PP/碳纳米管复合材料的结晶动力学研究

采用原子转移自由基(ATRP)活性聚合方法在多壁碳纳米管(MWNT)表面接枝丙烯酸丁酯聚合物(PBA),并以接枝聚合物MWNT-PBA对聚丙烯(PP)进行改性。红外光谱(FT-IR)及透射电子显微镜(TEM)测试结果表明,采用ATRP法成功地将PBA接枝到MWNT表面上。利用差示扫描量热仪(DSC)对PP/MWNT复合材料的非等温结晶动力学进行了研究。结果表明,PP/MWNT复合材料中由于MWNT的加入明显地提高了复合材料的结晶温度和结晶速率,并降低了结晶活化能。MWNT-PBA和MWNT-COOH(酸化MWNT)加入PP都有异相成核的作用,而MWNT-PBA比MWNT-COOH的作用更加明显。     

PVC/碳纳米管复合材料的制备

采用原子转移自由基聚合(ATRP)在多壁碳纳米管(MWNTs)表面接枝聚丙烯酸丁酯(PBA)得到MWNTs-PBA,并以此对聚氯乙烯(PVC)改性,采用熔融共混法制备了PVC/MWNTs-PBA复合材料。傅里叶变换红外光谱分析及透射电子显微镜观察结果表明:采用ATRP法成功地将PBA接枝到MWNTs的表面。接枝了聚合物的碳纳米管可以提高复合材料的结晶温度(5 oC左右)、耐热温度(20 oC左右);复合材料的流变性能、导电性能也同时得以提高。     

纳米CaCO_3的接枝改性及其填充PVC复合材料的性能

采用表面原位接枝聚合在纳米CaCO3颗粒表面引入聚甲基丙烯酸甲酯(PMMA)或聚丙烯酸丁酯(PBA),用共混法制备了纳米CaC03/PVC复合材料,研究了不同界面特性时纳米CaCO,/PVC复合材料的力学性能.研究结果表明:通过表面原位接枝聚合反应可以在纳米CaCO3颗粒表面接枝PMMA和PBA;表面接枝聚合改性大大促进了纳米CaCO3粒子在PVC基体中的分散行为,增加了复合材料的拉伸强度以及与聚合物的界面粘接强度,但复合材料的冲击强度有所下降.     

纳米二氧化硅颗粒表面设计及其填充聚氯乙烯复合材料的性能

利用表面原位接枝聚合在纳米二氧化硅颗粒表面引入聚甲基丙烯酸甲酯(PMMA)高分子链段,用共混法制备了nano-SiO2/PVC复合材料,研究了不同界面特性时SiO2/PVC复合材料的力学性能.研究结果表明通过表面原位接枝聚合反应可以在纳米二氧化硅颗粒表面接枝聚甲基丙烯酸甲酯;表面接枝PMMA的nano-SiO2/PVC复合材料在力学和加工性能等方面都优于偶联剂处理和表面未处理样品.在纳米二氧化硅颗粒填充量为0%～8%(wt)时,复合材料的拉伸强度和冲击强度随着填充量的提高先上升后下降,并在4%～6%(wt)达到最大值.经PMMA表面接枝后SiO2/PVC具有更强的界面作用,偶联剂KH570处理的次之,表面未处理样品的最差.     

PBT/碳纳米管复合材料结构与性能研究

采用原子转移自由基聚合（ATRP）活性聚合方法在多壁碳纳米管（MWCNT）表面接枝聚苯乙烯（PS）,用FTIR和TEM对多壁碳纳米管进行了表征。采用熔融共混法制备了PBT／MWCNT复合材料,对其力学性能和结晶行为进行了研究。结果表明：接枝聚合物的碳纳米管提高了复合材料的拉伸强度和弯曲强度,提高了PBT的结晶温度。     

PVC塑料复合材料的热性能和电导率的研究

实验测定了聚氯乙烯-多壁碳纳米管(PVC/MWNT)复合材料在直流、交流条件下的热性能和电导率。采用热压缩法制备了PVC/MWNT复合材料,实验结果显示:材料存在超低渗透阈值(φc)0.045%。电导率对温度的依赖关系表明,在PVC/MWNT复合材料中,离子电导率低于φc,而复合材料中沿MWNT相的电荷输运的电子类型高于(φc)。热力学分析表明,在聚合物基体的体积内形成了一个刚性的填充网络,限制了聚合物向塑性状态的转变。     

新型PVC/细沙复合材料的制备及性能研究

以细沙为填料,采用熔融共混法制备PVC/细沙复合材料。研究了细沙预处理、细沙表面改性,以及细沙与PVC的质量比对PVC/细沙复合材料的力学性能和耐热性的影响。结果表明:PVC/细沙复合材料的维卡软化点为100.4℃,冲击强度为21.75kJ/m2,拉伸强度为308.5 MPa,细沙填料提高了PVC的热分解温度。     

马来酸丁酯接枝聚氯乙烯的工艺与性能

以马来酸酐接枝聚氯乙烯(PVC-g-MAH)为原料,采用正丁醇(NBA)对其进行酯化反应,制备了内增塑剂马来酸丁酯接枝聚氯乙烯(PVC-g-DBM),并通过熔融共混法制备了PVC/PVC-g-DBM复合材料;探究了酯化反应的工艺条件,并对PVC/PVC-g-DBM复合材料的性能进行了对比分析。结果表明,DBM对PVC起内增塑作用,当醇(NBA)酸(MAH)摩尔比为2.15,催化剂、脱水剂的加入量分别为MAH的3%(质量分数,下同),反应时间为4h时,产物酯化率可达91.07%;与未添加PVC-g-DBM的PVC复合材料相比,PVC/PVC-g-DBM复合材料热稳定性、耐低温性能、耐迁移性能明显提高,同时加工性能和力学性能也有所改善。     

熔融接枝改性PVC树脂的研究

采用熔融接枝法制备了接枝聚氯乙烯(PVC)材料,研究了引发剂DCP、接枝单体MMA对PVC接枝物力学性能、耐热性、硬度及微观形态结构的影响。结果表明:接枝改性后PVC材料的力学性能、硬度均有所提高,具有较稳定的耐热性。在引发剂DCP用量为0.9%、接枝单体MMA用量为9%时,材料的综合性能达到最佳。     

ATRP法制备PVDF-g-PS共聚物及其表征

采用ATRP法制备了聚偏氟乙烯(PVDF)接枝苯乙烯共聚物(PVDF-g-PS),对产物的结构与性能进行了表征。结果表明:随着接枝率的提高,接枝共聚物的熔点和熔融焓下降,且PVDF在接枝后表面由光滑转变为凹凸不平的形貌。     

有机高分子化的无机微粒对PVC的填充改性

研究了微细SiO2胶囊化的复合无机粒子与聚氯乙烯共混的复合材料的力学性能的变化规律。结果表明：SiO2/HPMC-PMMA(SiO2经SDS预处理）和HPMC－g-PMMA使材料力学性能下降，而SiO2/HPMC-PMMA（未经SDS处理）使材料的力学性能有所提高。经柔性设计后的SiO2/HPMC-PBA/PMMA使材料的冲击强度提高幅度更大。SEM提供的证据也进一步证明了这一结论。     

ARGET ATRP法合成聚氯乙烯接枝丙烯酸丁酯共聚物

以不稳定氯含量高的聚氯乙烯（U-PVC）和氯乙烯-溴代异丁酸烯丙酯共聚物（PVC-co-ABrMP）为大分子引发剂,使用电子转移催化再生原子转移自由基聚合（ARGET ATRP）进行丙烯酸丁酯（BA）的溶液接枝共聚。在固定CuCl₂：三（2-吡啶甲基）胺：辛酸亚锡（摩尔比）时,当CuCl₂用量（相对于氯乙烯链节数）小于0.1%时,BA转化率随CuCl₂用量增加而明显增加;辛酸亚锡与CuCl₂摩尔比大于50时,辛酸亚锡用量对聚合速率的影响较小;相同催化体系用量下,采用PVC-co-ABrMP为引发剂,可获得更高的BA转化率。通过PVC-co-ABrMP酯基水解得到PBA支链,其分子量分布指数为1.29,符合“活性”自由基聚合的特征。接枝PBA对PVC有明显的内增塑效果,PBA摩尔分数为32.75%的PVC-g-BA的玻璃化温度为8.34℃。     

High electrical conductivity of nylon 6 composites obtained with hybrid multiwalled carbon nanotube/carbon fiber fillers

The synergetic effect of multiwalled carbon nanotubes (MWNTs) and carbon fibers (CFs) in enhancing the electrical conductivity of nylon 6 (PA6) composites was investigated. To improve the compatibility between the fillers and the PA6 resin, we grafted γ‐aminopropyltriethoxy silane (KH‐550) onto the MWNTs and CFs after carboxyl groups were generated on their surface by chemical oxidation with nitric acid. Fourier transform infrared spectroscopy and thermogravimetric analysis proved that the KH‐550 molecules were successfully grafted onto the surface of the MWNTs and CFs. Scanning electron microscopy and optical microscopy showed that the obtained modified fillers reduced the aggregation of fillers and resulted in better dispersion and interfacial compatibility. We found that the electrical percolation threshold of the MWNT/PA6 and CF/PA6 composites occurred when the volume fraction of the fillers were 4 and 5%, respectively. The MWNT/CF hybrid‐filler system exhibited a remarkable synergetic effect on the electrically conductive networks. The MWNT/7% CF hybrid‐filler system appeared to show a second percolation when the MWNT volume fraction was above 4% and a volume resistivity reduction of two orders of magnitude compared with the MWNT/PA6 system. The mechanical properties of different types of PA6 composites with variation in the filler volume content were also studied. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40923.     

Enhancement of PVC/ENR blend properties by poly(methyl acrylate) grafted oil palm empty fruit bunch fiber

Effect of oil palm empty fruit bunch (OPEFB) fiber and poly(methyl acrylate) grafted OPEFB on several mechanical properties of poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends were studied. The composites were prepared by mixing the fiber and the PVC/ENR blends using HAKEE Rheomixer at the rotor speed of 50 rpm, mixing temperature 150°C, and mixing period of 20 min. The fiber loadings were varied from 0 to 30% and the effect of fiber content in the composites on their ultimate tensile strength (UTS), Young's modulus, elongation at break, flexural modulus, hardness, and impact strength were determined. An increasing trend was observed in the Young's modulus, flexural modulus, and hardness with the addition of grafted and ungrafted fiber to the PVC/ENR blends. However the impact strength, UTS, and elongation at break of the composites were found to decrease with the increase in fiber loading. An increase in elongation at break and UTS and decrease in the flexural and Young's modulus was observed with the addition of PMA‐g‐OPEFB fiber compared to ungrafted fiber. This observation indicates that grafting of PMA onto OPEFB impart some flexibility to the blend. The morphology of cryogenically fractured and tensile fracture surfaces of the composites, examined by a scanning electron microscope shows that the adhesion between the fiber and the matrix is improved upon grafting of the OPEFB fiber. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Incorporation of 4‐aminobenzene functionalized multi‐walled carbon nanotubes in polyaniline for application in formic acid electrooxidation

Incorporation of carbon nanotubes (CNTs) in conducting polymer can lead to new composites with enhanced electrical and mechanical properties. However, the development of such composites has been hampered by the inability to disperse CNTs in polymer matrix due to the lack of chemical compatibility between polymers and CNTs. Covalent sidewall functionalization of carbon nanotube provides a feasible route to incorporate carbon nanotube in polymer. In this work, 4‐aminobenzene groups were grafted onto the surface of multi‐walled carbon nanotube (MWNT) via C? C covalent bond. Polyaniline (PANI)/MWNT composites were fabricated by electrochemical polymerization of aniline containing well‐dissolved functionalized MWNTs. The obtained composites can be used as catalyst supports for electrooxidation of formic acid. Cyclic voltammogram results show that platinum particles deposited in PANI/MWNT composite films exhibit higher electrocatalytic activity and better long‐term stability towards formic acid oxidation than that deposited in pure PANI films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polyelectrolyte-functionalized multiwalled carbon nanotubes: preparation, characterization and layer-by-layer self-assembly

Two kinds of polyelectrolyte: polyacrylic acid (PAA) and poly(sodium 4-styrenesulfonate) (PSS), were grafted onto the convex surfaces of multiwalled carbon nanotubes (MWNTs) by surface-initiating ATRP (atom transfer radical polymerization) from the initiating sites previously anchored onto the convex surfaces of MWNTs. The grafted polyelectrolyte can be efficiently quantified by the feed ratio of monomer to MWNT-based macroinitiator, and the maximum amount of grafted polymer is higher than 55 wt%. The polyelectrolyte-coated MWNTs resembled core-shell structures justified by the TEM images of the samples obtained, which provided direct evidence for the covalent modification of MWNT. FTIR, ¹H NMR and TGA were used to determine the chemical structure of the resulting products. Comparison of UV-Vis spectra demonstrated that the products were water-soluble, and that PSS was more effective for improving the water solubility of carbon nanotubes. Using the polyelectrolyte- and carboxylic acid-functionalized MWNTs as templates, and poly(2-(N,N-dimethylaminoethyl) methacrylate (PDMAEMA)/hyperbranched polysulfone amine (HPSA) and PSS as polycation and polyanion, respectively, layer-by-layer (LbL) electrostatic self-assembly was conducted in order to explore the application of the functionalized nanotubes. It was found that the functionalized MWNTs have a high efficiency for loading polyelectrolytes by the LbL approach (the adsorbed polymer quantity is higher than 10 wt% in one assembling step). TEM observations showed that the assembled polymer shell on the MWNT surfaces was very even and flat.     

Dynamic mechanical,rheological, and morphological studies of polyacrylate-graft-poly (vinyl chloride) suspension resin

A series of polyacrylate-graft-poly (vinyl chloride) (ACR-g-PVC) resins were prepared through suspension graft copolymerization. Three kinds of polyacrylate latices were grafted by vinyl chloride using suspension polymerization method at 57 ± 0.1°C, respectively. The dynamic mechanical and rheological properties and the morphology of the resulting ACR-g-PVC resins were investigated. Poly (butyl acrylate)-graft-poly (vinyl chloride) (PBA-g-PVC) resin exhibited better toughness, and the optimized content of PBA in ACR-g-PVC resin was 6–8 wt%. The melt viscosity of ACR-g-PVC resin was much lower than that of pure PVC. The nature of the fracture surfaces of ACR-g-PVC material indicated that it has good toughness. The impact strength of the PBA-g-PVC material was greatly improved compared with that of pure PVC. The Young's modulus of the ACR-g-PVC material containing less than 15 wt% of PBA was comparable to that of pure PVC according to their dynamic mechanical analysis curves. For all of the ACR-g-PVC resins, there were two individual relaxations in the low-temperature range. One was β transition of PVC, and the other was α transition of ACR. The glass transition temperature of PVC in the ACR-g-PVC resin shifted to lower temperature when the content of the PBA was above 50 wt%. POLYM. ENG. SCI., 47:996–1003, 2007. © 2007 Society of Plastics Engineers