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The density of T300 carbon fiber, as well as the amount of sizing and micro-structure were measured, before and after removing the sizing. The results showed that there was apparent stratification when measuring the density of the carbon fiber by the sink/float method, without removing the sizing. The upper sample layer was seriously flocculated with an excessive sizing amount of 2.17%, while the bottom-layer also flocculated. Two methods including acetone extraction and pyrolysis, were conducted to removing the sizing. It was shown that the measured amounts of sizing for the two methods were 1.20% and 1.53%, respectively. For the sample after immersion in acetone, there was still stratification in the sink/float test, with the upper sample layer flocculated because of the remaining sizing; while samples at the bottom dispersed relatively well. However, for the thermally treated samples the sizing was adequately removed, which resulted in the uniform density and dispersion during the test. This indicates that the non-uniform distribution of sizing agent on the surface of the CFs is the main reason for stratification during the density measurement. Therefore, the sizing must be fully removed in order to obtain an accurate density for the carbon fibers. Moreover, it can be seen that pyrolysis is an effective way to remove the CF sizing agent.

The aim of this work is to investigate the effect of moisture on the measured tensile strength of polyacrylonitrile (PAN) carbon fibers immersed in epoxy matrix under various moisture conditions. Tensile tests are carried out for the specimens, and a sharp decrease in measured tensile strength of the carbon fibers/epoxy system A immersed under high-moisture conditions is observed. Scanning electron microscope (SEM) is used to observe the effect of moisture on the surface structures of specimens. The results show that the decrease in the measured tensile strength is attributed to the microvoids of epoxy matrix formed in the preparation of the specimens. And the formation of microvoids in carbon fiber/epoxy matrix depends on viscosity change and curing condition of epoxy system. During the early stage of epoxy curing, both the solvent and absorbed water in the epoxy system escape from the immersed carbon fibers and form channels in the epoxy matrix. Once the viscosity of the epoxy system increased rapidly at a low curing temperature, the channels cannot be filled quickly by the surrounding resin and form microvoids finally. In order to verify these results, epoxy system B with a high curing temperature is chosen to prepare the specimens for tensile tests, and SEM images demonstrate that there are no microvoids that can be observed on the surfaces of specimens, even at such a high-moisture condition. And the measured tensile strengths remain unaffected in both low and high-moisture conditions. These results indicate that epoxy system with a high curing temperature is suitable for preparing the specimens for tensile tests regardless of moisture condition in the surrounding air.

Purpose – The purpose of this paper is a study aimed at overcoming the interface issue between nanopaper and polymer matrix in shape-memory polymer (SMP) composite laminates caused by their large dissimilarity in electrical/thermal conductive properties. The study attempted to develop an effective approach to fabricate free-standing carbon nanofibre (CNF) assembly in octagon shape formation. The structure design and thermal conductive performance of the resulting octagon-shaped CNF assembly were optimised and simulated. Design/methodology/approach – The CNF nanopaper was prepared based on a filtration method. The SMP nanocomposites were fabricated by incorporating these CNF assemblies with epoxy-based SMP resin by a resin-transfer modelling technique. Thermal conductivity of the octagon-shaped CNF assembly was simulated using the ANSYS FLUENT software for structure design and optimisation. The effect of the octagon-shaped CNF on the thermomechanical properties and thermally responsive shape-memory effect of the resulting SMP nanocomposites were characterised and interpreted. Findings – The CNF template incorporated with SMP to achieve Joule heating triggered shape recovery at a low electric voltage of 3-10 V, due to which the electrical resistivity of SMP nanocomposites was significantly improved and lowered to 0.20 O·cm by the CNF template. It was found that the octagon CNF template with 2 mm width of skeleton presented a highest thermally conductive performance to transfer resistive heat to the SMP matrix. Research limitations/implications – A simple way for fabricating electro-activated SMP nanocomposites has been developed by using an octagon CNF template. Low electrical voltage actuation in SMP has been achieved. Originality/value – The fabricated CNF template, the structure design and analysis of dynamic thermomechanical properties of SMP are novel.

An effective approach to improve the electrical properties and electro-activated performance of shape memory polymer (SMP) nanocomposites has been demonstrated via a synergistic effect from carbon fibre and self-assembled graphene oxide (GO). The surface modified GO has been grafted onto carbon fibre to enhance the interfacial strength with SMP matrix through van-der-Waals bonds and covalent crosslinking. Carbon fibre enhances the performance of electrical actuation of SMP through Joule heating. Furthermore, the temperature distribution within the SMP nanocomposite during Joule heating becomes uniform, resulting in a significant enhancement of shape recovery and electro-actuation performance of high recovery speed.

An effective approach to significantly improve electro-activated recovery performance of shape memory polymer (SMP) nanocomposites was investigated in this study, which is based on Joule heating triggered shape recovery through formation of a three-dimensional template of self-assembled carbon nanofibres (CNFs) inside the SMP. This template approach allows effective electro-actuation and resistive heating, mainly attributing to conductive CNF assembly. Electro-activated recovery of the SMP nanocomposites was monitored and the resultant temperature distribution in the SMP nanocomposite during recovery was characterized. Furthermore, the relative thermal conductivity was simulated using ANSYS FLUENT software in order to optimize the structure design for the CNF template.

The morphological control of calcium carbonate (CaCO3) colloidal particles, which allows us to obtain specific material properties, is one of the key challenges in various applications. To this end, we have studied the formation of CaCO3 particles by adding different long chain fatty acids—lauric acid, palmitic acid and stearic acid—into calcium hydroxide (Ca(OH)2) slurry, and then, by dispersing carbon dioxide (CO2) gas into the slurry via a micropore plate. Their polymorph, morphology and surface feature were characterized by XRD, TEM and FTIR, respectively. It is shown that the crystalline phase of CaCO3 particles leaves unchanged with respect to the used species and amounts of fatty acids, what is changed is the shape of CaCO3 particles from nano-cubic to micro-spindle. Thus we underlined the tuning mechanism of precipitation.

The aim of this work is to investigate the effect of a process-induced resin bead on the measured tensile strength of polyacrylonitrile-based carbon fibers. It is found that the resin bead was formed on the surface of carbon fiber specimens if the carbon fibers impregnated with resin were positioned horizontally during the tensile specimen preparation. Mechanical testing results indicated that the measured tensile strength of carbon fibers noticeably decreased by about 10 % due to the formation of the resin bead, and the initial fracture of carbon fibers usually occurred around the resin bead. Moreover, the bending of the filaments in the resin bead had been observed by optical microscope. It is concluded that the flowing and curing of excess resin lead to the bending of loose filaments in carbon fiber tow during specimen preparation; thus, internal stress was subsequently formed in the fiber specimen, which is detrimental to the measured tensile strength. Finally, based on the microscopic observations, theoretical analysis under the maximum stress criterion was employed to predict the tensile strength of carbon fibers with a resin bead, and the theoretical results agree well with the experimental results. It is verified that the bending angle and the fraction of the bending filaments in the resin bead play important roles in deteriorating the measured tensile strength. These conclusions can help to improve the tensile testing method for accurately measuring the tensile strength of high modulus carbon fibers.

In this paper, two kinds of organically modified montmorillonite (OMMT) were prepared using alkylammonium surfactants with different alkyl chain numbers. XRD results showed the interlayer spacing of OMMT increased with low concentration surfactants. With further increasing the surfactants concentration, the interlayer spacing of OMMT was unchanged. Meanwhile, FTIR was used to characterize the local environments of surfactants in the interlayer space of OMMT. The results suggested that the double chain surfactant D-18 preferred to adopt highly ordered conformation compared with single chain surfactant S-18 in interlayer space of OMMT. It indicated that the surface property of the OMMT is affected by the concentration and configuration of the intercalated surfactants. Moreover, the effect of the OMMT type, or more particularly the chemical nature of the organic modifier in the interlayer spacing and the poly(ethylene glycol) (PEG) concentration onintercalation behavior of PEG chains in OMMT were investigated with XRD and DSC.The results indicated that PEG chains could not intercalate into Na-MMT when the surfactants were saturated in interlayer space of Na-MMT. PEG chains could intercalate into the interlayer space of SM when the S-18 concentration was lower than 2.00CEC, implying that the low surfactant concentration modified SM provided a better environment (presumably through the balanced hydrophobic and hydrophilic surfaces) for the PEG intercalation as well. However, PEG did not intercalate into the interlayer space of DM when the D-18 concentration was higher than 1.00CEC. It could be attributed to the hydrophobic double alkyl chains of DM increased with D-18. The increased hydrophobic properties in the interlayer space of 1.50DM hybrids can prevent the intercalation of hydrophilic PEG.

The influence of the hydrogenated petroleum resin P125 on the crystallization behavior, crystallization kinetics, and optical properties of polypropylene (PP) were investigated. The results of differential scanning calorimetry, successive self-nucleation, and annealing fractionation demonstrated that P125 reduced the interaction between the PP molecules, decreased the crystallization, prevented PP from forming thick lamellae, and encouraged the formation of thin lamellae. The isothermal crystallization kinetics, self-nucleation isothermal crystallization kinetics, and polarized optical microscopy observations showed that P125 slightly decreased the nucleation rate, significantly decreased the crystal growth rate, generally reduced the overall crystallization rate, and effectively deceased the crystallite sizes of PP. The optical properties studies showed that P125 effectively decreased the haze and increased the surface glossiness and yellowness index of PP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The structure and conformation of poly(ethylene glycol) (PEG) chains in the confined space of montmorillonite (MMT) were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). A series of PEG/MMT hybrids were synthesized utilizing solution intercalation. Intercalated hybrids with monolayer and double layers of PEG chains were obtained both in Na-MMT and OMMT (DK1). However, the hydrophobic PEG chains cannot intercalate into the interlayer space of OMMT (DK4) due to the strong hydrophilic properties of DK4. There is a saturation ratio when PEG intercalated into the interlayer space of MMT. The deduced saturation ratios of PEG to Na-MMT and DK1 are 0.26 and 0.24, respectively. The structure and conformation of intercalated PEG chains exhibit different characteristics from those of the neat polymer, even more disorder in melting state. According to the results of XRD and FTIR, the structure and conformation of PEG chains in OMMT (DK1) are very similar to Na-MMT. Moreover, a possible model of PEG intercalated MMT is proposed. All PEG chains are intercalated into the interlayer spaces of MMT and form a disorder phase when PEG content is not saturated. In the cases of PEG: MMT = 1:10 or 3:10 in weight, the polymer chains form one or two polymer layers. A wider monolayer form when the weight ratio of PEG/MMT is 0.2.

In this study, Ca2+-montmorillonite (Ca2+-MMT) and organo-montmorillonite (OMMT) were modified by three compatibilizers with different degrees of polarity [poly(ethylene glycol) (PEG), alkyl-PEG, and polypropylene (PP)-g-PEG]. PP/MMT nanocomposites were prepared by melt blending and characterized using X-ray diffraction and transmission electron microscopy. The results showed the degree of dispersion of OMMT in the PP/PP-g-PEG/OMMT (PMOM) nanocomposite was considerably higher than those in the PP/PEG/OMMT and PP/alkyl-PEG/OMMT nanocomposites, which indicated that the dispersion was relative to the compatibility between modified OMMT and PP matrix. Linear viscoelasticity of PP/MMT nanocomposites in melt states was investigated by small amplitude dynamic rheology measurements. With the addition of the modified MMT, the shear viscosities and storage modulus of all the PP/MMT nanocomposites decreased. It can be attributed to the plasticization effect of PEG segments in the three modifiers. This rheological behavior was different from most surfactant modified MMT nanocomposites which typically showed an increase in dynamic modulus and viscosity relative to the polymer matrix. The unusual rheological observations were explained in terms of the compatibility between the polymer matrix and MMT. In addition, the mechanical properties of PP/MMT nanocomposites were improved. A simultaneous increase in the tensile strength and toughness was observed in PP/PMOM nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Hydrophobic poly(ethylene terephthalate) (PET) was prepared by reactive blending of PET with double epoxy groups modified polysiloxane (diepsi) or multiepoxy groups modified polysiloxane (multiepsi). The structure of the modified PET was characterized by 1H NMR and intrinsic viscosity. The grafted ratio of diepsi and multiepsi was 1.3 and 0.03 wt%, respectively. With the introduction of diepsi and multiepsi to PET, the water contact angle of modified PET increased from 73° to a maximum of 106°, showing the good hydrophobicity of the modified PET. The samples of modified PET were washed with different solvents and their water contact angles did not significantly decrease, indicating good durability of the hydrophobicity. Moreover, the films of modified PET prepared by solution casting (phenol and 1, 1, 2, 2-tetrachloroethane mixed solution) showed excellent hydrophobicity with the contact angle 151°. Scanning electron microscopy images showed the surface of the modified PET films to be rougher than those o...

In the present study, we investigated the influences of polymerization and crosslinking technologies on the branched-chain structures, crystallization behaviors, and gel networks of two types of low-density polyethylenes, LDPE1 and LDPE2, polymerized under different polymerization conditions in commercial large-capacity production lines. High temperature 13C NMR analysis suggests that the molar contents of both long-chain branches and short-chain branches of LDPE2 were markedly higher than those of LDPE1 due to a higher polymerization temperature for LDPE2. The high content of chain branches of LDPE2 leads to its relatively higher storage modulus, entanglement density, and gel content, as indicated by dynamic mechanical analysis. In addition, when the crosslinking temperature reached 180°C, the LDPE2 crosslinked with 2 wt% dicumylperoxide (XLPE2-D2) displayed a relatively wider processing time window and a faster crosslinking rate than XLPE1-D2. Successive self-nucleation and annealing fractionation indic...

In this work, montmorillonite (Mt) was modified by octadecyl amine ethoxylate ether (A) which has two poly(ethylene oxide) segments. Montmorillonite/polypropylene (Mt/PP) nanocomposites were prepared by a melt blending technique using different contents of modified Mt with and without maleic anhydride grafted polypropylene (PPg). The intercalated and exfoliated structures of Mt/PP nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Because of the typical intercalated and exfoliated structures, the mechanical properties of Mt/PP nanocomposites were improved significantly. The modified Mt in a PP matrix led to a significant reduction of melt viscosity and enhancement in Izod-notched impact strength and elongation at break. The Izod-notched impact strength and elongation at break of Mt/PP nanocomposites were 1.95 and 2.77 times as high as those of pure PP. The tensile strength of Mt/PP nanocomposites was also improved in the presence of PPg.

Atactic polypropylene (aPP) was chemically grafted onto attapulgite (ATP) via the bridge linking of a polymerizable cationic surfactant and poly(octadecyl acrylate) in the presence of ultrasonic oscillation and dicumyl peroxide, and then, the modified ATP was added to a polypropylene (PP) matrix to obtain PP nanocomposites by melt blending. The results of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed that aPP and poly(octadecyl acrylate) were chemically grafted onto ATP through a graft polymerization reaction. The results of the mechanical properties testing showed that the addition of modified ATP improved the toughness and strength of PP remarkably. The dynamic mechanical analysis indicated that the modified ATP significantly increased the storage modulus and decreased the glass-transition temperature of PP. The results of scanning electron microscopy and transmission electron microscopy showed that the modified ATP was uniformly dispersed into the PP matrix as crystal needles; this proved the presence of strong interactions between modified ATP and PP. The crystal structure analysis revealed that the β-form crystalline of PP was formed within the modified ATP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The effects of poly(ethylene glycol) (PEG)/montmorillonite (MMT) hybrids on the phase morphology, rheological behaviors and mechanical properties of polypropylene (PP) were investigated. The analysis of transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD) indicated that the PEG modified montmorillonite was intercalated and well dispersed into PP matrix. It was found that the addition of the PEG/MMT hybrids in PP matrix lead to a significant reduction of melt viscosity and enhancement in izod-notched impact strength and elongation at break, except that the tensile strength was without much obvious change. A quantitative analysis indicated that MMT was intercalated by PEG, which was responsible for the melt viscosity reduction of PP matrix. Differential scanning calorimetry (DSC) analysis indicated that the addition of PEG/MMT hybrids induced the formation of β-crystal of PP. Polarized light micrographs (PLM) analysis indicated that the dispersed MMT, which acted as a nucleating agent, lowered the spherulite dimension and increased the spherulite number, resulting in high izod-notched impact strength and elongation at break.

The compositional heterogeneity, morphology and melting behavior of two commercial high-impact polypropylene (HiPP) in-reactor alloys were systematically investigated by the combined use of thermal fractionation, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Correlations between the mechanical properties and the molecular architectures and phase morphologies were discussed. The results show that the mechanical properties of the alloys are strongly influenced by the contents of ethylene-propylene rubber (EPR) and ethylene-propylene block copolymer (EPC), intrinsic viscosity ratios of EPR and the matrix, and the morphology in polypropylene in-reactor alloys. The EPC component acts as a bridge connecting the dispersed amorphous phase and crystalline polypropylene matrix. The advanced impact toughness of the HiPP samples can be interpreted as a consequence of their high EPR content and the good compatibility between the different components in the multiphase system. When the xylene soluble (XS) component was 20 wt% and an intrinsic viscosity ratios (λ) of xylene soluble component and xylene insoluble (XIS) component was1.6, the impact strength and flexural modulus of the HiPP samples were higher than 50 kJ/m2 and 900 MPa, respectively.

Poor heat conduction in the interface between the carbon fiber and polymer matrix is a problem in the actuation of shape-memory polymer (SMP) composites by Joule heating. In this study, we investigated the effectiveness of grafting silver-nanoparticle-decorated graphene oxide (GO) onto carbon fibers to improve the electrothermal properties and Joule-heating-activated shape recovery of SMP composites. Self-assembled GO was grafted onto carbon fibers to enhance the bonding of the carbon fibers with the polymeric matrix via van der Waal's forces and covalent crosslinking, respectively. Silver nanoparticles were further self-assembled and deposited to decorate the GO assembly, which was used to decrease the thermal dissimilarity and facilitate heat transfer from the carbon fiber to the polymer matrix. The carbon fiber was incorporated with SMP to achieve the shape recovery induced by Joule heating. We found that the silver-nanoparticle-decorated GO helped us achieve a more uniform temperature distribution in the SMP composites compared to those without decoration. Furthermore, the shape-recovery behavior and temperature profile during the Joule heating of the SMP composites were characterized and compared. A unique synergistic effect of the carbon fibers and silver-nanoparticle-decorated GO was achieved to enhance the heat transfer and a higher speed of actuation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41673.