Diffusion coefficient of DMF in acrylic fiber formation

A H₂O/dimethyl formamide (DMF) mixture was used as the coagulation bath of wet‐spun process for acrylic fibers. Diffusion coefficient of DMF in the protofibers prepared by acrylonitrile/acrylamide copolymers was determined. It has been found that diffusion coefficient of DMF outflow of the protofibers prepared by acrylonitrile/acrylamide copolymers synthesized by solution polymerization is highest compared with those of acrylonitrile/acrylamide copolymers synthesized by H₂O/DMF mixture suspension polymerization and aqueous suspension polymerization. With an increase of copolymer concentration in the dope, diffusion coefficient of DMF decreases continuously. Diffusion coefficient of DMF increases along with the bath temperature, but the changes in diffusion coefficient values are less prominent as temperature goes beyond 55°C. When DMF concentration in the coagulation bath was 50%, the value of the diffusion coefficient of DMF was minimal. Diffusion coefficient of DMF increases along with jet stretch minus ratio increase. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3616–3619, 2006     

Kinetics of diffusion in polyacrylonitrile fiber formation

A H₂O/dimethyl sulfoxide (DMSO) mixture was used as the coagulation bath of the wet‐spun process for polyacrylonitrile fibers. Diffusion behaviors of coagulate and solvent of the protofibers were studied. Diffusion coefficients of H₂O and DMSO of the protofibers, prepared by acrylonitrile (AN) homopolymers, were also determined. It was found that diffusion coefficients of H₂O and DMSO in the protofibers prepared by AN homopolymers, synthesized by DMSO solution polymerization, are highest compared with those of AN homopolymers synthesized by H₂O/DMSO mixture suspension polymerization and aqueous suspension polymerization. With increasing polyacrylonitrile concentration in the dope, diffusion coefficients of H₂O and DMSO decreased continuously. Diffusion coefficients of H₂O and DMSO increased concomitantly with increasing bath temperature, but the changes of diffusion coefficient values were less prominent when the temperature increased beyond 60°C. When DMSO concentration in the coagulation bath was 55 wt %, the values of diffusion coefficients of H₂O and DMSO were minimal. Diffusion coefficients increased with increasing jet stretch minus ratio. When the protofiber radius was increased, there was a corresponding increase of diffusion coefficients of H₂O and DMSO. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1529–1533, 2005     

接枝法亲水改性腈纶的研究

采用两步法接枝共聚改性工艺实现腈纶织物亲水改性。通过探索溶胀剂、乳化剂、引发剂的种类和用量,以及活化预处理接枝共聚反应的工艺,确定接枝改性的最佳条件。结果表明:在溶胀剂氯苯7．0g／L, 乳化剂壬基酚聚氧乙烯醚(OP)2．1g／L,引发剂过氧化二苯甲酰(BPO)2．5g／L,亲水性酰胺类单体质量分数 2．0％,活化预处理温度75℃,活化时间30 min,接枝共聚反应温度85℃,反应时间60min,再经浓度为2．0g／ L碳酸钠溶液处理,腈纶织物的吸湿率达到7．0％。     

阻燃腈纶的制备

采用铜离子处理腈纶,再与水合肼及反应助剂组成的混合水溶液反应,制备了阻燃腈纶,探讨了处理工艺条件对纤维性能的影响。结果表明:在水合肼加入量20 mL,w(NaOH)为5%的NaOH 4.7 mL,质量分数为10%精炼剂9.4 mL,甩干时间3 min,热处理温度160℃,热处理时间180 min条件下,得到的阻燃腈纶断裂强度为2.15 cN/dtex,断裂伸长率为21.4%,极限氧指数为32.83%。     

亲水性多孔聚丙烯腈纤维的研究

将聚丙烯腈(PAN)与聚氧化乙烯(PEO)共混后湿法纺丝,经水洗后处理,制成具有不同微孔结构的改性PAN纤维,然后在NaOH溶液中水解,得到亲水性多孔PAN纤维(HM-PAN)。借助红外光谱和扫描电镜表征了HM-PAN的化学结构和形貌;讨论了HM-PAN的亲水性能和力学性能。结果表明:相同水解条件下,随PEO含量增大,HM-PAN中引入的亲水基团增多,表面形成的孔穴加深、数量增多,纤维的亲水性能提高;在相同PEO含量下,通过控制水解时间、HM-PAN的孔隙结构及亲水基团数量,可以提高HM-PAN对水分的吸收及转移性能。PEO质量分数为10%的HM-PAN试样的平衡吸水倍率可高达10.48 g/g,最大芯吸高度为13.5 cm,保水率高达98.1%。HM-PAN中微孔产生的应力集中以及大分子排列规整性的破坏,导致纤维的力学性能有所下降,而水解时张力的施加可有效降低其下降幅度。     

Study on the formation process of polyacrylonitrile as‐spun fiber

In this article, the coagulation rate of PAN/DMSO dope was studied by observing the boundary movement of the gelled rods in different coagulation bath. Then the effect of the nature of solvent and coagulant and the coagulation conditions on the coagulation rate was discussed. It was found that the molecular size and molecular structure of coagulants is the most significant variable affecting the coagulation rate. The intermolecular affinity between coagulant and solvent determines the activation energy of coagulants, whereas the molecular volume is not a dominant factor. The coagulation rate depends not only on the diffusion coefficient of coagulants but also the nature of solvents. A solvent with strong polarity usually leads to a low‐coagulation rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

工程用聚丙烯腈纤维为基体的羧酸纤维的制备

采用断裂强度为12.26 cN/dtex、玻璃化转变温度高于250℃ 的工程用聚丙烯腈纤维(PAN-EF)为基体纤维,通过二甲基亚砜(DMSO)和氢氧化钠(NaOH)混合水解制备羧基含量(MCOOH)高且力学性能好的PAN-EF基羧酸纤维(PAN-EF-COOH),探讨了DMSO浓度、反应温度和反应时间对纤维水解效果的...     

吸湿发热聚丙烯腈纤维的性能研究

采用傅立叶变换红外光谱、扫描电子显微镜、X射线衍射仪和热重分析仪对交联改性制备的吸湿发热聚丙烯腈(PAN)纤维的吸放湿性能进行表征,与普通PAN纤维及进口吸湿发热PAN纤维进行对比。结果表明:交联改性制备的吸湿发热PAN纤维红外光谱出现了较强的羟基峰和羧酸盐的伸缩振动峰,相比普通PAN纤维,表面沟槽加深、粗糙度增加,在100℃内失重率达17.17%,热分解温度提高近70℃,结晶度大幅下降,力学性能降低;交联改性PAN纤维的吸放湿性能较普通PAN纤维大幅度提高,并高于进口吸湿发热PAN纤维,其平衡回潮率约30%,吸湿积分热达155 J/g。     

聚丙烯腈纤维烯胺结构的形成及其氧化特性的研究

将聚丙烯腈(PAN)纤维在惰性气氛下进行热处理,通过傅里叶红外光谱(FT-IR)、1 3C固体核磁共振(13C-NMR)、差示扫描量热(DSC)等方法研究了PAN纤维中烯胺结构的形成及其氧化特性。结果表明:惰性气氛下PAN纤维在热处理过程中氰基发生键断裂形成亚胺结构,并在温度达到190℃时开始向烯胺结构转变;随着热稳定化过程的进行,亚胺结构增加到一定程度后呈现下降趋势,而烯胺结构不断增加;热处理温度越高,亚胺结构向烯胺结构转变的越多且速率越快;将在惰性气氛下经不同温度热处理得到的PAN纤维进行空气气氛下的DSC分析,发现氧化反应的放热量与烯胺结构含量存在较好的线性关系,表明烯胺结构比其他特征结构更容易发生氧化反应。     

建筑增强用聚丙烯腈纤维的耐海水腐蚀性研究

模拟混凝土应用的海洋环境,在常温(25℃)、氯化物浓度为5610 mg/L的海水中对建筑增强用聚丙烯腈(PAN)纤维进行浸泡处理,研究建筑增强用PAN纤维的耐海水腐蚀性,并与聚对苯二甲酸乙二醇酯(PET)增强纤维和聚丙烯(PP)增强纤维进行对比。结果表明:海水浸泡50 d后,建筑增强用PAN纤维的主要吸收特征峰无明显变化,且无新的吸收特征峰出现,纤维超分子结构变化较小,晶区取向度基本保持不变,结晶度略有增加;海水浸泡50 d后,建筑增强用PAN纤维的拉伸强度为1261 MPa、降幅0.63%,初始模量为18.6 GPa、增幅8.14%,其拉伸强度与PET增强纤维相当、约为PP增强纤维的1.8倍,初始模量约是PET增强纤维的1.4倍、PP增强纤维的3.2倍;建筑增强用PAN纤维、PET增强纤维、PP增强纤维的拉伸强度耐蚀系数分别为99.4%,99.2%,100.0%,建筑增强用PAN纤维的耐海水腐蚀性介于PP增强纤维和PET增强纤维之间,但其在海水中环境中具有优异的模量保持优势,可以更好地提高混凝土在海水环境中的耐受力。     

拉伸对异形聚丙烯腈原丝截面形状的影响

研究了湿法和于湿法纺制异形聚丙烯腈(PAN)纤维过程中拉伸对纤维截面形状的影响。结果表明:喷丝头拉伸对湿法纺制的PAN初生纤维截面影响明显,随着喷丝头拉伸倍数的增大,纤维异形度逐渐增大;喷丝头拉伸对于湿法纺制的纤维截面形状和异形度影响较小;沸水拉伸对二者的纤维截面形状和异形度几乎无影响。     

聚丙烯腈纤维吸湿改性方法及研究现状

综述了国内外吸湿性聚丙烯腈(PAN)纤维的研究现状;阐述了PAN纤维的吸湿机理及影响吸湿性的因素;详细介绍了改善PAN纤维的吸湿性的化学方法和物理方法;PAN纤维吸湿改性化学方法有通过聚合和共聚引进亲水基团、与亲水物质接枝共聚、对纤维表面进行碱减量处理、纤维表面的亲水整理、等离子体处理等;PAN纤维吸湿改性物理方法有与...     

关于我国碳纤维用聚丙烯腈原丝质量的若干认识

分析了我国碳纤维用聚丙烯腈原丝质量欠佳的原因,主要是生产工艺包括聚丙烯腈的聚合方法、聚合物相对分子质量及其分散性、纺丝原液的纯度及其流变性、纺丝方法以及拉伸工艺等存在弊端。指出我国碳纤维用聚丙烯腈原丝生产过程中,应加强对聚合物及纺丝原液的质量控制,开发干-湿法工艺,从而提高原丝质量。     

臭氧气氛中聚丙烯腈纤维预氧化过程中的热行为

通过测量聚丙烯腈(PAN)纤维在空气和臭氧气氛下预氧化过程中的热应力行为,比较空气和臭氧气氛中预氧化所得纤维的物化性质。结果表明:PAN纤维在臭氧气氛中进行预氧化时,纤维的物理收缩应力和化学收缩应力比空气中的小,应力松弛严重;纤维在臭氧气氛中的敏感温度均比空气中的高,化学反应推迟;相同的升温速率下,臭氧气氛中纤维发生化学反应的时间较空气中的少,臭氧中纤维的化学反应速率较空气中的快;两种气氛中纤维的体积密度相差很小,臭氧中纤维皮芯结构状况较严重。     

湍动流化床内固体颗粒扩散系数

将高速摄影及基于互相关原理的图像处理技术与颗粒扩散规律的研究进行结合,对湍动流化床中甲醇制烯烃催化剂SAPO-34颗粒的扩散系数进行了实验研究。实验表明,对于Geldart A类的SAPO-34颗粒,颗粒纵向扩散系数在10^-2～10^-1 m²·s^-1量级之间,横向扩散系数在10^-3～10^-2 m²·s^-1量级之间,两者均随流化风速的上升而增大。另外,在相同的流化风速下,粒径较小的颗粒具有更大的扩散系数。该结果对湍动床颗粒运动规律的研究有一定意义。     

聚丙烯腈预氧丝预氧化程度表征分析

为考察红外光谱与热分析对聚丙烯腈原丝预氧化程度表征的准确程度,用傅里叶变换红外光谱仪、综合热分析仪等对PAN原丝及其预氧丝进行了测试。对红外光谱测试中各影响因素进行了探讨,并依此对不同预氧丝的红外光谱及相对环化率进行了分析。对原丝及预氧丝在不同气氛下的热性能进行了比较,并对其环化度进行了分析。结果表明:红外光谱与热分析均能定性反映出预氧丝的预氧化程度,而定量计算出的相对环化率则不具可比性,环化度会较真实值偏高。     

Bamboo fiber reinforced thermosetting resin composites: Effect of graft copolymerization of fiber with methacrylamide

Epoxy and polyester resins have been reinforced with methacrylamide (MAA) treated bamboo strip matting to develop bamboo fiber reinforced plastic composites. Bamboo mats were graft copolymerized with 1, 3, and 5% solution of MAA. The mechanical (tensile strength, elastic modulus, flexural strength, and flexural modulus), thermal, and water absorption properties of the composites were determined. One percent treatment of bamboo with MAA gave optimum results with epoxy resin. The mechanical properties were improved. TGA results reveal that the degradation temperature of the composite has improved after grafting. The weight loss of 1% MAA treated bamboo–epoxy composite reached a value of 95.132% at 795°C compared to 97.655% at 685°C of untreated bamboo–epoxy composite. Water absorption in the composites was studied by long term immersion and 2 h boiling in distilled water. The process of water absorption indicates Fickian mode of diffusion. MAA treatment results in reduced water uptake. There was improvement in the properties of pretreated bamboo‐polyester matrix composite as well. Three percent treatment of bamboo with MAA gave optimum results with polyester resin. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

黄豆蛋白改性腈纶的研制

采用丙烯腈对黄豆蛋白进行疏水改性后,将其与聚丙烯腈共混纺丝,用常规腈纶的生产工艺纺制吸湿和吸水性良好的黄豆蛋白改性腈纶。采用黄豆蛋白质量分数为33％的改性黄豆蛋白与常规聚丙烯腈原液共混纺丝,当黄豆蛋白质量分数为10％时,获得的改性腈纶断裂强度2.75 cN／dtex,断裂伸长率25.4％,回潮率1.7％,保水率8.3％。     

二甲基亚砜干湿法制备高强度聚乙烯醇纤维的研究

以常规聚合度聚合的乙烯醇（PVA,聚合度1 700～2 600）为原料,以二甲基亚砜（DMSO）为溶剂,乙醇为凝固剂,甲醇为萃取剂,采用干湿法纺丝制备高强度的PVA纤维,最高强度可以达到19.4 cN/dtex。使用扫描电子显微镜对PVA纤维样品进行观测,纤维样品的形貌结构十分均匀,这对提高PVA纤维的断裂强度十分有利...     

碳纤维用聚丙烯腈合成工艺研究进展

综述了近年来碳纤维用聚丙烯腈(PAN)合成工艺的研究进展,介绍了均相溶液聚合、水相悬浮聚合和水相沉淀聚合等传统聚合方式的特点和不足。详细阐述了可逆加成断裂链转移自由基聚合(RAFT)新型聚合工艺,展望了新型工艺在碳纤维用PAN合成中的应用和未来发展方向。