聚碳酸酯在不同湿热自然环境下的老化行为

对聚碳酸酯(PC)在我国海南琼海及三亚2个典型湿热地区的自然曝露试验结果进行了研究,并利用红外特征指数对PC的老化机理进行了探讨。结果表明:在琼海湿热内陆地区曝晒的PC试样同时发生了氟利斯重排反应和光氧化反应,而在三亚湿热沿海地区曝晒的试样则可能发生了光氧化反应和盐致水解反应。     

聚碳酸酯自然老化行为研究

研究了在海南万宁自然曝露试验后的聚碳酸酯(PC)结构和性能的变化。结果表明,老化后,PC的拉伸强度下降,由韧性断裂逐渐转变为脆性断裂;老化过程中,PC试样表面产生裂纹等缺陷,导致透光率下降,而碳碳偶合双键的产生则是黄变的主要原因;傅里叶变换衰减全反射红外光谱分析显示,曝露面同时发生了氟利斯(Fries)重排和光氧老化反应,而背面仅发生氟利斯重排反应。     

聚碳酸酯自然老化的红外光谱研究

选取3个不同地区(北京、三亚、若羌)分别对聚碳酸酯(PC)进行自然暴晒试验,利用傅立叶变换红外光谱(FTIR)技术研究分子构型(反式-反式或反式-顺式)、羟基指数、羰基指数、氧气浓度及太阳辐照波长对PC户外自然老化机理的影响.结果表明,PC在户外自然老化过程中,PC以光氧老化途径为主,以光-弗里斯重排途径为辅.     

聚碳酸酯/原位还原石墨烯复合材料的光氧老化行为研究

研究了光氧老化对聚碳酸酯(PC)/原位还原石墨烯(IrGO)复合材料结构和性能的影响。傅里叶变换红外光谱分析显示PC分子在紫外辐照下发生了光氧化和弗里斯重排反应;同时在老化后,PC/IrGO辐照面的玻璃化转变温度和分子量均高于空白品PC。结合对样品辐照面的红外光谱逐层分析显示,还原石墨烯可以屏蔽紫外光从而抑制PC材料的光氧老化。力学性能测试和断面分析表明,相较于空白品PC,IrGO的存在使得PC/IrGO材料在长期光氧老化之后仍然能保持一定的韧性。     

接线套管聚碳酸酯复合材料热老化下力学性能和色差关联分析

热老化易导致玻璃纤维/聚碳酸酯(GF/PC)材料力学性能下降,因此实时评估GF/PC复合材料力学性能对提高其可靠性至关重要。考虑传统力学性能获取多采取有损检测,本文提出一种基于材料颜色变化量评估力学性能的无损检测构想。本文首先对GF/PC复合板进行85～145℃范围内不同温度的热时效处理,随后对不同热老化温度下的样品进行拉伸和弯曲实验,测试其拉伸强度和弯曲强度,同时研究不同热老化温度下材料颜色的变化规律,最后讨论了不同热老化程度下材料颜色变化与力学性能之间的关联性。测试结果表明,随着热老化作用温度的逐渐上升,GF/PC复合材料的拉伸强度和弯曲强度均保持先上升后下降的趋势,且材料的色差和亮度变化值与材料的力学性能密切相关。回归分析结果表明,色差对力学性能的解释程度极高,这为后续基于色差预测不同热老化程度下材料力学性能的变化提供了科学依据。     

典型干热自然环境对聚苯乙烯分子结构的影响

选择吐鲁番和若羌两个典型干热自然环境开展为期1年的大气暴露试验,研究聚苯乙烯（PS）在干热自然环境下分子结构的变化,并对老化后的PS进行傅里叶变换红外光谱、凝胶渗透色谱和差示扫描量热分析。结果表明,PS发生光氧化反应并发生分子链断裂,导致其相对分子质量降低、相对分子质量分布变大和玻璃化转变温度降低。     

二氟二甲基硅烷的分析

氟硅烷是近年出现的高效粮仓熏蒸杀虫剂之一,由氯硅烷与氟离子反应而制得。二氟二甲基硅烷常温为无色微臭气体,沸点为2.5℃。试验室制法:以正丁醇为溶剂,在盐酸溶液中二氯二甲基硅烷与氟化钙反应,气态产物用于冰冷却液化,贮于钢瓶中。从原料和反应条件看,钢瓶中的样品在室温下气相组份主要是二氟二甲基硅烷和空气。在提制纯品较困难和缺乏质谱、红外等检测仪器的情况下,我们研究出简易的二氟二甲基硅烷分子量测定和含量分析方法。一、分子量的测定分子量的测定,通常有熔点降低法、沸点     

食品级聚碳酸酯的光氧老化性能

研究了食品级聚碳酸酯(PC)在疝灯照射条件下的老化行为。通过力学性能测试、红外光谱仪、差示扫描量热仪、凝胶渗透色谱仪、热重分析仪等对光氧老化前后的PC进行表征。结果表明:随着老化时间的延长,光氧老化后PC的拉伸强度先增大,后期几乎不变,断裂拉伸应变降低,缺口冲击强度先减小而后期变化幅度小;硬度降幅很小;光氧老化降解后有双酚A产生,PC发生光氧化降解反应,热稳定性降低。     

基于热带雨林环境的GFRP自然老化性能

对玻璃纤维增强塑料(GFRP)在西双版纳热带雨林地区的大气暴露3年和库内暴露10年样品分别进行研究,考察了其拉伸强度、拉伸弹性模量、弯曲强度、弯曲弹性模量、压缩强度5种力学性能及变化趋势;采用扫描电子显微镜对样品形貌进行了微观分析;同时对热带雨林地区的GFRP进行了寿命预测,计算出弯曲性能保留率下降到初始值的75%所需要的时间。     

玻纤增强乙烯基酯树脂在漠河地区的自然老化研究

对玻纤增强乙烯基酯树脂在漠河地区的大气暴露三年和库内暴露八年的样品分别进行研究,考察了其拉伸强度、拉伸弹性模量、弯曲强度、弯曲弹性模量、压缩强度5种力学性能及变化趋势;对样品进行了扫描电镜微观分析;同时对漠河地区的玻纤增强乙烯基酯树脂进行了寿命预测,计算出材料弯曲性能保留率下降到75%时所需时间。     

Outdoor weathering behavior of polyamide 6 under various climates in China

The outdoor natural weathering of polyamide 6 (PA6) was performed at six national standard natural exposure stations (at Qionghai, Guangzhou, Qingdao, Lhasa, Hailaer, and Ruoqiang), which represented the six typical climates over China. The outdoor aging behavior was studied. We found that under high temperature and humidity in the areas of Guangzhou, Qionghai, and Qingdao, the concentration of the end carboxyl group of PA6 increased significantly and the molecular weight decreased because of serious hydrolytic degradation. This resulted in a deterioration of the mechanical properties, high yellowing degree, and serious damage of the sample surface. While in the areas of Lhasa and Ruoqiang, with the relatively low temperature, humidity, and oxygen content in the atmosphere, the aging degree and corrosion index were low, and this resulted in the slow change of performances. Humidity, temperature, and rainfall may be the main environmental factors affecting the degradation of PA6. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44231.     

Correlation between artificial and natural weathering tests on polystyrene‐block‐polybutadiene‐block‐polystyrene block copolymer

The effects of artificial and natural weathering tests on the structure and mechanical properties of polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS) block copolymer were studied by spectrophotometry, Fourier Transform Infrared (FTIR) Spectroscopy, hardness measurements, and tensile testing. The correlation between artificial and natural weathering tests was also investigated. The results showed that the surface of SBS became yellow with increasing aging time. FTIR spectra confirmed the formation of carbonyl group in the aging process. The elongation at break, the tensile strength, and the tear strength decreased rapidly in the initial stage of the aging process and then leveled off, while the hardness increased with aging time. The correlation between artificial and natural weathering tests in Wanning and Hailaer, in China, could be expressed in terms of t₁ = 2.50t₀^1.99 and t₂ = 1.92t₀^2.56, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.     

热处理对聚碳酸酯环境应力开裂性能的影响

对聚碳酸酯(PC)的耐环境应力开裂性和拉伸性能进行了研究。结果表明，在不同溶剂和热处理温度条件下，PC的耐环境应力开裂性差异很大。较大的二甲苯含量容易降低PC发生环境应力开裂的临界拉伸应力及材料的拉伸强度、断裂伸长率。玻璃化转变温度以下的热处理可以提高PC的拉伸强度，但是对改善材料的耐环境应力开裂性不利。     

Mechanical nondiscoloring and antistretching photonic crystal films based on Zn2+ coordination and hydroxypropyl methylcellulose

Mechanical nondiscoloring and antistretching photonic crystal (PC) films, especially those with stable structure colors during deformation, have great potential applications in wearable display devices, decoration, and packaging. Here, PC films with antistretching and invariant structural colors during deformation were prepared, by combining Zn²⁺ coordinated elastic material and hydroxypropyl methylcellulose (HPMC) with polystyrene@silica (PS@SiO₂) colloidal crystals. The PC films release energy by forming local fractures at a microscopic level during the straining process but the lattice spacing and effective refractive index of the local array do not change. According to the Bragg law, the structure color remains unchanged. The introduction of HPMC gave the PC films excellent tensile properties, and the maximum tensile strength reached 10 MPa. And after 100 times of stretching, bending and compression cycles, the structural color remained unchanged.     

甜玉米芯多糖纳米乳涂膜的制备及对水果的保鲜

以甜玉米芯多糖纳米乳和壳聚糖的冰乙酸溶液为原料,以甘油、阿拉伯胶水溶液为增稠剂,制成甜玉米芯多糖纳米乳涂膜（简称涂膜）。以涂膜拉伸强度为指标,通过单因素实验和响应面实验得到最优配方,即壳聚糖溶液质量浓度为10 g/L、阿拉伯胶水溶液质量浓度为150 g/L、壳聚糖溶液（10 mL）与阿拉伯胶水溶液的体积比1∶2、甘油1.8 mL、甜玉米芯多糖纳米乳1.2 mL,在该条件下制备的甜玉米芯多糖纳米乳涂膜拉伸强度为(92.37±2.07)k Pa。将涂膜用于千禧果、金钱橘、葡萄的保鲜处理,以水果的腐败率、失重率、颜色色差、多酚含量、可滴定酸含量、可溶性固形物含量为评价指标,测定其保鲜效果。结果表明,与未涂膜的水果相比,涂膜处理的水果营养指标与感官指标均有更好的结果。主成分分析结果表明,PC1和PC2的累积方差贡献率为92.354%,说明涂膜对水果保鲜有效。     

后处理工艺对聚碳酸酯激光烧结件性能的影响

采用环氧树脂（EP）对聚碳酸酯（PC）烧结件进行后处理,研究了后处理工艺对PC烧结件力学性能的影响。结果表明,经EP处理后的PC烧结件由多孔性物质变为密实性物质,其拉伸强度及模量、冲击强度等性能均大幅度提高,其中,拉伸强度由0.39～2.29 MPa提高到约40 MPa,拉伸模量由2.19～17.13 MPa提高到约500 MPa,冲击强度从0.92～3.13 kJ/m2提高到约7 kJ/m2。     

Effect of processing method on surface and weathering characteristics of wood–flour/HDPE composites

Wood–plastic lumber is promoted as a low‐maintenance high‐durability product. When exposed to accelerated weathering, however, wood–plastic composites may experience a color change and/or loss in mechanical properties. Different methods of manufacturing wood–plastic composites lead to different surface characteristics, which can influence weathering. In this study, 50% wood–flour‐filled high‐density polyethylene (HDPE) composite samples were injection molded, extruded, or extruded and then planed, to remove the manufacturing surface characteristics. Fourier transform infrared spectroscopy was used to chemically show the difference in surface components. The samples were weathered in a xenon‐arc weathering apparatus for 1000, 2000, and 3000 h and analyzed for color fade and loss of flexural modulus of elasticity and strength. Final color (lightness) after weathering was not dependent on the manufacturing method. However, the manufacturing method was related to mechanical property loss caused by weathering. Composites with more wood component at the surface (i.e., planed samples) experienced a larger percentage of total loss in flexural modulus of elasticity and strength after weathering. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1021–1030, 2004     

Morphologies and tensile properties of elastomer-modified epoxy and polycarbonate blended systems

The morphologies and tensile properties of an elastomer-modified epoxy (EME)/polycarbonate (PC) binary system and an EME/diglycidyl ether of bisphenol A (DGEBA)/PC ternary system were examined. In the EME system, a continuous elastomer-rich phase formed, while in the EME/DGEBA systems (unblended with PC), a continuous epoxy-rich phase formed. In both of these systems, two-phase structures were observed. In contrast, a microdispersed structure was observed when the PC was blended with either the EME or with the EME/DGEBA systems. It is suggested that blending of the epoxy with PC caused an increased solubility of the former into the elastomer phase. The tensile strength and tensile elongation of both the EME and EME/DGEBA systems were improved by blending with PC. In the EME/PC blend, the tensile elongation reached its maximum value (60%) at a PC content of approximately 10 p.h.r. (parts per hundred resin by weight), with this maximum being approximately one and a half times higher than that of the unblended EME. Tensile strength was also clearly increased by blending with small amounts of PC, but soon reached a steady value. In the EME/DGEBA/PC blends, the tensile properties were dependent on the weight ratio of EME to DGEBA. In the absence of PC, as this ratio increased, the tensile elongation also increased, while at the same time the tensile strength decreased. The tensile properties were also improved in this system, by blending with PC. From the results obtained, it was clear that the improvement in tensile properties was closely related to the changes in morphology. Therefore, blending of the PC induced a microdispersed structure and improved the elongation of the epoxy resin.     

材料线膨胀系数对拉伸剪切性能的影响

为了研究被粘接材料的线膨胀系数对胶接件拉伸剪切性能的影响,用改性环氧树脂(EP)胶粘剂粘接不同材料,并对该胶接件进行拉伸剪切强度试验和温度影响试验。研究结果表明,被粘接材料的线膨胀系数不同会导致胶层在热冷变化过程中受到内应力作用而破坏,同时热空气进入胶层会导致胶层氧化变色,致使胶粘剂界面结合强度和胶粘剂自身强度降低;两种被粘接材料的线膨胀系数差异越大,经热冷变化后胶接件的拉伸剪切性能越低;在相同条件下,热冷变化温差越大,胶接件的拉伸剪切性能越低。