有机玻璃玻璃化转变温度影响因素的研究

对有机玻璃的玻璃化转变温度从测试条件和工艺配方角度进行了一定的阐述。采用热机械分析方法,测试有机玻璃的玻璃化转变温度。讨论分析了影响玻璃化转变温度的因素,对有机玻璃性能的改进起到了一定的指导意义。     

有机玻璃在盐水条件下老化性能的研究

在盐水（50℃温度,3％NaCl溶液）条件下对有机玻璃做了70d左右的人工加速老化试验,对不同老化时间的有机玻璃试样进行了宏观力学性能测试,并进一步利用凝胶渗透色谱法（GPC）、示差扫描量热法（DSC）等手段分析了老化前后有机玻璃试样的结构和组成差异,结合老化前后有机玻璃力学性能的变化,揭示了有机玻璃在盐水条件下的老化规律和老化机理。实验表明,有机玻璃在温度为50℃,盐质量分数为3％的盐水条件下老化66d,拉伸强度、弯曲强度、弯曲模量都呈现下降趋势。有机玻璃在盐水条件下老化的主要机理是水对有机玻璃的化学作用和物理作用,有机玻璃由于水分渗入的结果影响,降低了分子间的相互作用力（范德华力）从而使材料机械性能下降;同时水对有机玻璃的化学作用没有引起力学性能的变化。     

潜水器观察窗用有机玻璃的损伤与破坏行为

潜水器观察窗是深海载人潜水器的唯一非金属结构部件,研究该观察窗用有机玻璃材料的损伤破坏行为以及抗裂纹扩展性能对潜水器观察窗使用寿命以及安全可靠性评估具有重要意义。根据观察窗有机玻璃的受载形式,进行拉伸、压缩、剪切、断裂韧性、应力银纹等测试,表征与服役损伤相关的关键力学性能;研究可能出现的损伤缺陷对有机玻璃关键力学性能的影响;结合潜水器观察窗玻璃的损伤缺陷情况,对观察窗用有机玻璃的缺陷(裂纹)扩展性能进行了研究。结果表明,潜水器观察窗用有机玻璃的压缩强度为115 MPa,剪切强度为62.6 MPa,与无机玻璃、定向有机玻璃、聚碳酸酯等材料相比,具有强度高、变形量小、不会突然发生破坏等优势;潜水器观察窗用有机玻璃的抗银纹引发以及抗裂纹扩展的性能较好,应力银纹强度为20.6 MPa、断裂韧性为1.66 MPa·m^1/2;有机玻璃银纹损伤对拉伸、压缩、剪切静强度基本无影响;与银纹损伤相比,微裂纹缺陷使得压缩屈服强度略有降低但裂纹不扩展,使剪切强度降低约15%且破坏程度剧烈,对拉伸强度影响最大,使其降低约70%。     

有机玻璃YB-DM-11的疲劳裂纹扩展特性研究

研究了试样类型、应力比对有机玻璃YB-DM-11疲劳裂纹扩展速率、疲劳裂纹扩展平均寿命的影响。结果表明：试样类型对有机玻璃疲劳裂纹扩展速率影响很小,但紧凑拉伸试样的寿命大于中心裂纹拉伸试样;对于中心裂纹拉伸试样,当应力比为正时,应力比增大,疲劳裂纹扩展速率增加,疲劳裂纹扩展平均寿命减小;应力比为负时,裂纹闭合效应导致裂纹扩展加速;负应力比时的裂纹扩展速率大于正应力比,但疲劳裂纹扩展平均寿命明显小于正应力比。     

有机玻璃在液体闪烁体环境中的老化研究

为了研究有机玻璃在液体闪烁体环境中老化后力学性能的变化情况,开展了老化试验。将有机玻璃试样分别浸泡在50、60以及70℃液体闪烁体中进行人工加速老化处理,并对老化30、60、124、180 d以及未老化处理的试样进行了拉伸性能测试,获得了试样在三种温度液体闪烁体环境中老化后的力学性能随老化时间的变化规律,并分析了老化机理。利用阿累尼乌斯方程外推法对有机玻璃长期力学性能进行预测,推算出有机玻璃在20℃液体闪烁体环境中使用20 a后的拉伸强度下降了约10%。     

防辐射有机玻璃研究现状及发展趋势

综述了国内外防辐射有机玻璃的特性，组成，制备技术及其性能测试的方法，并指出了防辐射有机玻璃的发展趋势。     

含磷不饱和酯改性有机玻璃的制备及性能

以磷酸三乙酯、乙二醇和甲基丙烯酸为原料,通过脱烷基化和酯化两步法合成含磷不饱和酯,并利用红外光谱对这种含磷不饱和酯进行结构表征。将这种含磷不饱和酯以不同比例加入到甲基丙烯酸甲酯单体中制备改性有机玻璃,并对这种有机玻璃的透光率、极限氧指数、冲击强度、玻璃化温度进行测试。结果表明:改性后的有机玻璃的阻燃性能大幅提高,且随着含磷不饱和酯含量的增大而增高;冲击强度和玻璃化温度随着不饱和酯含量的增大先增高后降低。     

增塑剂对有机玻璃性能的影响

为了对有机玻璃进行改性,考察了增塑剂对有机玻璃热变形温度、热松弛和冲击强度等性能的影响.结果 表明:增塑剂的加入降低了有机玻璃的热变形温度,增大了有机玻璃热松弛,小幅提高了有机玻璃的冲击强度,建议用量为1～2份.     

有机玻璃大气曝露中分子量分布的研究

本工作,用高效凝胶渗透色谱法(GPC),对有机玻璃的三种样品——A3~＃、B3~＃和D3~＃在经大气老化(本所的曝露试验场进行曝晒)1年和2年后,以由表至里的分层取样方法,对其向阳面和背阳面分别进行了分子量及其分布的测试和研究,探讨了三种有机玻璃在广州地区的大气环境下、影响其老化的主要因素和老化规律,发现了D3~＃玻璃老化后,其向阳面的里层存在着分子量分布的双峰现象,同时提出了有机玻璃分子量分布宽度的一种表征方程。     

飞机侧窗PMMA裂纹分析

某型飞机侧窗有机玻璃即聚甲基丙烯酸甲酯(PMMA)的边缘连接部位出现多处裂纹.对侧窗PMMA裂纹分布位置、形貌做了宏观分析,对裂纹断口进行了微观分析,对PMMA本体及其表面棕黄色带状区进行了傅立叶红外光谱分析,做了PMMA应力-溶剂腐蚀断裂试验;确定了侧窗PMMA裂纹为应力-腐蚀裂纹,主要是由于受到FN-303氟丁橡胶...     

Production of microcellular foam plastics by supercritical carbon dioxide

The production of microcellular plastic was studied in the polymethyl metacrylate (PMMA)-supercritical carbon dioxide and polycarbonate (PC)-supercritical carbon dioxide systems. The test pieces of PMMA and PC were put into a saturation vessel of which temperature and pressure were kept constant. Supercritical carbon dioxide at temperature between 303K and 393K and pressure between 100 bar and 250 bar was used as a foaming agent. After saturation of carbon dioxide, the pressure was quickly released to atmospheric pressure. The samples were immediately taken out from the vessel and heated in an oil bath. The fractured part of the sample was used for microstructure analysis with SEM. The effect of the saturation temperature, pressure of sorption and the foaming time on the cell mean size and cell density of the foam was investigated by considering the solubility of carbon dioxide in PMMA and PC. The foam morphologies of the foamed plastics were affected by solubility of carbon dioxide, which was directly related to saturation temperature and pressure. The cell density increased and, consequently, the cell size decreased with the solubility of carbon dioxide. The foaming time can be used a controlling factor to obtain the desired foam structure and the volume expansion ratio.     

PMMA/K2O 6TiO2复合粒子的制备及表征

采用乳液聚合方法，使甲基丙烯酸甲酯在钛酸钾晶须表面聚合，获得了表面包覆聚甲基丙烯酸甲酯的PMMA/K2O?6TiO2复合粒子. 考察了反应时间、引发剂浓度、单体浓度和温度对晶须增重率和单体转化率的影响. 通过TGA和SEM手段对钛酸钾晶须进行了表征. 测量了水对改性前、后晶须的动态润湿性变化，结果表明，改性后的钛酸钾晶须由亲水性向亲油性转变.     

湿热环境下有机玻璃性能研究

考察了湿热环境下有机玻璃的吸水率、断裂韧性K值、应力-溶剂银纹等几项性能,总结了加速老化情况下的一些规律。     

Interaction of poly(methyl methacrylate) and nafions

The thermal degradation of Nafion–H, Nafion–K, and the mixture of each of these with poly(methyl methacrylate) (PMMA) has been studied. A mechanism is proposed for the thermal degradation of Nafion–H that involves an initial cleavage of the carbon–sulfur bond leading to SO₂ and OH radical and a carbon-based radical. This carbon-based radical then undergoes further degradation. The addition of PMMA to Nafion–H inhibits further degradation of the Nafion carbon-based radical and instead radical recombination reactions between PMMA fragments and this Nafion radical dominate the reaction scheme. The replacement of the hydrogen in Nafion–H with a potassium (i.e., Nafion–K) produces a much more robust material that does not degrade under conditions similar to those used for Nafion–H. Nafion–K has little effect on the degradation of PMMA.     

超临界二氧化碳溶胀聚甲基丙烯酸甲酯的在线可视测量及热力学模拟计算

采用高压视窗釜配合高清晰相机研究了聚甲基丙烯酸甲酯(PMMA)在超临界二氧化碳(scCO₂)中溶胀行为,得到了PMMA在scCO₂中的平衡溶胀率。Sanchez-Lacombe(S-L)状态方程对于高压气体和聚合物系统的热力学性质有着很强的预测能力。将PMMA的PVT数据使用S-L状态方程进行拟合,得到压力、温度和密度的特征参数分别为：212.38 MPa、898.04 K以及1206.7 kg·m^-3 (8～25 MPa, 305～350 K),类似地可以得到二氧化碳(CO₂)的特征参数541.56 MPa、313.38 K以及1502.1 kg·m^-3 (8～25 MPa,305～325 K)。将实验得到的PMMA平衡溶胀率使用S-L状态方程拟合,可得二元相互作用参数为1.0671,结果表明在超临界区域,S-L状态方程模拟溶胀率与实验值吻合较好。     

聚合物溶液汽液相平衡测定及关联

建立了一套用差压法测定聚合物溶液汽液相平衡数据的实验装置．用乙醇纯溶剂及聚苯乙烯／甲苯溶液作为标准体系,对实验装置进行了校核．在温度范围为303.15K～333.15K及常压下,用本实验装置测定了4种聚合物（聚苯乙烯,聚氯乙烯,聚乙二醇,聚甲基丙烯酸甲酯）+6种溶剂（间-二甲苯,水,氯仿,乙酸乙酯,2-丁酮,环己酮）的14个二元体系汽液平衡数据,用简化空穴理论状态方程对实验数据进行了关联．     

Effect of the core/shell latex particle interphase on the mechanical behavior of rubber-toughened poly(methyl methacrylate)

Two- and three-layer composite latex particles were used to prepare rubber-toughened poly(methyl methacrylate) (RT-PMMA). The interfacial thicknesses of the multi-layered particles were varied by using different emulsion polymerization synthesis techniques. The resulting interphases were previously characterized by ¹³C nuclear magnetic resonance techniques. The poly(divinyl benzene)/poly(butyl acrylate) (PDVB/PBA) interphase thickness was found to be in the range of 5–7 nm. It was also found that the PBA/PMMA interphase thickness could be varied from 5 to 7 nm (batch addition of MMA) to 15 to 17 nm (interphase compatibilized with PMMA macromonomer). The interphase thickness was expected to play an important role in the mechanical behavior of PMMA. The effect of the interphase of two- and three-layer particles on the tensile and fracture behavior of PMMA composites was evaluated. The fracture surfaces were examined by scanning electron microscopy. The two-layer PBA/PMMA particles with a thicker interphase (15–17 nm) exhibited higher K_IC values with the PMMA composites compared with PBA/PMMA particles with a thinner interphase (5–7 nm). The three-layer particles were found to be more effective in toughening PMMA compared with the two-layer particles. The differences in toughening behavior are speculated to arise from the morphological effects caused by a thicker interphase, which in turn results in better coverage by the PMMA shell and a more uniform distribution of the toughening particles in the PMMA matrix. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:581–593, 1997     

Poly(methyl methacrylate)‐modified vinyl ester thermosets: Morphology,volume shrinkage,and mechanical properties

Thermoset materials obtained from styrene/vinyl ester resins of different molecular weights modified with poly(methyl methacrylate) (PMMA) were prepared and studied. Scanning electron microscopy and transmission electron microscopy micrographs of the fracture surfaces allowed the determination of a two‐phase morphology of the modified networks. Depending on the molecular weight of the vinyl ester oligomer, the initial content of the PMMA additive, and the selected curing temperature, different morphologies were obtained, including the dispersion of thermoplastic‐rich particles in a thermoset‐rich matrix, cocontinuous structures, and the dispersion of thermoset‐rich particles in a thermoplastic‐rich matrix (phase‐inverted structure). Density measurements were performed to determine the effect of the PMMA‐modifier concentration and curing temperature on the volume shrinkage of the final materials. The development of cocontinuous or thermoplastic‐rich matrices was not too effective in controlling the volume shrinkage of the studied vinyl ester systems. The evaluation of the dynamic mechanical behavior, flexural modulus, compressive yield stress, and fracture toughness showed that the addition of PMMA increased the fracture resistance without significantly compromising the thermal or mechanical properties of the vinyl ester networks. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Essential work of fracture of low‐filled poly(methyl methacrylate)/starch composites

In this study, poly(methyl methacrylate) (PMMA)/starch composites were prepared by a simple solvent casting method. The morphologies of the PMMA/starch composites were studied by scanning electron microscopy. The intermolecular interaction between PMMA and starch was investigated with Fourier transform infrared spectroscopy. The thermal properties of the PMMA/starch composites were compared with those of the pure PMMA sample. Thermogravimetric analysis showed that the thermal stability increased as the starch content increased in the composites. The biodegradability of the PMMA/starch composites was studied with a soil burial test. The degradability was measured in terms of mechanical strength, which increased as the starch content increased. The essential work of fracture (EWF) of the PMMA/starch composite films was investigated by the application of EWF theory under in‐plane (mode I) conditions, and we found that the toughness, in terms of the EWF of composites, increased compared to that of pure PMMA. The fracture of the composites was also evaluated by ANSYS software, and the results were compared to the experimental output. The increased toughness of these PMMA/starch composites may enable their application in the automobile and packaging industries. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A novel hysteresis test for studying crazing and shear yielding in rubber-toughened polymers

Tensile, tensile impact, compact tension, and fatigue tests were carried out on ABS (acrylonitrile-butadiene-styrene), HIPS (high impact polystyrene), and toughened PMMA (poly(methyl methacrylate)). Dumbbell specimens machined from test pieces were then subjected to sinusoidal tension-compression cycling at low stress amplitudes. The HIPS specimens produced asymmetrical hysteresis loops characteristic of multiple crazing, whereas PMMA gave more symmetrical, regularly shaped, loops. The behavior of the ABS polymers varied with loading history. It was concluded that the hysteresis test provides a useful additional technique for studying deformation mechanisms, especially under conditions that do not readily permit volumetric measurements.