芳纶热拉伸处理过程对氢键影响的研究

研究了热处理过程对聚对苯二甲酰对苯二胺(PPTA)结构与性能的影响。通过对PPTA纤维升温红外光谱分析可以看出:在较低的热处理温度下,随着温度的升高,发现在3 300 cm~(-1)处—NH—伸缩振动峰向高波数方向移动,峰型变宽,吸收峰强度减弱。采用傅里叶变换红外光谱仪和单丝强度仪、比浓对数黏度等研究发现:经热拉伸处理后的PPTA纤维内部分子间氢键作用力增加,自由氢键数减少,游离的—NH_2含量却增加,纤维比浓对数黏度和强度降低,说明纤维的拉伸强度是由分子间作用力以及分子链段的长度共同作用的。     

芳纶表面改性及其与丁腈橡胶复合材料的性能研究

为增强对位芳纶纤维(PPTA)与丁腈橡胶(NBR)之间的界面粘结强度,采用多巴胺(DA)-硅烷偶联剂对芳纶纤维联合改性并制备PPTA/NBR复合材料。结果表明,纤维改性后表面粗糙度增加;表面元素含量和种类都发生较大变化;在H试样抽出测试中,改性后的PPTA帘线/NBR试样抽出力相对于未改性试样增大64.02%,且黏附橡胶较多。改性后的PPTA/NBR试样,纤维含量相同时,断裂伸长率和拉伸强度相对未改性的PPTA/NBR试样增大;随着纤维含量的增加,使用同种方法处理的PPTA/NBR复合材料断裂伸长率减小,拉伸强度先增大后减小。     

Feasible Preparation of a Thin‐Film Composite Nanofiltration (TFC NF) Membrane with Enhanced Skin–Substrate Adhesion and Compaction Resistance: In Situ Construction of Rigid–Flexible Polymer Composited Microspheres (CPs) in the Casting Solution

Novel microspheres (CPs) composited by rigid and flexible polymers are synthesized and embedded in the supporting membranes to enhance both the skin–substrate adhesion and compaction resistance of the thin‐film composite (TFC) nanofiltration membranes. The CPs are in situ formed in the casting solution after the rigid poly(p‐phenylene terephthamide) (PPTA) is produced in the flexible poly(m‐phenylene isophthalamide) (PMIA) solution. Then the PPTA/PMIA in situ blending membranes are prepared by using the NIPs method, and the TFC NF membranes are fabricated via interfacial polymerization on them. The CPs are characterized via polarizing microscopy and TEM. The surface morphology and chemical composition of the blended membranes are characterized by using FESEM, AFM, FTIR, and WCA, respectively. As the results show, the supporting membrane with higher PPTA content exhibits higher permeability, thermal stability, and compaction resistance. Moreover, the adhesion strength between the TFC functional layer and the supporting membrane is improved significantly. It is proposed that this improvement can be attributed to the CPs that are exposed on the top surface of the supporting membrane, which leads to a great enhancement because of the anchoring effect between the functional layer and the CPs.     

硫酸预处理对PPTA短切纤维PFI打浆效果的影响

使用硫酸对PPTA纤维进行预处理后再使用PFI磨打浆,通过对原纤及粕保水值、浆粕原纸抗张强度的测定以及纤维表规形貌观察(SEM)等表征手段,探讨了硫酸预处理对PPTA短切纤维打浆效果的影响.实验发现,经质量分数为80%的硫酸处理后,PPTA短切纤维表面有轻微的溶解现象,部分纤维丰体上有小范围的浅层的纤维纵向劈裂现象;而经质量分数为85%的硫酸处理的PPTA短切纤维则纵向劈裂严重,小部分微纤已经裸露.由浆粕保水值及浆粕原纸紧度、抗张强度数据可知,经质量分数为80%和85%的硫酸处理后制备的浆粕原纤化程度较未处理的高.结合SEM照片发现,经顶处理后磨浆的浆粕具有更充分的原纤化效果,主干纤维破坏严重.     

Strain-induced internal fibrillation in looped aramid filaments

By mapping the small-angle X-ray scattering (SAXS) from a looped poly-(para-phenylene terephtalamide) (aramid, PPTA) filament using a synchrotron X-ray microbeam, we investigate the effects of axially compressive and tensile strain on internal fibrillar structures. Unique observations of oscillations in the highly anisotropic SAXS patterns indicate a regular internal structure. Upon increase of the applied compressive strain, a significant decrease in oscillation frequency is observed in the scattering pattern. With an increase in imposed tensile strain an increase in oscillation frequency in the scattering pattern is observed. One model capable of describing the intensity is a model of stacked cylinders. These cylinders could be part of the fibrillar structure present in the PPTA fibres, which consist of cylinder- to tape-like objects, the presence of which is supported by SEM images. One hypothetical physical interpretation presented here for the appearance of a regular internal structure is the occurrence of fibrillar separation in regions undergoing axially compressive strain, and the appearance of strain relief/slip planes between packs of fibrils in regions undergoing tensile strain. Compaction of these packs upon increase of tensile strain could increase the repetition distance in the structure as multiple packs combine to form a single pack.     

短切芳纶纤维增强复合材料的研究进展

综述了短切芳纶纤维增强环氧树脂、热塑性聚氨酯、尼龙、聚乙烯、聚苯硫醚、间规聚苯乙烯等复合材料的研究进展.芳纶纤维的加入影响了基体树脂的力学性能.纤维表面经过改性后,复合材料的力学性能得到了改善.     

PPTA低温硫酸溶解工艺研究

针对聚对苯二甲酰对苯二胺(PPTA)在硫酸中的溶解工艺进行实验和研究,系统的对比了PPTA各在固相硫酸中和液相硫酸中的溶解工艺,实验结果表明:固相硫酸溶解PPTA能提高溶解速度、浆液的均匀性和改善浆液的过滤性;同时能防止PPTA溶解时的热降解作用,非常有利于提高纤维的强度。     

对位芳纶纤维打浆及其对无石棉胶乳抄取板的影响

研究了芳纶纤维的打浆性能及其在无石棉胶乳抄取板中的应用。研究表明,芳纶纤维具有高的Zeta电位,呈现强负电性;随着磨浆转数提高,其打浆度逐渐增加,负电性逐渐下降;在磨浆转数为20000转时,纤维长度和粗度明显减小,细纤维化显著,打浆度为30oSR,此时用该芳纶纤维配抄的无石棉胶乳抄取板的抗张指数达到最大值。     

聚对苯二甲酰对苯二胺微观结构的研究

用透射电镜和X光衍射方法研究了聚对苯二甲酰对苯二胺(PPTA)的微观结构,并与其纤维(Kevlar,芳纶-Ⅲ)进行了对比。结果表明,PPTA由非晶区域和结晶完整的区域所组成;树脂和纤维具有相同的结晶结构,其晶粒尺寸和Bragg面间距基本一致;纤维结晶度的增加是由于在纺丝过程中结晶区域的扩大而造成的。     

高强有机合成纤维的结构形成

 对典型刚性结构的对位芳酰胺纤维和柔性结构的超高分子量聚乙烯纤维的结构特征及其形成过程进行分析,特别是纺丝及热处理工艺对纤维结构变化的影响,认为有机合成纤维高强化,应使纤维在结构上满足以下2个特征：高取向度和高结晶度;聚合物分子链能够充分伸展形成伸直链结晶。同时,介绍了PPTA纤维和UHMWPE纤维的目前进展情况。提出能够形成高取向、高结晶度且分子链充分伸直结构的聚合物,可以通过控制纺丝和热处理工艺制造出高强纤维。