紫外线辐射强度对聚丙烯长丝光氧老化的影响

 以聚丙烯长丝为研究对象,采用不同紫外线辐射强度的人工加速老化试验对其光氧老化过程进行研究。对老化过程中试样的断裂强力进行测试,并进行红外光谱分析。测试结果表明：采用2根和4根紫外荧光灯管的老化结果之间相关性较好,而与8根灯管老化结果之间的相关性较差。造成这种差别的原因在于,2根和4根灯管老化条件下的降解产物与8根灯管老化条件下的降解产物有所不同,即过高的紫外辐射强度会导致聚丙烯长丝光氧老化动力学过程的改变。     

PVC膜材料的光氧老化性能

以PVC膜材料为对象,采用不同辐射强度的紫外线人工加速老化实验对其光氧老化过程进行研究。对老化过程中试样的黄度指数进行测试,并进行红外光谱和紫外光谱分析。测试结果表明：不同辐射强度下试样的老化机制没有发生变化,但当累积紫外线辐射能相同时,试样的老化程度并不一致,这是因为试样在不同辐射强度下的光氧老化速度与辐射强度不成比例关系,因此,互易定律不适用于PVC涂层膜材料寿命预测模型的建立,而根据Schwarzschild定律可很好地建立不同辐射强度下试样老化结果的相关性。     

聚丙烯及聚酯纤维滤料耐紫外老化特性研究

以聚丙烯及聚酯纤维滤料为试验对象,采用UVC型紫外线辐射,进行人工老化试验,研究不同滤料紫外老化过程的性能变化。观察滤料形貌变化及纤维断裂情况,对老化过程中试样的拉伸断裂强度进行测试,并进行元素含量分析。同时,考察紫外线对箱体内的臭氧浓度的影响。测试结果表明:在一定辐射强度下,长时间紫外线辐射会导致滤料纤维的断裂降解,拉伸断裂强度下降及含氧量增加。不同滤料耐紫外线辐射的能力差异较大,造成这种差别的原因在于,滤料的材质成分及纤维直径不同。     

高强粗旦聚丙烯纺黏针刺非织造土工布的耐久性研究

采用耐酸碱、室外自然老化、抗热氧老化和抗冻融试验,研究高强粗旦聚丙烯纺黏针刺非织造土工布的耐久性,并将其与聚酯纺黏针刺土工布、抗紫外线(UV)高强粗旦聚丙烯纺黏针刺非织造土工布进行对比.结果 表明:同等面密度条件下,高强粗旦聚丙烯纺黏针刺土工布比聚酯纺黏针刺土工布具有更优的耐酸碱性能、抗冻融性能及抗热氧老化性能,但耐光氧老化性能较弱,可以通过添加抗UV助剂解决.该研究结果可为高强粗旦聚丙烯纺黏针刺非织造土工布在工程中的实际应用提供理论和技术支撑.     

聚氯乙烯膜材料的人工加速老化性能

以聚氯乙烯(PVC)涂层膜结构材料为对象,对其在紫外光源(4根UVB-313灯管)辐照下的人工加速老化性能进行研究。实验过程中对材料的黄度指数、力学性能进行了宏观测试,同时采用红外光谱、电镜等方法进行了微观分析。测试结果表明:随着紫外线辐照时间的增加,黄度指数逐渐上升,人工加速老化程度逐渐加深;涂层表面出现大量细小裂纹,以致于PVC涂层对基布的黏合束缚作用逐渐减少;在累积紫外辐照能达到一定程度时,膜材料的断裂伸长出现突增,但是膜材料的断裂强力基本保持不变。     

短周期非织造材料热氧降解性能及评价方法

通过鼓风式热氧降解烘箱将聚丙烯(PP)、聚乙烯(PE)、聚酯(PET)、聚乳酸(PLA)、粘胶(CV)材料分别在110℃温度条件下进行热氧降解处理,之后通过对各种材料进行力学性能测试、织物及纤维外观形态观察、熔融峰值测试以及红外光谱测试,以对其热氧降解性能进行分析评价,并采用这些方法比较不同纤维材料的热氧降解性能差异。     

土工布老化试验研究

本文主要是针对涤纶针刺非织造布和聚丙烯编织布，采用大气暴露老化，模拟覆盖老化等试验方法，对其强度的降解过程和降解速度进行测试与分析，希望对工程应用提供可鉴资料。     

纯棉机织物寿命预测

以纯棉机织物为研究对象,在3种老化试验条件--实验室自然放置、8根UVB-313型紫外线老化灯管辐照和1.25m水下浸泡处理不同时间后,测试织物拉伸断裂强力和抗皱性能的变化。结果表明,纯棉机织物在实验室自然存放一段时间后,拉伸断裂强力和抗皱性持续缓慢下降;紫外线辐射对织物抗皱性影响较大,水对织物拉伸断裂强力影响较大;水中微生物对织物老化起明显加速作用;同时提出纯棉机织物室外晾晒和仓库储存的寿命预测方程。     

聚丙烯纺黏针刺土工布的力学和耐光氧老化性能

为提高聚丙烯纺黏针刺土工布产品质量,测试和分析聚丙烯纺黏针刺土工布的力学性能和耐光氧老化性能.结果 表明:在相同工艺条件下,聚丙烯纺黏针刺土工布的力学性能优于聚酯纺黏针刺土工布;聚丙烯纺黏针刺土工布抗拉强度、撕破强力、顶破强力和刺破强力均随着面密度的增大而提高;灰色母粒和UV 88抗老化母粒均可提高聚丙烯纺黏针刺土工布的耐光氧老化性能,其中UV 88抗老化母粒的提升效果更显著.     

PP抗光氧老化纺粘非织造布的开发及其性能

利用ZN-P型紫外线耐气候试验机加速PP抗光氧老化纺粘布的老化过程,通过拉伸仪测试其老化试验前后的断裂强度和断裂伸长率,根据其损失率来判断抗光氧老化剂的种类、添加量及色母粒对所制备的PP纺粘布抗光氧老化性能的影响.结果表明,经阻胺类抗光氧老化剂改性的PP纺粘布,其抗光氧老化性能明显优于紫外线类抗光氧老化剂改性的PP纺粘布,当其质量分数为2%～2.2%时性价比最好.同时,色母粒的加入对PP纺粘布的抗光氧老化性能也有较大的影响.     

Spectral sensitivity of Bacillus subtilis spores and MS2 coliphage for validation testing of ultraviolet reactors for water disinfection

The microbicidal UV fluence under polychromatic radiation from UV lamps is typically measured using the DNA absorbance spectrum as a weighting factor for the relative wavelength effectiveness. However, this DNA-based weighting does not necessarily match the spectral sensitivity of the microorganism being tested. Bacillus subtilis spores are often used for UV reactor validation in Europe, while MS2 coliphage is typically used for validation testing in the United States. These organisms were exposed to quasi-monochromatic UV irradiation across the microbicidal spectrum at wavelengths of 214, 230, 240, 254, 265, 280, and 293 nm. MS2 was three times more sensitive to wavelengths near 214 nm compared to the 254 nm output of low-pressure lamps, while B. subtilis spores were most sensitive to wavelengths around 265 nm. Use of these action spectra, compared to the DNA-based weighting, resulted in differences in the calculated polychromatic UV fluence. Consequently, the action spectrum, which is specific for each microorganism, has implications on the uncertainty of UV fluence determination during validation of reactors with polychromatic UV lamps.     

Effect of UV irradiation on organic matter extracted from treated Ohio River water studied through the use of electrospray mass spectrometry

Ohio River water was treated by settling, sand filtration, and granular activated carbon filtration. It was then irradiated by low-pressure (monochromatic) and medium-pressure (polychromatic) UV lamps to investigate the effects of UV irradiation on the extracted organic matter (EOM). When the EOM, collected by solid phase extraction cartridges, was analyzed by conventional UV spectroscopy and size exclusion chromatography (SEC), no significant changes in the EOM were revealed for various UV doses. Positive and negative electrospray ionization mass spectrometry (ESI-MS) of the EOM produced mass spectra that vary significantly with UV dose. The UV dosage conditions also appear to affect the reactivity of the EOM to subsequent chlorination. The magnitude of the spectral changes is generally greater for medium-pressure lamps than for low pressure and increases with UV exposure. Based on the observed MS peaks, the changes may be due to the presence of lignin, resulting perhaps from photooxidation and/or photo rearrangement of macromolecules in the sample. When chlorination is used for secondary disinfection, these results suggest that it may be important to consider the effects of UV irradiation on the organic matter in the water before applying UV disinfection technology to a particular source water.     

Degradation of endocrine disrupting chemicals bisphenol A, ethinyl estradiol, and estradiol during UV photolysis and advanced oxidation processes

The degradation of three endocrine disrupting chemicals (EDCs), bisphenol A, ethinyl estradiol, and estradiol, was investigated via ultraviolet (UV) radiation photolysis and the UV/hydrogen peroxide advanced oxidation process (AOP). These EDCs have been detected at low levels in wastewaters and surface waters in both the United States and European countries, can cause adverse effects on humans and wildlife via interactions with the endocrine system, and thus must be treated before entering the public drinking water supply. Because many EDCs can only be partially removed with conventional water treatment systems, there is a need to evaluate alternative treatment processes. For each EDC tested, direct UV photolysis quantum yields were derived for use with both monochromatic low-pressure (LP) UV lamps and polychromatic medium-pressure (MP) UV lamps and second-order hydroxyl radical rate constants were developed. These parameters were utilized to successfully model UV treatment of the EDCs in laboratory and natural waters. The polychromatic MP UV radiation source was more effective for direct photolysis degradation as compared to conventional LP UV lamps emitting monochromatic UV 254 nm radiation. However, in all cases the EDCs were more effectively degraded utilizing UV/H2O2 advanced oxidation as compared to direct UV photolysis treatment.     

Continuous and Pulsed Ultraviolet Light for Nonthermal Treatment of Liquid Foods. Part 1: Effects on Quality of Fructose Solution, Apple Juice, and Milk

Performance of three innovative high-intensity pulsed (HIP) ultraviolet (UV) sources characterized by different emission spectra, energy per pulse, and frequency (HIP-1: 31 J/pulse, 8 Hz; HIP-2: 344 J/pulse, 0.75 Hz; HIP-3: 644 J/pulse, 0.5 Hz) was evaluated at UV fluence of 5 mJ/cm² by measuring the effects on quality parameters of 30% (w/v) fructose solution, apple juice and milk. The results were compared with the continuous monochromatic low pressure (LPM) and medium pressure polychromatic (MPM) mercury lamps at the UV fluence of 10 mJ/cm² that was determined based on 5-log microbial reduction requirement. The effects of HIP-1 and HIP-3 pulsed lamps on color, pH, and vitamin C, were comparable with the LPM lamp. For example, pH of fructose decreased by 1.94% for the LPM lamp and by 0.78% and 4.31% for HIP-1 and HIP-3, respectively. Treatment with the LPM lamp reduced the vitamin C content by 1.30% in apple juice and 35.13% in milk. In the case of pulsed lamps the reduction of vitamin C was 0.85% for HIP-1 and 1.78% for HIP-3 in apple juice, 12.31% (HIP-1) and 21.66% (HIP-3) in milk. HIP-2 and MPM lamps caused the most significant deterioration of the quality parameters in all tested liquids. The HIP-2 lamp decreased vitamin C by 8.52% in apple juice and 35.80% in milk, and also reduced pH of fructose solution by 5.29%. These results indicate that UV treatment with pulsed HIP-1 and HIP-3 sources could represent a promising alternative for the treatment of low UV transparent and opaque liquid foods.     

Microscopic and Spectroscopic Evaluation of Inactivation of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> by Pulsed UV Light and Infrared Heating

Pulsed UV light and infrared heat-treated Staphylococcus aureus cells were analyzed using transmission electron microscopy to identify the cell damage due to the treatment process. A 5-s treatment with pulsed UV light resulted in complete inactivation of S. aureus even after enrichment. The temperature increase during the pulsed UV light treatment was insignificant, which suggested a nonthermal treatment. S. aureus was also infrared heat treated using an infrared heating system with six infrared lamps. Five milliliters of S. aureus cells in phosphate buffer was treated at 700°C lamp temperature for 20 min. The microscopic observation clearly indicated that there was cell wall damage, cytoplasmic membrane shrinkage, cellular content leakage, and mesosome disintegration after both pulsed UV light and infrared treatments. Fourier transform infrared microspectrometry was successfully used to classify the pulsed UV light and infrared heat-treated S. aureus by discriminant analysis.     

Zygosaccharomyces bailii inactivation by means of UV light and low-frequency ultrasound treatments

Zygosaccharomyces bailii inactivation suspended in apple juice was evaluated under the effects of selected treatments: short-wave UV light (UVC, using one or two lamps), or low-frequency ultrasound (US), or their simultaneous combination. US treatments (20 kHz, 120-μm wave amplitude) were performed at 35°C in a double-wall vessel by using a 13-mm probe. The UVC device consists of two 90-cm-long stainless steel tubes with 40-W UVC lamps covered with quartz tubes, each one inside a stainless steel tube (annular inside diameter of 2.6 cm) connected to a peristaltic pump. Inoculated systems were recirculated through individual or simultaneous US and UVC treatments, samples were taken periodically, and yeast survivors were determined by the plate-count technique. Yeast survival curves demonstrated that UVC alone or in combination with US produced higher inactivation than US alone. Survival curves were appropriately described by the Weibull distribution of resistances model, obtaining model parameter values that adequately reflected the effect of the studied treatments. For every tested case, the distribution of resistances model revealed an absence of mode, while mean values and variances decreased when simultaneous UVC irradiation with two lamps and US were applied, reaching a 7-log cycle reduction after 40 min of treatment. Combined treatment was more effective than individual US or UVC treatments.     

UV photolysis of nitrate: effects of natural organic matter and dissolved inorganic carbon and implications for UV water disinfection

Nitrite (NO2-) formation during ultraviolet (UV) photolysis of nitrate was studied as a function of pH and natural organic matter (NOM) concentration to determine water-quality effects on quantum yields and overall formation potential during UV disinfection of drinking water with polychromatic, medium-pressure (MP) Hg lamps. Quantum yields measured at 228 nm are approximately 2 times higher than at 254 nm under all conditions studied. In the absence of NOM, NO2- quantum yields decrease with time. With addition of NOM, initial quantum yields increase, and the time-dependent decrease is eliminated. At 15 ppm dissolved organic carbon (DOC) as NOM, the quantum yield increases with time. Dissolved inorganic carbon significantly decreases NO2- yields at pH 8 but not pH 6, presumably by reaction of CO2(aq) with peroxynitrite, a major intermediate in NO2- formation. The results indicate important and previously unrecognized roles for NOM and CO2(aq) in nitrate photolysis. When photolysis was carried out using the full spectrum MPUV lamp and germicidally relevant UV doses, NO2- concentrations remained well below the U.S. maximum contaminant level of 1 ppm N, even with nitrate initially present at 10 ppm N. Under current U.S. regulations, NO2- formation should not pose a significant problem for water utilities during UV disinfection of drinking water with MP Hg lamps.     

UV disinfection of Giardia lamblia cysts in water

The human and animal pathogen Giardia lamblia is a waterborne risk to public health because the cysts are ubiquitous and persistent in water and wastewater, not completely removed by physical-chemical treatment processes, and relatively resistant to chemical disinfection. Given the recently recognized efficacy of UV irradiation against Cryptosporidium parvum oocysts, the inactivation of G. lamblia cysts in buffered saline water at pH 7.3 and room temperature by near monochromatic (254 nm) UV irradiation from low-pressure mercury vapor lamps was determined using a "collimated beam" exposure system. Reduction of G. lamblia infectivity for gerbils was very rapid and extensive, reaching a detection limit of >4 log within a dose of 10 JM-2. The ability of UV-irradiated G. lamblia cysts to repair UV-induced damage following typical drinking water and wastewater doses of 160 and 400 JM(-2) was also investigated using experimental protocols typical for bacterial and eucaryotic DNA repair under both light and dark conditions. The infectivity reduction of G. lamblia cysts at these UV doses remained unchanged after exposure to repair conditions. Therefore, no phenotypic evidence of either light or dark repair of DNA damage caused by LP UV irradiation of cysts was observed at the UV doses tested. We conclude that UV disinfection at practical doses achieves appreciable (much greater than 4 log) inactivation of G. lamblia cysts in water with no evidence of DNA repair leading to infectivity reactivation.     

紫外发光二极管（UV-LED）技术对食品微生物灭活应用的研究进展

紫外辐照是一种非热杀菌技术,汞蒸气紫外灯是现阶段用于食品卫生处理的主要设备,但受某些因素影响,汞灯的生产使用将逐渐变少,被环保节能的紫外发光二极管（UV-LED）取代是一种不可避免的趋势。本文根据UV-LED发光原理和多波长耦合应用的特点,综述了对微生物灭活的机理、探究了影响灭活效果的因素（波长、紫外剂量和物料特性）、处理食品的灭菌效果以及对部分食品品质的影响,为UV-LED在食品领域的杀菌处理工艺和设备参数优化提供参考。