂ brought about the good dispersion of TiO₂ in LDPE matrix and improved the hydrophilicity of composite film, which were able to facilitate the degradation of LDPE. The photocatalytic degradation mechanism of the films is briefly discussed.     

Surface modification of low density polyethylene (LDPE) film by low pressure O2 plasma treatment

In this work, low pressure glow discharge O₂ plasma has been used to increase wettability in a LDPE film in order to improve adhesion properties and make it useful for technical applications. Surface energy values have been estimated using contact angle measurements for different exposure times and different test liquids. In addition, plasma-treated samples have been subjected to an aging process to determine the durability of the plasma treatment. Characterization of the surface changes due to the plasma treatment has been carried out by means of Fourier transformed infrared spectroscopy (FTIR) to determine the presence of polar species such as carbonyl, carboxyl and hydroxyl groups. In addition to this, atomic force microscopy (AFM) analysis has been used to evaluate changes in surface morphology and roughness. Furthermore, and considering the semicrystalline nature of the LDPE film, a calorimetric study using differential scanning calorimetry (DSC) has been carried out to determine changes in crystallinity and degradation temperatures induced by the plasma treatment. The results show that low pressure O₂ plasma improves wettability in LDPE films and no significant changes can be observed at longer exposure times. Nevertheless, we can observe that short exposure times to low pressure O₂ plasma promote the formation of some polar species on the exposed surface and longer exposure times cause slight abrasion on LDPE films as observed by the little increase in surface roughness.     

The mechanism of biodegradation of polyethylene

LDPE films have been exposed to abiotic and biotic environments. The films were UV irradiated for periods of 0, 7, 14, 26 and 42 days before being mixed with water and soil.Degraded LDPE films were examined by infra-red spectroscopy. The carbonyl peak increased with time in the abiotic environment and the oxidative degradation reported in our earlier works was confirmed.In the presence of a biotic atmosphere, however, this peak decreased. At the same time there was an increase in double bonds which was related to weight loss. An explanation of this behavior is presented as a proposed mechanism for the biodegradation of polyethylene.This mechanism is compared, on the one hand, with abiotic photooxidation, Norrish type I and II degradation, and, on the other, with the biotic paraffin degradation. Abiotic, as well as biotic, ester formation mechanisms are also presented.An ESR spectrum confirms the presence of radicals on the polyethylene samples.At the beginning of the degradation the main agents seem to be UV light and/or oxidizing agents. When carbonyl groups have been produced, these are attacked by microorganisms which degrade the shorter segments of polyethylene chains and form carbon dioxide and water as end products.There is a synergistic effect between photooxidative degradation and biodegradation. The biodegradation of polyethylene can be compared with the biodegradation of paraffin.     

Effect of LDPE on the thermomechanical properties of LLDPE‐based films

The present study compares the properties of five films: one film of low‐density polyethylene (LDPE), two films of linear low density polyethylenes (1‐octene comonomer)—one made by metalllocene catalyst (mLLDPE) and the other by Ziegler–Natta (zLLDPE)—and two blend films, one of mLLDPE/LDPE (film A) and the other of zLLDPE/LDPE (film B). The effect of LDPE (22% by weight) on the thermomechanical properties of LLDPE‐based films is investigated by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and stress‐strain in the yield region measurements. The mechanical, dynamic, and thermal properties of film A are quite similar to a single component system (mLLDPE). The addition of this amount of LDPE does not affect the melting temperature of mLLDPE but it enhances its crystallinity. Film B is a rather inhomogeneous material, as opposed to film A, and its properties seem to be dependent on stretching conditions. Furthermore, the thermally activated rate process (Eyring's theory) is applied to analyze the yielding behavior of the two blend films. Double yielding manifested by film B is described with two thermally activated processes, while film A is satisfactorily described by a single process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1712–1727, 2005     

Comparing the effect of nanofillers as thermal stabilizers in low density polyethylene

A study of the thermal degradation under inert and oxidative conditions of LDPE and three 5-wt% nanocomposites has been performed. The bases of comparison were the geometries of the nanofillers (spherical, fibrous and laminar) and the sample thickness. Homogeneous and well-dispersed materials were obtained with the three nanoparticles, ensuring a relevant comparative analysis.The thermal degradation curves obtained from TGA under nitrogen flow did not show significant differences in behaviour within the nanocomposites and the reference LDPE. However, the results for the thermo-oxidation study showed a strong stabilization effect for both fibrous and laminar silicates, but not for the spherical silica nanoparticles. A kinetic study of the degradation under isothermal conditions showed that the nanocomposites made from fibrous and laminar silicates degraded following the mechanisms observed for thin films independent of the sample thickness. These results suggested the occurrence of a protective layer against thermo-oxidation on the film surface. Chemical analysis of the degraded surfaces by IR and EDX measurements gave data to explain these differences in behaviour.     

Influence of metal ion on the degradation of LDPE at the composting temperatures

Low Density Polyethylene(LDPE) films with additives that contain metal ions were subjected to accelerated degradation at simulated composting temperatures. The mechanical properties and viscosity-average molecular weight of the samples, during the degradation, were determined and the degradation mechanism was studied. The results show that the samples containing metal ion show considerable decreases. Percentage crystallinity of LDPE in the samples has changed obviously during the degradation. [POOH] increases during the early stage of degradation followed by a more or less flat maximum before it starts to decrease, but carbonyl index shows a polynomial increase during the degradation.