光弹法研究桥墩应力的初步尝试

选用光学敏感的聚碳酸酯材料,加工成与实际桥墩相似的几何模型。采用光弹法获得桥墩在不同位置承受集中荷载时的等差线,对聚碳酸酯模型光学试验结果进行分析,对桥墩在不同位置承受集中荷载时的弯曲状态进行力学分析。并对聚碳酸酯模型的试验结果与力学分析结果进行对比。研究表明聚碳酸酯模型的光弹试验与其力学分析结论相一致。     

Stiffening of Polycarbonate by Addition of a Highly Dispersed and Fibrillated Amorphous Polyamide‐Based Nanocomposite

Ternary systems consisting of blends of polycarbonate (PC) from bisphenol A and minority amounts of an amorphous polyamide reinforced with organically modified nanoclay (naPA), were obtained in the melt state. The nanoclay was widely exfoliated inside the dispersed naPA phase. The dispersed phase exhibited a very fine size (up to 0.36 µm), indicating compatibilization. Compatibilization was attributed to interactions between the aPA and the PC. The nanocomposite showed a lower compatibility than their corresponding blends. This lower compatibility of the nanocomposite was attributed to a hindrance of the interaction by the migrated surfactant of the organoclay. The presence of fibrillation in conjunction with a dispersed nanoclay resulted in additive enhancing effects on the modulus and yield stress. This led to modulus increases up to 46% with respect to that of the neat matrix upon the addition of 25% naPA‐10. Besides exhibiting these remarkable modulus values, these systems show an elongation at break similar to that of the neat PC matrix.

     

新型聚碳酸酯板屋面系统在深圳大运中心项目主体育馆中的应用

深圳大运中心项目主体育馆采用新型的聚碳酸酯板屋面系统,从原理上解决了聚碳酸酯板屋面温度变形和雨水渗漏的问题,对高透轻型屋面系统的开发和发展提供了新的设计思路。     

Effect of Interphase Structure on the Debonding of Polycarbonate from S-2 Glass Fibers

The effect of interphase structure on the debonding of polycarbonate from S-2 glass fibers has been studied. The shear strength, fracture toughness and hydrolyic stability of the interphases were measured in a single fiber composite of a continuous S-2 glass fiber embedded in a polycarbonate matrix. Polycarbonate oligomers were chemically grafted onto the glass fiber surfaces through use of a silicon tetrachloride intermediary and the properties of the resulting interphases were compared with those of two commercial sizings and ozone-cleaned surfaces. Evaluation was accomplished by measuring the stress transmission across the interphase, τ, by carrying the embedded single fiber fragmentation test to saturation and by using computer simulations and a finite element analysis to calculate the strain energy release rate, G, of the observed fiber-matrix debonding accompanying the first fiber fracture. The oligomer-grafted interphase exhibited improved stress transmissibility and toughness, after 24 hours in boiling water. The tenacity of the tightly bound oligomers was confirmed via DRIFT, TGA and GC/MS experiments on Soxhlet-extracted fibers.

The grafting reaction was modeled on a high surface area silica and studied using solid state NMR to determine reasons for the greater stability of the oligomer-treated surfaces. Measurements of chemical shifts and spin-lattice relaxation times indicate that the oligomers are chemically attached to the surfaces, providing for a well bonded, water resistant interphase. Parallel experiments on a monomeric Bisphenol A-primed silica surface provided evidence that chemical bonding was primarily responsible for the greater hydrolytic stability.     

Rates of carbonate bond formation: Implications for macrocyclization

High yields of cyclic oligomeric carbonates can be prepared using an amine-catalyzed reaction of bisphenol A–bischloroformate. We have studied the mechanistic aspets of this carbonate macrocyclization by the isolated study of key chemical events. Using stopped-flow FT-IR spectroscopy, we have found that the rate of carbonate formation between the intermediate acyl ammonium salt and 4-isopropylphenol is the same for the acyl ammonium salt derived from tri-n-butylamine, triethylamine and diethylmethylamine. Previously, we found that conversion of acyl ammonium salt to urethane was also insensitive to amine structure while the formation of acyl ammonium salt is profoundly dependent on amine structure. These results are consistent with a mechanism in which the selectivity toward macrocyclization versus linear oligomer or high polymer formation is related to acyl ammonium salt concentration.     

PET／PC共混物的形态结构的研究

用偏光显微镜、X-ray衍射仪和示差扫描量热计(DSC)研究了聚对苯二甲酸乙二酯/聚碳酸酯(PET/PC)共混物的形态结构。结果表明:在PET/PC共混物中,当PC含量在50％以下时,PC的晶粒与PET的球晶分别分散在非晶区中;当PC含量在50％以上时,PET的晶柱与PC的晶粒分别分散在非晶区中。随着PC含量的增加,PET晶体的完整性被破坏,晶粒变小,结晶度下降,熔点降低。     

原位红外光谱法研究聚碳酸酯的热稳定性和分解机理

采用原位红外光谱法研究PC的热稳定性。实验表明:同为光气法制备的PC,G—1比G—2热分解温度高;同为酯交换法生产PC,Z-1比Z-2热分解温度高。PC在升温过程中,首先断裂的是酯基中醚键,在较高温度,发生异丙基断裂,400℃后,主链才断裂。     

聚碳酸酯的分子量分布与热降解

除了用Ｍｗ，Ｍｎ和Ｍｗ／Ｍｎ表征聚碳酸酯（ＰＣ）分子量大小和分布宽度外，还采用了（Ｍｐ－Ｍ１０）和（Ｍ９０－Ｍｐ）来表征低分子量和高分子量尾端所延伸的宽度，并以两尾端的起始分子量作为参考参数。其中Ｍｐ为分子量微分分布曲线峰位分子量，而Ｍ１０和Ｍ９０则为累积分布曲线中１０％和９０％处的分子量。研究了这些参数与聚碳酸酯热降解的关系，发现除数均分子量外，高低分子量尾端部分与ＰＣ热稳定性关系密切，尤其是低分子量尾端分布状态和起始分子量大小，对ＰＣ热稳定性更为敏感。这与ＰＣ端ＯＨ基相对浓度同ＰＣ热降解率的关系相一致。     

碳酸二甲酯酯交换反应研究进展

综述了碳酸二甲酯酯交换合成下游产品的技术进展,重点介绍了国内外碳酸二甲酯酯交换合成碳酸二苯酯、聚碳酸酯、长链烷基碳酸酯、脂肪族低聚碳酸酯多元醇的催化剂研究进展。     

PC基光散射材料的制备研究

将丙烯酸、有机硅光扩散等助剂混合后,经过平行双螺杆挤出机制备了光扩散聚碳酸酯,研究不同配比的丙烯酸和有机硅光扩散剂对聚碳酸酯光学性能的影响。结果表明:采用不同含量的丙烯酸和有机硅光扩散剂复配,添加不同的量可得到不同光学性能的光扩散聚碳酸酯。