BOPP薄膜双向拉伸工艺的探讨

选取一种市场认可度高的市售BOPP原料,进行了薄膜双向拉伸加工实验,在不同拉伸工艺下制备了BOPP薄膜,并对所制备薄膜的拉伸过程及薄膜的光学性能、力学性能、均匀性等进行了研究,建立起了薄膜拉伸工艺与薄膜拉伸成型和薄膜性能间的对应关系,从而为BOPP薄膜的工业生产和原料开发提供借鉴。     

双向拉伸聚酯薄膜横拉工艺研究

通过对采用“一纵一横”逐次拉伸工艺生产双向拉伸聚酯薄膜的横向拉伸工艺研究,归纳出横向拉伸倍率与薄膜断裂强度、伸长以及薄膜横向厚度均匀性的相关性;分析总结出横向拉伸温度与进入横拉前薄膜结晶度的经验关系;提出了热定型时间、温度的确定原则;归纳出热定型松弛率与薄膜收缩率之间的关系;提出了横向拉伸与热定型过程中的弓曲现象对薄膜横向性能不均匀分布的影响及改善途径。     

双向拉伸聚氟乙烯薄膜的拉伸工艺研究

在聚氟乙烯双向拉伸薄膜（BOPVF）的生产过程中，影响薄膜质量的主要因素是片材的质量及拉伸的工艺条件。针对这个问题，结合双向拉伸聚氟乙烯薄膜的生产工艺及拉伸机理，分析了铸片过程中产生的主要问题及解决方法；探讨了最佳的拉伸工艺条件，即拉伸比、拉伸温度、热定型温度，为生产高质量的BOPVF薄膜提供了一定的经验数据。     

双向拉伸聚氟乙烯薄膜的拉伸工艺研究

探讨了聚氟乙烯(PVF)流延膜在制备过程中常见的缺陷及产生原因,并给出了具体的加工工艺参数。结合PVF 薄膜的双向拉伸机理,通过力学及热性能测试表明:膜片的纵向拉伸温度为120～135℃,拉伸比为2.5～3.0时,薄膜不会出现细颈现象,且所需拉伸应力较小;当横向拉伸温度控制在130～150℃,拉伸比为2.5～3.5时,薄膜厚度介于23～28μm之间,且力学性能基本保持各向同性;双向拉伸的薄膜经过170～180℃热定型之后,横、纵向收缩率均小于2%,具有良好的尺寸稳定性。     

同步拉伸速率对双向拉伸聚乙烯薄膜结晶结构及性能的影响

实验采用双向拉伸聚乙烯(BOPE)原料线型低密度聚乙烯(LLDPE),用同步双向拉伸的方法制备BOPE薄膜,研究了双向拉伸过程中拉伸速率对薄膜结构和性能的影响。使用偏光显微镜(PLM)和差示扫描量热法(DSC)对未拉伸聚乙烯流延片的结晶形貌和热性能进行了研究。研究了不同拉伸速率下机器方向(MD)拉伸力的实时变化趋势,用DSC表征了不同BOPE薄膜样品的热性能。发现拉伸速率影响拉伸过程中聚乙烯晶体和分子结构及最终样品的结晶度和晶片厚度分布。实验研究了BOPE薄膜的力学和光学性能,分析了薄膜的宏观性能和分子结构之间的关系。实验结果表明,较高的拉伸速率有利于薄膜性能的提高。     

PTFE薄膜横向拉伸变形行为及其有限元分析

采用分步位移加载和弹塑性材料模型,在应力应变曲线及材料基本参数的基础上,对PTFE薄膜横向拉伸过程进行了实验研究和有限元分析,得到了均匀横向拉伸和横向拉伸过程中薄膜的应力和位移变形分布状态及规律。实验和模拟结果表明,由于PTFE薄膜在低应力下易发生塑性变形,在横向拉伸过程中存在明显的应力和位移分布不匀,并导致薄膜在面内发生弓曲变形。研究结果对通过扩幅实现双向拉伸薄膜的非均匀变形控制具有参考价值。     

手工高分子薄膜材料拉伸试验研究

文章主要分析了高聚物薄膜的拉伸过程,研究了在不同加载速率下低密度聚乙烯薄膜纵向拉伸强度和断裂伸长率的变化规律。实验结果表明:用自制的手动拉伸仪器拉伸高聚物薄膜时,可以清楚的看到其屈服过程,并能分辨出横向与纵向拉伸现象的差别,而用机器拉伸时,无法明显观察到高聚物薄膜拉伸的整个过程,手动拉伸有助于观察与教学。     

拉伸倍率对BOPP薄膜性能的影响

选取一种双向拉伸聚丙烯（BOPP）薄膜专用料进行了双向拉伸实验,在不同拉伸倍率下制备了BOPP薄膜试样,并对原料性能及所制备薄膜的光学性能、力学性能等进行了研究,从而建立起了拉伸倍率与薄膜拉伸成型和薄膜性能间的对应关系。结果表明,随纵向（MD）拉伸倍率的增大,薄膜雾度降低,光泽度升高;而随横向（TD）拉伸倍率的增大,薄膜的TD向拉伸强度呈线性提高,BOPP薄膜的性能主要受TD向拉伸倍率的影响。     

双向拉伸尼龙薄膜生产工艺探讨

本文通过分析ＰＡ６分子结构与ＢＯＰＡ薄膜加工关系，归纳总结了ＢＯＰＡ薄膜拉伸中的一些理论问题，且在此基础上分析了国外生产ＢＯＰＡ薄膜的三种工艺方法，并提出了在我国发展ＢＯＰＡ薄膜的建议。     

双向拉伸聚酰胺6薄膜概述

在综述国内外有关文献的基础上,阐述了聚酰胺薄膜的性能特点以及在软塑料包装中的地位和作用,简要介绍了双向拉伸工艺聚酰胺拉伸薄膜国内外发展的现状和前景,从而对开发聚酰胺薄膜的方向进行了讨论,并提出了一些可供参考的看法。     

Study of the molecular structure of PET films obtained by an inverse stretching process. Part I: Constant speed drawing of amorphous films

The constant rate stretching of amorphous poly(ethylene terephthalate) films is the first step of the industrial “inverse” process. To study this process, films deformed under uniaxial planar symmetry conditions have been produced on a laboratory stretching machine in order to discuss the influence of macroscopic parameters, such as draw ratio, temperature and melt viscosity of the amorphous film, on the deformation mechanism. The structure of oriented films has been characterized by combining X-ray diffraction and refractive index measurements. Stress strain curves have been simultaneously recorded. The draw temperature and the molecular weight of the polymer are determining factors controlling the development of molecular orientation and crystalline structure in the stretched films. The major influence of relaxation processes is described and a comparison with constant force drawn films is given.     

共聚组分含量对BOPP薄膜性能的影响

采用具有不同共聚组分含量的PP原料,进行双向拉伸成型BOPP薄膜,并对薄膜拉伸过程中的拉伸力变化,以及薄膜性能进行了测试和研究.结果表明,随原料中共聚组分含量的增大,薄膜的成型拉伸力有所下降,薄膜的拉伸模量、强度等力学性能相应降低,而薄膜的雾度、光泽度等光学性能明显改善.     

Young modulus and degree of crystallization of highly‐elongated polyoxymethylene

The physical structure of polyoxymethylene (POM) drawn into two steps by a press and a simultaneous biaxial drawing machine was studied and the drawing dependency on the degree of the crystallization, the orientation, and the modulus were analyzed. The stretching ratio by the press reached 6.0 and the tensile modulus of elasticity increased from 2.5 to 4.5 GPa. However, the degree of crystallization decreased slightly. The rupture elongation increased in the lower drawing region and it peaked when the drawing ratio was 1.7. The film stretched by 2 times was drawn by the biaxial drawing machine. The high tensile modulus of elasticity was obtained and the maximum value was 11.5 GPa at 14 times of the drawing ratio. The lamella structure of POM was supposed to loosen and become oriented to the drawing axis ambiguously by the first drawing. The lamella was highly oriented by the second stretching procedure. The tensile strength and the elongation as well as the modulus were analyzed as a function of the degree of the stretching and the crystallization. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1223–1227, 2006     

NPG改性PET薄膜热收缩性能的研究

运用自制的反应装置，通过加入第三单体的方法对聚对苯二甲酸二醇酯（PET）进行了共聚改性，研究了第三单体新戊二醇（NPG）用量对PET玻璃化转变温度Tg、结晶熔融行为和热收缩性能的影响，同时对拉伸工艺对薄膜收缩率的影响也进行了研究。结果表明，通过NPG共聚改性的PET的结晶能力随NPG用量的增加而降低，热收缩能力有了明显的提高；无定型区增大，获得了在通常情况下不能结晶的PET无定型材料，从而使改性PET薄膜在拉伸时保持较高的取向度，并在高于其Tg时发生解取向热收缩；拉伸温度、拉伸倍数等拉伸工艺对于聚酯薄膜的热收缩率有着显著的影响。     

Micro deep drawing of micro cups by using DLC film coated blank holders and dies

Lubrication is one of the key problems in metal forming, and this is even more important in micro forming because of size effect on friction. Diamond like carbon (DLC) film coated blank holders and dies were used in forming micro cups with drawing blank diameters of 2 mm. A plasma immersion ion implantation and deposition (PIIID) process was proposed to treat the blank holders and drawing dies. Raman spectrum, scratch test, and ball-on-disc test were used to investigate the structure, adhesion strength, and tribological property of the DLC films. The micro deep drawing experiments were carried out at room temperature on a universal testing machine at a drawing velocity of 0.1 mm/s without lubrication, and under the lubrication of castor oil and DLC film. The results showed that the micro cups were well formed with a minimum inner diameter of 0.95 mm under the lubrication of DLC film. The DLC film which dramatically decreased the drawing force and increased the limit drawing ratio (LDR) was better than other lubrication conditions and can be chosen as a proper lubricant in micro forming for mass production.     

The role of molecular networks and thermally activated processes in the deformation behavior of polymers

The deformation behavior of three polymers, polyethylene terephthalate (PET), polymethylmethacrylate (PMMA), and linear polyethylene (LPE) is considered in terms of two key factors, the stretching of a molecular network and the influence of thermally activated processes. In PET the observation of a natural draw ratio leads to studies of shrinkage, shrinkage force, and optical birefringence to define the nature of the network. The network is further exemplified by measurements of the molecular reorientation in deformation bands, spectroscopic studies of molecular orientation in drawing, and the concept of a true stress-strain curve. Yield and plastic deformation are also to be considered as thermally activated processes, but it appears that a major part of the flow stress is associated with the stretching of the molecular network. In PMMA the concept of a true stress strain curve also appears to be valuable, but the possibility of network breakdown during deformation has to be admitted as an extra complexity. In LPE the concept of a molecular network embracing both crystalline and non-crystalline material is helpful in understanding the drawing behavior. There is also direct evidence for the existence of a network from measurements of shrinkage and shrinkage force, and the existence of a true-stress strain curve. However, the dominant contribution to the flow stress now appears to come from thermally activated processes, with a key contribution from a small activation volume process which is tentatively associated with slip in the crystalline regions.     

BOPP纵拉过程的应力应变行为

采用高温下挤出厚片纵拉过程的模拟反映出来的应力应变行为，对厚片高温纵拉过程的形变特征进行分析研究，结果表明，EB在加工过程中具有更大的形态能力和更宽范围拉伸速度的适应性，在实验范围内，不同温度下的拉伸屈服应力与对数应变速率均呈线性关系，同时也受到相对分子质量的影响：高温下拉伸比的变化不会改变厚片形变的基本特征，但拉伸比提高后，应力应变曲线后端的硬化现象比较明显；深入理解BOPP拉伸温区结构变化现理，对于提高挤出厚片的形变能力，降低拉伸过程中薄膜的破损，提高生产效率将起到重要作用。     

拉伸方法对高强高线密度PVA纤维结构性能的影响

聚乙烯醇经干湿法凝胶纺丝制得初生纤维后,采用不同的两级后拉伸方法,制得单纤线密度在200-300dtex的高线密度PVA纤维。探讨了两级不同拉伸条件对PVA纤维结构和性能的影响。结果表明：一级拉伸热定型,有利于折叠链晶体的完善,一级拉伸后再经二级拉伸定型,纤维结晶更完善,水中软化点和纤维断裂强度分别达到116℃和11.5cN／dtex。     

LIQUID FILM SPRAYED ON A STRETCHING CYLINDER

The fluid dynamics of a film sprayed on a stretching cylinder is solved using similarity transform. The problem is governed by a stretching Reynolds number R and the mass flux rate, which is related to the film thickness. Perturbation solutions for small and large R compare well with exact numerical solutions of the universal curves. The heat transfer problem is discussed.     

Orientational crystallization and orientational drawing as strengthening methods for polyethylene

This paper reports on the theoretical and experimental studies of structure formation and strengthening (stiffening) of flexible-chain polymers. Two techniques of strengthening relying on the melt extrusion, i.e., orientational crystallization (crystallization initiated by melt extension) and drawing (uniaxial stretching of a crystallized polymer) are analysed by theory. The experiments involved preparation and study of melt extruded films and film fibers of linear polyethylene formed by the two techniques mentioned above. The effect of the degree of orientation and other parameters of the formation processes on the mechanical characteristics and the factors limiting the ultimate values of these characteristics are discussed. It is shown that multistage drawing succeeds in achieving a higher tensile strength and elastic modulus (1.2 and 35 GPa, respectively) than the orientational crystallization, which gives 0.8 and 15 GPa. The strengthening by drawing is accompanied by microcrack formation. In contrast, no discontinuities are observed in orientationally crystallized samples up to their ultimate extension.