熔融加工丙烯腈-丙烯酸甲酯共聚物及纤维的研究

采用水相沉淀聚合法在不同的温度下合成了系列投料摩尔比为85/15的丙烯腈(AN)-丙烯酸甲酯(MA)共聚物(85/15 AN/MA),采用差示扫描量热仪(DSC)、熔体流动速率仪(MFR)对产物的热性能进行了分析.测试结果表明,85/15 AN/MA的熔融峰值温度在154～173℃之间,210℃时85/15 AN/MA的熔融指数在1.60～5.23之间.采用扫描电子显微镜(SEM)、电子单纱强力仪(EYST)等对纤维的表观形貌、力学性能进行了表征.结果表明,聚合温度为30℃时,熔纺纤维表面致密且光滑,适合进行可熔融加工.     

离子液体对静电纺丝成型及电纺纤维形貌的影响

静电纺微/纳米纤维毡在组织工程、过滤、防护等领域具有显著优势,目前广为使用的静电纺丝聚合物均以配置一定的溶液为前提,离子液体因其独特的溶解特性及“绿色”优势可替代部分具有毒性的溶剂.综述了离子液体在静电纺丝成型中的作用,包括作为单一溶剂、共溶剂,或者将离子液体聚合后参与共混静电纺丝成型,也包括采用离子液体对静电纺纤维毡进行后处理.离子液体的引入导致溶液性质变化,显著影响了静电纺丝成型过程,进而导致纤维直径、形貌以及纤维毡的物理性质均有一定程度的改变.     

磁场调控下制备可熔融丙烯腈-丙烯酸甲酯共聚物

外加不同强度间歇磁场(MF,0T,0.1T,0.3T,0.6T,0.9T和1.1T)的干预下,采用水相沉淀聚合法制备了一系列投料摩尔比为85/15的丙烯腈/丙烯酸甲酯共聚物(85/15AN/MA)。通过核磁共振分析仪、差示扫描量热分析仪和热台显微镜对共聚物进行了表征分析。结果表明,外加磁场对可熔融85/15AN/MA的共聚物组成、数均序列长度(NASBL)、立构规整性、热稳定性和熔融行为有较大的影响。当磁场强度为0.9T时,85/15AN/MA的共聚物组成与投料比最为接近,NASBL最短,三单元间规立构体含量最高,热稳定性高,在220℃时熔融行为更为明显,共聚物的可熔融加工性明显提高。     

类离子液体增塑改性聚乙烯醇的制备及性能

为了实现聚乙烯醇(PVA)的熔融纺丝,采用氯化胆碱(ChCl)与木糖醇(Xyl)合成类离子液体(PILs),将其作为增塑剂,辅以润滑剂硬脂酸钙和抗氧剂B225,对PVA进行增塑改性。通过差示扫描量热仪、热重分析仪、熔体流动速率仪研究了PILs对PVA热性能和流动性的影响;通过红外光谱仪、X射线衍射仪和扫描电镜对PILs增塑改性PVA的分子间氢键作用、结晶度和相容性进行了表征和分析;并研究了纺丝温度对改性PVA可纺性及力学性能的影响。结果表明,PILs能与PVA的羟基之间形成新的氢键,减弱PVA自身的氢键作用,从而降低PVA的熔点和结晶度,提高其热稳定性和流动性;当PILs的配比为1:2,质量占比为12.5时,改性PVA的热分解温度、熔点和熔体流动速率分别为291.2℃,169.4℃和6.20 g/10 min;改性PVA在230～250℃的温度时均能熔融纺丝,随着纺丝温度升高,纤维断裂强度逐渐降低,断裂伸长率先升高后降低。     

丙烯腈基含糖共聚物纳米纤维的制备

通过酶促合成法制备了含糖单体6-O-乙烯基癸二酸-D-吡喃型葡萄糖酯(OVSEG),采用水相沉淀聚合法将丙烯腈(AN)与OVSEG共聚,制备含糖聚合物poly(AN-co-OVSEG)。用1 H-NMR,傅里叶变换红外光谱(FT-IR),凝胶渗透色谱(GPC)对聚合产物进行了表征。利用静电纺丝技术将含糖聚合物制备成纳米纤维,通过正交实验,确定最佳纺丝条件为:电压14kV、接收距离18cm、流速0.75mL/h、纺丝液浓度30%,此条件下纤维粗细均匀,平均直径为146nm。     

含有低分子量聚乙二醇的丙烯腈-丙烯酸甲酯共聚物的结构与性能研究

在丙烯腈(AN)与丙烯酸甲酯(MA)的水相沉淀聚合过程中添加5%～30%的亲水性聚合物-聚乙二醇(PEG),合成含有PEG的丙烯腈基共聚物.采用傅立叶变换红外光谱(FTIR)、差示扫描量热仪(DSC)、热重分析(DTG)和X射线衍射分析(XRD)等方法对聚合产物进行了分析.结果表明,聚乙二醇不参与丙烯腈与丙烯酸甲酯的聚合反应,但对聚合物的热力学行为与结晶度产生一定的影响.随着PEG含量的增加,共聚物的分解温度先降低后升高,而熔融温度呈现出先升高后降低的变化趋势;聚合物的结晶度也随着PEG含量的增加先升高后降低.     

熔纺UHMWPE纤维在拉伸过程中的结构与力学性能

采用高流动性的超高分子量聚乙烯(UHMWPE)树脂颗粒,以熔融纺丝法制备出了拉伸强度为1.6GPa的UHMWPE纤维。利用热分析(DSC)、广角X射线衍射(WAXD)、小角X射线散射(SAXS)、拉伸试验研究了UHMWPE纤维在拉伸过程中结构和力学性能的变化。研究显示,随着拉伸倍数的增加,UHMWPE纤维的结晶度增加,晶粒尺寸下降,纤维的缺陷度逐渐下降,取向度逐渐增大,拉伸强度逐渐增加;其结构和力学性能变化规律与凝胶法相似;有效拉伸倍率低可能是导致熔纺UHMWPE纤维的拉伸性能不如凝胶纺丝纤维的主要原因。     

类离子液体增塑改性聚乙烯醇的制备及性能EI北大核心CSCD

为了实现聚乙烯醇(PVA)的熔融纺丝,采用氯化胆碱(ChCl)与木糖醇(Xyl)合成类离子液体(PILs),将其作为增塑剂,辅以润滑剂硬脂酸钙和抗氧剂B225,对PVA进行增塑改性。通过差示扫描量热仪、热重分析仪、熔体流动速率仪研究了PILs对PVA热性能和流动性的影响;通过红外光谱仪、X射线衍射仪和扫描电镜对PILs增塑改性PVA的分子间氢键作用、结晶度和相容性进行了表征和分析;并研究了纺丝温度对改性PVA可纺性及力学性能的影响。结果表明,PILs能与PVA的羟基之间形成新的氢键,减弱PVA自身的氢键作用,从而降低PVA的熔点和结晶度,提高其热稳定性和流动性;当PILs的配比为1:2,质量占比为12.5时,改性PVA的热分解温度、熔点和熔体流动速率分别为291.2℃,169.4℃和6.20 g/10 min;改性PVA在230~250℃的温度时均能熔融纺丝,随着纺丝温度升高,纤维断裂强度逐渐降低,断裂伸长率先升高后降低。     

丙烯腈-丙烯酸甲酯微孔膜的制备及成膜性能

以摩尔比为85/15的可熔融丙烯腈-丙烯酸甲酯共聚物(85/15AN-MA)为膜基体,用γ-丁内酯(γ-BA)和三乙酸甘油酯(GTA)复配作为混合稀释剂,采用热致相分离(TIPS)法制备了AN-MA基微孔膜。详细研究了聚合物浓度、混合稀释剂的配比和冷却速率对微孔膜的孔结构、孔隙率、水通量及力学性能的影响。研究结果表明,随着γ-BA含量的增加或凝固浴温度升高,微孔膜成型过程中存在小部分非溶剂致相分离(NIPS),形成不对称的横截面结构。增加GTA的比例或快的冷却速率更利于发生TIPS,γ-BA的质量分数为45%和50%时,微孔膜发生单纯的TIPS过程,凝固浴为0℃的乙醇浴时,AN-MA微孔膜具有更好的力学性能。     

聚合工艺参数对丙烯腈/丙烯酸甲酯水相沉淀共聚合反应的影响

以过硫酸铵(APS)为引发剂,采用水相沉淀聚合工艺合成了高分子量的丙烯腈/丙烯酸甲酯(AN/MA)共聚物。研究了各聚合反应因素对共聚反应的影响。结果表明:该聚合体系的反应速率及产率较高,制得的PAN共聚物具有较高的粘均分子量。     

聚丙烯腈/丙烯酰胺共聚物热性能研究

选用丙烯酰胺(AM)为共聚单体制备丙烯腈/丙烯酰胺共聚物。研究了共聚物的热性能。结果表明,AM的引入可使PAN预氧化的起始反应温度提前,在DSC曲线上形成双峰,使放热峰宽化,失重降低,降低放热反应速率,有利于促进PAN原丝在预氧化、碳化过程中形成均匀的环化梯形结构,最终可提高碳纤维的力学性能。     

Morphology and properties of acrylate styrene acrylonitrile/polybutylene terephthalate blends

The structure and mechanical properties of acrylate styrene acrylonitrile (ASA) and ASA/polybutylene terephthalate (PBT) blends have been studied. The morphology of ASA is found to conform to a previous model. 40/60 and 60/40 blends of ASA/PBT have a two-phase, dispersed morphology while the 50/50 blend is shown to have a co-continuous structure. As processing temperature is increased, the mechanical properties decrease, due to PBT degradation. The 60/40 ASA/PBT blend has very poor impact resistance because of the continuous, degraded PBT matrix. Better mechanical properties are observed for blends with a continuous ASA matrix, particularly in the 50/50 blend. Fracture surface analysis reveals a unique morphology of mushroom-like PBT fibrils for the low processing temperature samples near the crack tip. This is thought to occur due to the competition of cohesion and adhesion of the PBT with the ASA matrix.     

含侧甲基液晶双马来酰亚胺的合成及表征

通过甲基对苯二酚和对马来酰亚胺基苯甲酸,制得了一种低熔点的酯类液晶双马来酰亚胺.应用FT-IR、1H-NMR、DSC、HSPM对液晶双马来酰亚胺的结构和液晶行为进行了表征.结果表明,这类液晶双马来酰亚胺具有较低的熔点,侧甲基的存在使得液晶双马来酰亚胺的熔点下降了39℃.由HSPM观察到所合成的液晶单体具有向列型液晶所具有的典型的纹影织构,呈现出较好的热致液晶行为,并且液晶织构可以通过端基的交联聚合反应固定在交联网络中.     

Synthesis and self-assembly of temperature and anion double responsive ionic liquid block copolymers

In this paper, double hydrophilic ionic liquid block copolymers (ILBCs), poly(N-isopropylacrylamide)-block-poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)] (PNIPAM-b-PMMPImB), were polymerized by two-step reversible addition-fragmentation chain transfer (RAFT) process. The?composition and molecular weight distributions of ILBCs were characterized using ¹HNMR and gel permeation chromatography (GPC). The self-assembly and temperature- and anion-responsive behaviors of ILBCs were investigated by UV-Vis spectroscopy, TEM and dynamic light scattering (DLS). With increasing the concentration of (CF₃SO₂)₂N^--, the micellization of self-assembling PNIPAM-b-PMMPImB was induced to form a core--shell structure containing the core with hydrophilic PMMPIm-(CF₃SO₂)₂N^-- surrounded by the shell of PNIPAM via the anion-responsive properties of ILBCs. However, upon temperature increasing, PNIPAM-b-PMMPImB formed the micelles composing of PNIPAM core and PMMPImB shell. The ionic liquid segment with strong hydrophilic property enhanced the hydrogen bonding interaction which expanded the temperature range of phase transition and increased the lower critical solution temperature (LCST) of the system. These results indicate that ILBCs prepared in this paper have excellent temperature and anion double responsive properties, and may be applied as a kind of potential environmental responsive polymer nanoparticles.     

Temperature and anion responsive self-assembly of ionic liquid block copolymers coating gold nanoparticles

In this paper, double hydrophilic ionic liquid block copolymers (ILBCs), poly poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)]-block-(N-isopropylacrylamide) (PMMPImB-b-PNIPAAm) was first synthesized by reversible addition-fragmentation chain transfer (RAFT) and then attached on the surface of gold nanoparticles (Au NPs) via a strong gold-sulfur bonding for preparing hybrid nanoparticles (PMMPImB-b-PNIPAAm-@-Au NPs). The hybrid NPs had a three layers micelle-like structure, including a gold core, thermo-responsive inner shell and anion responsive outer corona. The self-assembling behavior of thermal- and anion-response from shell and corona were respectively investigated by change of temperature and addition of (CF₃SO₂)₂N^-. The results showed the hybrid NPs retained a stable dispersion beyond the lower critical solution temperature (LCST) because of the space or electrostatic protecting by outer PMMPImB. However, with increasing concentration of (CF₃SO₂)₂N^-, the micellization of self-assembling PMMPImB-b-PNIPAAm-@-Au NPs was induced to form micellar structure containing the core with hydrophobic PMMPImB-(CF₃SO₂)₂N^- surrounded by composite shell of Au NPs-PNIPAAm via the anion-responsive properties of ILBCs. These results indicated that the block copolymers protected plasmonic nanoparticles remain self-assembling properties of block copolymers when phase transition from outer corona polymer.     

The effect of glass bead content on the mechanical properties of acrylonitrile/styrene/acrylate copolymer

The influence of glass bead content and the loading rate on the mechanical properties of polyacrylonitrile/styrene acrylate (ASA) copolymer was investigated. For this copolymer, tensile yield strength and work to fracture were significantly reduced as the bead content was increased. Tensile yield strength decreased linearly with increasing glass bead content according to the Leinder equation. It was found that the variation of tensile yield strength with log (loading rate) follows that of Eyring's equation for yielding. The presence of the weldline reduced the tensile yield strength of both unfilled and filled materials. Flexural modulus and flexural strength also varied in a predictable fashion with glass bead concentration. The increase in modulus with glass bead content followed Kerner's equation.Crack growth resistance values of the unfilled ASA and its composites were measured at three loading rates using the generalized locus method. It was found that the resistance to steady crack propagation,J _R, was a sensitive function of glass bead content and loading rate. Within the range of these experiments,J _R decreased with increasing glass bead content and loading rate.