纤维增强树脂基复合材料中的横穿结晶研究

在以结晶性聚合物为基体树脂的纤维或织物增强复合材料中,经常出现横穿结晶(横晶)界面相。本文综述了近年来对纤维增强树脂基复合材料中横穿结晶的研究,内容包括横晶的概念,纤维表面诱导成核的机理,纤维诱导成核的能力和条件,横晶的生长和终止以及横晶的力学效应等。在不同的树脂/纤维复合材料体系中,由于其横穿结晶本身和本体球晶在尺寸和数目比例等方面呈现各不相同的复杂局面,横晶对复合材料性能的影响显得复杂。通过各种手段调控横晶的形态、尺寸及数量,使横晶的存在有利于复合材料整体性能的提高,是进行纤维增强结晶性聚合物基复合材料设计时应该遵循的一个基本原则。     

橫晶与纤维界面的形态观察

在纤维表面的异相成核密度达到足够高的程度时,晶粒的生长由径向转变为沿垂直于纤维表面的方向生长,即横晶生长(transcrystalline growth)。在许多纤维增强的高聚物复合材料中都可以得到横晶结构。横晶的结构和球晶是完全相同的。横晶是球晶的一种特殊情况,即取向球晶。虽然横晶中片晶的生长方向是相同的,但是在横晶与纤维之间,即在纤维表面区域却是非取向的。利用刻蚀剂或离子对材料进行刻蚀处理,控制刻蚀程度,可以使纤维和取向的横晶之间的非取向区首先被刻蚀液或离子刻蚀破坏掉。而取向的横晶结构区域则被保留下来。用扫描电子显微镜就可以观察到这两种结构区。     

β晶型聚丙烯研究进展

β晶型聚丙烯(β-PP)由于其优异的力学性能及其拉伸能形成微孔等特性已成为聚丙烯改性研究的热点.本文综述了近年来β晶型聚丙烯的研究发展状况.介绍了生成β-PP的四种方法,重点说明了添加β成核剂诱导生成β晶型的方法;β成核剂的发展历史、分类及成核效率和成核机理;β-PP的几种超分子结构:β球晶、β六方晶、β横晶、β柱晶;β→a相转变类型及机理;温度、剪切、退火、热历史及不同工艺条件对生成β-PP的影响,为生成高β含量制品提供了参考.并对未来的研究发展趋势做了展望.     

铅卤钙钛矿-聚合物复合材料的制备及应用

铅卤钙钛矿纳米晶具有优异的光电性能,在太阳能电池、光电探测和生物成像等领域展现出巨大的发展潜力。然而,铅卤钙钛矿纳米晶自身稳定性差的缺陷制约了其在实际生活中的应用。将铅卤钙钛矿纳米晶嵌入到聚合物中以制备钙钛矿-聚合物复合材料是近年来发展起来的一种有效增强钙钛矿稳定性的策略,特别是致密的聚合物基质赋予钙钛矿纳米晶优异的水稳定性。本文综述了近十年钙钛矿-聚合物复合材料的制备方法及在发光器件和生物医药等领域的应用,探讨了目前仍存在的一些问题和解决方法,并对未来这一领域的发展进行了展望。     

剪切条件下等规聚丙烯的结晶行为

聚丙烯是工业中应用最广泛的聚合物。聚丙烯在静态结晶时生成球晶，剪切后会生成排核，最终长成柱晶或纤维晶；在强剪切条件下会生成串晶。聚丙烯是一种存在多种晶型的聚合物，α型晶是热动力学最稳定的晶型，在一般实验条件下很难得到其他晶型；在剪切条件下聚丙烯会生成β晶-热动力学亚稳晶型。剪切会显著影响聚丙烯的结晶动力学：增加球晶的生长速率，缩短结晶诱导时间，增加活化晶核密度。人们提出了许多模型来解释剪切加速结晶动力学的实验现象，但是都有不足之处。     

聚甲基丙烯酸甲酯的分子构型对淬火过程中聚偏氟乙烯(PVF_2)β相生成的影响

<正> 聚偏氟乙烯(PVF_2)是一种半结晶聚合物,它至少存在α、β、γ和δ四种晶相结构。其中β相由于其与PVF_2的压电性和热电性直接相关而引起人们的广泛关注。在以前的工作中,我们研究了超速淬火对PVP_2晶相结构的影响。本工作用傅里叶变换红外光谱(FTIR)技术研究了聚甲基丙烯酸甲酯(PMMA)分子构型对淬火过程中PVF_2β相生成温度的影响.     

聚丙烯的结晶形态调控与高性能化

聚丙烯作为目前最重要的通用塑料之一,对其进行高质化改性具有重大的现实意义.基于聚丙烯的同质多晶态行为,加入成核剂进行β结晶改性是改善聚丙烯韧性和热稳定性的有效方式.过去的研究主要关注结晶度、β晶含量等对性能的影响.而近年来我们提出通过调控聚丙烯的β结晶形态来实现其高性能化的新思路,并开展了卓有成效的研究工作:(1)利用小分子成核剂的溶解性及自组装影响聚丙烯的结晶行为,获得了如球晶、横晶、花瓣状晶等形态,实现了对β结晶形态的有效调控;(2)特定的结晶形态能够使聚丙烯的韧性显著增加,并且热变形温度进一步提高,证实结晶形态会对宏观性能发挥重要作用;(3)β结晶形态调控有利于获得更佳的成孔均匀性与高的孔隙率,对制备高品质锂电池隔膜有明显的指导意义.结晶形态调控可望成为实现结晶性聚合物高性能化与功能化通行的、高效的策略.     

PTh / ZnO复合纳米粉的固相合成及其光谱特性

0引言导电聚合物/无机物纳米复合材料具有纳米材料和导电聚合物的共同特性,因此在电催化、二次充电电池材料、超级电容器材料等方面具有良好的应用前景[1]。聚噻吩(PTh)以及取代聚噻吩是导电聚合物领域中较早发现的具有环境稳定性和可加工性的材料之一。近年来,有关聚噻吩/无机物纳米复合材料的制备及其光电性能的研究倍受关注,Gebeyehu等[2]用PTh敏化纳米晶TiO2光伏电池,发现其光伏效率明显优于固态光伏电池;Jayant等[3]研究了PTh中的羧基基团的影响以及在纳米晶TiO2     

聚苯硫醚及其聚醚砜共混物结晶形态的研究

本文借用偏光显微镜(PLM)、扫描电子显微镜(SEM)、小角激光光散射仪(SALS)及蚀刻的方法,研完了聚苯硫醚及其与聚醚砜共混物的结晶形态和织构,讨论了共混方法及其共混组成对其共混物的结晶形态的影响。结果表明,聚苯硫醚在应力作用下能生成横晶;溶液共混物和粉末机械共混物呈现不同的共混结晶形态;随着聚醚砜组分的增加,共混物的织构从聚苯硫醚为连续相逐渐转变为聚醚砜为连续相,同时,聚醚砜的聚集区域从分散在聚苯硫醚的球晶之间转变为聚集在聚苯硫醚的球晶内,使聚苯硫醚的球晶形态逐渐变得不规整。     

微孔发泡聚合物基导电复合材料的研究进展

概述了用超临界流体作为物理发泡剂对聚合物基导电复合材料进行微孔发泡的基本原理,总结了聚合物基导电复合材料及其微发泡复合材料的几种导电机理,简要介绍了近年来微孔发泡聚合物基导电复合材料电学性能的研究现状。并从微发泡聚合物基导电复合材料的基体特性、所使用的导电填料类型、导电填料的含量、填料在基体中的分散方法及微发泡复合材料的泡孔形态等几个方面,分析了影响微孔发泡聚合物基导电复合材料电学性能的主要因素,并展望了新型微孔发泡聚合物基导电复合材料的研究和发展趋势。     

Surface treatment of Basalt fiber for use in automotive composites

Balancing the performance, durability and safety requirements of automotive systems with the regulatory landscape in an environment of climate change has accelerated the search for sustainable fiber reinforced polymer composites for automobile structures. Glass fiber reinforced thermoplastic polymer composites (GFRP) are widely used in certain structures like front end modules and liftgate; However, they cannot be used in more demanding applications due to their low mechanical properties. Carbon fiber reinforced thermoplastic polymer composites (CFRP) are promising candidates for applications like bonnet, but their use is constrained by cost. Basalt fiber reinforced thermoplastic polymer composites (BFRP) are sustainable materials that can be positioned between GFRP and CFRP in terms of performance and cost-effectiveness. The mechanical performance of the BFRP depend on the quality of the fiber-matrix interface that aids in efficient load transfer from the matrix to the fiber. Typically, basalt fibers are inert in nature and need treatments to improve its adhesion to polymeric matrices. The major chemical treatments that are reviewed in this article include matrix functionalization, silane treatment, functionalized nanomaterial coating and plasma polymerization. The physical treatments reviewed include plasma treatment and milling. It is evident that chemically treating the basalt fiber with a functionalized nanomaterial yields BFRP with a good stiffness – toughness balance that can be used for challenging metal replacements as also in new emerging areas like sensing and 3D printing.     

Computer simulation of crystallization kinetics and morphology in fiber-reinforced thermoplastic composites. II. Three-dimensional case

A three-dimensional computer simulation has been used to predict crystallization kinetics and crystalline morphology in composite materials that are based on crystallizable thermoplastics. Reinforcing fibers in three-dimensional simulations show similar behavior to those in two-dimensional simulations; fibers suppress crystallization relative to an unreinforced polymer since they constrain spherulitic growth by an impingement mechanism, and also enhance crystallization by providing added surface nucleation sites. The effects of varying controlling parameters on crystallization kinetics and morphology are qualitatively the same as those observed in the two-dimensional case. The relative bulk and fiber nucleation denisities, in addition to the fiber volume fraction, fiber diameter, and spherulitic growth rate control the crystallization kinetics and crystalline morphology that develop in reinforced thermoplastic composites. It is more difficult to achieve the transcrystalline morphology in slices of three-dimensional composites than it is in two-dimensional composites because nuclei in 3-D systems are not constrained to positions in or near a 2-D plane. © 1993 John Wiley & Sons, Inc.     

A review on flammability of epoxy polymer,cellulosic and non‐cellulosic fiber reinforced epoxy composites

Natural fiber is well‐known reinforcement filler in polymer‐matrix composites. Composite components like organic polymers and natural fibers are natural fire conductors as the natural fiber consists of cellulose, hemicellulose, and lignin, and hence are as highly flammable as wood. Natural fiber reinforced composite materials are progressively being used in a variety of applications where their fire response is a hazardous consideration, for example, in the automotive (transportation) and building‐construction industries. As a result, an awareness of their performance or response during a fire and the use of conventional fire retardants are of great importance, as they are subject to thermal decomposition when exposed to intensive high heat or fire sources. In this review paper, fire flammability is the main concern for cellulosic and non‐cellulosic fiber‐reinforced polymer composites, especially epoxy composites. This paper reviews the literature on the recent developments in flammability studies concerning polymers, epoxy polymers, cellulosic‐fibers, and non‐cellulosic fiber‐reinforced epoxy bio‐composites. The prime objective of this review is to expand the reach of “fire retardants for polymer materials and composites” to the science community, including physicists, chemists, and engineers in order to broaden the range of their applications. Copyright © 2015 John Wiley & Sons, Ltd.     

由结晶动力学评价含结晶聚合物共混物相容性的研究进展

介绍了用结晶动力学分析的方法评价含结晶聚合物共混物的混合状态的基本理论和解析原理,综述了最新研究进展.     

Biodegradable polyesters reinforced with surface-modified vegetable fibers

Flax fibers are investigated as reinforcing agents for biodegradable polyesters (Bionolle and poly(lactic acid) plasticized with 15 wt.-% of acetyltributyl citrate, p-PLLA). The composites are obtained either by high temperature compression molding fiber mats sandwiched between polymer films, or by batch mixing fibers with the molten polymer. Fibers in composites obtained by the latter method are much shorter (140-200 microm) than those of the mats (5,000 microm). Flax fibers are found to reinforce both p-PLLA and Bionolle (i.e. tensile modulus and strength increase) when composites based on fiber mats are investigated. Conversely, analogous composites obtained by batch mixing show poor mechanical properties. The observed behavior is attributed to the combined effect of fiber length and fiber-matrix adhesion. If flax fibers with a modified surface chemistry are used, the strength of short fiber composites is seen to improve significantly because the interface strengthens and load is more efficiently transferred. Appropriate surface modifications are performed by heterogeneous acylation reactions or by grafting poly(ethylene glycol) chains (PEG, molecular weight 350 and 750). The highest tensile strength of p-PLLA composites is reached when PEG-grafted flax fibers are used, whereas in the case of Bionolle the best performance is observed with acylated fibers.     

Effect of surface‐grafted ionic groups on the performance of cellulose‐fiber‐reinforced thermoplastic composites

The influence of the surface chemistry of the cellulose fiber and polymer matrix on the mechanical and thermal dynamic mechanical properties of cellulose‐fiber‐reinforced polymer composites was investigated. The cellulose fiber was treated either with a coupling agent or with a coupling‐agent treatment followed by the introduction of quaternary ammonium groups onto the fiber surface, whereas the polymer matrix, with opposite polar groups such as polystyrene incorporated with sulfonated polystyrene and poly(ethylene‐co‐methacrylic acid), was compounded with the fiber. The grafting of the fiber surface was investigated with Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. Experimental results showed that an obvious improvement in the mechanical strength could be achieved for composites with an ionic interface between the fiber and the polymer matrix because of the adhesion enhancement of the fiber and the matrix. The improved adhesion could be ascribed to the grafted ionic groups at the cellulose‐fiber surface. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2022–2032, 2003     

碳纳米管/聚合物复合材料

本文简要介绍了碳纳米管的纯化和表面改性方法，着重对碳纳米管/聚合物复合材料的制备方法、微观结构表征及其力学、电学、光学等性能的研究进行了综述；简述了此类复合材料在电学、电磁屏蔽材料及吸波隐身材料、纤维材料以及航天工业等领域的应用，探讨了该研究领域所面临的一些问题及今后的发展方向。     

Review: Raw Natural Fiber–Based Polymer Composites

The effective utilization of raw natural fibers as indispensable component in polymers for developing novel low-cost eco-friendly composites with properties such as acceptable specific strength, low density, high toughness, good thermal properties, and biodegradability is one of the most rapidly emerging fields of research in polymer engineering and science. In fact, raw natural fiber–reinforced composites are the subject of numerous scientific and research projects, as well as many commercial programs. Keeping in mind the immense advantages of raw natural fibers, in the present article we concisely review raw natural fiber/polymer matrix composites with particular focus on their mechanical properties.     

Interfacial Banded Transcrystallization of Polyoxymethylene/Poly(butylene succinate) Blends Induced by the Polyamide 6 Fiber

Interfacial crystallization of polyoxymethylene/poly(butylene succinate) blends induced by the polyamide 6 (PA6) fiber was investigated. Due to strong heterogeneous nucleating ability, dense nuclei were generated on the surface of the PA6 fiber, which compelled the growth of twisted lamellae perpendicular to the PA6 fiber. As a result, unique interfacial banded transcrystallization was formed, which is rarely found before. Crystallization temperature was dominant in determining the nucleation activity of the PA6 fiber, further affecting the architecture of banded transcrystallization. With the increase of crystallization temperature, the nucleation density decreased to give more growth space for the twisted lamellae around the fiber. The wave-like banded stripes were transformed into fan-like stripes. Accordingly, band spacing and eccentricity respectively showed positive and negative correlation with crystallization temperature. These meaningful results shed light on regulating the architecture of banded crystals in polymer composites.

     

Reversible Amidation Chemistry Enables Closed-Loop Chemical Recycling of Carbon Fiber Reinforced Polymer Composites to Monomers and Fibers

Highly efficient recycling of carbon fiber reinforced polymer composites into monomers and fibers is a formidable challenge. Herein, we present a closed-loop recycling approach for carbon fiber reinforced polymer composites using reversible amidation chemistry, which enables the complete recovery of intact carbon fibers and pure monomers. The polymer network, synthesized by amidation between a macromonomer linear polyethyleneimine and a bifunctional maleic anhydride cross-linker, serves as a matrix for the construction of composites with exceptional mechanical properties, thermal stability and solvent resistance. The matrices can be fully depolymerized under the acidic condition at ambient temperature, allowing the effective separation and recovery of both carbon fibers and the two monomers. The reclaimed carbon fibers retain nearly identical mechanical properties to pristine ones, while pure monomers are recycled with high separation yields (>93 %). They can be reused in for multiple cycles for the manufacture of new composites, whose mechanical properties recover over 95 % of their original properties. This line of research presents a promising approach for the design of high-performance and sustainable thermoset composites, offering significant environmental and economic benefits.