PAN纤维在惰性气氛中的热行为研究

聚丙烯腈(PAN)纤维在惰性气氛中的热行为主要包括3个反应:热致收缩反应、环化反应和热解反应。通过差示扫描量热仪和热重分析仪研究了PAN纤维在惰性气氛中的热行为。结果表明,热致收缩和热解反应并无明显的吸放热现象,而环化反应放热剧烈且短促。环化反应过程中存在明显的传热过程,环化反应速率达到最大值时,温度随着升温速率的提高而上升。热解反应使得可发生环化反应的原料总量下降,且随着升温速率的提高,反应放热量下降。分别采用Ozawa法与Kissinger法计算了环化反应的表观活化能,并建立了修正后的动力学模型。该模型可以有效地描述不同升温速率条件下的反应过程。     

炭纤维原丝用丙烯腈/衣康酸单甲酯共聚物的制备及热性能

研究了单体浓度、配比对丙烯腈/衣康酸单甲酯共聚反应的影响,利用傅立叶红外(FT-IR)、差热扫描量热仪(DSC)、热重分析(TGA)对样品的结构与性能进行分析和表征。结果表明,单体质量百分含量的增大,聚合反应的转化率及分子量增大;衣康酸单甲酯比例的增加,聚合物的转化率及分子量下降;同时发现,衣康酸单甲酯的加入,使环化过程放热起始温度降低,放热峰明显加宽,有效改善了均聚丙烯腈环化过程放热集中的缺点,另外衣康酸单甲酯的加入,有效地提高了聚丙烯腈的热稳定性,这些均有利于聚丙烯腈原丝的预氧化。     

DSC法研究PAN纤维的低温热解特性

利用DSC法(差示扫描量热法)考察了三种PAN(聚丙烯腈)纤维在空气条件下热稳定化过程。实验结果表明:不同的样品其环化反应热效应各不相同,吉林丝呈现出两个放热峰,而榆次丝仅有一个放热峰。同时,随着样品本体羧基基团的引入,环化反应活化能下降,使其反应易于进行。而且,利用Sharp法和Ellerstein法对反应动力学参数进行了求解,其值较为接近。另外,还讨论了温速对其放热量的影响。     

超高分子量聚乙烯/石墨烯纳米复合材料的制备及其热性能的研究

为了提高超高分子量聚乙烯的热性能,本文通过溶液共混的方法利用氧化石墨烯改性不同分子量的超高分子量聚乙烯,然后利用红外测试(FTIR)、X射线衍射测试(XRD)、扫描电镜测试(SEM)、差热扫描量热分析仪(DSC)和热失重分析(TG)的方法对超高分子量聚乙烯/石墨烯纳米复合材料的结构、表面形态和性能进行了研究.通过分析测试表明氧化石墨烯在超高分子量聚乙烯/石墨烯纳米复合材料中的分散性良好,氧化石墨烯的添加量为0.3%时,石墨烯/超高分子量聚乙烯的复合材料的热稳定性等性能最好,与原材料相比提高了3℃.     

聚丙烯腈/膨胀石墨插层纳米复合材料静电纺丝性能

利用化学氧化和高温膨胀将天然鳞片石墨制备成膨胀石墨(EG),采用沉淀聚合制备聚丙烯腈/膨胀石墨(PAN/EG)插层复合物,进行静电纺丝,对PAN/EG插层复合物及其纤维膜的微观结构、力学性能和热性能进行分析表征。结果表明:EG含量增加,纤维膜的拉伸强度和耐热性增加,纤维直径减小,PAN的平均直径550nm;EG含量为0.5%(wt,质量分数,下同)时,纤维平均直径350nm,此时拉伸强度与PAN相比,在未处理、冷压和热处理的情况下分别提高了95.9%,129%和164%。EG为1%时,玻璃化温度提高了17℃,PAN在氮气中的环化反应放热峰值提高了7℃。     

聚丙烯腈原丝的预氧化过程研究

采用密度分析、红外吸收光谱(FT-IR)分析仪、广角X射线衍射(WXRD)仪、差示扫描量热(DSC)分析仪和扫描电子显微镜( SEM)等手段,系统地研究了聚丙烯腈(PAN)原丝预氧化过程中的结构变化.结果表明,在预氧化过程中,PAN原丝的密度和相对环化率均增加,结晶尺寸先变大后变小,结晶度降低,说明环化反应先主要在非晶...     

石墨烯改性聚丙烯腈基纳米炭纤维的制备及其性能

以氧化石墨为前驱体,采用真空热膨胀还原法获得了功能化的石墨烯材料。以石墨烯为纳米填料,采用静电纺丝法制备了一系列石墨烯改性聚丙烯腈(PAN)纳米复合纤维,经进一步预氧化和炭化得到纳米炭纤维。使用扫描电镜(SEM)、X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、元素分析(EA)、热重(TGA)和差示扫描量热仪(DSC)研究了石墨烯对纳米炭纤维的宏观性能与微观结构的影响。结果表明,加入石墨烯后,PAN纳米纤维中分子取向变大,结晶度下降。对氧化、环化和脱氢反应可产生一定的抑制作用,导致预氧化反应程度下降。同时,石墨烯可作为炭化阶段微晶生长的晶核,有利于碳网平面的快速生长。     

静电纺丝法制备聚丙烯腈基纳米炭纤维及其表面结构表征

通过稳定化、炭化静电纺制的聚丙烯腈(PAN)前驱体纤维制备了直径为100nm～300nm的纳米炭纤维.用扫描电镜(SEM)、场发射扫描电镜(FESEM)、扫描隧道显微镜(STM)及扫描量热分析法(DSC)研究了纳米炭纤维及其前驱体纤维的形貌及结构.结果表明:纳米炭纤维及其前驱体纤维的直径表现为对数正态分布.静电纺制纤维的环化放热峰移向低温,表明静电纺制纤维可在较低的温度下引发环化.由于静电纺制纤维的粗糙表面及在热处理过程中的收缩行为,在纳米炭纤维表面形成了长度为10nm宽度为5nm的凹坑.     

聚丙烯腈纳米纤维的辐射氧化及热性能变化

采用静电纺丝法制备出平均直径300nm左右的聚丙烯腈(PAN)纤维,利用γ射线在室温及空气气氛中对PAN纳米纤维进行辐照处理,吸收剂量50~500kGy。采用红外光谱仪、X射线光电子能谱仪、差示扫描量热仪及热失重分析仪研究了辐射氧化对PAN纳米纤维结构以及热性能的影响。结果表明,辐射氧化可直接在PAN纳米纤维分子链上引入含氧官能团,有利于预氧化过程中脱氢反应的发生。同时可在室温下引发PAN纳米纤维的部分环化反应生成-C=N-共轭结构,其含量随吸收剂量的增加而增加,可有效降低环化放热峰的强度并缓和放热行为。这些结果表明辐射氧化工艺在碳纳米纤维制造领域有很好的潜在应用价值。     

碳纤维原丝用二元丙烯腈聚合物的合成及性能

设计合成了双功能共聚单体3-羧基-3-丁烯酰胺(CBA),采用溶液聚合的方法制备丙烯腈二元共聚物作为碳纤维前驱体,详细研究了单体配比对聚合反应、聚合物结构和预氧化性的影响。结果表明,随着单体投料中CBA含量的增加,聚合物中CBA含量增加,而相对分子质量和转化率均逐渐降低;红外光谱和差示扫描量热分析表明CBA单体能够通过离子机理引发环化,使预氧化温度降低60℃以上,且随着CBA单体含量的增加,离子环化反应加强,放热速率降低,有利于避免集中放热,CBA可以明显改善聚丙烯腈(PAN)的预氧化性能,有利于制备高性能碳纤维。     

温度对堆叠双层石墨烯层间耦合的影响

将不同层数堆叠和化学气相沉积法（CVD）生长的石墨烯在室温下进行拉曼光谱表征分析其层间耦合状态,并分析了不同温度下堆叠和CVD生长的双层石墨烯温度对其层间耦合的影响。研究结果表明:室温下CVD生长双层石墨烯和堆叠双层石墨烯的层间耦合状态截然不同;在25～250 ℃范围内,层间没有耦合作用或存在弱耦合作用的堆叠双层石墨烯的G峰峰位温度系数小于存在电子耦合的CVD生长双层石墨烯;超过250 ℃后,堆叠双层石墨烯G峰峰位温度系数变为正值,层与层之间可能产生了耦合,性质发生改变;在25～400 ℃ 范围内两种材料的2D峰半峰宽和G峰/2D峰强度比变化趋势几乎相同,但堆叠双层石墨烯波动大,对温度更敏感。     

原位聚合尼龙11/石墨烯氧化物纳米复合材料的等温结晶和熔融行为

采用原位聚合法制备了尼龙11/石墨烯氧化物纳米复合材料,并利用差示扫描量热分析仪(DSC)研究了材料的等温结晶动力学和熔融行为。研究结果表明,Avrami方程能够较好地描述尼龙11及其纳米复合材料的等温结晶动力学;尼龙11结晶速率受晶体生长速率控制,而纳米复合材料的结晶速率在不同的结晶温度范围内分别受晶体生长速率或成核速率控制;与纯尼龙11相比较,复合材料具有较低的平衡熔点和表面折叠自由能。     

Preparation and properties of reduced graphene oxide/polyacrylonitrile nanocomposites using polyvinyl phenol

Nanocomposites of polyacrylonitrile (PAN) with reduced graphene oxide (rGO) were prepared using a solution mixing technique employing polyvinyl phenol (PVP) as a compatibilizer. The PVP can facilitate composite formation by interacting with both rGO and PAN via π-π and H-bonding respectively. Various amounts of rGO were used to prepare PAN nanocomposites. The cross-sectional morphology of the composite films shows a uniform dispersion of rGO sheets in the PAN matrix. The Fourier transform infrared (FT-IR) studies revealed that good interaction of the rGO/PVP hybrid with PAN. The wide angle x-ray diffraction (WAXS) study confirms that the rGO sheets were uniformely dispersed as individual sheets in the PAN matrix. Thermogravimetric analysis shows enhanced thermal stability of the composite compared to pure PAN. The tensile strength and elastic modulus of the nanocomposites increased with increasing rGO content. A 102% enhancement in tensile strength and a 62.9% enhancement in elastic modulus were observed in the nanocomposite with 5% rGO.     

Acrylonitrile-capped poly(propyleneimine) dendrimer curing agent for epoxy resins: Model-free isoconversional curing kinetics,thermal decomposition and mechanical properties

Acrylonitrile-modified aliphatic amine adducts are often used as curing agents for room-temperature epoxy formulations (coatings, adhesives, sealants, castings, etc.), yet the curing reaction and properties of resultant epoxy systems still remain less fundamentally understood. Herein we systematically investigate our newly-developed acrylonitrile-modified multifunctional polyamine curing agent for bisphenol A epoxy resin (DGEBA): an acrylonitrile-capped poly(propyleneimine) dendrimer (PAN4). The impact of the molecular structure of PAN4 and a controlled poly(propyleneimine) dendrimer (1.0GPPI) on the curing reactivity, reaction mechanisms, thermal stability, viscoelastic response and mechanical properties of the epoxy systems are highlighted. Differential scanning calorimetry (DSC) confirms DGEBA/PAN4 shows markedly lower reactivity and reaction exotherm than DGEBA/1.0GPPI, and the model-free isoconversional kinetic analysis reveals that DGEBA/PAN4 has the generally lower reaction activation energy. To be quantitative, the progress of the isothermal cure is predicted from the dynamic cure by using the Vyazovkin equation. The isothermal kinetic prediction shows that DGEBA/PAN4 requires about 10 times longer time to achieve the same conversion than DGEBA/1.0GPPI, which agrees with the experimentally observed much longer gel time of DGEBA/PAN4. Subsequently, dynamic mechanical analysis shows that PAN4 results in the cured epoxy network with the lower β- and glass-relaxation temperatures, crosslink density, relaxation activation energy, enthalpy, entropy, but the higher damping near room temperature than 1.0GPPI. Finally, thermogravimetric analysis (TGA) demonstrates cured DGEBA/PAN4 is thermally stable up to 200 °C, and mechanical property tests substantiate that PAN4 endows the cured epoxy with much higher impact and adhesion strengths than 1.0GPPI. Our data can provide a deeper insight into acrylonitrile-modified aliphatic amine curing agents from the two good model compounds (PAN4 and 1.0GPPI).     

Poly(lactic acid)/graphene nanocomposites prepared via solution blending using chloroform as a mutual solvent

Poly(lactic acid) (PLA)/graphene nanocomposites were prepared by direct solution blending of PLA with graphene using chloroform as a mutual solvent. Graphene was prepared by a solution-phase processing followed by thermal reduction, which can be dispersed stably in chloroform for more than one month. Transmission electron microscopy (TEM) was used to examine the quality of the dispersion of graphene in the PLA matrix. The thermal properties and crystallization behavior of the nanocomposites were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and polar optical microscopy (POM). The results showed that the thermal stability of PLA was significantly improved with a very low loading of graphene and the addition of graphene had a great effect on spherulite morphology of PLA.     

静电纺丝法制备PAN/Fe3O4磁性纳米纤维

采用化学共沉淀法制备纳米四氧化三铁,选用曲拉通X-100为分散剂,利用静电纺丝法制备PAN/Fe3O4磁性纳米复合材料。X射线衍射仪(XRD)验证了四氧化三铁在复合纳米纤维中的存在。同时使用扫描电镜(SEM)和透射电镜(TEM)对复合纳米纤维的微观形貌和Fe3O4在纤维中的分布进行了观察,利用热重(TGA)对纳米复合材料的热稳定性进行分析;通过磁性实验分析了纳米复合材料的磁性性能。结果表明,所制备PAN/Fe3O4磁性纳米纤维成型良好,且Fe3O4磁性颗粒在纤维中分散均匀,其与PAN是物理复合。纳米复合材料具有一定磁性,并可由磁性颗粒的加入量进行控制。     

多尺度功能性填料PVDF基纳米复合材料的制备和性能

先以两种直径(50 nm,100 nm)的羟基化钛酸钡(BT)和两种长度(10~20 nm,20~40 nm)的酸化多壁碳纳米管(MWCNTs)为功能填料,进行液相反应制备四种BT/MWCNTs杂化纳米填料(分别记为BT-A/MWCNTs-B,其中A=5,10;B=1,2),再用熔融共混-压板成型技术分别将其与PVDF复合制备出BT-A/MWCNTs-B/PVDF纳米复合材料。使用X射线衍射(XRD)、红外光谱(FTIR)、差示扫描量热分析(DSC)、扫描电子显微镜(SEM)、拉伸性能测试和介电性能测试系统研究了多尺度功能性填料BT-A/MWCNTs-B对这种纳米复合材料的组织结构和结晶性能、介电性能和力学性能的影响。结果表明,与BT/PVDF和MWCNTs/PVDF体系相比,BT-A/MWCNTs-B/PVDF纳米复合材料具有更高的结晶度和热性能,BT-10的含量(质量分数,下同)为16%、MWCNTs-2的含量为5%的BT-10/MWCNTs-2/PVDF纳米复合材料其熔融温度可达173.8℃,比纯PVDF(159.6℃)提高了14.2℃,其结晶度可达43.1%。三相BT-A/MWCNTs-B/PVDF纳米复合材料比两相纳米复合材料具有更优异的介电性能,BT-10/MWCNTs-2/PVDF纳米复合材料100Hz下的介电常数为119,为纯PVDF的14倍,其介电损耗只有0.051。BT-10/MWCNTs-2/PVDF纳米复合材料的拉伸强度和弹性模量分别达到57.7 MPa和1226 MPa。     

Graphene–Ruthenium(II) Complex Composites for Sensitive ECL Immunosensors

Non‐covalent modi?cation method has been proven as an effective strategy for enhancing the chemical properties of graphene while the structure and electronic properties of graphene can be retained. This work describes a novel strategy to fabricate a solid‐state electrochemiluminescent (ECL) immunosensor based on ruthenium(II) complex/3,4,9,10‐perylenetetracarboxylic acid (PTCA)/graphene nanocomposites (Ru‐PTCA/G) for sensitive detection of α‐fetoprotein (AFP). It is found that immobilization of PTCA and reduction of GO can be simultaneously achieved in one‐pot synthesis method under alkaline condition and moderate temperature, forming PTCA/G nanocomposites. Further covalent attachment of ruthenium(II) complex to the PTCA assembled on graphene sheets produces the functional Ru‐PTCA/G nanocomposites which show good electrochemical activity and ca. 21 times higher luminescence quantum efficiency than the adsorbed derivative ruthenium(II) complex. The Ru‐PTCA/G nanocomposites based solid‐state ECL sensor exhibits high stability toward the determination of tripropylamine (TPA) coreactant. In addition, a new ECL immunosensor based on steric hindrance effect is fabricated by cross‐linking α‐fetoprotein antibody (anti‐AFP) with chitosan covered on Ru‐PTCA/G composites modi?ed electrode for detection of cancer biomarker AFP. This ECL immunosensor shows an extremely sensitive response to AFP in a linear range of 5 pg·mL^‐1–10 ng·mL^‐1 with a detection limit of 0.2 pg·mL^‐1. The present approach is effective for various molecules immobilization and may become a promising technique for biomolecular detection.     

衣康酸铵改性对聚丙烯腈热性能的影响

在二甲基亚砜溶液体系中,制备了丙烯腈一衣康酸铵共聚树脂。用差示扫描量热和热失重一质谱仪分析了衣康酸铵对聚丙烯腈预氧化稳定化放热曲线和炭化裂解过程的影响。衣康酸铵有效地降低了树脂的预氧化放热峰起始温度和放热量,拓宽放热峰,提高了炭化收率;衣康酸铵含量从0．2％增至1．0％时,炭化收率逐渐增大;含1．0％衣康酸铵的共聚PAN与均聚PAN相比,炭化过程中部分主要挥发性产物的释放量减小。     

聚碳酸亚丙酯/凹凸棒纳米复合材料制备与热稳定性研究

通过溶液共混法制备了聚碳酸亚丙酯/凹凸棒纳米复合材料。利用FT-IR、XRD和SEM表征手段研究了复合材料的结构。研究表明有机改性的凹凸棒在聚碳酸亚丙酯中分散均匀,平均粒径为70nm。利用TG研究了聚碳酸亚丙酯/凹凸棒纳米复合材料的热稳定性,结果发现纳米尺寸凹凸棒的引入能够显著提高聚碳酸亚丙酯的热稳定性,其中凹凸棒含量为0.5%的复合材料热稳定性最好,其5%、50%和最大热分解温度分别为273℃、291℃和289℃,相比PPC分别提高了63℃、53℃和52℃。