Processing and structural properties of in situ polymerized poly(tetrafluoroethylene)/graphite fluoride composites

Novel poly(tetrafluorethylene)‐based composites were polymerized in situ on the fluorinated petroleum coke as graphite fluoride microparticles. This allows providing high adhesion between poly(tetrafluorethylene) and filler particles which is of much important to improve sufficiently mechanical properties of the polymer. The present work aimed at investigating the relationships between mechanisms of polymerization kinetics and structural properties of the composites. In the presence of fluorinated coke, the polymerization kinetics of tetrafluorethylene, started at the surface of the filler, is characterized by a long induction period followed by the explosive growth rate. This effect was supposed to be originated by the particles exfoliation due to the anchoring of growing polymer chains to the accessible interface of the filler. Scanning electron microscope confirmed this hypothesis showing fragmentation of graphite fluoride microparticles. The resulting fragments are show to be well distributed in the polymer matrix. Wide‐angle X‐ray diffraction experiments demonstrates that graphite fluoride crystals are still present after polymerization of poly(tetrafluorethylene) without modification of the crystalline peak (001) position. This asserts that no overall exfoliation mechanism of graphite fluoride into (CF)_n monolayers is active during the in situ polymerization. POLYM. ENG. SCI., 53:2549–2555, 2013. © 2013 Society of Plastics Engineers     

Investigation on the microstructure and the electric property of poly(propylene)/chlorinated poly(propylene)/poly(aniline) composites

The article presents results of studies on composites made from poly(propylene) (PP) modified with poly(aniline) (PANI) doped with dodecylbenzene sulfonic acid (DBSA) and chlorinated poly(propylene) (CPP). The volume resistivity of PP/CPP/PANI composites was detected, and the results show that the volume resistivity decreases with increasing CPP content, and there exists a minimum volume resistivity. Effects of CPP on the microstructure and crystalline structure of the PP/CPP/PANI composites and the relationship between the effects and the electric property were carefully analyzed by scanning electron microscope (SEM) and wide angle X‐ray diffraction (WAXD). The method that the specimens of SEM are polished is appropriate to investigate the morphology of conducting polymer composites. The obtained results illuminate that the area of conducting parts and insulating parts obtained from the digital analysis of the SEM image is obviously influenced by the CPP content, the parameters of the lamellar‐like structure are immediately related to CPP content and denote the dispersion of PANI‐DBSA, and the percent crystallinity and mean crystal size of PP are directly correlated with the CPP content. The increasing area of conducting parts, the increasement of layer distance, the decreasement of size and layer number of the lamellar‐like structure of PANI‐DBSA, and the increasement of the percent crystallinity and mean crystal size of PP are beneficial to the improvement of the conductive property of PP/CPP/PANI composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and electrochemical properties of poly(2,3‐dimethylaniline)/polyaniline composites

In this study, poly(2,3‐dimethylaniline)/polyaniline (P(2,3‐DMA)/PANI) composite was prepared by in situ polymerization of aniline on the surface of P(2,3‐DMA) particles in hydrochloric acid solution. Fourier transform infrared spectra and X‐ray diffraction results of the composites indicated that P(2,3‐DMA) was successfully modified by PANI. The electrochemical activity and electrical conductivity of the P(2,3‐DMA)/PANI composite were discussed by cyclic voltammetry and standard four‐probe tests, respectively. The results showed that the conductivity of the composite increased with the increasing aniline concentration, which can expand the potential applications of P(2,3‐DMA), such as use in anti‐static coatings or electronic devices. The P(2,3‐DMA)/PANI composite also showed better solubility and anticorrosive property than PANI. POLYM. COMPOS., 36:1541–1545, 2015. © 2014 Society of Plastics Engineers     

Crystallization and thermal conductivity of poly (vinylidene fluoride)/boron nitride nanosheets composites

ABSTRACT

In this work, boron nitride (BN) and exfoliated boron nitride nanosheets (BNNs) were employed as thermal conductive fillers to improve the thermal conductivity of poly(vinylidene fluoride) (PVDF) composites. Results suggested that the thermal conductivity of PVDF increases significantly with an increase in loading content of functional fillers. When the mass ratio of fillers was more than 30 wt%, the heat conduction network was formed. BNNs were capable of forming denser heat conduction network as per the SEM observations. In this scenario, PVDF/BNNs composites demonstrated excellent thermal conductivity. For example, the thermal conductivity of PVDF/BNNs (60/40) was 0.82 W/mK, which was 2.4 times and 17% higher than that of neat PVDF and PVDF/BN (60/40) counterpart, respectively. The non-isothermal crystallization of corresponding composite was studied by Mo method. Combining with XRD results, both BN and BNNs acted as the nucleation agents but had no effect on crystal forms.     

Photo‐induced protonation and conductivity of polyaniline/poly(ethylene glycol) and polyaniline/[poly(ethylene glycol)‐grafted polyaniline] composites

Composites of polyaniline in its emeraldine base form (PANI‐EB) and photo‐acid generators (PAG) show an increase in conductivity upon photo‐irradiation due to the protonation of PANI‐EB. Such materials may be utilized to fabricate conducting patterns by photo‐irradiation. However, the conductivity obtained by direct irradiation of PANI‐EB/PAG composites was normally quite low (<10^?3 S/cm) due to aggregation of highly loaded PAG. In this work, poly(ethylene glycol) (PEG), which is a proton transfer polymer, was added to PANI‐EB/PAG. Results showed that addition of low M_w (550) PEG significantly enhance the photo‐induced conductivity. Conductivities as high as 10^?1–10⁰ S/cm were observed after photo‐irradiation. This conductivity is comparable to that of PANI‐salt synthesized by oxidizing aniline in the presence of an acid. High M_w (8000) PEG is much less effective than PEG 550, which is attributed to its lower compatibility with PANI. PEG‐grafted PANI (N‐PEG‐PANI) was also studied as an additive. Composites of PANI‐EB and N‐PEG‐PANI showed conductivity as high as 10² S/cm after treatment with HCl vapor. The photo‐induced conductivity of the N‐PEG‐PANI/PANI‐EB/PAG composite reached 10^?2–10^?1 S/cm. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Morphology and mechanical properties of poly (phenylene sulfide)/isotactic polypropylene in situ microfibrillar blends

The morphology and mechanical properties of the in situ microfibrillar blend based on isotactic polypropylene (iPP) and poly (phenylene sulfide) (PPS) were examined. The microfibrillar PPS/iPP blend was prepared through a slit‐die extrusion, hot stretching, and water quenching process. Morphological observation indicated that the well‐defined PPS microfibrils were achieved by the method used in this study, which provided a promising method for both PPS and PP recycling. The morphology study showed that the minimum diameter of PPS phase was independent of PPS concentration. The diameter of most PPS fibrils in the microfibrillar blend was unexpectedly comparable to that of the PPS particles in the common blend at the same PPS content. The tensile strength of microfibrillar blend was higher than that of common blend, indicating the mechanical enhancement of microfibrillar processing to the PPS/iPP blend. The tensile strength of the microfibrillar blend also increased with stretching. POLYM. ENG. SCI., 45:1303–1311, 2005. © 2005 Society of Plastics Engineers     

Characterization and electrical conductivity of poly(ethylene glycol)/polyacrylonitrile/multiwalled carbon nanotube composites

Poly(Lactic acid) (PLA)‐layered silicate nanocomposite films were prepared by solvent casting method. The films were irradiated with Co⁶⁰ radiation facility at dose of 30 kGy. The effect of γ irradiation on mechanical properties of the neat PLA and nanocomposites was evaluated by data obtained from tensile testing measurements. The tensile strength of the irradiated PLA films increased with addition of 1 wt % triallyl cyanurate indicating crosslink formation. Significant ductile behavior was observed in the PLA nanocomposites containing 4 pph of nanoclay. Incorporation of nanoclay particles in the PLA matrix stimulated crystal growth as it was studied by differential scanning calorimetry. The morphology of the nanocomposites characterized by transmission electron microscopy and X‐ray diffraction revealed an exfoliated morphology in the PLA nanocomposite films containing 4 pph of nanoclay. Only very small changes were observed in the chemical structure of the irradiated samples as it was investigated by Fourier transform infrared spectroscopy. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrical conductivity of poly(vinylidene fluoride)/carbon nanotube composites with a spherical substructure

Poly(vinylidene fluoride) (PVDF)/multiwalled carbon nanotube (MWCNT) conducting composites were prepared with a percolation threshold as low as 0.07 wt%. The MWCNTs in a PVDF solution can lead to the formation of spherical PVDF/MWCNT composite particles by sonication. The MWCNTs coated on the surfaces of the spherical particles form a conduction network when the spheres coalesce to form a solid composite. The existence of the spherical particles with a substructure results in the reduction in MWCNT content and improves the electrical conductivity of the composites.     

Suppression of AC conductivity by crystalline transformation in poly(vinylidene fluoride)/carbon nanofiber composites

Poly(vinylidene fluoride) (PVDF) is an important ferroelectric semi-crystalline polymer with multiple-phase behavior. In this study, remarkable effects of the various crystalline structures of PVDF nanocomposites on alternating current (AC) conductivity were discovered using carbon nanofibers (CNF). It was found that the transformation from α-phase to β-phase in PVDF, induced by the addition of CNFs, had a surprisingly suppressive effect on the AC conductivity of the nanocomposites. These unexpected results indicate that the decline in conductivity occurs after re-crystallization treatment (annealing) of the nanocomposites, and the reduction levels increase with increasing amounts of CNFs. Interestingly, the AC conductivity of annealed 5 wt% CNF/PVDF composites becomes even lower than that of re-crystallized nanocomposites with 3 wt% CNFs. These findings are believed to be very significant for fabrication and long-term service of PVDF composites in industry, which often involves exposure to repeated thermal cycling.     

Optimization of mechanical properties of in situ polymerized poly(methyl methacrylate)/alumina nanoparticles nanocomposites using Taguchi approach

Polymer Bulletin - Alumina nanoparticles are among important metal oxides with specific properties but chemically incompatible with an organic matrix such as poly(methyl methacrylate) (PMMA). In...     

Physical properties and crystallization behavior of poly(lactide)/poly(methyl methacrylate)/silica composites

Poly(lactide)/poly(methyl methacrylate)/silica (PLA/PMMA/SiO₂) composites were fabricated using a twin‐screw extruder. Nanosilica particles were incorporated to improve the toughness of the brittle PLA, and a chain extender reagent (Joncryl ADR 4368S) was used to reduce the hydrolysis of the PLA during fabrication. Highly transparent PLA and PMMA were designated to blend to obtain the miscible and transparent blends. To estimate the performance of the PLA/PMMA/SiO₂ composites, a series of measurements was conducted, including tensile and Izod impact tests, light transmission and haze measurements, thermomechanical analysis, and isothermal crystallization behavior determination. A chain extender increases the ultimate tensile strength of the PLA/PMMA/SiO₂ composites by ～43%, and both a chain extender and nanosilica particles increase Young's modulus and Izod impact strength of the composites. Including 0.5 wt % nanosilica particles increase the elongation at break and Izod impact strength by ～287 and 163%, respectively, compared with those of the neat PLA. On account of the mechanical performances, the optimal blending ratio may be between PLA/PMMA/SiO₂ (90/10) and PLA/PMMA/SiO₂ (80/20). The total light transmittance of the PLA/PMMA/SiO₂ composites reaches as high as 91%, indicating a high miscible PLA/PMMA blend. The haze value of the PLA/PMMA/SiO₂ composites is less than 35%. Incorporating nanosilica particles can increase the crystallization sites and crystallinities of the PLA/PMMA/SiO₂ composites with a simultaneous decrease of the spherulite dimension. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42378.     

Morphology,crystallization, and mechanical properties of poly(ethylene terephthalate)/multiwalled carbon nanotubes composites

Poly(ethylene terephthalate)/multiwalled carbon nanotubes (PET/MWCNTs) with different MWCNTs loadings have been prepared by in situ polymerization of ethylene glycol (EG) containing dispersed MWCNTs and terephthalic acid (TPA). From scanning electronic microscopy images of nanocomposites, it can be clearly seen that the PET/MWCNTs composites with low‐MWCNTs contents (0.2 and 0.4 wt %) get better MWCNTs dispersion than analogous with high‐tube loadings (0.6 and 0.8 wt %). The nonisothermal crystallization kinetics was analyzed by differential scanning calorimetry using Mo kinetics equation, and the results showed that the incorporation of MWCNTs accelerates the crystallization process obviously. Mechanical testing shows that, in comparison with neat PET, the Young's modulus and the yield strength of the PET nanocomposites with incorporating 0.4 wt % MWCNTs are effectively improved by about 25% and 15%, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

聚乙撑二氧噻吩/二氧化硅复合材料制备及导电性研究

以表面含磺酸基团的改性二氧化硅纳米微球为填料,以三氯化铁(FeCl3)为氧化剂,对甲苯磺酸钠(TSANa)为掺杂剂,氧化聚合乙撑二氧噻吩(EDOT),制备了具有良好导电性的PEDOT/SiO2复合材料。并利用X射线光电子能谱(XPS)、扫描电子显微镜(SEM)和四探针等手段进行了表征。结果表明:当FeCl3与EDOT的摩尔比为0.8,TSANa的质量分数为10%,反应时间为4 h,得到的复合材料具有较高的电导率。     

Flame retardancy and thermal properties of poly(butylene succinate)/ nano-boehmite composites prepared via in situ polymerization

Poly(butylene succinate) (PBS) and its nanocomposites with nanoboehmite (nBhm) were synthesized via direct esterification between succinic acid and butylene glycol (BG). Boehmite (Bhm) nanoparticles, up to 2%, were added in the polycondensation step. Repeatability of runs was observed by the amount of the gathered water. Temperature trajectory was considered as an indication of the polycondensation start. Mixing torque was measured and its rapid increase, up to 0.6 Nm, was deliberated as the end of the process. Polycondensation time decreases with an increase in amount of nBhm due to the catalytic role of aluminum in Bhm. The chemical structure of PBS was proved through Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopies. XRD spectrum and scanning electron microscope images show a good distribution of nanoparticles in the polymer matrix. Differential scanning calorimetric results determine that T_g increases with the nanoparticle content. Improved Avrami equation was fitted to study the kinetics of the crystallization of samples. As a result, spherulite crystal growth was determined based on the Avrami index. Thermal gravimetric analysis trends are the same, however, nanocomposites show more residual ash. Atomic force microscopy images show that nanocomposites have a rough surface. It was observed that the flame advancement decreases up to 60% and limiting oxygen index increases up to 8%.     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/poly(ethylene terephthalate)/glass fiber composites

The influences of the glass fiber (GF) content and the cooling rate for nonisothermal crystallization process of poly(butylene terephthalate)/poly(ethylene terephthalate) (PBT/PET) blends were investigated. The nonisothermal crystallization kinetics of samples were detected by differential scanning calorimetry (DSC) at cooling rates of 5°C/min, 10°C/min, 15°C/min, 20°C/min, 25°C/min, respectively. The Jeziony and Mozhishen methods were used to analyze the DSC data. The crystalline morphology of samples was observed with polarized light microscope. Results showed that the Jeziony and Mozhishen methods were available for the analysis of the nonisothermal crystallization process. The peaks of crystallization temperature (T_p) move to low temperature with the cooling rate increasing, crystallization half‐time (t_1/2) decrease accordingly. The crystallization rate of PBT/PET blends increase with the lower GF contents while it is baffled by higher GF contents. POLYM. COMPOS. 36:510–516, 2015. © 2014 Society of Plastics Engineers     

UV aging of poly(propylene)/wood-fiber composites

The effect of accelerated UV-aging on properties of PP/wood-fiber composites has been studied. Plates containing 0, 25 and 50 wt% wood-fibers were subjected to accelerated UV-aging in a QUV weatherometer for up to 8 weeks. Stabilization against UV-degradation was made by adding 3% of a UV stabilizer. The results showed that both the unfilled PP and the PP/wood-fiber composites displayed good UV resistance with regard to mechanical properties. The color of the PP/wood-fiber composite plates changed from brown to chalky white at the exposed area because of the formation of a thin, strongly degraded surface layer. Physical and chemical analysis of these surface layers using differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy showed that degradation of the PP matrix had occurred, leading to chemicrystallization and extensive surface cracking. A decrease in PP melting temperature was also noted, due to molecular chain scission and the formation of extraneous groups, such as carbonyls and hydroperoxides. These results indicate that the wood-fibers act as chromophores when incorporated in the PP matrix. Increasing the fiber content from 25 to 50 wt% increases the rate of degradation of the PP matrix by approximately a factor of two. Polym. Compos. 25:543–553, 2004. © 2004 Society of Plastics Engineers.     

Synthesis and properties of poly(methyl methacrylate)/carbon nanotube composites covalently integrated through in situ radical polymerization

Poly(methyl methacrylate) (PMMA)/single‐walled carbon nanotube (SWNT) composites were synthesized by the grafting of PMMA onto the sidewalls of SWNTs via in situ radical polymerization. The free‐radical initiators were covalently attached to the SWNTs by a well‐known esterification method and confirmed by means of thermogravimetric analysis and Fourier transform infrared spectroscopy. Scanning electron microscopy and transmission electron microscopy were used to image the PMMA–SWNT composites; these images showed the presence of polymer layers on the surfaces of debundled, individual nanotubes. The PMMA–SWNT composites exhibited better solubility in chloroform than the solution‐blended composite materials. On the other hand, compared to the neat PMMA, the PMMA–SWNT nanocomposites displayed a glass‐transition temperature up to 6.0°C higher and a maximum thermal decomposition temperature up to 56.6°C higher. The unique properties of the nanocomposites resulted from the strong interactions between the SWNTs and the PMMA chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Non-isothermal crystallization of in situ polymerized poly(ε-caprolactone) functionalized-SWNT nanocomposites

The non-isothermal crystallization behavior of three in situ polymerized, partially tethered poly(ε-caprolactone) with functionalized single walled carbon nanotube (SWNT) nanocomposites are examined using differential scanning calorimetry and corroborated using small and wide angle X-ray scattering. While the nanotubes are strong nucleators of the crystals of poly(ε-caprolactone) and dramatically accelerate the crystallization of the polymer, they do not alter the unit-cell, the melting temperature and the fractional crystallinity of the polymer crystals.     

Morphology studies of poly(ethylene terephthalate)/silica nanocomposites

Poly(ethylene terephthalate)/silica nanocomposites have been prepared through in situ polymerization. The morphology was investigated by atomic force microscopy in the tapping mode and scanning electron microscope. The interface morphological structure of the poly(ethylene terephthalate)/silica nanocomposites strongly depends on the ratio of silica in the matrix. When silica weight fraction is lower than 3 wt%, the system consists of aggregated silica particles dispersed in the organic matrix; beyond this concentration, the structure is co-continuous with that of the organic matrix. Surface of poly(ethylene terephthalate) was smooth; while nanocomposites were rough, there are good interfacial adhesion and compatibility between the polymer matrix and the nanofillers.