T_g以下温度退火对无规聚苯乙烯性能的影响

用调幅式ＤＳＣ等新技术研究了物理老化对无规聚苯乙烯多种性能的影响．随着老化时间的延长，试样的玻璃化转变温度、热焓松弛、峰温、峰高和热焓提高；老化使材料的初始模量，屈服应力和断裂强度都有不同程度的提高；使样品的溶剂扩散速率降低，但对样品的密度和声传播速度几乎没有影响．以上这些结果可从物理老化引起试样中凝聚缠结增加的观点来进行解释．     

物理老化对PEK-C、PES-C及其复合材料的玻璃化转变热焓松弛特征的影响

本文用DSC技术研究了物理老化对PEK-C、PES-C及其共混物和复合材料玻璃化转变的影响.老化时间(t)延长,玻璃化转变温度(T_g)、热焓松弛峰温(T_(max))、峰高(△C_(pmax))和热焓(△H)提高;△H与lgt成线性关系.碳黑或碳纤维对PES-C的物理老化行为无影响,而反应性乙炔端基砜(ATS)固化物能限制PEK-C和PES-C在T_g以下温度的物理老化过程.利用物理老化能更为方便地判断多相体系的相容性,结果表明PEK-C/PSF为相容体系,而PEK-C/PES-C相容性较差.     

环氧交联网T_g转变的tanδ-T曲线解析

本文系统地研完了预聚物分子量、固化剂配比和固化条件对环氧交联网T_g松弛内耗峰松弛时间分布的影响。本实验和理论研究结果首次证明了环氧交联网T_g松弛过程具有单一松弛时间描述的线性标准固体的特征,与预聚体分子量、固化剂配比和固化条件无关。此结果可用环氧交联网的两相结构特征加以解释。     

过剩热焓松弛CO_2和甲苯在PET薄膜中渗透的影响

本文研究了非晶态、未取向PET薄膜样品在低于T_g温度以下热处理,结构的变化和过剩热焓松弛对CO_2和甲苯溶剂在样品中渗透速率的影响。结果表明,随退火时间增加,从T_g转变吸热峰确定的过剩热焓松弛量、 T_g温度、密度增加,而反式构象含量减少。除分子链堆砌密度提高或自由体积下降外,没有发现非晶相有结构上的变化。因此,CO_2在样品中随退火时间的增加渗透速率下降。然而,由于样品脆性增加和甲苯的溶胀作用,样品表面出现裂纹,使甲苯在样品中的表观渗透速率增加。     

EFFECT OF EXCESS ENTHALPY RELAXATION ON PERMEATION OF CO_2 AND TOLUENE THROUGH PET FILM

Structural change in an unoriented, amorphous PET film annealed at temperatures below T_gand the effect of excess enthalpy relaxation on permeation rates of CO_2 gas and toluene liquid intreated samples have been studied. The results suggest that the amount of excess enthalpy relaxa-tion as determined from the endothermic peak in T_g interval, the T_g and density all increase withannealing time, but the trans-conformation component of samples decreases. No change of struc-ture in the amorphous phase was found other than the normal densification of the molecular chainpacking or a reduction in free volume had occurred during the annealing regimes. Therefore, thepermeation rate of CO_2 gas in treated samples reduced. While the apparent permeation rate oftoluene liquid increased with annealing time because of a creation of extensive cracks at film surfacearising from both the increase in embrittlement of polymer and the swelling action of toluene liquidon treated samples.     

用热焓松弛行为研究聚苯醚和改性聚苯醚共混体系的相容性

用DSC分别探讨了苯酰化聚苯醚(PPO)(BA~(31.0)-PPO和BA~(43.4)-PPO)/PPO共混体系的热焓松弛变化规律与差异.发现已知是相容体系的BA~(31.0)-PPO/PPO在低于T_g等温退火过程中只出现一个吸热峰;典型的相容体系PPO/PS也表现出类似的行为.而未知相容性的BA~(43.4)-PPO/PPO在等温退火过程中出现两个吸热峰,此两峰的T_p值随退火时间的变化类似于各纯组分相应条件下的变化.电子显微镜结果表明,BA~(43.4)-PPO/PPO是相分离体系.因此对T_g非常接近的较刚性主链的PP0及其改性物的共混体系可用热焓松弛行为确定其相容性.     

CTBN-TOUGHENED EPOXY RESINS——EFFECT OF CURING MECHANISM ON NETWORK STRUCTURE OF THE RUBBER PHASE

Epoxy resins toughened with carboxyl-terminated butadieneacrylonitrile copolymers (CTBN) are two-phase thermosets. The network of the in situ formed rubber particles depends upon the curing mechanism of the resin. When a primary polyamine such as triethylene tetramine was used as curing agent, the network of the rubber phase was quite incomplete, whereas a perfect rubber network was formed with 2-ethyl-4-methyl imidazole as the curing agent.     

THE EFFECT OF CROSS-LINKING ON PHOTOCYCLING ACTIVITY OF BACTERIORHODOPSIN

Abstract— Purple membrane preparations from Halobacterium halobium were chemically modified with imidoesters. Dimethyl adipimidate (8.3 Å chain length) amidinates about five of the six free lysine residues whereas dimethyl suberimidate (11.3 Å) under the same conditions reacts with only 2–3 residues. Gel electrophoresis showed that the shorter chain length imidoesters were less effective than dimethyl suberimidate in oligomer formation. However, dimethyl adipimidate resulted in a more marked inhibition of the photoreaction activity. Monofunctional imidates, methyl acetimidate and methyl butyrimi-date, at comparable degrees of amidination, did not appreciably affect activity indicating that the presence of bulky groups on the exposed lysine residues does not cause the effects observed. Hence, the introduction of molecular mobility constraints by intramolecular cross-linking slows photocycling, and, therefore, inhibits proton pumping activity of bacteriorhodopsin. This indicates that conforma-tional changes of the protein moiety of bacteriorhodopsin occur during photocycling activity.     

活性酯固化环氧树脂物性的研究

主要对活性酯固化环氧树脂的吸水性、高耐湿性、电气特性等方面进行了研究,同时也对其树脂极性、交联结构、分子链运动等方面也进行了研究．     

聚酯型扩链脲改性环氧树脂E-51/DDS体系反应活性研究

提高二氨基二苯砜(DDS)固化环氧树脂体系的反应活性,降低反应温度、提高反应速率,具有重要的研究意义和实用价值.本研究以聚酯(PEGA1000,2000,PNGA1000,2000)、甲苯-2,4-二异氰酸酯(TDI)、二甲胺为原料合成了含有聚酯型柔性间隔基的扩链脲U-PEGA1000,2000,U-PNGA1000,2000,用其改性环氧树脂E-51/DDS体系,采用DSC系统考察了改性体系的固化反应活性.结果表明,改性体系固化反应活性明显提高,固化反应表现活化能降低,固化反应峰顶温度从230℃降至170℃,固化反应的表观活化能由67.74kJ/mol降至47.80kJ/mol.     

分子拓扑指数在晶格能中的应用

分子拓扑指数在晶格能中的应用凌天才（重庆师范学院化学系重庆６３００４７）关键词拓扑指数，晶格能分子拓扑指数实际上是分子图的不变量。自ｗｉｅｎｅｒ￣［１］于１９４７年首次提出ｗｉｅｎｅｒ指数并用以关联烃类的沸点等数据以来，分子拓扑指数广泛用于关联与预测...     

THE EFFECT OF EC ON ORIENTATION AND RELAXATION OF PP OBTAINED VIA DYNAMIC PACKING INJECTION MOLDING

As a long term project aiming at engineering plastics based on polypropylene (PP), in this work, we report the effect of ethylene-cellulose (EC) on the orientation and relaxation of PP obtained via dynamic packing injection molding (DPIM). 2d-WAXD results showed that PP with a highly oriented structure and a shish-kebab structure were achieved by DIPM, leading to an increase of tensile strength from 35.0MPa to 48.6MPa. The degree of orientation of PP was increased by adding only 1% of EC, resulting in a further increase of tensile strength from 48.6MPa to 53.8MPa. Shish was found to exist not only in the oriented layer but also in the core of the sample after adding EC, as evidenced by DSC result.This was understood as due to the overall decrease of viscosity by the addition of EC, thus an increasing of shear rate. Higher shear rate can favor the orientation of molecules and continuous growth of shish structure, resulting in a change of shish distribution along the sample thickness. On the other hand, the relaxation mode of shish in the melt recrystallization of PP is also greatly affected by the presence of EC. A retarded relaxation of PP macromolecules was seen.Even more, SEM results showed that EC could form the short fibers in PP matrix along the shear flow direction. Compared with the morphology obtained by conventional injection molding, a much better dispersion and easy break-up of EC in PP matrix were observed for samples obtained by dynamic packing injection molding.     

层状硅酸盐累托石/环氧树脂纳米复合材料的结构和性能研究

用有机改性的层状累托石与环氧树脂复合制备出纳米复合材料 .通过改变累托石含量发现在很低含量 (0 5W % )时纳米复合材料具有最佳力学和热学性能 ,冲击强度增加 12 0 % ,断裂伸长率增加 330 %玻璃化转变温度提高 2 8℃ .用X衍射、透射电镜和红外吸收光谱研究了材料的微观结构 ,结果表明层状累托石和环氧树脂发生了化学反应 ,观测到了层状累托石完全剥离和插层两种结构形态 ,且累托石含量较低时容易形成剥离型 .具有大的比表面积、高的反应活性的累托石片层分散于环氧基体中形成剥离型为主的结构有利于改善复合材料的力学性能并增加其热稳定性 .     

等温DSC法研究树枝状大分子PAMAM与环氧树脂的固化反应动力学

聚酰胺-胺(PAMAM)树枝状大分子是近些年来在科学界引起广泛关注的一种聚合物[1~3].它具有高度规整的分子结构,形状接近球体,表面存在密集的官能团,而内部则存在大量的空腔,这些特殊结构导致了它的许多性质与线性高分子存在很大差异,从而吸引了众多的科学家投入对它特殊性能和特     

混合条件对环氧有机土纳米复合材料插层剥离行为及性能的影响

采用X 射线衍射仪、透射电镜 (TEM )研究了混合条件 ,即混合温度和时间 ,对环氧 /16 烷基胺有机蒙脱土体系在固化前的混合物以及加入固化剂、促进剂固化后有机土的插层与剥离行为的影响 .同时采用拉伸试验机、冲击试验机和热机械分析仪测定了插层与剥离型纳米复合材料的物理力学性能 .从X 射线衍射看出 ,有机土很容易在混合过程被环氧所插层 .混合物经固化后可以形成插层型或剥离型纳米复合材料 .存在一个混合温度 时间 插层剥离转变的 3 T图 .只有在一定的混合条件的区域内才能形成剥离型纳米复合材料 .剥离型比插层型纳米复合材料具有较高的力学性能     

环氧树脂潜伏性固化促进剂的研究

对环氧树脂/桐油酸酐/乙酰丙酮钕体系的热固化反应进行了研究。用DSC、TBA和固化仪等手段测定了凝胶化时间和表观反应活化能,计算了反应动力学参数。结果表明,乙酰丙酮钕对体系的固化具有潜伏性促进作用。     

气相生长碳纤维对环氧树脂固化反应的影响及其复合物固化动力学研究

用示差扫描量热方法研究了气相生长碳纤维作为填料对4,4′-二氨基二苯甲烷四缩水甘油环氧树脂(TGDDM)/4,4′-二氨基二苯基砜(DDS)等温固化反应的影响.与纯环氧树脂一样,气相生长碳纤维复合物的固化反应也属于自催化反应类型.气相生长碳纤维对环氧树脂的固化反应动力学影响很小.固化反应的过程可以用一种修正过的自催化动力学模型来描述,在整个固化反应过程中纯TGDDM/DDS环氧树脂及其气相生长碳纤维复合物模型拟合得到的结果和实验数据相当一致.     

橡胶增韧环氧树脂机理的研究

本文研究了固化剂种类、环氧基体平均网链长度和分散相与基体间键合情况对体系韧性等的影响.结果说明,基体平均网链长度是一个更为重要的影响因素.分散相与基体间的化学键合也是重要的.文中对橡胶增韧环氧树脂的机理提出了见解.在交联密度较低的材料中,在橡胶颗粒附近叠加的应力场诱发下发生纵深度较大的断裂过程.分散相与基体间的化学键合增大该应力场强度有利于加大断裂过程区.     

环氧树脂的物理老化

本工作发展了补偿式示差扫描量热(CDSC)法,用于环氧树脂热焓松弛研究,实验结果证明CDSC法较DSC法灵敏并能提供更多的信息。用CDSC法研究了交联度对环氧树脂热焓松弛动力学的影响,计算了活化能,对结果进行了讨论。     

晶格能的键参数拓扑指数关联

拓扑指数或分子连通性指数法在研究有机化合物结构与性能关系方面,已作了大量工作,并得到了广泛的应用。拓扑指数只与分子的几何结构有关,而不考虑原子的性质;键参数法虽然研究无机化合物结构与性能方面已获得了巨大的成功,但键参数法只考虑原子的性质,而不考虑分子的几何结构,使它们的应用受到了一定的限制。Berysz,张宏光和辛厚文等在将键参数和拓扑指数结合起来方面和了有益的尝试。本文提出了一种将分子的几何结构与组成分子的原子性质较好结合起来的键参数拓扑指数。