注塑成型模具温度对PP制品结晶形态的影响

以某聚丙烯(PP)平板塑件为例,通过注塑成型实验并结合X射线衍射技术分析了不同模具温度下制品结晶度、晶粒尺寸以及晶粒取向的变化趋势,得到模具温度对制品最终结晶形态的影响规律。结果表明:随着模具表面温度的提高,制品的结晶度呈非线性递增趋势,且表面温度越高结晶度增幅越大;结晶晶粒尺寸与模具温度正相关,而结晶区的取向度则与模具温度负相关。     

模具温度对PP塑料注塑成型结晶形态的影响

以某款医用注射器筒产品为例,以结晶性塑料聚丙烯(PP)为实验材料,基于注射成型、X射线衍射实验及数据处理技术相结合的方法研究了模具温度对PP塑件产品内部分子结晶形态的相关指标影响规律。研究表明,随着模具温度的逐渐增加,塑料产品的结晶度呈现非线性递增的变化趋势,且递增梯度逐步增大;晶粒尺度的大小同样与模具温度具有正相关性,而晶区取向度呈相反的下降变化趋势。     

热处理对聚丙烯结晶结构和力学性能的影响

研究了不同热处理温度和热处理时间对聚丙烯(PP)结晶结构和力学性能的影响.结果表明:热处理对PP球晶分布、晶粒尺寸影响不大;退火处理使PP晶格参数略为下降;在90℃以上,随着热处理温度的提高,PP的结晶度不断增大;随热处理时间的延长,PP的结晶度先增大后趋于稳定;随热处理温度的提高和热处理时间的延长,PP拉伸强度提高,屈服强度增大,弹性模量增大,断裂伸长率和静力韧度下降,其变化规律与结晶度的变化相对应.     

双向同步拉伸工艺对PET聚酯薄膜性能的影响

为阐明双向同步拉伸工艺对聚酯薄膜性能的影响，利用聚对苯二甲酸乙二醇酯(PET)聚酯切片进行挤出铸片，并在不同拉伸温度、拉伸倍率和拉伸速度下进行双向同步拉伸制膜，研究了拉伸工艺对聚酯薄膜的拉伸行为、拉伸取向和结晶行为的影响。研究表明，随拉伸温度的提高，聚酯在拉伸过程中的拉伸应力减小，聚酯薄膜取向度降低，结晶度降低，但晶粒尺寸增加，薄膜雾度升高；随拉伸倍率的提高，拉伸应力增大，取向度升高，结晶度升高；随拉伸速度的提高，拉伸应力增大，取向度升高，结晶度升高，但晶粒尺寸变化不大，薄膜雾度相当。     

熔融纺丝成形条件对PET初生丝超分子结构及其力学性能的影响——第2报 单丝线密度、喷丝头拉伸比及侧吹风速对PET初生丝结晶作用及力学强度的影响

本文考察了单丝线密度、侧吹风速度以及喷丝头拉伸比对PET初生丝结晶作用及力学强度的影响。表明PET初生丝的结晶作用对单丝线密度的变化极为敏感。当单丝纤度减少时,初生丝的结晶度、侧向晶粒尺寸均大幅度增加,且最大结晶度出现的位置移向低纺速区。增大喷丝头拉伸比的作用有点类似于减少单丝线密度。但当喷丝头拉伸比超过一定值之后,结晶度虽仍在增加,而侧向晶粒尺寸却似乎已达饱和值。强化冷却条件,即加大侧吹风速,虽然也能使PET初生丝的结晶度和侧向晶粒尺寸增加,但其作用却并不象我们所预期的那么大。此外,实验还表明,除单丝线密度变化时,PET初生丝的断裂强度出现反常现象外,一般说来断裂强度总是随取向度和结晶度的增加而增大,延伸度则相应减小。     

PP/PA6共混比例对其水辅助注塑管件性能及微观形态的影响

以聚丙烯 (PP)为基材,聚酰胺6(PA6)为分散相,制备了4种共混比例的PP/PA6复合材料,考察了共混比例对其水辅助注射成型技术（WAIM）管件拉伸强度及微观形态的影响。结果表明,试样拉伸强度随PA6含量增加先减小后增大;近模壁层和近水层的PA6分散相为大长厚比的长条状或长片状,中间层分散相为椭球状,且随PA6含量增加各层分散相有聚集长大的趋势;管件近模壁层和近水层的晶粒小而密且沿流动方向排列,而中间层晶粒相对更粗大;PP只形成了一种晶型,PA6形成了2种晶型;近水层和近模壁层PP结晶度高于中间层;PA6随其含量增加其结晶度有增大的趋势,且近模壁层结晶度较高。     

PBS/PP共混膜的制备及表征

采用熔融共混法和溶液共混法制备了PBS/PP共混膜,通过扫描电子显微镜、XRD、OCA20分别研究了共混体系的结晶性、相容性以及降解性能。结果表明,其结晶形态为球晶,两者相容性稍差。对于熔融法制备PBS膜,结晶度随温度变化不大。对于溶液法成膜,在相同的温度条件下,随浓度增大球晶尺寸先减小后增大,浓度为2.5g/20mL时,球晶尺寸最小。在相同的浓度条件下,随温度升高,球晶尺寸、结晶度均增大。PBS的混入加快了PP膜的降解。     

超声辐照对聚丙烯及聚丙烯／成核剂体系结晶行为的影响

用静态超声辐照装置,研究了超声对聚丙烯及聚丙烯／成核剂体系结晶行为的影响,通过宽角X射线衍射分析,发现超声会引起PP结晶度、晶面间距、晶型及晶粒尺寸等发生变化。而且超声辐照使PP、PP／苯甲酸钠体系出现了β-晶,而PP／滑石粉体系虽无β晶生成,超声却使其α晶的（040）晶面生长有择优性。超声作用对PP微晶尺寸的影响与成核剂种类及晶面择优生长有关。     

涤纶工业丝的晶态结构与性能的关系

采用广角X射线衍射(WAXD)方法分析了高强型(HT)、高强低伸型(HTLE)、高模低收缩型(HMLS)3种涤纶工业丝的晶态结构与其性能的关系。结果表明:对于断裂强度最大的HT型纤维,结晶度大(37%)、晶粒尺寸大、结晶完善程度好;对于断裂伸长率小的HTLE型纤维,晶粒尺寸较小、非晶区取向度较大(0.91),结晶区对无定形区链段运动的限制程度大;对于热收缩率小的HMLS型纤维,晶区取向度高但非晶区取向度小(0.84),高温下不易发生解取向,尺寸稳定性好。     

医用iPP混合二次料的多重结晶行为对制品脆裂的影响

针对医用等规聚丙烯(i PP)二次料的添加对医用制品容易产生脆裂的问题,制备了混合不同比例的二次料的系列i PP样品,利用旋转流变测试、广角X射线衍射(XRD)以及万能力学试验等方法研究了混合不同比例二次料对i PP样品的流变特性、结晶行为以及力学性能的影响。结果表明,二次料的比例会明显影响体系的黏度和剪切应力变化;二次料的加入会改变聚合物结晶行为,导致样品内部存在α和γ多重结晶结构,γ晶产生影响制品性能,其含量与二次料比例存在正相关的关系;体系结晶度随二次料比例增加而上升,晶粒取向度变化规律则与之正好相反,所有这些在宏观上表现出拉伸强度随二次料比例增加稍有上升,弹性模量则随二次料增加呈下降趋势。     

注塑成型条件对聚甲醛制品冲击性能的影响

用精密注塑机加工成型聚甲醛制品，考察了注塑成型条件如注射压力、注射时间、冷却时间、模具温度、后处理条件等对制品冲击性能的影响，找到了最佳工艺条件，制得了冲击性能优良的聚甲醛制品。由扫描电镜观察、结晶度测定和Ｘ射线衍射分析表明，聚甲醛制品的冲击韧性与其局部缺陷、裂纹、结晶度、晶粒大小等有关，只有改善制品的均匀性，减少局部缺陷的产生控制结晶度和晶粒大小在适当范围，才能制得冲击性能优良的制品。     

纤维素经液氨预处理对其结构和晶型的影响

棉短绒纤维素在室温和工1.03MPn压力下用无水液氢进行预处理，并经蒸发除去大部分氨，研究液氮处理前后纤维素微细结构和结晶形态的变化，讨论氛对纤维素的作用机理。结果表明，液氮处理后纤维素的侧序分布、结晶度、微晶尺寸、晶格形态都发生深刻的变化。X-射线结晶度下降21％，微晶横向尺寸减少20％-40％，晶格由纤维素I转化为纤维素I。纤维素结构中较高序态区向低序和无序部分转移，这种物理结构的变化将增进纤维素的可及度，提高纤维素在制备行生物时的反应性。     

Modification of Crystallinity and Structure in Powder Processing of Polytetra Fluoroethylene

Abstract

The modification of structure, crystallinity and orientation have been studied in powder processed polytetrafluoroethylene by various techniques. It was found that crystallinity (as determined from regression curve analysis) in unsintered samples decreased with increase of compaction pressure while in sintered specimen it increased with increase of pressure. The crystallinity was also found to vary inversely with logarithm of cooling rate. Microfocus X-ray diffraction revealed the orientation of c-axis lying preferentially in the plane perpendicular to applied pressure. There was slight variation in the lattice dimension especially the c-axis in completely sintered specimen. The infrared studies showed the presence of some of the bands depended upon the molding/sintering conditions. These various findings have been explained on the basis of compaction and recrystallization behaviour under constrained conditions.     

The effect of methods of drying on the fine structure,density, and some mechanical properties of jute and allied fibers

The degree of crystallinity and crystallite orientation in jute, mesta, and roselle fibers have been studied by x-ray diffraction. Removal of water, indirectly, has been carried out by alternate immersion in methanol and benzene. It has been found that an increase in crystallinity and a decrease in crystallite orientation take place in these fibers as a result of direct drying, presumably because of the formation of an increased number of hydrogen bonds associated with direct drying. Density, tenacity, and rigidity of the fiber in the two drying conditions are in agreement with the x-ray results.     

注水参数对水辅助注射成型充填过程影响的数值模拟

建立水辅助注射成型二维、瞬态、非定常流动模型,采用黏度幂律模型,在k ω湍流模型下,充分考虑注射水的湍流特性以及熔体前沿的喷注效应,采用有限体积法（VOF）对充填过程中的注水速度、注水温度和注水延迟时间等注水控制参数的影响进行数值模拟。结果表明,注水速度的增加会增加水在熔体中的穿透长度,并且会减小残余壁厚;注水温度对水的穿透长度和残余壁厚的影响均不显著;随着注水延迟时间的增长,水的穿透长度和残余壁厚均有增加的趋势。     

The effect of ultrasonic waves on the structure of polyester fibers (PET)

The effect of ultrasonic waves at constant intensity of 20 W/cm² and frequency of 2 × 10⁶ Hz on the microstructure of polyester fibers has been examined. Crystallinity, crystallite size, total orientation, and crystallite orientation have been estimated. It has been found that when subjected to different ultrasonic tests, the degree of fiber orientation decreases and crystalline perfection improves. The changes in crystallinity and crystallite size proved to be particularly difficult to determine with certainty.     

Enhanced oxygen barrier property of poly(ethylene oxide) films crystallite-oriented by adding cellulose single nanofibers

In this study, we investigated the influence of cellulose single nanofibers (CSNFs) added to poly(ethylene oxide) (PEO) on the microstructure and property to create high gas barrier films. The CSNF/PEO nanocomposite films were prepared by solvent casting. The PEO crystallite orientation was measured using wide-angle X-ray diffraction of the SPring-8 synchrotron radiation facility. The degree of crystallite orientation was evaluated from the reflections of the PEO (1 2 0) lattice planes to investigate quantitatively the effect of different amounts of the additive CSNFs. The crystallite orientation of PEO increased with the addition of the CSNF. Furthermore, the oxygen barrier property for each nanocomposite film was found to be higher than that of the pure PEO film. The 5 wt% addition of CSNFs was mostly effective in enhancing the PEO crystallite orientation and oxygen barrier.     

Structure–property relationship in heat-set poly(ethylene terephthalate) fibers. I. Structure and morphology

Poly(ethylene terephthalate) (PET) fibers having a range of structure and morphology were prepared by heat-setting commercial PET yarn at temperatures of 100–250°C for 5 min under two conditions, while the yarn was free to relax and when it was held taut at constant length. The crystallinity, crystallinity orientation, and crystallite size were determined by X-ray diffraction while birefringence was measured with the help of optical microscopy. The amorphous orientation factor was computed from the structural parameters. The coupling between the crystalline and amorphous regions was determined using the Takayanagi model. While crystallinity and crystallite orientation values for the corresponding samples of the free-annealed and taut-annealed series did not show very large differences, the free-annealed samples had much lower amorphous orientation, especially when heat-set at higher temperatures. Also while the free-annealed samples showed a predominantly series type of coupling between the crystalline and amorphous regions, the taut-annealed samples showed a significant degree of parallel coupling. It is shown that samples in which there is distinct phase separation between the crystalline and amorphous regions have a predominantly series type coupling.     

Crystallinity and crystallite size measurement in polyamide and polyester fibres

X-ray diffraction methods for evaluating crystallinity and crystallite size in fibres generally neglect the possibility of peak overlap, and separate peaks and background by arbitrary procedures. The method described here is based on the resolution of normalized diffraction peaks in terms of combined Gaussian-Cauchy profiles for each peak, together with a polynomial background. Peak area crystallinity is then measured as the total area under the resolved peaks over a defined range. Measurements of apparent crystallite size are obtained from the widths of the resolved peaks. Application of this method to high tenacity nylon-6, nylon-6,6, and PET fibres after annealing, indicates that peak area crystallinity is about 100% for the polyamides and 85% for the polyester. The increase in apparent crystallite size is considered to be due to both an increase in the true mean size and to improvements in local lattice order.     

Disorder in cellulosic fibers

Ruland's concept of an isotropic disorder function is applied to estimate the disorder parameter and the degree of crystallinity in a few cellulosic fibers: two cottons, native ramie, and a high-tenacity rayon. The results indicate an increase in disorder without any change in crystallinity on mercerization of native celluloses. On hydrolysis, with or without a pretreatment of mercerization, the samples exhibit a higher crystallinity, disorder remaining the same as for native celluloses. A ball-milled sample of “amorphous” cellulose is still found to be fairly crystalline with the lowest disorder. On being wetted in water and oven-dried, a distorted form of cellulose II with higher crystallinity and disorder was obtained. The polynosic fiber, Tufcel, has low values for the degree of crystallinity, disorder parameter, as well as crystallite dimension. A strong dependence of the degree of crystallinity on the crystallite size, particularly the lateral, is observed.