PPTA树脂在甲磺酸中的溶解及其溶液性质初探

实验首次用甲磺酸(MSA)对聚对苯二甲酰对苯二胺(PPTA)树脂进行溶解制备PPTA/MSA溶液,并对所形成溶液性质进行研究并制备PPTA浆粕。通过偏光显微镜观察了PPTA树脂在MSA中的溶解规律,用树脂比浓对数粘度随时间的变化研究了树脂在MSA中的稳定性。并通过比表面积(BET)分析、X射线衍射(XRD)分析和热失重分析(TGA)研究了PPTA浆粕的比表面积、结晶度和热性能。结果表明:在低浓度下,PPTA树脂能与MSA混合均匀得到均一稳定的溶液,由所得溶液制备的PPTA浆粕性能优于同条件下用PPTA/硫酸溶液制备的浆粕性能。     

凝固浴工艺对聚对苯二甲酰对苯二胺膜性能的影响

将聚对苯二甲酰对苯二胺(PPTA)树脂和浓硫酸进行高温溶解,经过脱泡处理,得到PPTA-H_2SO_4溶液,在凝固浴中凝固制备PPTA膜,研究了凝固浴种类及工艺对PPTA膜的结构与性能的影响。结果表明:在质量分数为7%的H_2SO_4、质量分数为4%的Na OH、H_2O 3种凝固浴中,H_2SO_4凝固浴适合PPTA树脂成膜;PPTA膜最佳凝固浴工艺条件为凝固浴H_2SO_4质量分数7%,凝固浴温度3℃,凝固时间3.0 min,在此条件下PPTA膜具有均匀致密的结构,出现明显的彩色条纹状的液晶现象,热稳定性能最好,其拉伸强度约68MPa,900℃时质量保持率达59.81%。     

硫酸钠对水泥砂浆的物理侵蚀作用

采用150 g/L的硫酸钠溶液半浸泡的试验方法,以砂浆抗蚀系数为指标,研究了相对湿度和温度变化条件下,硫酸钠溶液的不同结晶产物Na2SO4(无水芒硝)与Na2SO4·10H2O(芒硝)对砂浆试件的物理侵蚀作用和不同条件下硫酸钠溶液的物理侵蚀特性及相关机理.结果表明:与环境温度变化条件相比,硫酸钠溶液在相对湿度变化条件下对砂浆试件造成物理侵蚀作用更为严重,这主要是在相对湿度变化条件下,硫酸钠溶液的结晶产物Na2SO4与Na2SO4·10H2O发生相互转化造成的.硫酸钠溶液形成Na2SO4结晶产物时,其对砂浆造成的物理侵蚀破坏作用较形成的Na2SO4·10H2O结晶产物更为显著.     

芳纶浆粕增强橡胶密封垫材料的研究

以丁腈橡胶（NBR）为基材,芳纶浆粕（PPTA）和白炭黑为增强材料制备了NBR/PPTA复合材料,研究了PPTA和白炭黑用量以及硫化条件对复合材料性能的影响。结果表明,PPTA可与NBR形成良好的填料/橡胶界面作用;复合材料在平行和垂直纤维方向具有明显的各向异性;在PPTA/白炭黑配比一定和适宜硫化条件下,复合材料具有优异的综合性能。     

3，4＇-ODA改性PPTA共聚物溶液性质的研究

为了改善聚对苯二甲酰对苯二胺（PPTA）的溶解性能，在PPTA的聚合过程中添加第三单体3,4’-二氨基二苯醚（3．4＇-ODA），得到了PPTA的共聚体溶液。主要讨论不同的溶剂体系（NMP或DMAc）中共聚物溶液的凝固性和稳定性，包括凝固剂的种类，溶剂的浓度，CaCl2的含量和温度对溶液的凝固值和临界浓度的影响。实验结果表明：水是非常强的凝固剂：随着凝固液中溶剂浓度的提高，凝固值增大；随着CaCl2含量的增大凝固值逐渐增大；温度影响不是太大，变化趋势比较缓和；共聚物溶液在室温和60℃下都具有非常好的稳定性。     

3,4'-ODA改性PPTA共聚物溶液性质的研究

为了改善聚对苯二甲酰对苯二胺(PPTA)的溶解性能,在PPTA的聚合过程中添加第三单体3,4'-二氨基二苯醚(3.4'-ODA),得到了PPTA的共聚体溶液.主要讨论不同的溶剂体系(NMP或DMAc)中共聚物溶液的凝固性和稳定性,包括凝固剂的种类,溶剂的浓度,CaCl2的含量和温度对溶液的凝固值和临界浓度的影响.实验结果表明:水是非常强的凝固剂;随着凝固液中溶剂浓度的提高,凝固值增大;随着CaCl2含量的增大凝固值逐渐增大;温度影响不是太大,变化趋势比较缓和;共聚物溶液在室温和60℃下都具有非常好的稳定性.     

比较芳纶短纤维和芳纶浆粕对绝热材料性能的影响

比较了芳纶短纤维粕(PPTA short-fiber)/三元乙丙橡胶(EPDM)和芳纶浆粕(PPTA pulp)/三元乙丙橡胶的分散性、耐烧蚀性能与力学性能。结果表明,芳纶浆粕比芳纶短纤维在EPDM橡胶中有更好的分散性,芳纶浆粕的拉伸强度和扯断伸长率均优于PPTA short-fiber/EPDM,同时可以得到更高的填充量。芳纶浆粕的最优含量为12.0%,PPTA pulp/EPDM橡胶线烧蚀率为0.064 mm/s,拉伸强度为3.0 MPa,扯断伸长率为210%,具有优异的耐烧蚀性能和力学性能,可以代替芳纶短纤维作为高性能绝热材料而广泛应用。     

赤泥酸浸提钒

采用H2SO4, HCl, HNO3三种浸出剂提取赤泥中的钒,考察了酸浓度对钒浸出率的影响,对赤泥、浸出液和浸出渣进行了分析,研究了钒溶液的热力学,绘制了不同价态钒浓度对数与pH值关系图. 结果表明,H2SO4最适合赤泥酸浸提钒,在液固比5 mL/g、反应温度90℃、反应时间1 h和H2SO4浓度5.5 mol/L条件下,钒浸出率为88%. 经H2SO4浸出后,赤泥中的板钛矿、钙钛矿、白云石、赤铁矿和白云母均一定程度溶解,出现硬石膏物相. 浸出液pH=0.47,溶液呈蓝色,钒呈4价,钒浓度为0.006773 mol/L,赤泥中的V(IV)与SO42-形成VOSO4,提高了钒的溶解度,拓宽了其稳定存在区间. 随H2SO4浓度升高,VO2更易溶解且溶解产物VOSO4更稳定.     

半连续化直接缩聚法制备聚对苯二甲酰对苯二胺浆粕

采用啮合同向旋转的双螺杆挤出机作为主反应器,半连续化直接缩聚法制备了聚对苯二甲酰对苯二胺（PPTA）浆粕.结果发现,较低的预缩聚反应温度有利于得到高相对分子质量的PPTA浆粕;而在双螺杆挤出机中主反应温度则应控制在70℃左右为宜;物料在双螺杆中的停留时间超过3 min,才满足制备PPTA浆粕的工艺要求.螺杆的转速对PPTA 浆粕的相对分子质量的提高不显著,若转速太快,使物料在双螺杆中的停留时间缩短,反而不利于得到性能较好的PPTA浆粕.本研究为直接缩聚法制备PPTA浆粕的进一步放大打下了基础.     

凝固浴条件对对位芳纶成形的影响

将聚对苯二酰对苯二胺(PPTA)浆液浸入凝固浴来模拟纺丝过程中纤维的凝固过程。通过偏光显微镜分析了不同凝固浴条件下非溶剂在PPTA浆液中的扩散速率;用XRD分析了不同凝固浴条件下PPTA膜的结晶情况;用SEM分析了不同凝固浴条件下PPTA膜的表面形貌。结果表明,随着凝固浴温度和硫酸质量分数的升高,PPTA膜的致密程度不断下降,且由于边缘和中心区域相分离模式的不同其致密程度也不同。验证了PPTA纤维在凝固浴中形成皮芯层结构的结论。     

ON THE FORMATION OF POLY (P-PHENYLENE TEREPHTHALAMIDE) PULPS FROM STIRRED SOLUTIONS

PPTA (poly (p-phenylene terephthalamide)) may precipitate directly from stirred solution by the use of glycerol or glycerol/water coagulant in fibrous pulp form—short fibers with attached fine fibrils that are called PPTA pulp. Scanning electron micrographs show that the precipitated PPTA pulps have a ribbon-like structure similar to Twaron pulps. The wide-angle X-ray diffraction patters of the resultant pulps exhibit three diffraction peaks at 2θ–20.5, 23.5, and 28.5 corresponding to the {110}, {200}, and {004} crystal faces of PPTA fibers, and the peaks are not as sharp as those of fibers. The process yields PPTA pulps with properties such as specific surface areas and mean length depending on the stirring speed, and the ratio of the viscosity of the PPTA/H₂SO₄ solution to that of the coagulant. The inherent viscosity of the pulps determined by that of the PPTA bulk, which can be easily polycondensated to the desired specification.     

芳纶浆粕取代石棉摩擦材料的摩擦学性能

对本实验室直接缩聚法制备的芳纶浆粕以及传统的纺丝切割法制备的Kevlar浆粕和Twaron浆粕取代石棉在酚醛树脂基摩擦材料中的摩擦性能进行了研究.结果表明,3种芳纶浆粕增强的摩擦材料都具有优良的摩擦磨损性能,特别是随着温度升高,摩擦系数有较大提高的同时,磨损率明显下降,克服了石棉增强的摩擦材料在较高温度下磨损率较大的缺点.直接缩聚法制备的PPTA浆粕增强的摩擦材料摩擦性能与Kevlar浆粕和Twaron浆粕增强的相近,为芳纶浆粕增强摩擦材料的国产化奠定了基础.     

Polymer composite of rigid and flexible molecules: Blend systems of poly(p-phenylene terephthalamide) and ABS resin

Homogeneous coagulant of poly(p-phenylene terephthalamide) (PPTA) and ABS resin was obtained by pouring the dimethylsulfoxide solution of N-sodium PPTA and ABS into acidic water. Transmission electron microscopic observation proved that PPTA was dispersed in the matrix in a form of microfibril with a diameter of 10–30 nm. The T_g of the resin component in ABS shifted to higher temperatures with increasing fraction of PPTA. Stress-strain behavior of the polymer composite showed increased tensile modulus and strength with addition of PPTA. The transition temperature from brittle to ductile fracture, however, shifted to higher temperature resulting in lower extensibility. Incorporation of the block copolymer of PPTA and polybutadiene into ABS improved the ultimate extensibility, i.e., increased toughness was provided compared with the simple composite systems of ABS and PPTA microfibrils. Scanning electron microscopic observation showed that the polymer composite made with the block copolymer generated many crazes upon deformation, while the composite with PPTA homopolymer fractured without remarkable craze formation. Thus, a new type of thermoplastic with improved mechanical properties was obtained by use of PPTA block copolymer as compatibilizer.     

聚对苯二甲酰对苯二胺短纤维在高温下的力学性能

聚对苯二甲酰对苯二胺(PPTA)纤维具有优良的耐热性,通过对进口PPTA短纤维和两种国产PPTA短纤维耐高温性能的研究,探讨在不同温度和停留时间下其力学性能和外观色相的变化情况。结果表明:进口和国产PPTA短纤维耐高温性能相差不大。     

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.     

PPTA纤维原纤化的研究进展

阐述了聚对苯二甲酰对苯二胺(PPTA)纤维的结晶结构及其原纤化的机理,综述了国内外PPTA纤维原纤化的研究进展。PPTA纤维具有皮芯结构,芯层含有高度取向的多重原纤。PPTA浆粕的制备方法主要分为机械法以及直接成型法,其关键技术在于控制纤维原纤化程度,保持纤维强度以及解决分散性能。机械法制备浆粕的方法包括磨浆设备的改进,在聚合体系中添加其他聚合物改善纤维的磨浆性能以及混合其他易原纤化纤维磨浆等。直接成型法包括沉析法和凝胶法,相对于机械法制浆,直接成型法具有工艺流程简单的优点,但是使用此方法制备浆粕,难以控制原纤的形状,纤维强度低。     

含苯并咪唑的芳香族聚酰胺共聚物的合成与表征

采用低温溶液缩聚法,在N-甲基吡咯烷酮(NMP)-氯化锂(LiCl)溶剂体系中加入2-(4-氨基苯基)-5-氨基苯并咪唑(DAPBI)作为第三单体,与对苯二胺(PPD)和对苯二甲酰氯(TPC)共聚得到改性对苯二甲酰对苯二胺(PPTA)共聚物。控制共聚单体投料顺序,设计合成出一系列序列结构不同的杂环段与PPTA硬段相间的嵌段聚合物。研究了序列结构和DAPBI含量对共聚物比浓对数黏度的影响,采用红外光谱、X射线衍射、热重分析仪等对共聚物结构和性能进行表征。试验结果表明:DAPBI成功引入到了PPTA分子链中,改性PPTA树脂为非晶结构,所得有规嵌段共聚物比无规共聚物拥有更好的有序性和结晶性能,共聚物能保持良好的耐热性能,溶解性能和力学性能得到了提升。     

Uniplanar orientation of poly(p-phenylene terephthalamide) crystal in thin film and its effect on mechanical properties

The uniplanar orientation of poly(p-phenylene terephthalamide) (PPTA) crystal was investigated by x-ray and infrared measurements. Thin PPTA films 3–15 μm thick were prepared by coagulating a sulfuric acid solution of PPTA with various coagulants. Two types of uniplanar orientation were observed, depending on the coagulant used. Thin film coagulated with water exhibits (0k0) uniplanar orientation and film coagulated with other coagulants such as methanol, ethanol, and acetone exhibits (h00) uniplanar orientation. These (h00) and (0k0) uniplanar orientations are formed with crystal modifications I and II, respectively. The (0k0) uniplanar orientation transforms to (h00) upon annealing, accompanying crystal transformation from modification II to modifications I. These uniplanar orientations may result from anisotropic crystal growth due to polymer–coagulant interaction along the hydrogen bond direction. The effect of these uniplanar orientations on the mechanical properties was also examined. The thin film having the (0k0) uniplanar orientation shows ductile fracture, whereas the one having the (h00) uniplanar orientation shows brittle fracture upon tensile deformation. These results are explained on the basis of the direction of the uniplanar orientation of the hydrogen-bonded sheet.     

A novel preparation method of polyaluminum chloride/polyacrylamide composite coagulant: Composition and characteristic

Inorganic/organic composite coagulants have drawn a wide attention through the years owing to its superior coagulation behaviors. In this study, polyaluminum chloride (PAC)/polyacrylamide (PAM) composite coagulant was synthesized by ultraviolet (UV) irradiation by using PAC and acrylamide (AM) as raw materials, urea as a solubilizer, and 2,2′‐Azobis[2‐(2‐imidazolin‐2‐yl)propane]dihydrochloride (VA‐044) as an initiator. The effect of total monomer mass fraction, solubilizer dosage and initiator dosage on the viscosity and molecular weight of PAC/PAM composite coagulant was discussed. The results suggest that the composite coagulant with high polymerization degree, intrinsic viscosity of 1483 mL/g and molecular weight of 7.38 million, could be obtained when the total monomer mass fraction of 40%, urea dosage of 1.5% and initiator dosage of 0.6% are chosen in the preparation. It is a potential preparation method of composite coagulant with short preparation time and high preparation efficiency. Fourier transform infrared spectrum and ¹H nuclear magnetic resonance spectroscopy represent that the coagulant for polyaluminum chloride and polypropylene are copolymer. Thermal gravimetric analysis describes the high thermal stability of composite coagulant. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44500.