中空硬弹聚丙烯单丝超分子结构和物理—机械性能的研究

研究了单、双两种组分的中空硬弹聚丙烯单丝在不同纺丝温度和拉伸倍数下的超分子结构及性质变化,并与硬弹、普通中空聚丙烯单丝进行了比较。发现单、双两种组分的中空硬弹聚丙烯单丝与普通中空聚丙烯单丝在结构和性质上有很大的差别,而与硬弹聚丙烯单丝基本相似。随着拉伸倍数的增加,单、双两组分的中空硬弹聚丙烯单丝,其取向,断裂强度均有一个最小值;回弹率有一最大值;单丝的晶轴取向与硬弹处理有关,而晶型变化与硬弹处理无直接联系,结晶度高于普通单丝。纺丝温度低,有利于取向和弹性的提高。     

圆中空仿羽绒聚酯纤维的研制 第1报 熔融纺丝成形条件及后拉伸倍数对圆中空聚酯纤维中空度的影响

本文就熔融纺丝成形条件及后拉伸倍数对圆中空聚酯纤维中空度的影响进行了探讨。发现卷绕丝之中空度受凝固速率控制。强化成形条件,使凝固速率加快,则中空度增加。纤维在剪切拉伸过程中,中空度与拉伸倍数的关系同力与伸长的关系相似。拉伸丝中空度的增加,系空腔部份的减少不及纤维壁的变薄来得大所致。     

牵引速率对聚丙烯中空纤维膜结构与性能的影响

采用熔纺-拉伸法制备了一系列聚丙烯中空纤维膜。研究了牵引速率对中空纤维及微孔膜的结晶性、弹性回复率、表观形貌等性能的影响。结果表明:牵引速率对聚丙烯中空纤维的结晶行为有较大影响,牵引速率越大,越有利于shish-kebab晶体的形成与均匀分布,从而改善纤维的硬弹性;随着牵引速率的提高,中空纤维膜的表面结构发生相应变化,同时其孔隙率和水通量均增大,内外径及拉伸强度均减小;当牵引速率为350和420 m/min时,制得的中空纤维微孔膜结构与性能较好。     

β晶相聚丙烯纤维的纺制及其性能的研究

本文研究了纺丝冷却条件对β晶相聚丙烯初生纤维中β晶相含量的影响和拉伸工艺条件与制得纤维的结构及其性质的关系。研定表明,纺丝冷却速率是纺制含β晶相聚丙烯纤维的关键工艺因素,初生纤维中的K值、拉伸温度和拉伸倍数是纺制含微孔聚丙烯纤维的主要参数。用密度法、压汞法证实制得纤维具有微孔结构,其平衡吸湿率比普通浆丙烯纤维有明显的提高。     

聚烯烃纤维

20055117通过与液晶共聚物的混合来提高聚丙烯单丝的模量Sukananta Pakavadee…;Journal of Applied PolymerScience,2003,90(5),p.1337(英)在双螺杆挤出机中制备一种不相溶的由聚丙烯(PP)和以80/20摩尔比的对羟基苯甲酸/聚对苯二甲酸乙二酯共聚酯的向列性液晶聚合物(TLCP,商品名RodrunLC5000)的混合物。该混合物挤出制成单丝,所用的生产线为单螺杆挤出机。初生的长丝在120℃下拉伸以提高分子取向。研究初生纤维和拉伸后单丝的两种形态,即热抗张、动态力学性能。在复合的初生单丝中可以观察到PP介质中TLCP长纤维几乎是连续性分布。…     

生产硬弹性PP单丝的关键技术

随着塑料制刷业的兴起,硬弹性PP单丝(φ0,8～1mm)的需求量越来越大.由于用途上特殊的硬弹性需求,其生产技术也不同一般.目前,国内仅有几家企业能够生产,本文根据生产实践,研究讨论了硬弹性单丝的生产技术.1 硬弹性PP单丝的特殊性与通常单丝相比,硬弹性PP单丝直径大且具有较高的弯曲刚性和弯曲变形回弹性.已知PP单丝的硬弹性受分子量大小,结晶度高低,球晶完善程度,单丝内部空穴多少(大小)等因素影响,除此之外在很大程度上还取决于PP分子取向度.经验表明PP拉伸比≥19时,单丝的硬弹性达到理想范围.如此大的拉伸比,要求用较粗的拉伸条(如φ1mm单丝需要用φ4.3～4.5mm粗的拉伸     

热定形超喂率对大直径涤纶单丝结构与性能的影响

探究了在热定形过程中超喂率对大直径涤纶单丝结构与力学性能的影响。对制备的单丝进行了拉伸和热收缩性能测试,并通过广角X射线衍射、小角X射线散射及声速取向等方法对微观结构进行了表征。结果表明,随着超喂率的降低,单丝在热定形中受到的张力增大,有利于链段沿着拉伸方向排入晶格,结晶度小幅上升,而在纤维径向上的晶粒尺寸及片晶直径减小。超喂率对单丝非晶区结构影响显著,低超喂率下获得的单丝内部形成的非晶区分子链的取向程度大且含量低,导致纤维断裂强度及初始模量较大且断裂伸长低。此外,低超喂率条件下单丝纤维非晶区取向高,致使热收缩率较大。     

卧式一步法丙纶高强丝生产工艺研究

在意大利ＦＡＲＥ公司卧式一步法丙纶高强丝设备上，研究了聚丙烯熔融指数与丙纶高强丝强度的关系。探讨了纺丝温度、冷却条件、单丝纤度、拉伸倍数等主要工艺条件对丙纶高强丝强度的影响。     

细旦丙纶一步法拉伸丝试制工艺探讨

本文介绍了在进口FDY纺丝设备上,用国产聚丙烯切片(MI30左右)纺制细旦丙纶拉伸丝的工艺,同时还研究了纺丝速度,拉伸倍数对纤维性能的影响。结果表明,分子量分布窄的聚丙烯切片纺丝性能良好,卷绕速度为3000m/min时制得单丝纤度为1.88dtex的纤维强度可达3.79cN/dtex。     

高强粗旦聚丙烯工业丝加工条件对其结构及性能的影响

以液体冷却成形代替风冷成形,采用两步法生产工艺制得1 980 dtex/60 f高强粗旦聚丙烯工业丝,研究了喷丝头拉伸倍数、液体冷却温度、二级拉伸倍数对其结构及性能的影响。结果表明:从喷丝板挤出的聚丙烯熔体通过液浴骤冷获得的初生单丝含有3个α晶面衍射峰、1个β晶面衍射峰,初生单丝经拉伸作用后,分子中的β晶面消失,结晶度增大;当喷丝头拉伸倍数为3.5、液体冷却温度为30℃、油浴拉伸速度为140 m/min、油浴拉伸倍数为6.5、二级拉伸倍数为2.2时,聚丙烯工业丝的断裂强度最高,为7.42 cN/dtex,力学性能最好,且纺丝较稳定,无长短丝,产品线密度均匀性好。     

Lamellar crystalline structure of hard elastic HDPE films and its influence on microporous membrane formation

The development of hard elastic high-density polyethylene (HDPE) precursor films and its influence on the microporous membrane formation have been investigated. As a first step, the HDPE precursor films with ‘row-nucleated lamellar crystalline’ structure were prepared by applying elongation stress to the HDPE melt during T-die cast film extrusion and subsequently annealing the extruded films. This unusual crystalline structure was analyzed in terms of lamellar crystalline orientation, long-period lamellar spacing, crystallite size, and degree of crystallinity. The processing (melt extension and annealing temperature)-structure (lamellar crystalline structure)-property (hard elasticity) relationship of HDPE precursor films was also investigated. The uniaxial stretching of hard elastic HDPE precursor films induces the bending of crystalline lamellae, which leads to the formation of micropores between them. The observation of morphology and air permeability for the HDPE microporous membranes have revealed that the well-developed porous structures characterized by superior air permeability were established preferably from the precursor films prepared by the high stress levels and the high annealing temperatures. Finally, the relationship between the hard elasticity of HDPE precursor films and the air permeability of corresponding microporous membranes was discussed.     

聚丙烯硬弹性膜的挤出流延工艺及拉伸成孔性

以某进口均聚聚丙烯(PP)(PP1)为原料,通过挤出流延工艺制备了PP1硬弹性膜并在130℃下对其进行热处理,研究了挤出温度、流延辊转速及温度、热处理温度和时间等工艺参数对PP1硬弹性膜弹性回复率的影响,得到了最佳工艺条件,即挤出温度为195℃、流延辊温度及转速分别为90℃,26 r/min,热处理温度和时间分别为145℃,30 min。将该工艺应用于分子量及其分布与PP1基本相似的国产PP(PP2),发现由此工艺制备的PP2硬弹性膜的弹性回复率可达94.6%,与PP1硬弹性膜相差不大。通过冷热单向拉伸将PP1和PP2硬弹性膜制备成微孔膜,发现两者具有相似且优异的微孔结构。在此基础上,通过扫描电子显微镜研究了冷热拉伸工艺参数对PP2微孔膜拉伸成孔性的影响。结果表明,当冷拉伸倍数为15%,热拉伸倍数为100%,冷热拉伸速率均为50 mm/min时,制备的PP2微孔膜形成了完整规则的多孔结构。     

硬弹性HDPE流延基膜冷拉过程中显微结构的变化

以不同拉伸倍率和拉伸速度在室温下对硬弹性HDPE流延基膜施加冷拉作用,通过原子力显微镜、场发射扫描电镜、X射线衍射以及孔隙率和透气率测定来观察冷拉前后薄膜中片晶结构的变化,并且了解这些显微结构变化对微孔膜结构和性能的影响。研究发现,提高冷拉倍率可以增加拉伸膜中片晶分离程度,有利于形成具有较高孔隙率和透气率的微孔膜,但冷拉倍率过高会使片晶弯曲崩溃,部分微孔闭合;随冷拉速度增加,拉伸膜中片晶分离更加彻底,使得微孔膜中微孔数目增多且分布更加均匀;冷拉过程中拉伸应力下结晶的较长连接链和应力作用下破坏的片晶边缘的微次晶共同构成了拉伸膜中分离片晶间的初始桥结构。     

热拉伸比对熔融挤出拉伸法制备聚丙烯微孔膜的影响

通过固定冷拉伸比,改变热拉伸比制备了具有不同微孔结构的聚丙烯微孔膜,通过扫描电子显微镜(SEM)观测了微孔的形貌,通过差示扫描量热法(DSC)测试了微孔膜的片晶厚度,研究了热拉伸过程中微孔形成过程以及微孔尺寸和数量,微孔膜孔隙率随热拉伸比的变化情况.结果表明,冷拉伸过程主要是片晶间微裂纹的形成过程,微裂纹均匀的分布在试...     

Novel ideas in the theory of the physical adsorption of vapors on micropore adsorbents

A general equation has been derived for the physical adsorption of vapors on adsorbents with nonhomogeneous microporous structure, in which the energy of adsorption is increased as a result of the effect of superposition of dispersion force fields of the opposite micropore walls. The equation is based on experimentally determined reciprocal dependence of the generalized dimensions of the micropores expressed as their radii of inertia and the characteristic adsorption energy. The expression of the inertia radii of micropores takes into account their geometrical sizes. The nonhomogeneity of the microporous structure is described in terms of normal distribution of the micropore volumes with respect to reciprocal values of the characteristic adsorption energies. For a homogeneous elementary micropore volume, the adsorption equation derived from the theory of volume filling of the micropores is used. The adsorption equation obtained contains three parameters: the total micropore volume, the characteristic adsorption energy at the maximum of the distribution curve and the dispersion. The equation can be used for micropores with various geometric shapes. It leads to the following consequences: If the dispersion equals zero, then the Dubinin-Radushkewich equation is obtained for homogeneous microporous structures; the Dubinin-Stoeckli equation is obtained for the model of slitlike micropores in carbonaceous adsorbents. The parameters of the equation were found to be effective quantities for increased mesopore surface areas in microporous adsorbents. We considered methods for determining the specific surface areas of mesopores; these methods are necessary for obtaining realistic parameters for the microporous structure of adsorbent.     

Preparation of microporous activated carbon from Aegle marmelos fruit shell by KOH activation

Activated carbon (AC) is well‐known for its unique properties; hence, the search for new precursors and the investigation of new methods for the preparation of AC is still drawing attention of many researchers. In the present work, microporous AC was prepared from Aegle marmelos fruit shell (AMFS) by potassium hydroxide (KOH) activation. The effect of process parameters such as impregnation ratio, carbonisation temperature and holding time on porous characteristics was investigated. The porous characteristics of prepared AC samples were analysed by N₂ adsorption–desorption isotherms, and it was found that the isotherms obtained resemble typical microporous solids (Type‐I). The Langmuir surface area and total pore volume of the sample prepared at optimum conditions were found to be 937 m²/g and 0.33 cm³/g, respectively. The contribution of micropores to the porous characteristics of the prepared AC is very much appreciable, and about 97% of the total surface area and pore volume is attained by micropores. Pore size distribution (PSD) by Dubinin–Astakhov (DA) and micro‐pore (MP) methods confirmed the presence of micropores to a great extent with insignificant mesoporosity. © 2013 Canadian Society for Chemical Engineering     

聚丙烯微孔膜高能电子束辐照改性及其性能研究

采用高能电子束辐照的方法在聚丙烯微孔膜的表面接枝丙烯酸锂,研究不同的辐照剂量对聚丙烯微孔膜表面接枝丙烯酸锂的接枝率的影响,并对辐照接枝后的聚丙烯微孔膜的结构和性能进行了研究。红外光谱测试结果表明:通过高能电子束辐照,聚丙烯微孔膜的表面能够成功地接枝上丙烯酸锂;表面水接触角测试结果表明,经辐照接枝丙烯酸锂后,聚丙烯微孔膜的表面水接触角减小,表面极性增加,表面亲水性得到提高;SEM观察结果表明,辐照后聚丙烯微孔膜的孔径减小;DSC测试结果表明:辐照后聚丙烯微孔膜的结晶峰温度向高温方向移动,结晶能力得到提高,结晶更加完善。     

Adsorption properties and microporous structures of carbonaceous adsorbents

The theory underlying the absorption behavior of carbons is discussed as a basis for quantitative analysis of their adsorption properties and microporous structure. The equations of the theory of volume filling of micropores for homogeneous and inhomogeneous microporous structures and a rational method for determining the specific surface area of micropores are considered. Four principal parameters are proposed which describe the physical vapor adsorption with good accuracy and quantitatively characterize the microporous structure of carbonaceous adsorbents.     

Microporous polyurethane-acrylamide film cured by electron beam irradiation

The morphology and aggregation structure of electron beam (EB)-cured microporous polyurethane-acrylamide film was investigated. The urethane-acrylamide prepolymer was synthesized by the reaction of poly(butylene adipate)diol, 4,4′-diphenylmethane diisocyanate, and N-(hydroxymethyl)acrylamide. It was found from scanning electron microscopy that the urethane-acrylamide film, which was prepared by using a methyl ethyl ketone and dimethylformamide (3:1 v/v) mixture as casting solvent, had a microporous structure with pore size of several micrometres, and that the morphology was fixed by EB irradiation. The pore volume of the EB-cured microporous film was determined to be about 460 mm³ g⁻¹ by mercury porosimetry. The micropores were not destroyed even after immersing in solvent, possibly because the cured film had high crystallinity and dense crosslinking. Moreover, it was found by X-ray photoelectron spectroscopy that terminal portions of urethane-acrylamide were localized at the film surface.