聚乙烯薄膜光降解过程特性研究

通过牵拉伸、热重(TG)及傅立叶变换红外光谱(FTIR)测试，分析了3种可降解聚乙烯薄膜样品在人工加速老化实验过程中的光降解特性。结果表明，光照过程中母料在3种薄膜中发生引发反应，从而引入羰基；而且羰基指数随薄膜中母料含量的增加而增多，母料的加入有利于聚乙烯薄膜降解。随着光照进行，薄膜的力学性能和热学性能下降。3种样品在第1周期(24h)后进入衰变期，在第3周期(光照时间72h)后进入脆变期。     

超细煤粉对聚乙烯地膜光降解性能的影响

利用煤结构中的羧基、羟基、羰基、甲氧基、醌基、烷基侧链等活性官能团在光热氧作用下的氧化、分解产生自由基的特性,将超细煤粉作为光降解添加剂,研究其对聚乙烯(PE)地膜的光催化降解性能.通过拉伸强度、断裂伸长保留率、黏均摩尔质量以及羰基指数的测定,分析了PE在煤光催化降解过程中力学性能与分子结构的变化.结果表明:羰基指数先增加后降低,引起聚合物的结晶性、薄膜刚性和强度发生变化,导致薄膜的拉伸强度、断裂伸长率先增加后降低;薄膜中聚合物的摩尔质量在光照后可降解至8 000 g/mol,能够达到被土壤细菌吞噬进行生物降解的要求;聚乙烯中煤粉质量分数为5%时降解效果最佳.     

二乙基二硫代氨基甲酸铁对聚乙烯光降解性能的影响

借助人工加速光老化试验,通过测定含二乙基二硫代氨基甲酸铁聚乙烯薄膜的断裂伸长率,熔体流动速率,凝胶含量,羰基含量和脆化时间等指标,考察了ＦｅＤＥＣ对聚乙烯光降解性能的影响,证实ＦｅＤＥＣ在光氧化初期起抗氧剂作用,抑制了光氧化交联反应,使聚乙烯出现一个光降解诱导期;而在光氧化后期起光活性剂作用,加速断链反应,从而促进了聚乙烯的光降解,两种作用均与ＦｅＤＥＣ浓度成正比,通过调整ＦｅＤＥＣ用量,可以改变     

聚对苯二甲酸丁二醇酯在超临界甲醇中降解机理的研究

在高压间歇无搅拌反应器中研究了聚对苯二甲酸丁二醇酯(PBT)在高温甲醇溶液中的降解行为,通过对降解产物的各种定性和定量的分析,提出了超临界甲醇降解PBT的机理为在甲醇的作用下聚合物分子链的随机断裂和酯交换反应双重作用下发生的降解反应,建立了降解-反应模型.PBT在甲醇溶液中的降解可分为超临界区、非超临界区和中间过渡区三个区域.通过分子量测定考察了PBT在不同的区域中降解规律.在非临界区PBT在溶剂中处于溶胀状态,其数均分子量Mn下降缓慢,解聚程度低;在过渡区PBT的溶解性能提高,聚合物大分子发生断裂,降解速率加快;在超临界区,Mn随反应的进行而迅速下降,聚合物很快完全降解.在超临界区中PBT可实现完全降解,其主要产物为单体对苯二甲酸二甲酯(DMT)和丁二醇(BG),它们的收率可分别可达98.1%和72.3%.     

抗氧剂对聚乙烯光降解膜结构及性能的影响

采用紫外光加速老化的方法研究了抗氧剂1010对聚乙烯(PE)光降解膜的影响,并通过红外光谱、紫外光谱分析和拉伸性能测试对老化前后的薄膜的结构和性能进行了研究。结果表明,抗氧剂1010能抑制PE的光氧化降解,且导致薄膜光降解过程中羰基化合物的生成量和类型减少;添加抗氧剂1010的光降解薄膜降解的诱导期延长,PE光降解膜紫外照射3 d后其断裂伸长保留率小于80 %,而添加0.3 %（质量分数,下同）抗氧剂1010的PE光降解膜照射4~5 d后其断裂伸长保留率小于80 %。     

光化学交联聚乙烯薄膜

本文概述了光化学交联低密度聚乙烯的原理和方法。试验中采用多种光敏剂。结果表明,在紫外线照射下聚乙烯发生交联,最初5分钟光照时间内,凝胶含量增加,以后的6-10分钟内,凝胶含量基本保持不变。聚乙烯光化学交联同时发生断链、致使交联聚乙烯薄膜的强度降低。交联改善了聚乙烯薄膜的耐热性,使低密度聚乙烯交联薄膜可用作罐式硫化(155℃,30分钟)电线和电缆的隔离层材料。     

MoS_2/Bi_2S_3/Ni_3S_4黑暗下热催化降解低密度聚乙烯膜

以硫代乙酰胺、硝酸铋、硝酸镍、钼酸铵为主要原料,采用回流法合成了热敏催化剂MoS_2/Bi_2S_3/Ni_3S_4,将其与低密度聚乙烯(LDPE)熔融共混制得复合薄膜,并置于黑暗烘箱中热催化降解。通过SEM、EDS、AFM、TG、GPC、FTIR及力学性能测试,对热敏催化剂的结构和复合薄膜的热降解性能进行了考察。结果表明:纯聚乙烯薄膜在黑暗条件、55℃下热降解60 d后,热分解温度仅降低2.3℃,相对分子质量减小了17 451;而复合薄膜的降解效果明显优于纯聚乙烯薄膜,添加质量分数4%热敏催化剂的复合薄膜的热分解温度下降了20.5℃,相对分子质量减小了92 408,断裂伸长保留率低于5%,拉伸强度保留率低于20%,表面粗糙度明显增加且周围出现了不同程度的褶皱与鳞片状结构,甚至于剥落现象。此外,添加热敏催化剂的聚乙烯膜在降解过程中会出现大量的活性基团(·OH和HOO·等),可使聚乙烯发生链段降解,从而导致其分解温度降低。     

新型光降解体系对光/生物降解薄膜光降解行为的影响

研究了由光敏剂硬脂酸铁和抗氧剂 10 76组成的光降解体系的光 /生物双降解聚乙烯薄膜在紫外灯辐照下的断裂伸长率保留率、分子量、脆化期、诱导期等的变化规律。结果表明 ,硬脂酸铁具有促进光降解和抑制交联的双重作用 ;抗氧剂 10 76对薄膜光降解作用的影响没有硬脂酸铁显著 ;由它们组成的光降解体系具有较好的时控光降解效应 ,能使薄膜诱导期在较大时间范围内调控     

光/生物双降解薄膜的降解性能研究

研究了由光敏剂硬脂酸铁和抗氧剂1076组成的光降解体系的光/生物双降解聚乙烯薄膜在紫外灯辐照下的分子量、脆化期、诱导期、生物降解性能等的变化规律,并用红外光谱仪表征了塑料膜的化学结构变化,用电子显微镜观察了薄膜表面的微生物生长丰度.结果表明硬脂酸铁具有促进光降解和抑制交联的双重作用;抗氧剂1076具有较强的抑制光降解作用;硬脂酸铁和抗氧剂1076对诱导期的影响均比脆化期强;由它们组成的光降解体系经过光照后具有较强的生物降解性能.     

几种光敏降解聚乙烯薄膜的户外降解特性

用红外光谱法,分子量测定和力学性能测定研究了几种国内外生产的光敏降解聚乙烯薄膜在自然气候曝露时的化学—物理变化。建立了羰基生成,链端乙烯基增长或分子量下降与入射试样表面的太阳紫外光剂量的相关关系。发现曝露薄膜的降解具有季节性。     

Syntheses and properties of photodegradable polystyrene-containing carbonyl group

The copolymerizations of styrene (St) and methyl vinyl ketone (MVK) or phenyl vinyl ketone (PVK) were carried out in benzene by using azobisisobutylonitrile (AIBN). The synthesized copolymers, poly(St-co-MVK) and poly(St-co-PVK), were identified by infrared (IR) spectroscopy. Under the presence of oxygen, the copolymers containing carbonyl group after UV irradiation showed photodegradable properties that caused by Norrish Type II reaction. The new IR characteristic peaks, such as carbonyl and vinyl groups of the photooxidized copolymers, increased by increasing UV irradiation time. In the photodegradation property, the color differences of the synthesized copolymers were higher than those of polystyrene with increasing UV irradiation time, which was caused by the inherent photodegradable property of carbonyl unit in copolymers. The average molecular weights of samples after UV irradiation for 300 h decreased, as compared with polymers before irradiation. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1237–1242, 1998     

Studies on Linear Low-Density Polyethylene Functionalized by Ultraviolet Irradiation and Its Compatibilization

Summary Some groups containing oxygen such as C-O, C-OH and C=O were introduced onto the molecular chains of linear low-density polyethylene (LLDPE) through ultraviolet irradiation in air. The concentration of these groups containing oxygen increased with increasing irradiation time. After irradiation, the molecular weight of the LLDPE decreased, and its distribution widened. It was found that the gelation occurred after the LLDPE was irradiated for 12 h, and the gel content increased with increasing irradiation time. The crystal shape and space of the crystalline plane for irradiated LLDPE remained. Compared with those of LLDPE, the melt flow index, tensile strength and elongation at break of the irradiated LLDPE decreased, but its hydrophilicity increased and its toughness retained good. The polyamide 66 (PA66)/LLDPE/irradiated LLDPE blends were prepared by blending a small percentage of irradiated LLDPE with PA66. The melting temperature and crystallinity of both the LLDPE and PA66 components in the blends decreased with increasing irradiation time. The compatibility, dispersion and interfacial interaction between PA66 and LLDPE were improved after blending. With the addition of 5% LLDPE irradiated for 36 h, the tensile strength, bending strength and notched impact strength of the blends was enhanced from 48.3 MPa, 64.8 MPa and 30.8 J/m to 57.4 MPa, 71.5 MPa and 101.2 J/m, respectively.     

An Investigation into the UV-Photo-Oxidative Degradation of LDPE by Using Cobalt Naphthenate as Photosensitizer

The effect of cobalt naphthenate on photo degradation of low density polyethylene was studied. The carbonyl index, tensile strength, elongation at break, density and relative crystallinity of the samples were measured. The samples were made of different concentrations of LDPE and cobalt naphthenate. Parts of uniform thickness were cut for testing before and after UV-irradiation at every 30-days interval for 90 days. From the results of FTIR, and other measurements, it was observed that the UV-irradiation affects on the LDPE films and the rate of degradation increased with increasing both the concentration of the photosensitizer and time of irradiation.     

Grafting of styrene onto polyethylene in near critical media

In this work, near critical n‐heptane is used as reaction medium for the copolymerization of polyethylene with styrene monomer, using alkylation reaction with different amounts of aluminum chloride (AlCl₃) as catalyst. In this way, polyethylene chains will be more available to react with the catalyst. The reaction effect on pure reactants, as well as, the catalyst activity was previously investigated. The reaction occurrence was corroborated by analyzing the reaction products before and after careful polystyrene extraction with tetrahydrofuran. The reaction products were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry, and size exclusion chromatography. The possible architecture for the copolymer molecule was proposed from the molecular characterization results. On the other hand, the polystyrene grafting modifies final properties of polyethylene, increasing the oxygen barrier properties without deteriorating significantly the mechanical properties of the films. In this sense this reaction seems to be a promising route to modify PE films to increase the barrier properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Formation of 2,4-dinitrophenylhydrazones in high-density polyethylene film irradiated with ultraviolet light

Polyethylene films were irradiated in air by ultraviolet light. 2,4-Dinitrophenylhydrazine was reacted on the irradiated films. The changes in amounts of carbonyl groups and 2,4-dinitrophenynlhydrazones formed in the films were inferred by comparing their absorptions in the infrared and ultraviolet spectra, respectively. It seems that the contents of carbonyl groups formed in the amorphous regions in the high-density polyethylene films by the irradiation were larger than the contents of carbonyl groups formed in the amorphous regions in the low-density polyethylene films. The decreases in contact angles of water on the high-density polyethylene films by the irradiation were larger than the decreases in the contact angles on the low-density polyethylene films. The amounts of 2,4-dinitrophenylhydrazones formed in the irradiated high-density polyethylene films were less than the amounts of 2,4-dinitrophenylhydrazones formed in the irradiated low-density polyethylene films.     

Crosslinking of ultra-high strength polyethylene fibers by means of γ-radiation

Summary Ultra-high strength polyethylene fibers, with a tensile strength at break varying from 1.6 up to 3.5 GPa, were irradiated, at room temperature under vacuum by means of ⁶⁰Co -radiation. Sol-gel analysis showed a ratio of crosslinking to main-chain scissioning of about 1. The tensile strength at break decreased upon irradiation. The decrease of tensile strength at break depended on initial fiber strength and could be attributed to main-chain scissioning. It was concluded that stressed chains break preferentially upon irradiation. Fiber networks exhibited a deformation ratio of 16 during stress-strain measurements.     

山梨醇醚存在下聚乙烯的光氧化降解特性研究

通过特性粘度、凝胶含量、羧基含量及红外光谱测试,分析了山梨醇醚含量为0%、0.1%、0.3%、0.5%、l%、5%、8%的7种聚乙烯膜样品在人工加速老化实验下的光氧降解特性研究,并通过扫描电镜对山梨醇醚含量为1%的聚乙烯膜表面形貌进行了分析.结果表明,光照过程中,山梨醇醚在7种膜中引发自由基反应,致使聚乙烯分子交联、断...