Electrical,Thermal, and Mechanical Characterization of Poly(propylene)/Carbon Nanotube/Clay Hybrid Composite Materials

A set of hybrid composite materials based on a PP matrix with multiwalled CNTs and clay particles is prepared and characterized. The incorporation of clay particles into a percolated composite with 3 wt% CNT disrupts the percolation, decreasing dramatically the electrical conductivity. As expected for layered fillers, PP/CNT/clay hybrid composite materials and PP/clay composites display increases as high as 100 °C in the temperature for the maximum rate of weight loss. Surprisingly, these temperatures are just slightly higher than those of PP/CNT composites. PP/CNT composites display viscosities that are considerably lower than those of PP/clay composites. A synergistic effect of both fillers is observed in the viscoelastic response of PP/CNT/clay materials.

     

原位聚合法制备聚对苯二甲酸丙二醇酯／蒙脱土复合材料及其表征

采用原位聚合法制备了聚对苯二甲酸丙二醇酯(PTT)像脱土(MMT)复合材料。X射线衍射和透射电子显微镜扫描结果表明所得复合材料为剥离型或部分剥离型结构。与纯PTT、相比，由于MMT、在PTT基体中达到纳米尺寸分散，PTT／MMT复合材料的热稳定性能、结晶性能和拉伸性能都得到了明显提高。     

Multiwalled carbon nanotube/polyacrylonitrile composite fibers prepared by in situ polymerization

Multi‐walled carbon nanotubes (CNTs) were mixed with polyacrylonitrile (PAN) by in situ polymerization or by mechanically mixing. The mixtures were then wet‐spun into fibers, respectively. The effects of mixing method on the interfacial bonding between the components in the fibers and the properties of the fiber were investigated by Raman spectroscopy, TEM, SEM, and tensile strength testing. By in situ polymerization mixing, a thin layer of PAN molecules is observed to cover the surface of the CNT, which increases the diameter of CNT evidently. Results of Raman spectroscopy indicate that the layer of PAN molecules are strongly attached onto the surface of CNT through grafting polymerization, leading to strong chemical bonding between CNTs and PAN matrix in the obtained fibers. In contrast, no obvious chemical interactions are observed between them in the fibers prepared by mechanically mixing. In both cases, the CNTs have significantly strengthened the PAN fibers. However, the fibers prepared from in situ polymerization mixing are much stronger because of the interfacial bonding effect between the PAN molecules and CNTs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of New PI/MWCNT Containing Sulfone Groups via In Situ Polymerization: Study on Thermal,Electrical, and Optical Properties

New series of polyimide (PI) nanocomposites reinforced with three different amounts of multiwalled carbon nanotubes (MWCNT; 0.5, 1, and 3 wt%) were prepared by casting, evaporation and thermal imidization. Homogeneous dispersion of MWCNT in PI matrix was investigated by transmission electron microscopy. The effects of MWCNT on the thermal properties of the PI were investigated by thermogravimetric analysis. The results showed that the thermal stability of the nanocomposites enhanced with the increasing MWCNTs content. The resultant PI/MWCNT nanocomposites were electrically conductive with significant conductivity enhancement at 3 wt% MWCNT, which is favorable for many practical uses.     

Mechanical,Thermal, and Electrical Properties of Epoxy Matrix Composites Reinforced With Polyamide-Grafted-MWCNT/poly(azo-pyridine-benzophenone-imide)/Polyaniline Nanofibers

Friedel-Crafts acylation and in situ polymerization were adopted to graft polyamide on multi-walled carbon nanotube (MWCNT) surface to form MWCNT-PA using γ-Phenyl-?-caprolactone. Via electrospinning, MWCNT-PA/PAPBI and MWCNT-PA/PAPBI/PANI nanofibers were prepared using MWCNT-PA, poly(azo-pyridine-benzophenone-imide) (PAPBI) and polyaniline (PANI) and DGEBA as matrix. Compared with 3 wt% MWCNT-PA/PAPBI nanofibers (20.2 GPa), tensile modulus for film reinforced with 3 wt% MWCNT-PA/PAPBI/PANI nanofibers (27.6 GPa) was considerably increased. Thermal stability of MWCNT-PA/PAPBI/PANI nanofibers reinforced epoxy was higher with T₁₀ 633–654°C and T_g 283–291°C relative to DGEBAMWCNT-PA/PAPBI system. The filler loading also increased the electrical conductivity of DGEBA/MWCNT-PA/PAPBI/PANI from 3.44 to 6.01 S cm^?1.     

原位聚合聚氯乙烯树脂的合成及性能

研究了氯乙烯悬浮聚合时添加氯化聚乙烯(CPE)冲击改性剂、CaCO3填料、润滑剂及热稳定剂对聚合反应的影响，并对得到的可直接加工的原位聚合聚氯乙烯(RTUPVC)树脂的性能进行了表征。结果发现：CPE和CaCO3的加入均使达到相同压降的聚合时间缩短，氯乙烯聚合转化率相应减小；RTUPVC树脂的粒径随CPE粒径和用量的增大而增大，而CaCO3含量对RTUPVC树脂粒径影响不大；润滑剂和热稳定剂的加入，对聚合反应起延缓作用，但对RTUPVC树脂粒径影响不大；RTUPVC树脂加工塑化时间随CPE含量的增加而减少；相同CPE用量时，RTUPVC树脂的冲击强度和拉伸强度明显高于PVC/CPE共混物。     

Green Synthesis of Salicylic Acid-Based Poly(amide-imide) in Ionic Liquid and Composite Formation with Multiwalled Carbon Nanotube

A new salicylic acid-containing diacid monomer was synthesized by an established synthetic procedure from readily available reagents. The obtained diacid was used in the preparation of a thermally stable poly(amide-imide) by direct polycondensation with 4,4′-diphenylmethanediamine using 1,3-diisopropylimidazolium bromide ionic liquid as a green medium. The prepared polymer was used as matrix for preparation of multiwalled carbon nanotube/poly(amide-imide) composites in three multiwalled carbon nanotube concentrations (5, 10, and 15?wt%). The products were characterized for assessing the spectroscopic, thermal, and morphological properties by several methods. A homogeneous dispersion of multiwalled carbon nanotubes in the poly(amide-imide) matrix was observed by microscopy techniques.     

聚氯乙烯/埃洛石纳米管复合材料的制备与性能研究

通过熔融混炼法制备了聚氯乙烯（PVC）/埃洛石纳米管（HNTs）复合材料,通过力学性能测试和扫描电子显微镜、透射电子显微镜等方法研究了HNTs含量对复合材料形貌与性能的影响,并分析了HNTs的作用机理。结果表明,HNTs可以对PVC产生增强增韧的作用;PVC/HNTs复合材料的储能模量和玻璃化转变温度相对纯PVC均有所增加;不同含量的HNTs在PVC基体中的分散性均较好且无大面积团聚的现象;HNTs与PVC间具有较强的界面作用力,其界面作用半经验参数（B）值为4.35。     

聚甲基丙烯酸甲酯／纳米SiO2复合粒子的制备与表征

采用甲基丙烯酸-3-甲氧基硅丙酯（MPs）对分散于甲基丙烯酸甲酯（MMA）中的纳米SiO2粒子进行偶联改性，得到了表面改性的纳米SiO2单体分散液，用原位悬浮聚合方法制备了不同SiO2含量的PMMA／纳米SiO2复合粒子。通过红外光谱、透射电镜、差示扫描量热分析和热重分析等方法对制备的纳米复合粒子进行了表征，结果表明，纳米SiO2粒子在PMMA中分散良好；MMA可通过与MPS的共聚而有效地接枝到SiO2粒子表面，当SiO2含量为6．6％（质量分数，下同）、MPS用量为0．06g／gSiO2时，其接枝率可达73．8％；同时，纳米SiO2的引入可提高PMMA的耐热性能，当Si02含量为14.7％时，其玻璃化转变温度和最大热分解速率时的温度分别提高了11．8℃和18．8℃。     

聚乙烯咔唑共价修饰多壁碳纳米管的合成与表征

利用PVK-NH2和酰氯化的多壁碳纳米管(MWNTs)之间的酰胺化反应制备了聚乙烯咔唑共价接枝的碳纳米管杂化材料MWNT-PVK。该材料在许多常见的有机溶剂中具有良好的溶解度。在514.5nm激光的激发下,观察到的D-带和G-带强度比(ID/IG)分别从MWNTs的0.96增加到MWNT-COOH的1.05再增加到MWNT-PVK的1.19,这意味着羧基和PVK分别共价接枝到MWNTs的表面。PVK在MWNTs上的共价接枝导致了PVK的荧光强度大幅度下降,这种荧光淬灭现象,说明了在材料体系中处于激发单重态的MWNTs与给电子的PVK之间可能发生了电荷转移现象。     

磺化聚醚醚酮/接枝多壁碳纳米管复合膜的制备与表征

以浓硫酸为磺化剂,室温下制备了磺化聚醚醚酮(SPEEK)。以N,N-二环己基碳酰亚胺(DCC)为催化剂,将对氨基苯磺酸接枝到多壁碳纳米管(MWCNTs)的表面。采用溶液共混法制备了SPEEK/g-MWCNTs复合膜。采用傅里叶变换红外光谱仪(FT-IR)分析了复合膜的化学结构,采用光学显微镜以及扫描电子显微镜(FESEM)观察了膜的表面和断面结构,并采用交流阻抗法考察了膜的质子传导性能。结果表明:碳纳米管在复合膜中分散均匀,树脂基体包覆在碳管表面,复合膜的质子传导性和拉伸强度均优于磺化聚醚醚酮纯膜。     

A Novel Approach for Preparation of Nano-gold Particles/Carbon Nanotube Composites from Gold Film,Poly(ferrocenylsilane) and Acetylene

A novel approach for preparing nano-gold particles/carbon nanotube composites from gold film, poly(ferrocenylsilane) and acetylene has been developed. The morphologies of resultant nano-gold particles/carbon nanotube composites were examined. This paper is submitted to Journal of Inorganic and Organometallic Polymers and Materials to honor Professor Dr. Ian Manners.     

In situ polymerization and photophysical properties of poly(p‐phenylene benzobisoxazole)/multiwalled carbon nanotubes composites

Poly(p‐phenylene benzobisoxazole)/multiwalled carbon nanotubes (PBO‐MWCNT) composites with different MWCNT compositions were prepared through in situ polymerization of PBO in the presence of carboxylated MWCNTs. The nanocomposite's structure, thermal and photophysical properties were investigated and compared with their blend counterparts (PBO/MWCNT) using Fourier transform infrared spectra, Raman spectra, Wide‐angle X‐ray diffraction, thermogravimetric analysis, UV‐vis absorption, and photoluminescence. The results showed that MWCNTs had a strong interaction with PBO through covalent bonding. The incorporation of MWCNTs increased the distance between two neighboring PBO chains and also improved the thermal resistance of PBO. The investigation of UV‐vis absorption and fluorescence emission spectra exhibited that in situ PBO‐MWCNT composites had a stronger absorbance and obvious trend of red‐shift compared with blend PBO/MWCNT composites for all compositions. This behavior can be attributed to the efficient energy transfer through forming conjugated bonding interactions in the PBO‐MWCNT composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A Novel Carbon Dots/Thermo-Sensitive In Situ Gel for a Composite Ocular Drug Delivery System: Characterization,Ex-Vivo Imaging,and In Vivo Evaluation

We developed a potential composite ocular drug delivery system for the topical administration of diclofenac sodium (DS). The novel carbon dot CD_C-HP was synthesized by the pyrolysis of hyaluronic acid and carboxymethyl chitosan through a one-step hydrothermal method and then embedded in a thermosensitive in situ gel of poloxamer 407 and poloxamer 188 through swelling loading. The physicochemical characteristics of these carbon dots were investigated. The results of the in vitro release test showed that this composite ocular drug delivery system (DS-CD_C-HP-Gel) exhibited sustained release for 12 h. The study of the ex vivo fluorescence distribution in ocular tissues showed that it could be used for bioimaging and tracing in ocular tissues and prolong precorneal retention. Elimination profiles in tears corresponded to the study of ex vivo fluorescence imaging. The area under the curve of DS in the aqueous humor in the DS-CD_C-HP-Gel group was 3.45-fold that in the DS eye drops group, indicating a longer precorneal retention time. DS-CD_C-HP with a positive charge and combined with a thermosensitive in situ gel might strengthen adherence to the corneal surface and prolong the ocular surface retention time to improve the bioavailability. This composite ocular delivery system possesses potential applications in ocular imaging and drug delivery.     

Impact,Thermal, and Morphological Properties of Poly(Lactic Acid)/Poly(Methyl Methacrylate)/Halloysite Nanotube Nanocomposites

Poly(lactic acid)/poly(methyl methacrylate) blends containing halloysite nanotube (2 and 5 phr) and epoxidized natural rubber (5–15 phr) were prepared by melt mixing. The impact strength of poly(lactic acid)/poly(methyl methacrylate) blend was slightly improved by the addition of halloysite nanotube. Adding epoxidized natural rubber further increased the impact strength of poly(lactic acid)/poly(methyl methacrylate)/halloysite nanotube nanocomposite. Single T_g of poly(lactic acid)/poly(methyl methacrylate) is observed and this indicates that poly(lactic acid)/poly(methyl methacrylate) blend is miscible. The addition of halloysite nanotube into poly(lactic acid)/poly(methyl methacrylate) slightly increased the T_g of the blends. The epoxidized natural rubber could encapsulate some of the halloysite nanotube and prevent the halloysite nanotube from breaking into shorter length tube during the melt shearing process.     

Recyclability of In Situ Microfibrillar Poly(ethylene terephthalate)/High‐Density Polyethylene Blends

Repetitive processing was employed to assess the recyclability of in situ microfibrillar poly(ethylene terephthalate) (PET)/high‐density polyethylene (HDPE) blends which were fabricated through a “rectangular slit die extrusion–hot stretching–quenching” process. For comparison, the conventional PET/HDPE blends were also obtained using the same processing operation but without hot stretching. The morphological observation indicated that slit die extrusion and hot stretching successfully made the dispersed PET phase deform in situ into well‐defined microfibrils. The average diameter of the microfibrils increased with the processing cycles. The rheological properties obtained from the parallel‐plate dynamic rheometer suggested that the microfibrillar blends have higher viscosity and viscoelastic moduli (storage and loss moduli) as well as better flow stability than the conventional PET/HDPE blend. More importantly, with the increase in the processing cycles, an increase in yield strength and unchanged tensile modulus were observed for in situ microfibrillar blends, while a decrease in these properties for conventional blend, indicating that the in situ microfibrillar PET/HDPE blends have promising recycling potential.

     

Study on Thermal Properties and Crystallization Behavior of Blends of Poly(phenylene sulfide)/Poly(ether imide)

The thermal behavior of poly(phenylene sulfide) (PPS) blends with poly(ether imide) (PEI) was studied by differential scanning calorimeter (DSC). The crystallization temperature of PPS in blends shifted from 216.8°C to 226.4°C upon addition of 20–70% PEI contents. The heat of crystallization remained unchanged with less than 50% PEI in blends, whereas the heat of fusion decreased with increasing PEI content. The isothermal crystallization indicated that incorporating PEI would accelerate the crystallization rate of PPS. The activation energy of crystallization increased with addition of PEI. The equilibrium melting point of PPS/PEI blends was not changed with compositions.     

Electromagnetic Interference Shielding Foams Based on Poly(vinylidene fluoride)/Carbon Nanotubes Composite

Polymeric electromagnetic interference (EMI) shielding foaming materials are found and applied in many frontier fields such as aerospace, transportation, and portable electronics. In this paper, a foam based on a composite system of poly(vinylidene fluoride) (PVDF) filled with carbon nanotubes (CNTs) is prepared for EMI shielding properties by using a solid-state supercritical CO₂ foaming strategy. PVDF is chosen as the matrix because of its excellent chemical resistance, thermal stability, and flame retardancy. The inclusion of CNTs renders this composite system enhanced complex viscosity and storage modulus by about two orders of magnitude. The electrical conductivity and EMI specific shielding effectiveness of obtained foams can be adjusted and reached the optimum value of 0.024 S m⁻¹ and 29.1 dB cm³ g⁻¹, respectively, originating from the gradual development of interconnected CNTs and conductive CNTs network as well as the introduction of cell structure in PVDF matrix. Interestingly, the reorientation of CNTs caused by foaming process results in electrical conductivity percolation threshold of PVDF/CNTs foams markedly decreases, in comparison to their unfoamed samples. This study provides a facile, efficient, green, and economic route for the preparation of EMI shielding foams consisted of fluorinated polymers and carbonaceous fillers.     

Poly(propylene)/Carbon Nanofiber Nanocomposites: Ex Situ Solvent‐Assisted Preparation and Analysis of Electrical and Electronic Properties

CNF‐reinforced PP nanocomposites were fabricated from CNFs dispersed in a boiling PP/xylene solution. Their thermal properties were characterized by TGA and DSC and shown to exhibit improved thermal stability and higher crystallinity. They were further processed into thin films by compression molding. The electrical conductivity and dielectric property of the PP/CNF nanocomposite thin films were studied. Both electric conductivity and real permittivity increased with increasing fiber loading. Electrical conductivity percolation is observed between 3.0 and 5.0 wt.‐% fiber loading. The rheological behavior of the nanocomposite melts were also investigated. It was found that a small fiber concentration affects the modulus and viscosity of PP melt significantly.