论文选摘

合成纤维的形态近年来,关于结晶高聚物结构的概念已有很大的改变。研究表明,高聚物晶体是层状的,由长链分子折迭而成。然而这种新概念对拉伸纤维来说是否适用还研究得很少。本文作者用70—85℃的硝酸腐蚀拉伸聚乙烯小     

不同结晶速率的PET薄膜在拉伸过程中的结晶与取向

用多种方法对两个结晶速率不同的PET样品在拉伸过程中的结晶和取向进行了研究。结果表明在同样的拉伸条件下,结晶速率较快的样品的结晶度和取向程度均比另一样品要高得多,这种结构变化上的差别说明把拉伸行为的差别归因于结晶速率的不同是合理的。     

超高分子量聚乙烯冻胶纺丝-拉伸纤维结构的研究

以煤油为溶剂,汽油为萃取剂,采用冻胶纺丝 拉伸技术纺制了超高分子量聚乙烯（ＵＨＭＷ ＰＥ）纤维．利用广角Ｘ 射线衍射（ＷＡＸＤ）试验、偏光显微镜（ＰＯＭ）观察等方法研究了拉伸过程中纤维结构的变化．结果表明,在拉伸过程中,纤维大分子折叠链向伸直链转变的同时,斜方结晶的堆砌密度增大,微晶尺寸分布变窄并趋于均匀,拉伸４０倍纤维的晶胞参数为ａ＝０７３２ｎｍ,ｂ＝０４９１ｎｍ,ｃ＝０２５４ｎｍ．在拉伸４０倍左右的纤维中还能观察到因大分子结晶晶面滑移而产生的折皱带结构．在作者研究条件下,观察不到折皱带结构对纤维整体的取向态和结晶态结构的影响．     

拉伸热历史对取向聚对苯二甲酸乙二酯膜在热处理过程中收缩和伸长的影响

弄清取向非晶态聚合物在热处理过程中的收缩和伸长的变化规律,以及所对应的结构变化,有较大的实用意义和科学意义。 对于取向聚对苯二甲酸乙二酯的热收缩和热伸长已有很多研究,但对于拉伸热历史对取向PET在热处理过程中的尺寸变化的影响尚缺乏系统的研究。在热拉伸的过程中发生分子链的取向、热弛豫和结晶三个相互竞争的过程。因此,改变拉伸条件可以得到具有各种不同取向和结晶的PET试样。当非晶态PET膜片在80-105℃以较低     

取向对聚左旋乳酸/聚右旋乳酸复合物纤维结晶性能的影响

通过熔融纺丝的方法制备了PLLA/PDLA复合物初生纤维,在60℃拉伸获得高取向的牵伸纤维.采用X-ray散射为主要表征手段,结合差示扫描量热(DSC)、扫描电子显微镜(SEM)以及傅里叶变换红外光谱(FTIR)等技术,系统研究了不同初始结构的PLLA/PDLA复合物纤维在不同温度下的结晶行为,重点阐明了取向对PLA复合物纤维结晶结构的影响.结果表明,取向促进复合物纤维中立构晶的形成;将纤维升温至200℃停留3 min后,再进行降温,降温过程中,高度取向的牵伸纤维只有立构晶形成,而初生纤维则在150℃左右出现α晶,表明纤维中取向的立构晶会抑制α晶的形成.综合实验结果发现,通过低温牵伸初生纤维,然后高温(α晶熔点以上)退火,可制备出高取向且具有高立构晶含量的PLLA/PDLA复合物纤维.     

高取向聚对苯二甲酸乙二酯纤维的热收缩应力

为得到具有更高拉伸强度和模量的半晶聚合物纤维,需要使分子链充分结晶和取向,然而这种高度取向样品受热时,随着温度的升高,取向的非晶态分子链熵力增大,解取向可以自发进行.在外加张力较小时,纤维产生热收缩;在定长状态下,表现为外加张力增大,此过程被视为取向材料中＂冻结＂内应力的释放,通常将这种内应力称为热收缩应力。     

聚乙烯串晶在单轴拉伸形变过程中的微结构变化和机理

本文采用电子显微镜和小角Ｘ－射线散射（ＳＡＸＳ）技术研究了含有串晶结构（Ｓｈｉｓｈ—ｋｅｂａｂ）的高密度聚乙烯（ＨＤＰＥ）／超高分子量聚乙烯（ＵＨＭＷＰＥ）共混物高取向膜在单轴拉伸过程中的微结构变化．深入探讨了拉伸温度对聚乙烯在形变过程中微结构变化的影响．室温拉伸时，聚乙烯串晶结构主要发生了解结晶过程；高温（１１５℃）形变时，主要表现为折叠链片晶直接转变为伸展链纤维晶的应变诱导结晶过程．     

超高分子量聚乙烯膜轴向压缩变形结构的研究

继刚性聚合物经溶液液晶(如芳香族聚酰胺)或熔融液晶(如芳香族聚酯)纺丝制取高性能纤维获得成功后,利用冻胶纺丝等技术制取超高分子量聚乙烯(UHMW-PE)高性能纤维的研究已取得突破性进展。这类纤维具有伸直链结构,大分子沿材料拉伸方向高度取向和结晶,显示出优异的抗张性能,具有很大的拉伸强度和模量。     

天然橡胶在单向拉伸下的结晶与取向

<正> 从研究聚乙烯由球晶结构转变到纤维结构的过程得知,聚乙烯纤维由一束平行排列的细纤维(microfibril)组成,细纤维则由垂直于纤维轴互相平行排列的折迭链块(foldedchain block)组成,折迭链块之间有链段相连.处于高弹态的天然橡胶(-78°—28℃),进行单向拉伸,可发生取向并同时结晶,形成纤维,但是它与聚乙烯的起始态不同,为阐明天然橡胶拉伸后是否也有类似聚乙烯纤维的结构单元,本文采用透射式电子     

含少量共聚组分聚乙烯熔体拉伸薄膜的形态结构

利用透射电子显微学(TEM)和示差扫描量热学(DSC)等方法研究了含少量丁烯-1组分(摩尔分数为0.64%)的聚乙烯共聚物(PE100)熔体拉伸高取向薄膜的形态结构. 结果表明, 在PE100熔体拉伸薄膜中, 除存在高取向片晶结构外, 还含有大量的纤维晶, 纤维晶平行于拉伸方向, 穿过几个片晶区, 平均直径约为12 nm. 模拟实验结果表明, 纤维晶的生成源于聚乙烯共聚物中的超高分子量组分, 但不同于传统意义上的伸直链纤维晶, 其形态特征应为晶桥结构. 由此提出了晶桥结构纤维晶模型, 该模型不但有助于深入理解和认识聚合物取向结晶机理, 同时也为该材料的高性能化提供了理论依据.     

取向非晶态聚对苯二甲酸乙二酯(PET)膜的结晶

采用小角和广角X-散射法比较了未拉和热拉PET膜在结晶性能方面的差别,热拉试样在分子链段的小尺度范围内基本上是无规取向,而在分子链的大尺度范围内却是高度取向的。研究结果表明:热拉PET膜的结晶诱导期较短,长周期发展得较快,结晶后小角X-线散射表现出明显的各向异性,在热处理过程中先出现显著的热收缩,随后又表现出结晶伸长现象,这些都和未拉试样有明显的差别。     

Influence of an interfacial agent on the structure of polypropylene-polyamide fibres

In this paper the structure and properties of fibres prepared from the polypropylene/polyamide (PP/PA6) blend have been studied as a function of the interfacial-agent (IFA) content. For this purpose the grafted polypropylene-maleic anhydride copolymer was used. Fibres containing 20% of PA6 and 80% of PP possess the phase matrix-fibril structure. The size and distribution of fibres in the dispersed PA6 phase in the PP matrix depend on the interfacial-agent amount. Due to the indirect nucleating effect the PA6 phase has been found to act, in the presence of the interfacial agent, on the PP crystallization during fibre formation. As a result, undrawn fibres have the more pre-oriented and crystalline PP matrix with the morphological rod-like structure. The pre-orientation of the dispersed fibrilar PA6 phase is minimum. Mechanical properties of the drawn blended fibres are favourably influenced provided that the interfacial-agent concentration is higher than 1%. The growing rate of the mutual interaction between the components was mostly reflected in the increased values of Young's modulus.     

分子链大尺度取向对非晶态聚对苯二甲酸乙二酯结晶行为的影响

用ＤＳＣ和溶剂诱导结晶（ＳＩＮＣ）的方法对比研究了（ＧＯＬＲ）态和未取向聚对苯二甲酸乙二酯（ＰＥＴ）纤维样品的结晶行为．实验结果表明，样品的大尺度取向可有效地降低样品的冷结晶温度（Ｔｃｃ），证明大尺度取向对样品的结晶行为可起到促进作用．     

Calorimetric study of blends of poly(butylene terephthalate) and liquid crystalline copolyester

A calorimetric study of blends of poly(ethylene terephthalate-co-p-oxybenzoate), PET/PHB, with poly(butylene terephthalate), PBT has been carried out in the form of as-spun and drawn fibres. DSC melting and crystallization results show that PBT is compatible with LCP and the crystallization of PBT decreases by the addition of LCP in the matrix. The crystallization behaviour of blend fibres is investigated as a function of temperature of crystallization. A detailed analysis of the crystallization course has been made utilizing the Avrami expression. The isothermal calorimetric measurements provide evidence of decrease of rate of crystallization of PBT on addition of the liquid crystalline component up to about 50% by weight. The values of the Avrami exponents change in the temperature range from 200° to 215°C. Dimensionality changes in crystallization could be due to LCP mesophase-transition.     

Cold crystallization and thermal shrinkage of uniaxially drawn poly(ethylene 2,6-naphthalate) by solid-state coextrusion

Solid-state coextrusion has been used to prepare uniaxially drawn films from isotropic poly(ethylene 2,6-naphthalate) (PEN) of a minimum degree of crystallinity (ca. 5%) both below and above its glass transition temperature T_g. The onset of cold crystallization (T_c) of the drawn films has been studied as a function of the extrusion temperature (ET) and the draw ratio (EDR). It has been shown that T_c decreases markedly on draw, as much as 95°C, and, at constant draw ratio T_c goes through a minimum in the T_g region. For undrawn PEN, annealing below 153°C has no significant effect on T_c. To evaluate the crystallization rate constant (k) and the activation energy (E_a) of the drawn specimens, a nonisothermal DSC procedure has been used. With increasing EDR, k increases markedly and E_a goes down over threefold compared with the undrawn polymer. At high ET, strain-induced crystallization has also been shown to play an important role in lowering E_a for cold crystallization. Thermal shrinkage above T_m indicates a high elastic recovery, underlining the efficiency of deformation, ca. 93%, achieved by solid-state coextrusion.     

预热处理对超高分子量聚乙烯层积状片晶凝胶膜结构的影响

由准稀溶液速冷制备的超高分子量聚乙烯（ＵＨＭＷＰＥ）凝胶膜，具有片晶（Ｌａｍｅｌｌａ）取向平行于膜面的层积状结构，在１２９—１３４℃的温度范围内拉伸，可获得超高拉伸比（λ＞２００）．通过ＩＲ及Ｘ－ｒａｙ衍射等方法研究发现，拉伸前用不同温度退火处理后，凝胶膜的片晶微结构产生明显变化，在对应于超高拉伸温度范围内，其结晶度增加，微晶的ｃ和ｂ轴方向尺寸变大，而ａ轴方向的尺寸减小，从理论上对这一变化过程作了考察，并讨论了超高拉伸取向性与这些结构变化的关系以及可超拉伸取向性的最佳温度范围．     

聚对苯二甲酸乙二酯的熔融双峰

未拉伸聚对苯二甲酸乙二酯(PET)、单轴拉伸PET、双轴拉伸PET在不同条件下热处理,并进行了DSC热分析、X-射线衍射分析、红外分析。结果表明:熔融双峰现象起因于DSC等速升温过程中PET的部分熔融和重结晶;低温峰是等温热处理过程中形成的不完善微晶的熔融峰,高温峰是重结晶后较完善的微晶的熔融峰;在等速升温过程中,PET晶胞参数不变、晶格完善、晶粒增大,并且规则折迭链增加,但晶粒随温度增大的过程中出现低谷。     

THE DOUBLE MELTING PEAKS OF POLY(ETHYLENE TEREPHTHALATE)

Three sets of PET samples, comprising original (undrawn), uniaxially drawn and biaxially ones, after annealed at 230°, 240°and 250℃respectively, were subjected to DSC thermal analysis, X-ray diffraction analysis and IR analysis. The results indicate that the phenomenon of double melting peaks during DSC analysis is due to the partial melting and recrystallization of the crystallite at the moment of thermal scanning. The lower temperature peak, which varies slightly according to annealing condition, corresponds to the melting of imperfect crystallite, and the higher temperature peak corresponds to the melting of better organized crystallite. In the course of temperature scanning, the unit cell parameters of PET remains unchanged while the crystals turn to better crystal lattice, greater crystal size and more regular folding.We also found that there is a slight reduction in crystal size between the two melting peaks, and an explanation is suggested for this phenomenon.     

复合成核剂对聚丙烯结晶行为的影响

以超细橡胶粒子与有机磷酸盐成核剂复配的方法制备了一种新型复合成核剂,通过示差扫描量热法(DSC)比较了复合成核剂改性PP以及有机磷酸盐成核剂改性PP的结晶温度、等温结晶行为及等温结晶动力学;利用扫描电子显微镜(SEM)的能谱附件和透射电子显微镜(TEM)研究了复合成核剂的微观形态及其在PP中的分散情况.研究结果表明,复合成核剂中超细橡胶粒子作为载体使有机磷酸盐成核剂附着在其表面,提高了成核剂在聚丙烯中的分散性,因而提高了成核剂的成核效率,当成核剂用量较小时,即可明显提高PP的结晶速率和力学性能.     

Changes in defect concentration within polymer crystals: annealing of isotropic and drawn polyethylene

An estimation of the changes in the level of chain defects (branches) accommodated within crystals of undrawn and drawn branched polyethylene, subsequently annealed, is carried out in the light of unit cell expansion data. The results reveal that annealing affects the estimated crystalline defect concentration differently depending on whether the material was drawn or undrawn. Thus, annealing of drawn polyethylene with a defect concentration of 3 % results in a healing of crystal defects, due to a preferential rejection of branches from the crystals. In contrast, annealing of melt crystallized branched polyethylene does not influence the average concentration of chain defects within the crystal despite the increase in lamellar thickness. The branches are trapped into the much wider lamellar crystals with fewer grain boundaries available and defect sequences cannot diffuse out of the crystals.Cordially dedicated to Prof. Dr. H.-G. Kilian on the occasion of his 60th birthday.