红外辐射用于塑料片材成型加热原理和设计

红外辐射在热成型包装中用于塑料片材成型加热具有重要应用价值。本文在阐述红外辐射加热原理的基础上，就对材加热元件及加热装置中有关工艺和结构参考作了必要的探讨性设计，并就加热电功率问题提出了若干简单估算方法。     

Thermoforming of film-based biomedical microdevices

For roughly ten years now, a new class of polymer micromoulding processes comes more and more into the focus both of the microtechnology and the biomedical engineering community. These processes can be subsumed under the term "microthermoforming". In microthermoforming, thin polymer films are heated to a softened, but still solid state and formed to thin-walled microdevices by three-dimensional stretching. The high material coherence during forming is in contrast to common polymer microreplication processes where the material is processed in a liquid or flowing state. It enables the preservation of premodifications of the film material. In this progress report, we review the still young state of the art of microthermoforming technology as well as its first applications. So far, the applications are mainly in the biomedical field. They benefit from the fact that thermoformed microdevices have unique properties resulting from their special, unusual morphology. The focus of this paper is on the impact of the new class of micromoulding processes and the processed film materials on the characteristics of the moulded microdevices and on their applications.     

Numerical and experimental investigation of polycarbonate vacuum-forming process

This research investigates the influence of process variables on the quality of vacuum-formed thermoplastic products and provides guidelines for polycarbonate (PC) thermoforming optimization. The process variables investigated include: operating temperature, non-uniform temperature of the PC sheet, and applied pressure. A series of thermo-coupled numerical simulations are conducted to examine the quality of the vacuum-formed parts. Three general hyperelastic constitutive models are used to describe the mechanical behavior of PC during the thermoforming process and to examine its reliability. The forming limit and the thickness distribution predicted by the numerical simulations for the axisymmetric vacuum-formed parts are compared with the experimental results of vacuum-forming. Good agreement is found between the numerical simulations and the experimental results. In addition, the effect of temperature on the surface smoothness and the deformation results of the thermoformed parts are discussed. Based on the results of the experiments and numerical analyses, guidelines for the PC thermoforming process are proposed.     

医用泡罩包装容器热成型仿真及工艺参数优化

目的通过数值模拟技术,仿真某医用泡罩包装热成型容器在柱塞辅助热成型工艺过程中,不同时刻片材的厚度变化规律及分布情况,并验证有限元仿真模拟结果的可靠性。仿真拉伸头不同预拉伸深度下的热成型容器的壁厚分布情况,找出使壁厚分布更加均匀的最佳预拉伸深度值,以优化工艺参数。方法利用Solid Works软件建立了有限元模型,通过Ansys Polyflow软件仿真该医用泡罩包装容器的热成型工艺过程。并通过对实际热成型产品进行热成型实验,验证了有限元仿真模拟结果的可靠性。结果仿真值与实验值的相对误差约为2%,仿真结果与实际情况大体一致,仿真结果比较可靠。结论通过有限元仿真模拟得到该医用泡罩包装制品的最佳热成型预拉伸深度值为6.5 mm。     

PVC包装盒热成型模设计

分析了PVC包装盒热成型的工艺特点,介绍了热成型模具的结构、气道的设计特点、冷却水道的结构和密封方式。该模具有效地解决了大批量生产过程中模具模温不易控制的问题,克服了制件脱模以后收缩率大的缺点,实现了大批量自动化生产。     

微孔泡沫塑料技术进展

综述了微孔泡沫塑的生产方法,介绍了其研究进展。     

吹塑和热成型过程的数值分析II.有限元方法

将逐步给出用于热成型和吹塑模拟的薄膜大变形有限元法。由于无论是热成型还是吹塑过程 ,成型制件是薄壁结构 ,聚合物将被模拟成膜 ,只考虑聚合物的拉伸 ,而忽略聚合物的抗弯性 ,有限元分析涉及到大应变、非线性材料行为以及接触问题等 ,在分析过程中 ,碰撞计算将连续进行以确定接触是否发生。当接触发生后 ,塑料膜上的接触点将永久固定在模具表面而不允许再移动。     

Moulded pulp products manufacturing with thermoforming

Over the past years, eco‐friendly packaging solutions such as moulded pulp have resonated with a growing number of consumers. Among all of them, the thermoformed products make use of the most recent manufacturing approach that produces high‐quality, thin‐walled items. However, it remains an underresearched area, and the development of an efficient and precise manufacturing process is fundamental in order to increase the implementation of sustainable packaging. With the purpose of setting a step towards in the standardization of design and testing practices of eco‐friendly packaging, this work focused on the characterization of the thermoforming process of moulded pulp products and their characteristics. Three different analyses were carried out for this purpose, covering the dewatering efficiency of the process, a quantification of the moulding geometrical accuracy, and an analysis of the internal microstructure of the parts. Experimental results and statistical analysis show that the dewatering efficiency is mainly governed by the mould's temperature while the duration of the contact time is not influential. In the second investigation, the geometrical accuracy of the mouldability of microfeatures was assessed. The process appeared to be dependently related to the pulp type employed. Finally, the internal microstructure was documented using X‐ray computed tomography. The analysis shows an increase in the internal void fraction linked with an increase in the mould's temperature. The role of the water change of phase in the thermoforming process is also discussed by reference to the work conducted on impulse drying.     

Effect of the unidirectional drawing on the thermal and mechanical properties of PLA films with different L‐isomer content

This work simulates the thermoforming process of two different L ‐isomer content PLA grades (95.6 and 98%), studying the influence on the induced morphology and the variation in the thermal and tensile properties. The thermoforming process was simulated with uniaxial tensile tests performed at different temperatures and strain rates, reporting the tensile behavior before, during, and after the test. The resulting structural changes were analyzed by wide‐angle X‐ray scattering and Fourier transformed infrared spectroscopy. Thermal characterization was carried out with differential scanning calorimetry and dynamomechanical thermal analysis. The results showed that, regardless the L ‐isomer content, drawing at 70°C produced a stable mesomorphic phase that showed greater tensile properties than the original films. This mesomorphic phase, indeed, could be reordered into a crystalline structure under mild annealing conditions (5 min/75°C), if compared with those needed for similar amorphous PLA specimens (60 min/120°C), thus providing a processing opportunity for obtaining thermally stable PLA products at temperatures above 100°C. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013