PE膜氧化-生物降解研究进展

聚乙烯(PE)中添加助氧化剂是解决废弃PE薄膜环境污染问题的一种有效方法。助氧化剂通过促进光和热降解导致聚合物分子链断裂而使塑料制品更易于生物降解。本文对近年来有关PE膜的氧化反应与微生物降解的研究进展进行了综述。     

Calendar of events

The growth of Cu and Al films thermally evaporated onto polyethylene (PE) and polyethyleneterephthalate (PET) surfaces is followed in situ by XPS (X-ray Photoelectron Spectroscopy) and XAES (X-ray Auger Electron Spectroscopy) from the early submonolayer stages up to the completion of a metallic film. PE and PET surfaces were metallized first without any preliminary treatment. A second series of metallization experiments were run on the polymer surfaces but pretreated by a remote O₂ microwave plasma (2.45 GHz). These metal films have also been investigated by AFM (Atomic Force Microscopy) in air. Both metals are shown not to undergo chemical interaction with low surface energy polyolefin such as PE. While an abrupt interface is seen with A1, a diffusion of Cu into the bulk of the polymer is demonstrated. Large size clusters are evidenced by AFM in the initial steps of deposition. Cu and A1 are both shown to react with PET, but not in the same way. In the case of A1, the chemical interaction across the metal/polymer interface proceeds through an electron transfer from the metal toward the ester group O=C-O. With Cu, the chemical interaction is not so clearly evidenced and the Cu is found to diffuse into the PET. Oxygenated functionalities grafted by O₂ plasma on PE and PET are C-O, C=O, O-C-O, O-C=O, and O₂C=O. The roughness of the PE and PET surfaces is observed by AFM to increase with the plasma treatment. A metal-CO type complex is clearly observed with Al/treated PE and Cu/treated PET. No chemical interaction was observed at the Cu/treated PE interface.     

Plasma-modified polyethylene membrane as a separator for lithium-ion polymer battery

The surface of polyethylene (PE) membranes as a separator for lithium-ion polymer battery was modified with acrylonitrile (AN) using the plasma technology. The plasma-induced acrylonitrile coated PE (PiAN-PE) membrane was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and contact angle measurement. The electrochemical performance of the lithium-ion polymer cell fabricated with the PE and the PiAN-PE membranes were also analyzed. The surface characterization demonstrates that the enhanced adhesion of the PiAN-PE membrane resulted from the increased polar component of surface energy for the PiAN-PE membrane. The presence of the PiAN induced onto the surface of the membrane via the plasma modification plays a critical role in improving the wettability and electrolyte retention, the interfacial adhesion between the electrodes and the separator, the cycle performance of the resulting lithium-ion polymer cell assembly. The PiAN-PE membrane modified by the plasma treatment holds a great potential to be used as a high-performance and cost-effective separator for lithium-ion polymer battery.     

Control of the migration behavior of slip agents in polyolefin‐based films

Unsaturated long‐chain carboxylic acid amides like Erucamide are very efficient as slipping agents in polyolefin films and other polymers. A problem is the uncontrolled migration of this additive. The main goal of the present project was therefore the study and understanding of Erucamide diffusion through the film and how the diffusion behavior can be altered using plasma surface treatments or additional additives with varying molecular weights and hydrophilic–hydrophobic balance. The determination of the amount of Erucamide and co‐additive at the surface of the polymer film has been carried out by attenuated total reflectance (ATR) spectroscopy. The study shows that the system is highly sensible to the chemical structure of the surface modifier and particularly their hydrophilic–hydrophobic balance and their molecular weight. The most efficient surface modifier tested in this work was a block‐co‐oligomer with 50% polyethylene (PE) and 50% polyethylene oxide (PEO) sequences that can successfully be used to reduce Erucamide migration at both sides of the three‐layer‐PE‐films. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Proliferation rate of fibroblast cells on polyethylene surfaces with wettability gradient

Surface wettability on anchorage‐dependent cells has an important role in cell growth rate. In our previous studies, we prepared a wettability gradient on polyethylene (PE) surfaces using corona discharge treatment from a knife‐type electrode whose power increased gradually along the sample length. The PE surfaces were oxidized gradually with increasing power and characterized by Fourier transform infrared spectroscopy, contact angle goniometry, and electron spectroscopy for chemical analysis. The purpose of this study is to determine the rate of proliferation on polymer surfaces with different wettability. The behavior of cell growth for NIH/3T3 fibroblast cells attached on the polymer surfaces with different hydrophilicity was investigated using wettability gradient PE surfaces prepared by corona discharge treatment. They were investigated for the number of grown cells from 24 to 60 h in terms of surface wettability. From the slope of cell number on PE gradient surface versus culture time, the proliferation rates (number of cell/cm² · h) were calculated. It was observed that the proliferation rate was increased more on positions with moderate hydrophilicity of the wettability gradient surface than on the more hydrophobic or hydrophilic positions, i.e., 1111 (number of cell/cm² · h) of 57° of water contact angle at the 2.5‐cm position (P < 0.05). This result seems closely related to the serum protein adsorption on the surface: the serum proteins were also adsorbed more on the moderately hydrophilic surface. In conclusion, surface wettability plays an important role in cell adhesion, spreading, and proliferation on the polymer surfaces. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 599–606, 2004     

Investigating the effect of power/time in the wettability of Ar and O2 gas plasma-treated low-density polyethylene

Low-pressure glow discharges of Ar or O₂ gas plasmas were used to increase the wettability of low-density polyethylene (LDPE) films in order to improve their adhesion properties hence making them useful in technical applications. Surface free energies of such films were estimated by the aid of contact angle measurements at different exposure power/time combinations for a series of test liquids. Additionally, plasma-treated samples were subjected to several aging processes to determine the durability of different plasma treatments. Characterization of the surface changes due to plasma treatments were carried out by means of attenuated total reflectance, Fourier transform infrared spectroscopy (FTIR-ATR) to determine the presence of polar species such as hydroxyl, carbonyl, carboxyl, etc. groups. Furthermore, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to evaluate changes in surface morphology and roughness. Considering the semi-crystalline nature of the LDPE film, XRD studies were also carried out to determine changes in the percentage of crystalinity. The results showed that all low-pressure Ar or O₂ gas plasmas improve the wettability properties of LDPE films. Contact angles decreased significantly depending on the discharge powers and exposure times. Surface morphology was also found to vary with plasma discharge powers, exposure times, and the type of gas being used. Ar gas plasmas comparatively produced superior results.     

Investigation of high-density polyethylene film surface treated with chromic acid mixture by use of 2,4-dinitrophenylhydrazine

High-density polyethylene films were treated with chromic acid mixture. 2,4-Dinitrophenylhydrazine was reacted on the treated films. The changes in amounts of 2,4-dinitrophenylhydrazones formed in the films were inferred by comparing the absorptions in the ultraviolet spectra. The changes in the film surfaces by chromic acid mixture treatment were investigated by comparing the changes in the amount of the hydrazones with changes in water wettability of the treated films. Scanning electron micrographs of the treated film surfaces were taken. Oxidation of the film surface zone, partial breakdown of polymer in the film surface zone, and oxidation of surface zone bared from the film inner zone seem to have occurred with increase in treatment time. When the treatment temperature was raised, the increase in carbonyl groups in the surface of the high-density polyethylene film with rise in treatment temperature seems to have been prevented by an increase in partial breakdown of polymer in the film surface.     

Adhesion of flame-treated polyolefins to styrene butadiene rubber

Samples of polyethylene and polypropylene have been submitted to repeated short duration (75 ms) flame treatments, at optimum flaming conditions. Surface energies of untreated and flamed specimens were determined by liquid contact angle measurements. It appears that the surface energy of polyethylene increases much more than that of polypropylene after flame treatment. The flamed polymer surfaces were further examined by electron spectroscopy, Fourier Transform IR spectroscopy and secondary ions mass spectrometry. The adhesion properties of modified polymer surfaces were studied by testing in peel the bonded Styrene Butadiene Rubber/polyolefins assemblies. Scanning electron microscopy (SEM) and water contact angle measurements have been used to observe the locus of failure. Good correlations were obtained between surface energy and adhesion strength, the increase in adhesion strength being particularly important for flamed PE/SBR assemblies. In addition, the peeling in a liquid medium allowed the determination of the respective contribution to adhesion of chemical and physical interactions. It is shown that a major part of the adhesion strength increase is of chemical origin, particularly for the bonded flamed PE/SBR assemblies.     

Hot-melt adhesion and wettability between polyethylene and other polymers in the vicinity of the adherend melting point

The effect of bonding temperature on the bonding strength of polyethylene to polypropylene or other polymers was investigated. It became clear that the interfacial bonding strength reached maximum strength at a bonding temperature in the vicinity of the melting point of the adherend (i.e., the polymer having the higher melting point). The effect of temperature on the contact angle of the molten polymer having the lower melting point on the adherend surface was also investigated. The wettability of the adherend by the molten polymer drop was considerably reduced at the temperature near the melting point of the adherend. The relationship of increasing adhesiveness to decreasing wettability was found out.     

An organic bioactive pro-oxidant behavior in thermal degradation kinetics of polypropylene films

Due to its versatility and low cost, polypropylene (PP) is one of the most widely used polymers in the world. However, since it does not easily degrade in natural environment, various methods have been studied to reduce its lifetime. The pro-degrading additives promote the polymer degradation process by accelerating the polymer degradation under heat and/or UV. Eco-one is an organic bioactive pro-oxidant additive that induces biodegradation when it is incorporated into a polymeric matrix by attracting microorganisms in the biotic phase. The aim of this work was to investigate the abiotic degradability of this organic bioactive pro-oxidant additive in PP films. Thermal oxidation studies of the specimens were carried out to investigate the abiotic degradability. We analyzed compositions of PP films containing 1, 3, and 5% Eco-one by mass. These films were characterized by thermogravimetric analysis to calculate the activation energy (E _α) and to estimate their lifetime. Differential scanning calorimetry was conducted to provide oxidative induction time. The samples were then aged at 80 °C and characterized by Fourier transform infrared spectroscopy to obtain the carbonyl index (CI). Compositions containing 1% Eco-one additive showed the optimal composition with lower activation energy, and shorter predicted lifetime, suggesting easier thermal degradation. Furthermore, high CI was also observed in samples containing 1% additive, indicating thermodegradation for this composition.     

复合硫化物近常温热催化降解低密度聚乙烯薄膜

采用回流法合成新型热敏催化剂,将其与低密度聚乙烯(LDPE)熔融共混制得复合薄膜,并置于近常温黑暗烘箱中热催化降解。通过扫瞄式电子显微镜(SEM)、X射线能量色散光谱分析(EDX)、力学性能、原子力显微镜(AFM)、热重分析(TG)、凝胶渗透色谱(GPC)和傅里叶变换红外光谱(FT-IR)等表征手段对研究复合薄膜的热降解性能进行了研究。结果表明：纯聚乙烯薄膜在黑暗近常温条件下亦能发生热降解,但效果甚微;而复合薄膜的降解效果明显优于纯聚乙烯薄膜。在55℃下热降解45 d后,复合薄膜力学性能明显下降,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,热分解温度下降13℃,分子量亦明显减小,同时出现了羧基和羟基等特征吸收峰。     

Selective surface modification of ethylene-vinyl acetate and ethylene polymer blend by UV–ozone treatment

Ethylene-vinyl acetate (EVA) copolymers intended for sport sole manufacturing may contain noticeable amounts of polyethylene (LDPE) for improving abrasion resistance and decrease cost; however, this blend (EVA–PE) had low polarity and showed poor adhesion. In this study an effective environmentally friendly and fast surface treatment based on UV–ozone has been used to increase the wettability, polarity and roughness of EVA–PE material. Both the length of the UV–ozone treatment and the distance between the material surface and the UV-radiation source were tested. The UV–ozone treated EVA–PE material was characterized by ATR-IR spectroscopy using Ge prism, water contact angle measurements, X-Ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Adhesion properties were obtained from T peel tests of as-received and UV–ozone treated EVA–PE/polyurethane adhesive/leather joints.The more extended length of treatment and the shorter UV source–substrate distance increased the wettability of the EVA–PE material. Oxidation of the EVA–PE surface was produced by UV–ozone treatment creating new carbonyl groups mainly, and the amounts of hydroxyl and carboxylic groups were increased. The UV–ozone treatment produced ablation and etching of the EVA–PE material surface, mainly in the vinyl acetate, creating a particular roughness consisting on ruffles with deep crevices; this topography was also produced by heating produced during UV–ozone treatment. For low length of UV treatment or high UV source–material distance, the modifications of the EVA–PE material were mainly produced in the ethylene causing the selective removal of vinyl acetate, whereas more aggressive conditions produced strong oxidation in the EVA–PE material. Finally, adhesive strength was noticeably increased in the UV–ozone treated EVA–PE/polyurethane adhesive joints, and a cohesive failure in the leather was obtained.     

Surface resistivity,surface wettability and thermal stability of the 1-ethyl-2,3-dimethylimidazolium ethyl sulfate and methyl-tri-n-butylammonium methyl sulfate modified polyethylene

ABSTRACT

In this paper, experiments have been performed to further the development of conductivity of the polyethylene. This study mainly investigated the surface resistivity and surface wettability of the polyethylene (PE) after ionic liquid modifications. In order to activate the surface, PE was pre-treated with chromic acid and then modified with 1-ethyl-2,3-dimethylimidazolium ethyl sulfate (IL1) and methyl-tri-n-butylammonium methyl sulfate (IL2) ionic liquids. The effect of the type and concentration of the ionic liquid IL1 and IL2 concentrations is examined by Fourier Transform Infrared (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), surface resistivity and surface wettability. Results showed that thermal stability of the PE deteriorated after ionic liquid modifications. Both untreated and modified fabrics exhibited resembling crystallinity parameters. Nearly 57% enhancement in surface wettability of the PE was achieved. The pre-treatment process decreased the surface resistivity and increased surface wettability of the PE. The main success in this research is that IL1 and IL2 modifications reduced the resistivity data from 10¹¹ ohm/sq to 10⁷ ohm/sq and 10⁸ ohm/sq, respectively.     

Investigating effect of ferric stearate on stabilization efficiency of a phenolic antioxidant during thermal oxidation of polyethylene

This study aimed to achieve a formulation for an additive to produce oxo-biodegradable films that accelerates oxidative degradation of the films after preservation of properties over a span of desired service life. Thermal oxidation behavior of high-density polyethylene (HDPE) films (approximately 250 μm thick) containing various weight ratios of a commercially used phenolic antioxidant (Irganox 1010) to ferric stearate as pro-oxidant has been studied in both melt and solid states. Thermo-oxidative stability in melt state was studied using differential scanning calorimetry. The rate of thermal oxidation in solid state was investigated via oven aging experiments at 90 °C followed by measuring changes in tensile properties, gel content, carbonyl index and density. Comparing thermo-oxidative stability of the HDPE samples containing a combination of Irganox 1010 and ferric stearate with the samples containing Irganox 1010 alone confirmed that ferric stearate reduces the stabilization efficiency of the phenolic antioxidant in the polymer either in melt or in solid state. It was also shown that the efficiency of the phenolic antioxidant in thermo-oxidative stabilization of the polymer in both melt and solid states could be changed by altering weight ratio of Irganox 1010/ferric stearate. On the basis of the obtained results, it was concluded that weight ratio of 0.1/0.1 wt% of the antioxidant to the pro-oxidant is suitable for attaining desired stability during melt processing as well as retaining properties during a reasonable service life when is used as a film and a favorable rate of thermal oxidation after the service life.     

Simple route for the preparation of graphene/poly(styrene‐b‐butadiene‐b‐styrene) nanocomposite films with enhanced electrical conductivity and hydrophobicity

This paper reports a simple route for the preparation of graphene/poly(styrene‐b‐butadiene‐b‐styrene) (SBS) nanocomposite films employing a vacuum filtration method. Graphene is exfoliated well by an electrochemical procedure and homogeneously dispersed in the polymer matrix. The prepared nanocomposite films were characterized by XRD, Fourier transform IR (FTIR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, AFM and SEM. Morphological studies showed that graphene formed a smooth coating over the surface of SBS. The increase in graphene concentration induces the wrinkling of graphene sheets at the composite surface which causes a further increase in surface roughness. The FTIR, Raman and XPS spectra of graphene/SBS nanocomposite films indicate the strong interactions between graphene and the polymer matrix. According to the XRD patterns, introducing SBS into graphene did not modify the graphene structure additionally, i.e. the crystal lattice parameters do not depend on SBS content in graphene/SBS nanocomposite films. The graphene/SBS nanocomposite films also exhibited better hydrophobicity due to the increased surface roughness and lower sheet resistivity (reduced 10 times) compared to exfoliated graphene. © 2018 Society of Chemical Industry     

PE基聚硅氧烷/改性SiO2超疏水薄膜的构筑

使用十八烷基三甲氧基硅烷(OTMS)对纳米SiO2进行表面疏水改性,将得到的改性纳米SiO2(OTMS-SiO2)添加到有机硅树脂(SI)中,然后采用两步法在聚乙烯(PE)薄膜表面固化制备了复合涂层SI/OTMS-SiO2.通过FTIR、1HNMR、29SiNMR、TGA对OTMS-SiO2及复合涂层进行了表征,采用接触角测量仪、SEM、AFM对复合涂层疏水特性和形貌进行了测试和观察,最后对复合涂层的耐磨性和附着力进行了分析.结果表明,SiO2表面成功引入了OTMS,且OTMS-SiO2均匀附着在硅树脂涂层上,增加了表面粗糙度,得到了PE基固化超疏水复合涂层.当OTMS-SiO2添加量为正己烷质量的8％时,制得的复合涂层的水接触角为154°,滚动角为7°,并具有良好的耐磨性,其附着力可达4A等级.     

Cell Adhesion and Proliferation on Plasma-Treated and Poly(ethylene glycol)-Grafted Polyethylene

Polyethylene (PE) was modified by an Ar plasma. The plasma-activated PE surface was grafted with poly(ethylene glycol) (PEG, molecular weight 300 and 20 000). The depth profiles of the oxygen in the modified PE samples were determined using Rutherford Backscattering Spectroscopy (RBS). The changes in the surface wettability were examined by goniometry, and Atomic Force Microscopy (AFM) was used to determine the surface roughness and morphology. The modified PE samples were seeded with rat vascular smooth muscle cells (VSMCs) and their adhesion and proliferation was studied. The plasma treatment and the subsequent PEG grafting leads to dramatic changes in the PE surface morphology, roughness and wettability. The PEG grafting of the plasma-treated PE does not increase VSMC adhesion but it results in dramatic increase of VSMC proliferation.     

Functionalizing polymer surfaces by field‐induced migration of copolymer additives—role of shear fields

Flow‐induced migration polyethylene‐co‐methacrylic acid (PE‐co‐MA) and polystyrene‐b‐polydimethylsiloxane (PS‐b‐PD MS) copolymer additives in commercial long‐chain branch polyethylene (PE) and narrow‐molecular distribution polystyrene (PS) hosts was investigated in a capillary flow device. Attenuated Total Reflection Fourier Transform Infrared (ATR‐FTIR) spectroscopy and Dynamic Contact Angle (DCA) measurements were used to characterize surface composition of polymer specimen following extrusion through metallic dies with various length‐to‐diameter (L/D) ratios, (1100 ? L/D ? 3000). Results from experiments covering a broad range of shear rates and polymer residence times in the dies are reported. Provided that the polymer residence time in the die is sufficiently long, shear is found to increase the concentrations of low molecular weight copolymer additives on the host polymer's surface. The surface composition of copolymer additive is found to vary strongly with the wall shear rate and die L/D ratio. Decreasing the die diameter at fixed flow rate is found, for example, to be a more effective method for enhancing transport of additive to a polymer's surface than increasing shear rate at fixed diameter. A mechanism based on shear‐induced diffusion is proposed to explain the observed migration.     

热致相分离法制备聚乙烯/纳米二氧化钛共混膜

采用相对分子质量为130 000的聚乙烯(PE)为膜材、DIDP为稀释剂、平均直径为180 nm的TiO2粉末作添加剂,用热致相分离(TIPS)法制备了PE膜和PE/TiO2共混膜。研究了共混组成和冷却速率对膜结构的影响。所有制备的膜均是海绵状孔,冷却速率越大,膜孔越小。对PE质量分数为15%,当PE与TiO2的质量比大于1时,TiO2在膜内的分布不均匀,当PE与TiO2的质量比为0.5时,TiO2能比较均匀的分布于膜内。共混膜浸于水中经过紫外照射后,其亲水性显著增加。     

A comparative study on the effect of VUV radiation in plasma SiOx-coated polyimide and polypropylene films

Wettability of polyimide (PI) and polypropylene (PP) films have been improved using SiO_x-like thin layers deposited from a mixture of hexamethyldisiloxane (HMDSO) and oxygen in a microwave distributed electron cyclotron resonance plasma reactor. The films wettability evolution behaviors were evaluated through the results of contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The plasma depositions of SiO_x thin layers in presence of VUV radiation induce a contact angle decrease to about 7° and 35° for PI and PP films, respectively. XPS data showed that such difference in wettability is attributed to the increase of hydrophilic group's proportion at the surface of coated PI films due to VUV irradiation. AFM images showed that the PI surface topography remains relatively smooth when coated in presence of VUV radiation. However, in the case of PP films, AFM images revealed the growth of irregular structure due to a substrate etching effect supported by VUV radiation. For polymers coated without VUV irradiation, the deconvolution of the C1s peaks showed a significant decrease of CO bonds for both PI and PP substrates.