不同老化模式对光伏背板中PET结晶度的影响

分别研究了在湿热老化、加速湿热老化、紫外辐照老化模式下,背板力学性能和PET层结晶度的变化,归纳了背板失效与其PET层结晶度的关系,并对几种老化模式进行了比较.结果表明,湿热老化和加速湿热老化时,PET层趋于结晶,为了保证背板不失效,结晶度应该控制在38%以下;紫外辐照老化时,分子结构破坏为主导,通过比较力学性能发现,...     

玻璃纤维增强聚酰胺老化机理的研究

以30％玻纤增强的聚酰胺66（PA66）为对象，用紫外加速仪研究了辐照时间对玻纤增强PA66的吸湿率、力学性能和形貌的影响进行研究，探讨了玻纤增强PA66的老化机理。实验结果表明：玻纤增强聚酰胺经紫外老化后的吸湿率显著低于未增强聚酰胺；玻纤增强聚酰胺的拉伸强度、弯曲强度显著提高，紫外老化后力学性能保持率较高；玻纤增强聚酰胺抗老化的机理可能是玻璃纤维阻止了聚酰胺老化裂纹的进一步扩展，同时减缓了外界因素对聚酰胺本体的进一步侵蚀，老化速度减慢。     

玻璃纤维-铝合金层合板湿热老化性能研究

通过研究玻璃纤维-铝合金层板在70℃、RH85%湿热环境下不同老化周期后的力学性能、基体红外光谱、铝合金表面形貌及元素变化,分析了层板的湿热老化机理。结果表明:在加速湿热老化条件下,复合材料层内部基体会发生吸湿塑化,并破坏树脂与纤维以及铝合金层的界面,影响了材料内部应力的传递,使与界面及桥接应力相关的性能发生明显退化;表层铝合金层随湿热老化时间的延长,表面氧化加剧,使铝合金塑性降低,主要影响依靠铝合金承载的力学性能。     

合成乳胶海绵的热老化行为研究

采用加速老化试验对合成乳胶海绵的热老化行为进行研究,考察了其热氧老化前后的表面形貌、黄度和白度指数、交联密度及傅里叶红外光谱。结果表明:随着老化时间的延长,合成乳胶海绵的多孔结构被破坏,当老化时间为48 d时,合成乳胶海绵部分大孔结构被破坏,其他孔结构完整;老化48 d后,合成乳胶海绵的黄度指数由11.74增大至42.73,白度指数由88.38减小至77.81,黄度变化大于白度变化;由黄度指数和白度指数表征的合成乳胶海绵老化速率分别为0.7023和0.2272 d^(-1);由交联密度表征的合成乳胶海绵老化速率为2.7082×10^(-5) mol·cm^(-3)·d^(-1);在热氧老化过程中,合成乳胶海绵发生了加成和氧化反应。     

汞灯紫外光源的强度分布分析及其对PVC老化作用的研究

采用紫外辐照计测定了矩形空间中汞灯紫外光源的辐照度分布,并通过FTIR、SEM跟踪了汞灯作为老化光源时PVC老化过程的结构及微观形貌变化.结果表明:矩形空间中辐照强度分布较复杂,当平面与灯轴的距离一定时,平面上汞灯投影处辐照强度最大,逐渐向边缘处衰减.随平面到灯轴距离的增大,汞灯投影部分辐照强度分布呈规律性衰减,而汞灯灯轴外延部分辐照强度分布呈无规衰减.汞灯作为紫外光源,所引起的人工加速老化过程中PVC结构变化主要是羰基峰的出现和增强.同时,老化过程中PVC辐照面微观形貌也发生急剧变化,随着老化时间的延长,表面孔洞不断增多、增大,最终完全粉化.     

HTPB推进剂湿热加速老化实验研究

对HTPB推进剂进行了不同湿热条件下的加速老化实验,并测量了不同老化时间推进剂的失重百分数、力学性能以及恢复吸湿后力学性能的恢复情况,描述了湿热老化实验过程中的实验现象,结合温度和湿度对推进剂作用机理,对实验现象、力学性能的变化和恢复情况进行了分析。结果表明：HTPB推进剂在湿热老化过程中发生了组分分解、降解和迁移,同时产生“晶析”现象;湿热老化过程可以分为三个阶段,其中第一阶段为吸湿占主导的阶段,第三阶段为氧化交联占主导的阶段,第二阶段与湿热老化的应力水平有关,温度≥60℃、湿度≥75%RH条件下为高聚物断链稍占优势的阶段,60℃/65%RH条件下为氧化交联稍占优势的阶段;不同湿热老化条件对HTPB推进剂失重的影响机理不同,85%RH湿度条件下以吸湿占主导作用,≤75%RH湿度条件下吸湿、组分的分解和迁移随老化时间分阶段起作用,温度对化学变化起加速作用;物理老化引起的力学性能几乎可以完全恢复,由化学老化引起的性能退化无法恢复。     

聚氨酯防腐涂层实验室光加速老化对比研究

基于聚氨酯防腐涂层/碳钢体系,进行人工氙灯加速老化试验及荧光紫外(UVA、UVB)光加速老化试验,通过颜色变化及失光率变化说明老化前后宏观性能的改变,用扫描电子显微镜(SEM)及衰减全反射-傅里叶红外光谱(FT-IR)分析老化前后微观形貌结构特征的变化。结果表明:在3种实验室光加速老化试验中,样品的色差均呈现上升趋势,而失光率的变化趋势差异显著;通过微观形貌结构分析样品的变化可知,氙灯加速老化试验中,聚氨酯前期以水解降解方式为主,老化后期发生光氧化降解;而荧光紫外加速试验以光氧化降解为主,UVA老化的光氧化降解主要发生在试验后期,UVB老化的光氧化降解主要发生在试验前期。     

聚甲醛加速老化试验研究

对聚甲醛（POM）进行了光加速老化试验和湿热老化试验研究。利用电子显微镜，差示扫描量热仪和X光电子能谱对材料在老化过程中的物理和化学性能进行了分析。结果表明，POM在老化过程中物理力学性能下降的主要原因是表面无定形区域的光氧化。     

玻纤增强热塑性聚酯复合材料湿热老化研究

研究了玻璃纤维增强热塑性聚酯（PET、PBT）复合材料在加速老化条件下力学性能的变化。结果表明,复合材料在湿热环境下的老化是由水解和界面脱粘共同作用引起的。依据树脂基体不同,材料老化速度和老化后强度均有所不同;老化温度提高,老化加快。采用拉伸强度与冲击强度测试、端基分析及扫描电镜分析等手段探讨了PET、PBT复合材料的老化机理和老化性能。     

湿热环境对浇铸改性双基推进剂力学和燃烧性能的影响

研究了JZSJ浇铸改性双基推进剂在65℃、相对湿度(RH)80%的湿热老化条件下力学性能(表面硬度)和燃烧性能(燃速)的变化规律,并与65℃热老化条件下的性能变化进行了比较。结果表明,在65℃、RH 80%的湿热老化条件下,随老化时间延长,推进剂表面硬度上升,燃速下降;与热老化相比,湿热老化对推进剂硬度和燃速影响显著。分析认为推进剂中硝化甘油(NG)含量的损失是引起推进剂硬度和燃速急剧变化的主要原因,这是由于在湿热老化条件下NG不仅挥发、分解而且会水解所致。     

改性聚碳酸酯板材的制备及性能研究

采用由丙烯酸类树脂、有机溶剂和紫外线吸收剂(UVA)组成的抗紫外线透明涂层制备改性聚碳酸酯(PC)板材,通过透光率/雾度测定仪、加速老化测试仪、分光光度计研究了涂层对PC板材光学和力学性能的影响。结果表明,抗紫外线涂层与PC板表面具有极佳的附着力,这种涂层具有优异的抗紫外线性能,未涂覆涂层的PC板经紫外光老化120h后黄色指数达到11左右,而涂覆该涂层的PC板的黄色指数仅为1左右,同时该板材能有85%以上的可见光透过率,120h紫外光加速老化后,板材的可见光透过率和力学性能基本保持不变。     

Influence of the environment during a photodegradation of multilayer films

The influence of different stratosphere parameters on the degradation of a multilayer film was investigated. The selected multilayer was a three polymeric layers film, a polyamide 6 film inserted between two poly(ethylene terephthalate) (PET) films. Samples were exposed for several ageing under ultraviolet radiations (filtered at 270 nm), varying the atmosphere at 55 mbar pressure (atm, atm + ozone, N₂, and T = ?55 °C or +23 °C). Evolution of it mechanical properties defined by uniaxial tractions, thermo‐optical properties defined by spectrophotometry UV–vis‐NIR, chemical properties defined by FTIR‐ATR, and thermal and dielectric properties defined, respectively, by differential scanning calorimetry (DSC) and dynamical dielectric spectroscopy (DDS), were investigated. Our results showed that UV irradiation causes multilayer films degradations, that is, principally decrease of UV transmittance and stress and strain at break (?50%). An increase of the ageing temperature causes an acceleration of these degradations. Degradations principally occur on the PET side of the multilayer exposed to UV radiation. Moreover, the DDS analysis shows a plasticization effect of the primary mode in the polyamide 6 due to photo‐oxidation. Oxygen diffusion is the principal element for this plasticization, indeed it not occurs in a nonoxidative environment (nitrogen), or at low ageing temperature (?55 °C). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44075.     

Investigating the surface properties of polyurethane based anti‐graffiti coatings against UV exposure

A permanent anti‐graffiti coating based on a polyurethane resin was prepared by incorporating different levels of an OH‐functional silicone modified polyacrylate additive. Static contact angle measurements and dynamic mechanical thermal analysis (DMTA) were employed to evaluate surface free energy and mechanical properties of the coating specimens, respectively. Effect of ageing condition on the graffiti properties of the coating samples was evaluated utilizing an accelerated weathering test. Color changes, surface morphology, and variations in the mechanical properties were also examined prior to and after being exposed to UV irradiation for 864 h in a QUV chamber. Results showed that surface free energy of the samples decreased with replacement of polyol with additive up to 5 mol %. A Scanning electron microscope equipped with energy dispersive X‐ray detector revealed that for the samples containing more than 5 mol % additive, there was an enrichment of silicone at the interface of films and air. At long exposure times and higher concentrations of additive, depreciation of graffiti properties was seen. DMTA and attenuated total reflectance‐fourier transform infra‐red studies before and after ageing showed that the silicone additive tended to degrade while it could cause an increase in crosslinking density. Water contact angles and atomic force microscopy images after ageing revealed that the cause of the depletion in anti‐graffiti properties was attributed to the deterioration of the silicone additive. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Jute fiber reinforced polypropylene produced by continuous extrusion compounding,part 1: Processing and ageing properties

This article addresses the processing and ageing properties of jute fiber reinforced polypropylene (PP) composites. The composite has been manufactured by a continuous extrusion process and results in free flowing composite granules, comprising up to 50 weight percent (wt %) jute fiber in PP. These granules have similar shape and diameter as commercially available PP granules. Rheological analysis shows that viscosity of the compounds follows the same shear rate dependency as PP and is on the same level as glass‐PP compounds. The mechanical properties show very little variation and exhibit strength and stiffness values at the upper range of competing natural fiber reinforced compounds for injection molding. The mechanical performance reduces gradually upon prolonged thermal loading and immersion in water. The low water diffusion coefficient of the 50 wt % jute‐PP composites indicates that the fibers are not forming a continuous network throughout the polymer. The jute fibers exhibit a stabilizing effect against ultra violet irradiation (UV) on PP polymer and, as a consequence, the mechanical properties of jute‐PP composites hardly decrease during an accelerated UV ageing test. Bacteria, fungi, and garden mold grow easily on the compound material, but only have a limited effect on mechanical properties. The resistance to growth of bacteria on the materials surface can be increased using a biostabilizer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Increased reliability of modified polyolefin backsheet over commonly used polyester backsheets for crystalline PV modules

The weathering stability of polymeric backsheets is very important for the reliability of photovoltaic (PV) modules. In addition to reliability, cost reduction and sustainability are upcoming challenges the PV backsheet industry is facing with. The most commonly used material for PV backsheets is poly(ethylene-terephthalate)-PET. However, PET is in general very sensitive to hydrolysis, which leads to chain scission and causes embrittlement, cracking, delamination, and dimensional instability of the backsheet. Compared to that newly developed modified polyolefin backsheets have favorable selective permeation properties and high mechanical flexibility, which could be key properties for backsheets in terms of higher PV module reliability. In this work, the weathering stability of PET/fluoropolymer backsheet and an alternative coextruded polyolefin-backsheet was investigated in terms of thermal and mechanical stability. Both materials were artificially aged and the changes caused by aging were investigated. The polyester-based backsheet showed embrittlement and reduced elongation at break for 70%. The polyolefin-based backsheet retained its mechanical flexibility even after 2000 h of aging under damp-heat conditions, with no significant physical or chemical aging processes occurring. The comparison of the results of both backsheets suggests that the polyolefin backsheet is a promising candidate for the reduction of cracks and delamination in the field. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48899.     

Characterization of metallized biaxially oriented polypropylene film

The effect of corona unit energy applied for retreatment of metallized biaxially oriented polypropylene film surfaces before the lamination process was studied using optical, scanning electron, and atomic force microscopies. Increased surface roughness and polarity due to oxygen groups were detected, and these changes became more evident with the increase of corona treatment intensity. The number and size of spots on the surface, possibly deriving from processing aids incorporated as additives into the polymer, increase with corona treatment. The response of specimens in accelerated aging was also studied for evaluation of the outdoor stability of these composite structures. Specimens were exposed to the combined action of UV‐radiation, humidity, and heat, and the stability of yellow, orange‐yellow, orange, green, and bordeaux colors was determined as a function of the exposure time. Minor color changes were recorded for exposure up to 100 h, which became more significant for longer exposure intervals depending on the type of color. Finally, a 40% decrease in tensile strength was observed after 216 h of ageing, accompanied with a decrease of 15% of modulus and an increase of 160% in the elongation at break, possibly because of the plasticizing effect taking place during the ageing process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

新型防老剂555PD用于丁苯橡胶SBR1500防老化

用热空气老化的方法考察了防老剂555PD不同加入量对丁苯橡胶SBR1500的热空气老化防护性能及物理机械性能的影响。并与防老剂PPDB进行了对比研究。实验结果表明,防老剂555PD热空气防老化性能优于PPDB,对丁苯橡胶物理机械性能没有明显影响,用于丁苯橡胶SBR1500可降低生产成本,具有一定的经济效益。     

Adhesion failure of antiscratch coatings on polycarbonate under UV irradiation

The adhesion failure of antiscratch (AS) coatings on unmodified and plasma‐modified polycarbonate (PC) substrate was studied using both chemical and physical methods while considering the surface and interface changes between coatings and PC under ultraviolet (UV) irradiation. The differences in the wettability and surface elemental compositions of the PC surface (PCs) and AS coatings after UV ageing were evaluated by contact angle and Fourier transform infrared (FTIR) measurements. The nanoindentation technique was employed for the quantitative assessment of the changes in the nanomechanical properties of both PCs and AS coatings under UV irradiation. The adhesion of coating on plasma‐modified PC was found to be significantly better than that of unmodified substrates. The hydrophilicity and polarity of PCs covered by AS coatings were significantly increased because of the photodegradation of PCs, whereas silicon coatings remained invariant. Nanoindentation tests revealed an obvious enhancement in stiffness of the coating and exposed PC after ageing. Based on these experiments, we proposed that adhesion failure under UV irradiation may be caused by two reasons: first, the photodegradation that occurred at the PCs covered by AS coatings; and second, the stress induced by the changes in stiffness of both AS and PCs under UV ageing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40507.