The effect of ultraviolet light on the mechanical properties of polyethylene and polypropylene films

Measurements were made of dynamic mechanical response spectra and stress–strain properties at room temperature on films of isotactic polypropylene and low-density polyethylene prior and after ultraviolet irradiation in a Xenotest 450 apparatus. The period of irradiation that caused a deep deterioration of ultimate mechanical properties influenced the dynamic mechanical properties only insignificantly. This is attributed to the heterogeneous nature of the photo-oxidative degradation process which is concentrated in a finite number of sites, thus forming crack precursors rather than changing the material properties in bulk. For a biaxially oriented tubular film of low-density polyethylene, anisotropic embrittlement after exposure in Xenotest 450 was observed. This even reversed the order of strain-at-break values in the two main directions of the film. This is remarkably similar to the effect of artificial incisions introduced into the specimens.     

Biodegradability of photooxidized polyalkylenes

Representative polyolefin films were exposed to UV radiation from light sources having different intensities and spectral distribution including the quartz mercury arc fluorescent lamps, xenon arc, and sunlight. Films exposed were polyethylene, polypropylene, and sensitized polyethylene. The oligomer fractions supported microbial growth, but the high polymers gave minimal or no growth. It was concluded that photooxidative degradation of polyolefins does not per se induce progressive attack by microorganisms. Oligomers present originally in the polymer are augmented by those produced by photooxidation. These oligomers support growth if separated from the polymer matrix. These observations explain some of the contradictory reports in the literature concerning the microbial degradation of sensitized polyolefins.     

Investigation of the atmospheric resistance and light resistance of polypropylene fibres and films

Conclusions With respect to a number of characteristics, pilot plant lots of polypropylene and fibrous materials based on it which have been stabilized, with compounds from the SHA class displaying the greatest atmosphere resistance and light resistance.A good correlation is observed between data obtained on exposure of fibrous materials under laboratory conditions (Xenotest 1200) and under natural climatic conditions of the middle and southern zones of this country.The buildup of carbonyl groups in light- and oxidative-degradation of polypropylene films in the Xenotest 1200 correlates well with the decrease in strength of industrial lots of fibrillated yarns and with the rise in melt yield point of experimental lots of polymer in atmospheric aging.Translated from Khimicheskie Volokna, No. 5, pp. 28–30, September–October, 1984.     

三氯化铁对聚丙烯光氧化降解的作用

用红外及紫外光谱法研究了三氯化铁(FeCl_3)对聚丙烯(PP)光氧化降解的影响。实验结果表明,FeCl_3对聚丙烯光氧化有显著的促进作用,但促进作用与FcCl_3含量之间不成线性关系,存在一促进作用的极大值(在本实验条件下,FeCl_3含量为0.5％时,促进作用最大)。实验还表明,FeCl_3的作用可能包含了通过光解产生自由基引发PP光氧化反应、催化分解氢过氧化物以及光屏蔽等几种作用。根据FeCl_3的作用机理,解释了FeCl_3对PP光氧化降解的促进作用与其含量的依赖关系中存在的极位现象。     

Realisation of polyester fabrics with low transmission for ultraviolet light

Due to the hazardous impact of ultraviolet (UV) light, textiles with UV‐protective properties are in great demand. This paper is related to the equipment of polyester textiles, with three different organic and water‐insoluble UV absorbers containing a cinnamate basic structure. To apply the UV absorbers from water‐based recipes, they are combined with polyethylene glycol PEG200 and different dispersing agents. The application onto two different polyester textiles is performed with a conventional high temperature process driven at 130°C with a process duration of more than 1 hour. Alternatively, an innovative microwave‐assisted process of a shorter duration of only 15 minutes is performed at 130°C. This microwave process is performed under solvothermal conditions using a CEM discover microwave machine. The sample evaluation is performed by UV‐visible spectroscopy in an arrangement of diffusive transmission with a special view of the spectral region from 300 to 500 nm. Finally, polyester fabrics with enhanced UV‐protective properties are realised. It is possible to decrease the diffusive transmission for the complete range of UV light to values of smaller than 5%. By contrast, the influence on the interaction with visible light is low, so the coloration properties of the treated polyester fabrics are less affected. The developed process can be used to realise polyester fabrics for various UV‐protective applications by a simple approach. The developed microwave process allows a decrease in process duration to more than 75% compared with the analogously presented high temperature process.     

Neue Befunde zum natürlichen und künstlichen Lichtschutz der Haut

New Observations on the Natural and Artificial Light Protection of Skin The hitherto known properties and mechanism of action of artificial light protection agents on human skin have been compared with author's own investigations pertaining to the base on which the preparations are formulated, significance of the UV B-absorption and the interrelationships between erythema and pigment reaction. Following results could be established: 1. Solutions of light filters in volatile solvents can act strongly light protecting; 2. the light protecting action is not only dependent on the protective film formed on the skin; 3. substances without appreciable UV B-absorption (purines and pyrimidines) have light protecting action; 4. intensity of browning of the skin is dependent on the preceding erythema reaction.     

Chain structure and mechanical properties of polyethylene/polypropylene/poly(ethylene‐co‐propylene)in‐reactor alloys synthesized with a spherical Ziegler–Natta catalyst by gas‐phase polymerization

Two polyethylene/polypropylene/poly(ethylene‐co‐propylene) in‐reactor alloy samples with a good polymer particle morphology were synthesized by sequential multistage gas‐phase polymerization with a spherical Ziegler–Natta catalyst. The alloys showed excellent mechanical properties, including both toughness and stiffness. With temperature‐gradient extraction fractionation, both alloys were fractionated into five fractions. The chain structures of the fractions were studied with Fourier transform infrared, ¹³C‐NMR, and thermal analysis. The alloys were mainly composed of polyethylene, polyethylene‐b‐polypropylene block copolymer, and polypropylene. There also were minor amounts of an ethylene–propylene segmented copolymer with very low crystallinity and an ethylene–propylene random copolymer. The block copolymer fraction accounted for more than 44 wt % of the alloys. The coexistence of these components with different structures was apparently the key factor resulting in the excellent toughness–stiffness balance of the materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 640–647, 2005     

The synthesis and application of Pb‐doped GLYMO/chelated‐zirconium complex coating materials for UV‐light absorption

New glass coating materials containing γ‐glycidoxypropyltrimethoxy‐silane/zirconium(IV)‐n‐propoxide(2‐methoxyethylacetoacetate)/lead(II) nitrate were developed for UV‐light absorption by sol‐gel process. The effect of agitation time, temperature, and Zr complex and Pb²⁺ ion concentrations on UV light absorption were investigated. Zr complex was characterized by using ¹H‐NMR, ¹³C‐NMR, and FTIR spectroscopy. Ultraviolet visible spectroscopy was utilized to determine the optical properties of coating materials. Results showed that coated glass has very low transmission in the UV region (300–400 nm) relative to uncoated glass, especially at 150°C for 15 h agitation. UV light transmission of coated glasses treated at 80, 100, 450, or 500°C was not different from uncoated glass. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1175–1179, 2006     

Quantitative determination of antioxidants and ultraviolet stabilizers in polymers by high performance liquid chromatography

The quantitative determination of antioxidants and ultraviolet (UV) stabilizers in a polymer matrix has been standardized using HPLC. The additives were extracted out of the matrix using low boiling solvents in order to minimize the degradation of additives at elevated temperatures. Carbon tetrachloride and tetrahydrofuran have been found to be most suitable solvents for low density polyethylene and polypropylene respectively. The method has been found to be highly reproducible and the standard deviation is very low. This method does not suffer from the problems like overlapping frequencies as observed in spectroscopic methods.     

Surface hydrophilic–hydrophobic property on transparent mesoporous silica thin films containing chromium oxide single-site photocatalyst

Using a sol–gel/spin-coating method with organic template, the transparent mesoporous silica thin films containing chromium oxide moieties can be prepared on quartz plate. The spectroscopic characterization has revealed that these thin films contain isolated and tetrahedrally coordinated chromium oxide moieties (single-site photocatalyst) in their frameworks. Even before UV light irradiation these Cr-containing mesoporous silica (CrMS) thin films have demonstrated a hydrophilic surface property more strongly than Cr-containing non-porous silica films and mesoporous silica thin films without chromium oxide. Furthermore, the Cr-containing mesoporous silica thin films showed the super-hydrophilic property not only under UV light irradiation but also even under visible light irradiation from a fluorescent lamp. In the presence of ethylene gas, the polyethylene was successfully formed on the surface of the CrMS thin film under UV light irradiation. After the formation of polyethylene the surface property of the CrMS thin film was converted into hydrophobic while keeping its transparency. The isolated and tetrahedrally coordinated chromium oxide moieties are responsible for these photo-induced surface reactions.     

Surface modification of polyolefine by UV light/ozone treatment

The surface modification of polyethylene (PE) and polypropylene (PP) was investigated by UV light/ozone (UVO) treatment. The surface oxygenation was determined by electron spectroscopy for chemical analysis (ESCA). As shown from ESCA spectra, after UVO treatment, oxygen-containing functional groups, such as carbonyl, carboxyl, and ether groups, were produced in the sample surface. The dependence of oxygenation extent (as measured by O_1s/C_1s value of ESCA spectra) on different experimental conditions, such as irradiation time, temperature, and O₂ flow rate, was obtained. It was shown that after UVO treatment at suitable conditions the surface properties of polyolefine samples, such as hydrophilicity, adhesion property, and dyeability, were improved remarkably. Furthermore, UVO treatment in short time does not have notable effect on the ageing property. It was concluded that UVO treatment is a promising technique to modify polyolefine surface properties. © 1996 John Wiley & Sons, Inc.     

New generation of long‐term stabilizers for polyolefins

Polyolefins are under evaluation for a variety of applications with increasingly stringent requirements, including long‐term exposure outdoors. While the range of physical properties and appearance has been extended by the development of new resins, additives are required to help maintain those properties upon exposure to sunlight, heat, and weather. The benefits of a new generation of light stabilizer with extraordinary efficiency in polyethylene (PE), polypropylene (PP), and other resins are discussed.     

Puerarin,an efficient natural stabilizer for both polyethylene and polypropylene

Puerarin, a natural compound, was used as multifunctional protector for polyethylene (PE) and polypropylene (PP). Firstly, puerarin and tetrakis(2,4-di-tert-butylphenol)[1,1-biphenyl]-4,4′-diylbisphosphite (PEPQ) could protect PE and PP against thermos-oxidative degradation: after modification, the oxidation induction time (OIT) of increased ca. 4,160% (PE-P₁₂₀₀-P sample) and 130% (PP-P₁₂₀₀-P sample); the carbonyl index (CI) obtained through accelerated aging decreased ca. 58% (PE-P₁₂₀₀-P sample). Secondly, it is excited to find that puerarin and PEPQ could pretect PE agianst photooxidative degradation: CI value decreased ca. 35% after modification. Thridly, the coorperation of puerarin and PEPQ was also benefit for the processing stability: the change of melt flow rate (MFR) between first and fifth extrusions decreased ca. 83% (PE-P₁₂₀₀-P sample) and 99% (PP-P₁₂₀₀-P sample). Forthly, puerarin and PEPQ could still protect PE against degradation after five extrusions: the loss of tensile strength and elongation at break decreased ca. 96% and 95% after modification. Finally, the interaction of puerarin with PEPQ was discussed and the role of puerarin in protecting polyolefins was proposed.     

Surface crosslinking of polyethylene using a hydrogen glow discharge

Linear high-density polyethylene is crosslinked by exposing it to a hydrogen glow discharge and alternatively by exposing it to a low-pressure Hg–A ultraviolet lamp in a dry nitrogen atmosphere. For the UV lamp case, the crosslinked gel is measured as a function of the radiation dose. For the plasma case, the crosslinked gel is measured as a function of the exposure time. The two gelation curves are alternatively compared to an exponentially attenuated light theory and a diffusion theory. Excellent agreement exists between the measured gel-versus-dose curve and the theoretical curve based on the light theory for a monochromatic light beam at 1849 Å. The gelation curve for the hydrogen glow discharge case can be explained using the identical theory but applied to a spectrum of light covering the range from 1200 Å to 1900 Å. The different curves can be explained in terms of the different spectra. Energy transfer between the plasma and the polymer due to excited atoms, and/or charged particles, is not required to account for the different gel curves.     

Photodegradable vinyl plastics. III. Comparison of ultraviolet light and sunlight exposure

Polystyrene (PS), polypropylene (PP), and polyethylene (PE) films, blended with additives to enhance photodegradability, were irradiated with UV light and sunlight. In almost every case, photodegradation was greater with outdoor exposure than under laboratory conditions. Explanations for the differences in degradation obtained by the two methods of irradiation are discussed. Based on IR measurements and molecular weight determinations, photo-oxidative changes that occur in PS induced by UV light appear similar to those induced by sunlight. In addition to the additives previously reported, several new classes of photoinitiators were evaluated. These include selected halocarbonyl compounds, haloalkyl sulfur compounds, and halogen compounds containing certain electron-withdrawing groups. The performance of the additives in vinyl polymer blends is discussed.     

硫酸盐腐蚀对混杂纤维混凝土弯曲韧性的影响研究

为了研究混杂纤维混凝土经硫酸盐腐蚀后的弯曲性能,首先对不同掺量的聚乙烯纤维(PE)与聚丙烯粗合成纤维(HPP)混凝土进行了硫酸盐干湿循环腐蚀和长期浸泡腐蚀试验,然后以三分点弯曲试验为基础,结合美国ASTMC1018和奥地利ORS评价方法,对比分析了混杂纤维混凝土在硫酸盐腐蚀前后其弯曲韧性变化及最佳纤维掺量.结果表明,纤维的掺入使得混凝土的破坏类型发生了变化,破坏时的最大荷载和挠度均明显增大,混凝土I5、I10、I20、R5,10和R10,20显著提高,韧性水平也明显高于普通混凝土;在硫酸盐腐蚀作用后不同纤维掺量的混凝土其弯曲韧性均出现了不同程度的下降,其中干湿循环腐蚀条件下比长期浸泡腐蚀条件下的混凝土的弯曲韧性受损更为严重;聚乙烯纤维(PE)与聚丙烯粗合成纤维(HPP)掺量为0.8％～1.2％的混凝土在经受450d长期浸泡腐蚀作用后的I5、I10与R5,10值分别提高了32.2％、19.6％和6.8％,具有良好的耐硫酸盐腐蚀性能和弯曲韧性.     

An Evaluation of the AATCC Light–fastness Reference Fabric

The purple reference fabric (LRF-1) proposed by the AA TCC for the calibration of fading lamps together with the ISO Blue Wool Light–fastness Standards 1–5 and the AA TCC Blue Wool Light–fastness Standards L2–L5 were exposed in the Xenotest 150 under different effective humidity conditions, as well as in daylight. It is concluded that, for use in calibrating fading lamps, the LRF–1 fabric shows no advantages over the Blue Wool Standards. On the contrary, its very high heat–sensitivity is a serious defect. As a light–fastness standard it is use/ess, in view of its low fastness to light.     

光敏变色聚丙烯纤维的研究

本文采用共混熔融纺丝法比较成功地制得了两种具有良好光致变色能力的光敏变色聚丙烯纤维:经阳光照射后,一种由白色变为蓝色,另一种由黄色变为绿色。文章探索了它们的纺丝及拉伸工艺条件,研究了光敏剂的不同加入量对于纤维变色性能、力学性能以及其结构的影响。并测试了该纤维的耐皂洗性和光照耐久性。     

聚乙烯成型品正己烷浸泡液蒸发残渣测量不确定度的评定

依照GB/T5009.60—2003测量食品包装用聚乙烯、聚苯乙烯、聚丙烯成型品卫生标准的分析方法,探索测定聚乙烯成型品蒸发残渣(正己烷)的不确定度评定方式。该检测方法的不确定度评定结果为3.31 mg/L(k=2)。     

Polypropylene/polyethylene terephthalate blends compatibilized through functionalization

In attempts to improve the compatibility of polypropylene with polyethylene terephthalate, an acrylic acid functionalized polypropylene was evaluated as the blend component in polyblends containing 40 percent by weight polyethylene terephthalate and compared with an unmodified polypropylene. The preliminary experiments in a batch laboratory mixer were followed by compounding in a co-rotating twin-screw extruder. Additives such as magnesium acetate and p-toluenesulfonic acid were evaluated as catalysts for potential interchange or esterification reactions that could occur in the melt. The blends were characterized through scanning electron microscopy, infrared spectroscopy, differential scanning calorimetry, and for mechanical properties. The results show that the functionalized polypropylene promotes a fine dispersed phase morphology, improves processability and mechanical properties, and modifies the crystallization behavior of the polyester component. These effects are attributed to enhanced phase interactions resulting in reduced interfacial tension (calculated as a 4-fold decrease). The presence of the additives does not, in general, improve any further the blend morphology and properties, or its processability.