Effects of thermal annealing as polymer processing step on poly(lactic acid)

Thermal annealing as an additional polymer processing step or post-treatment processing step enables the structural changes of amorphous parts into crystalline parts. This paper investigates the feasibility of thermal annealing at 100°C up to 90?min used as an additional processing step to modify the crystalline structure and the thermo-mechanical stability of poly(lactic acid) (PLA). Moreover, the crystallization ability of PLA has been amended by the addition of 3?wt% of wood flour and kaolin. The values of the degree of crystallinity and lamellar thickness determined by wide-angle-X-ray scattering showed that the thermal annealing of PLA samples modified with nucleating agents was an efficient processing step to increase the final crystallinity of PLA. Moreover, altered crystalline structure helped to improve the thermomechanical stability of PLA.     

夹布酚醛树脂导向环热成型工艺研究

夹布酚醛树脂是一种抗压强度较高的导向支撑材料,在工程液压缸中广泛运用。但夹布酚醛树脂导向带在小规格液压缸的安装中存在一定的困难。通过对夹布酚醛树脂在热空气中老化后的抗压强度测试,以及在乳化液中的加热并浸泡后的抗压强度测试,确定夹布酚醛树脂的成形工艺;通过模具的设计,进行夹布酚醛树脂导向带的成型试验,使带状夹布酚醛树脂导向带成型为环状导向环,解决了小规格夹布酚醛树脂导向带在活塞杆中安装困难的问题。     

热成型不锈钢圆管混凝土轴压短柱受力性能试验研究

对热成型不锈钢圆管混凝土短柱在轴向压力作用下的承载性能进行试验研究,试验主要参数为混凝土强度（C30和C40）、不锈钢管壁厚t（0.9 mm、1.0 mm和1.2 mm）和试件的高径比λ（3.0、3.5、4.0）,试验观测了不锈钢圆管混凝土短柱在轴向压力作用下的破坏现象、试件荷载-轴向变形曲线、荷载-环向应变曲线、荷载-轴向应变曲线等。根据试验的破坏现象,将试件分为5种破坏模式,并分析了不锈钢管壁厚t和试件的高径比λ对试件的承载力、延性、刚度的影响。分析结果表明：试件在屈服后表现出明显的承载力提高;随着钢管壁厚的增加,试件的受压承载力、延性及刚度均有所提高;随着试件高径比增大,试件的延性增大,刚度降低;试件的受压承载力在高径比3.5时最大,4.0时次之,3.0时最小。与普通钢管混凝土相比,不锈钢管混凝土约束放大系数有一定的提高。     

基于网络控制的多工位真空成型机的研究与开发

研究并开发了一种集网络控制、气压比例吸泡及脱模控制、液压比例控制、伺服控制等先进技术于一体的现代化集成制造系统——多工位真空成型机，可广泛用于火车内饰件、汽车内饰件和冰箱（柜）内胆的批量生产。     

一种弯管加热成型回转系统的设计

随着弯管在各个行业的需求量急剧增加,对弯管成型的工艺以及设备的研究已渐渐引发热潮.论文在北京国电富通公司对弯管成型工艺流程的实验基础上,对于弯管成型的自动化工艺进行了研究,设计了一种流水线回转系统,为今后弯管成型的自动化设备的设计提供参考.     

以LOM原型为基础的电铸载体选择

本文以LOM原型为基础，分别制作环氧树脂模型、硅胶模型、吸塑件模型石膏模型，并对这四种模型做电铸载体的可行性进行分析，在不影响电铸质量的前提下，根据不同结构特征可以选择合适的电铸载体。     

Thermoforming starch‐graft‐polycaprolactone biocomposites via one‐pot microwave assisted ring opening polymerization

A thermoformable starch‐graft‐polycaprolactone biocomposite was prepared by initiating ring‐open polymerization of caprolactone monomer onto starch under microwave irradiation. In this case, the thermoplastic and hydrophobic modification of starch could be realized by one‐pot grafting PCL, where the grafted PCL chains acted as the “plasticizing” tails of thermoforming and as the hydrophobic species of water‐resistance. The resultant biocomposites were injection‐molded as the sheets and their structure and properties were investigated by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, contact angle measurement, and tensile testing. In this case, the grafted PCL chains entangled each other, and hence contributed to the strength and elongation of biocomposites. This work provided a simple strategy of one‐pot thermoplastic and hydrophobic modification of starch, and may be applied in a continuous process of modification, compounding, and molding. Meanwhile, the resultant biocomposites containing starch are believed to have a great potential application as an environment‐friendly and/or biomedical material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Moulded pulp products manufacturing with thermoforming

For an effective optimization of pulp thermoforming and of the moulded pulp products manufactured by this process, a full understanding of the process physics combined with full knowledge of the pressing equipment is necessary. For this reason, in this Addendum, we clarify how the process parameters “Holding time,” “Vacuum time,” “Cycle time,” and “Temperature” were interpreted and subsequently defined for the analysis of the process and product‐related outputs of the thermoforming experiments.     

A coupled boundary/finite-element approach for the three-dimensional simulation of air venting in blow molding and thermoforming

We examine the three-dimensional potential flow of a fluid (air) inside a cavity as it is induced by the advancement of an isotropic homogeneous membrane (parison) of general shape. This problem is of direct relevance to the processes of blow molding and thermoforming whereby air is evacuated through a number of vents of various sizes that are optimally positioned on the surface of the mold. The membrane material is assumed to obey the Mooney–Rivlin constitutive model, and the resulting deformation field is obtained using a Galerkin based finite-element method. The flow field in the domain bounded by the inflating membrane and the cavity (mold) is obtained using the boundary-element method. The accuracies of the original finite- and boundary-element codes are assessed separately against existing numerical results and analytical solution. The coupled finite/boundary element formulation is used to examine the air flow inside a rectangular mold with an insert and through a number of vents of various sizes at each pressure step of inflation. The accuracy of the coupled method is assessed on the basis of conservation of mass of air flow. © 1998 John Wiley & Sons, Ltd.     

弹性卡箍断裂原因分析

卡箍铆接于舱体内部,用于捆扎、固定电缆束。尾段舱体卡箍在卡装电缆束时发生断裂,中段舱体卡箍在卡装电缆束后约5.5 h发生断裂。通过外观检查、化学成分分析、金相组织检查、硬度测定、断口微观观察、含H量测试等,对卡箍断裂的原因和性质进行了分析。结果表明:尾段舱体卡箍由于存在裂纹缺陷,因承载能力不足导致了断裂,卡箍热成形中工艺控制不到位,裂纹在应变较大区域萌生;中段舱体卡箍断裂性质为氢致延迟断裂,H含量偏高,同时较高的强度对断裂的发生起到了促进作用。