P（3HB-co-4HB）／PLA共混物的扩链改性研究

以异佛尔酮二异氰酸酯（IPDI）和亚磷酸三苯酯（TPP）为扩链剂,对聚（3-羟基丁酸酯-co-4-羟基丁酸酯）／聚乳酸[P（3HB-co-4HB）／（PLA）]共混物进行扩链改性．采用毛细管流变仪、电子万能试验机、差示扫描量热仪和扫描电子显微镜等研究两种扩链剂及用量对扩链前后共混物的流变性能、力学性能、结晶性能及断面形态的影响．结果表明：两种扩链剂均显著提高了共混物的熔体剪切黏度和两组分间的相容性,IPDI和TPP添加量分别为1．5份和1．0份时,改性效果最明显,共混物断裂伸长率及缺口冲击强度分别提高了34．5％、69．6％和89．6％、81．0％;IPDI扩链体系的拉伸强度提高8．3％,而TPP扩链体系的拉伸强度略有下降,表明IPDI扩链效果优于TPP．     

相邻锅炉一次热风联络技术在CFB锅炉上的应用

针对循环流化床锅炉冷态启动用油量较大的问题,采用两台相邻锅炉一次热风风道联络的方法,实践中利用邻炉一次热风进行锅炉冷态启动,以煤代油缩短锅炉点火投油时间。结果表明:此方法使锅炉冷态启动时的用油量大幅下降,达到了显著的节能效果,并在此基础上展望了一次热风联络技术在锅炉防腐保养、冬季防冻等方面的应用前景。     

Air/CO2 cooling garment: Description and benefits of use for subjects exposed to a hot and humid climate during physical activities

The severity of the hot and humid conditions to which miners are exposed increases as the depth of the work site increases. This can cause heat stress that can greatly affect the health and safety of workers. To resolve this, a cooling garment has been developed that uses an atmospheric discharge of liquid CO₂ to create a cool microclimate with an average temperature of 12.5 (±0.4) °C beneath the garment. To evaluate the garment’s cooling efficiency, 19 male subjects participated in an experimental procedure. The two modes, cooling on and off, were compared. Significant physiological differences were found between the two modes after minute 27 (p < 0.05) until the end of the recovery phase for the heart rate (maximum difference of 10 beats per minute) and the internal body temperature (maximum difference of 0.33 °C). It was found that the modes also affected the subjects’ perceptions. The ON-mode was associated with better well-being and thermal comfort, and reduced humidity sensation. Perceptions of exertion were lower in the ON-mode condition from minute 2. The findings provide strong evidence of the ability of this cooling garment to reduce heat stress in hot and humid conditions similar to those encountered in deep mines.     

PBT/PET熔融共混体结晶的研究

应用示差扫描量热仪和红外光谱研究了PBT/PET熔融共混体的热性能。结果表明,在熔融共混体中,PBT和PET分别结晶,在不同组成下,两者对各组分的结晶互相促进。     

推压余过程挤压机的振动测试与分析

分析了管型材挤压机推压余过程的振动,并进行了现场实测。建立了推压余过程挤压机的动力学模型。指出压余与挤压筒之间的摩擦是产生振动的主要原因,提出了减振措施。     

Temperature distribution for controlled-dwell extrusion of γ-TiAl

Ti-47Al-2Cr-2Nb-0.15B alloy (atom fraction) was extruded at temperatures(Ta) of 1250 and 1330℃,respectively. The method of adding a thermal insulating layer was used to overcome the problem associated with the flow stress mismatch between the can and the billet during extrusion. Effects of two kinds of insulations, ZrO2 powders and silica fibers, on the quality of extrude bar along the radial direction were studied, and the process parameters were optimized by combining with finite element method (FEM). Tensile properties of the extruded alloy at room and elevated temperature were tested. The results show that the silica fibers has better thermal insulating property than ZrO2 powders. The temperature distribution in radial is more homogeneous using silica fibers. The alloy has a good balance of yield strength and room temperature ductility and the values are 680 MPa and 3.5%, respectively.     

改性聚酰胺树脂的合成及其在热熔胶领域的应用

以国产低分子聚酰胺树脂为基本原料 ,经过接枝、交联改性 ,在不同合成条件下 ,合成出适应于不同应用场合的三种电性能优异的韧性难燃聚酰胺树脂。该产品可作为热熔粘合剂广泛应用于电子电器、汽车、热缩材料等领域。由于合成中采用来源丰富的国产原料 ,并适量加入废聚酯 ,大大降低了原料成本。测试和应用试验表明 ,产品性能已达到进口同类产品水平。因此该产品具有较大的应用潜力 ,其经济效益和社会效应显而易见     

高速纺涤纶切片及粉屑的热分析

本文分析了高速纺涤纶生、干切片及粉屑的热性能等。发现同一工厂生产的切片，其羧基含量和热性能波动较大，与一些优质切片相比存在一定的差距。随分子量分布加宽切片的热性能变差。干切片粉屑与干切片的熔点接近，但熔融结晶峰值温度高于切片，过冷度降低，峰底宽变窄，它会在纺丝中造成纤维固化结晶时间的不同，影响ＰＥＴＰＯＹ结构的均一。     

Microstructure and tensile behavior of hot extruded AZ91 alloys at room temperature

AZ91 alloys were prepared by hot extrusion and its microstructure and tensile behavior at room temperature were investigated.Compared to as-cast ingot,the grain size of hot-extruded material is more refined,the intermetallic phase Mg17Al12 is broken and dispersed discontinuously.Both strenth and elongation of AZ91 are improved by hot extrusion.Tensile behavior and fracture surface of the experimental material were studied.Due to the change in microstructure,the fracture mechanism of extruded material is different from that of as-cast ingot,the latter is mainly a brittle fracture,Ductile fracture plays a role in hot-extruded AZ91 failure at room temperature.     

Using multiple‐mode models for fitting and predicting the rheological properties of polymeric melts. II. Single and double step‐strain flows

Several classes of multiple‐mode rheological constitutive equations are examined for predicting the viscoelastic flow properties of a typical polymer melt in single and double step‐strain flows. The phenomenological parameters appearing in these models have been obtained by the fitting of experimental data taken in small‐amplitude oscillatory shear and steady shear flows. The performance of the models for predicting the experimental data in the step‐strain experiments is examined in detail. Specifically, we examine whether or not mode coupling is necessary to describe the experimental behavior under step‐strain flows. Furthermore, it is demonstrated that the reversing double step‐strain experiment is a very powerful tool for testing viscoelastic constitutive equations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007