Effects of vapor‐phase‐formaldehyde treatments on thermal conductivity and diffusivity of ramie fibers in the range of low temperature

To understand the influence to thermal conductivity by bridging in the polymer fibers, the thermal conductivity, and thermal diffusivity of ramie fiber and those bridged by formaldehyde (HCHO) using vapor‐phase method (VP‐HCHO treatment) were investigated in the lower temperature range. The thermal conductivities of ramie fiber with and without VP‐HCHO treatments decreased with decreasing temperature. Thermal diffusivities of ramie fiber with and without VP‐HCHO treatments were almost constant in the temperature range of 250–50 K, and increased by decreasing temperature below 50 K. Thermal conductivity and thermal diffusivity of ramie fiber decreased by VP‐HCHO treatment. The crystallinities and orientation angles of ramie fibers with and without VP‐HCHO treatment were measured using solid state NMR and X‐ray diffraction. These were almost independent of VP‐HCHO treatment. Although tensile modulus decreased slightly by VP‐HCHO treatment, the decrease could not explain the decrease in thermal conductivity and diffusivity with decreasing sound velocity. The decrease of the thermal diffusivity and thermal conductivity by VP‐HCHO treatment suggested the possibility of the reduction of the mean free path of phonon by HCHO in VP‐HCHO treated ramie fiber. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2754–2766, 2005     

Surface modification of ultrahigh‐molecular‐weight polyethylene fibers

To prevent the loss of fiber strength, ultrahigh‐molecular‐weight polyethylene (UHMWPE) fibers were treated with an ultraviolet radiation technique combined with a corona‐discharge treatment. The physical and chemical changes in the fiber surface were examined with scanning electron microscopy and Fourier transform infrared/attenuated total reflectance. The gel contents of the fibers were measured by a standard device. The mechanical properties of the treated fibers and the interfacial adhesion properties of UHMWPE‐fiber‐reinforced vinyl ester resin composites were investigated with tensile testing. After 20 min or so of ultraviolet radiation based on 6‐kW corona treatment, the T‐peel strength of the treated UHMWPE‐fiber composite was one to two times greater than that of the as‐received UHMWPE‐fiber composite, whereas the tensile strength of the treated UHMWPE fibers was still up to 3.5 GPa. The integrated mechanical properties of the treated UHMWPE fibers were also optimum. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 463–472, 2004     

Water‐sorption kinetics in oil palm fibers

Oil palm fibers represent a very abundant and natural resource for raw materials that can be efficiently utilized as reinforcement in polymers. The sorption characteristics of two types of oil palm fibers—oil palm empty‐fruit‐bunch (OPEFB) fiber and oil palm mesocarp fiber‐in distilled water, mineral water, and water containing salt at four different temperatures were investigated. The uptake of water decreased with an increase in temperature. The OPEFB fiber showed higher sorption than the mesocarp fiber. This was due to the uptake associated with the capillary action in the OPEFB fiber. The thermodynamic parameters of the sorption process were calculated. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1215–1223, 2001     

Effect of Fiber Treatment on Dimensional Stability and Chemical Resistance Properties of Hybrid Composites

In this work, oil palm empty fruit bunch (EFB) and jute fibers were treated by 2-hydroxy ethyl acrylate (2-HEA) to enhance interaction with the epoxy matrix in hybrid composites. Hybrid composites were fabricated by the hand lay-up technique by reinforcing chemical-treated oil palm EFB and jute fibers in an epoxy matrix. Physical (density, void content, water absorption, and thickness swelling) and chemical resistance properties of treated hybrid composites were characterized. Chemically treated oil palm EFB/jute fiber reinforced hybrid composites display better dimensional stability (water absorption and thickness swelling) and chemical resistance as compared to untreated hybrid composites.     

Effect of Oil Palm and Jute Fiber Treatment on Mechanical Performance of Epoxy Hybrid Composites

In this work, oil palm empty fruit bunch (EFB) and jute fibers were treated with 2-hydroxy ethyl acrylate (2-HEA) to improve interfacial bonding of oil palm EFB and jute fibers with epoxy matrix. Hybrid composites were fabricated by incorporation of modified oil palm EFB and jute fibers into an epoxy matrix by the hand lay-up technique. Mechanical (flexural and impact) and morphological properties of modified hybrid composites were measured. Results indicated that flexural and impact properties of modified fiber–reinforced hybrid composites improved as compared to untreated hybrid composites due to better fiber/matrix interfacial bonding, which was confirmed by scanning electron microscopy. We confirmed that treated oil palm/jute hybrid composite may be fabricated by advanced techniques such as resin transfer molding, extrusion, and injection molding for industrial applications in the automotive sector.     

Ultrahigh‐molecular‐weight‐polyethylene‐fiber surface treatment by electron‐beam‐irradiation‐induced graft polymerization and its effect on adhesion in a styrene–butadiene rubber matrix

Aiming to develop a high‐performance fiber‐reinforced rubber from styrene–butadiene rubber (SBR), we applied a special technique using electron‐beam (EB)‐irradiation‐induced graft polymerization to ultrahigh‐molecular‐weight‐polyethylene (UHMWPE) fibers. The molecular interaction between the grafted UHMWPE fibers and an SBR matrix was studied through the evaluation of the adhesive behavior of the fibers in the SBR matrix. Although UHMWPE was chemically inert, two monomers, styrene and N‐vinyl formamide (NVF), were examined for graft polymerization onto the UHMWPE fiber surface. Styrene was not effective, but NVF was graft‐polymerized onto the UHMWPE fibers with this special method. A methanol/water mixture and dioxane were used as solvents for NVF, and the effects of the solvents on the grafting percentage of NVF were also examined. The methanol/water mixture was more effective. A grafting percentage of 16.4% was the highest obtained. This improved the adhesive force threefold with respect to that of untreated UHMWPE fibers. These results demonstrated that EB irradiation enabled graft polymerization to occur even on the inert surface of UHMWPE fibers. However, the mechanical properties of the fibers could be compromised according to the dose of EB irradiation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2595–2603, 2004     

The oxidation‐treated interface on tribological properties of carbon fibers‐reinforced PTFE composite under oil‐lubricated condition

The effect of air oxidation and ozone surface treatment of carbon fibers (CF) on tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites under oil‐lubricated condition was investigated. Experimental results revealed that ozone treated CF reinforced PTFE (CF–PTFE) composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air‐oxidated composites. X‐ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that, after ozone treatment, oxygen concentration was obviously increased, and the amount of oxygen‐containing groups on CF surfaces was largely increased. The increase in the amount of oxygen‐containing groups enhanced interfacial adhesion between CF and PTFE matrix. With strong interfacial adhesion of the composite, stress could be effectively transmitted to carbon fibers; carbon fibers were strongly bonded with PTFE matrix and large scale rubbing‐off of PTFE was prevented, therefore, the tribological properties of the composite were improved. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermal conductivity of high strength polyethylene fiber in low temperature

High strength polyethylene fiber (Toyobo, Dyneema® fiber, hereinafter abbreviated to DF) used as reinforcement of fiber‐reinforced plastics for cryogenic use has a high thermal conductivity. To understand the thermal conductivity of DF, the relation between fiber structure and thermal conductivity of several kinds of polyethylene fibers having different modulus from 15 to 134 GPa (hereinafter abbreviated to DFs) was investigated. The mechanical series‐parallel model composed of crystal and amorphous was applied to DFs for thermal conductivity. This mechanical model was obtained by crystallinity and crystal orientation angle measured by solid state NMR and X‐ray. Thermal conductivity of DF in fiber direction was dominated by that of the continuous crystal region. The thermal conductivity of the continuous crystal part estimated by the mechanical model increases from 16 to 900 mw/cmK by the increasing temperature from 10 to 150K, and thermal diffusivity of the continuous crystal part was estimated to about 100 mm²/s, which is almost temperature independent. The phonon mean free path of the continuous crystal region of DF obtained by thermal diffusivity is almost temperature independent and its value about 200 Å. With the aforementioned, the mechanical series‐parallel model composed of crystal and amorphous regions could be applied to DFs for thermal conductivity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1495–1503, 2005     

Effect of surface‐grafted ionic groups on the performance of cellulose‐fiber‐reinforced thermoplastic composites

The influence of the surface chemistry of the cellulose fiber and polymer matrix on the mechanical and thermal dynamic mechanical properties of cellulose‐fiber‐reinforced polymer composites was investigated. The cellulose fiber was treated either with a coupling agent or with a coupling‐agent treatment followed by the introduction of quaternary ammonium groups onto the fiber surface, whereas the polymer matrix, with opposite polar groups such as polystyrene incorporated with sulfonated polystyrene and poly(ethylene‐co‐methacrylic acid), was compounded with the fiber. The grafting of the fiber surface was investigated with Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. Experimental results showed that an obvious improvement in the mechanical strength could be achieved for composites with an ionic interface between the fiber and the polymer matrix because of the adhesion enhancement of the fiber and the matrix. The improved adhesion could be ascribed to the grafted ionic groups at the cellulose‐fiber surface. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2022–2032, 2003     

Biodegradable fibers of poly(3‐hydroxybutyrate) produced by high‐speed melt spinning and spin drawing

The effects of high‐speed melt spinning and spin drawing on the structure and resulting properties of bacterial generated poly(3‐hydroxybutyrate) (PHB) fibers were investigated. The fibers were characterized by their degree of crystallinity by differential scanning calorimetry (DSC) and wide‐angle X‐ray scattering (WAXS), their orientation by WAXS, and the textile physical properties. The WAXS studies revealed that the fibers spun at high speeds and high draw ratios possessed orthorhombic (α modification) and hexagonal (β modification) crystals, the latter as a result of stress‐induced crystallization. The fiber structures formed during these processes were fibril‐like as the atomic force microscopy images demonstrated. The maximum physical break stress, the modulus, and the elongation at break observed in the fibril‐like spin drawn fibers were about 330 MPa, 7.7 GPa, and 37%, respectively. The fibers obtained by a low draw ratio of 4.0 had spherulitic structures and poor textile physical properties. The PHB pellets were analyzed by their degradation during the processes of drying and spinning and by their thermal and rheological properties. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2841–2850, 2000     

Shapeable matrix‐free Spectra® fiber‐reinforced polymeric composites via high‐temperature high‐pressure sintering: Process‐structure‐property relationship

In an exploratory effort to find a new way to make high‐performance composites used in ballistic protective applications, matrix‐free Spectra® fiber‐reinforced polymeric composites are produced via a novel processing method called high‐temperature high‐pressure sintering. Mechanical testing at ambient and elevated temperatures proves that the fibers can maintain their properties after processing. The characteristics and properties of the final products vary with different processing conditions. Their microstructure and morphology were investigated using SEM and WAXD. Their mechanical properties, including interlayer adhesion, rigidity, and ballistic performance, were measured and compared with those of the conventional composites. The sintering mechanism is proposed and verified. Spectra cloth is capable of being shaped to produce complex double curvatures by a thermoforming process, using a simple hemispherical mold. Success in different molding sequences and procedures shows the versatility in manufacturing. The theoretical background for the thermoformability is explained in terms of molecular interaction, microstructure, and morphology. Selective thermomechanical properties of the molded structures were measured. By combining the knowledge and information from the aforementioned studies, the process‐structure‐property relationship is established, which gives in‐depth and better understanding of this unique high‐temperature high‐pressure sintering process for consolidating Spectra cloth. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2767–2789, 2005     

A review on flammability of epoxy polymer,cellulosic and non‐cellulosic fiber reinforced epoxy composites

Natural fiber is well‐known reinforcement filler in polymer‐matrix composites. Composite components like organic polymers and natural fibers are natural fire conductors as the natural fiber consists of cellulose, hemicellulose, and lignin, and hence are as highly flammable as wood. Natural fiber reinforced composite materials are progressively being used in a variety of applications where their fire response is a hazardous consideration, for example, in the automotive (transportation) and building‐construction industries. As a result, an awareness of their performance or response during a fire and the use of conventional fire retardants are of great importance, as they are subject to thermal decomposition when exposed to intensive high heat or fire sources. In this review paper, fire flammability is the main concern for cellulosic and non‐cellulosic fiber‐reinforced polymer composites, especially epoxy composites. This paper reviews the literature on the recent developments in flammability studies concerning polymers, epoxy polymers, cellulosic‐fibers, and non‐cellulosic fiber‐reinforced epoxy bio‐composites. The prime objective of this review is to expand the reach of “fire retardants for polymer materials and composites” to the science community, including physicists, chemists, and engineers in order to broaden the range of their applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Photo and Thermal Cured Silicon‐Containing Diethynylbenzene Fibers via Melt Electrospinning with Enhanced Thermal Stability

An inorganic–organic hybrid material, poly(dimethylsilylene ethynylenephenyleneethynylene) (PMSEPE), was synthesized in a mild condition and its microfiber was successfully produced by melt electrospinning. The electrospinning parameters, which affected the morphology and diameter of fibers, were well investigated. To maintain the fiber structure at thermal cured temperature (above melting point), the PMSEPE fibers were enhanced via thiol‐yne photo polymerization. Followed by the thermal curing reaction, the heat‐resistance and mechanical properties of fibers were enhanced. The mechanism of two‐step curing was explored and confirmed by means of Fourier transform infrared, differential scanning calorimetry, and X‐ray photoelectron spectroscopy (XPS). Thermaogravimetric analysis and scanning electron microscopy results show that after carbonization at 800 °C, the two‐step cured fibers had only a small weight loss (20%) and the fibers can still maintain the original morphology. Moreover, the two‐step cured fiber exhibited a high tensile strength (55.4 MPa) and a small elongation at break (0.02%). All the results indicate that the fibers could be applied as fiber‐reinforced materials. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2815–2823     

Sorption and diffusion of carbon dioxide in wood‐fiber/polystyrene composites

In this study, sorption and diffusion of carbon dioxide (CO₂) in wood‐fiber/polystyrene composites were investigated. The effects of gas pressure and fiber content on the solubility and diffusion coefficients were evaluated. A statistical analysis indicated that pressure is more important than fiber content in determining the solubility and diffusivity of CO₂. An increase in saturation pressure causes an increase in the solubility and diffusion coefficients, whereas inclusion of the fibers decreases both of these properties. Models were developed to predict the uptake and diffusion coefficients of CO₂ in the composite samples as functions of pressure and fiber content. A theoretical model based on Henry's law and the Langmuir equation compared favorably to the experimental data for CO₂ solubility. This dual mode model also described both the transient sorption and desorption data, but only if the concentration‐dependent value of diffusivity was treated as a history‐dependent parameter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 723–735, 2002     

Flexural properties of fiber‐reinforced polypropylene composites with and without a transcrystalline layer

The flexural properties of isotactic polypropylene (PP) matrix composites reinforced with 5–30 vol% of unidirectional pitch‐based carbon, polyacrylonitrile (PAN)‐based carbon, e‐glass or aramid fibers were measured using both static and dynamic test methods. Previous research has shown that these pitch‐based carbon and aramid fibers are capable of densely nucleating PP crystals at the fiber surface, leading to the growth of an oriented interphase termed a “transcrystalline layer” (TCL), while the e‐glass and PAN‐based carbon fibers show no nucleating ability. The PP matrices examined included unmodified homopolymers, nucleated homopolymers and PP grafted with maleic anhydride (MA). The composites based on the unmodified PP homopolymers all exhibited poor fiber/matrix adhesion, regardless of fiber type and presence or absence of a TCL. The addition of nucleating agent to the PP matrix had no measurable effect on either the amount of TCL material in pitch‐based carbon‐fiber‐reinforced composites, as measured by wide‐angle X‐ray scattering, WAXS, or the static flexural properties of the composites reinforced with either type of carbon fiber. However, MA grafting reduced the transcrystalline fraction of the matrix in pitch‐based carbon‐fiber‐reinforced composites; at the highest level of MA grafting, the TCL was completely suppressed. In addition, high levels of MA grafting improved the transverse flexural modulus of the composites containing both types of carbon fibers, and reduced the extent of fiber pull‐out, indicating an improvement in fiber/matrix adhesion. Copyright © 1999 John Wiley & Sons, Ltd.     

Effect of Chemical Modifications of Fibers on Tensile Properties of Epoxy Hybrid Composites

Treatment of oil palm empty fruit bunch (EFB) and jute fibers is carried out by using 2-hydroxy ethyl acrylate (2-HEA) to increase the interfacial bonding of fibers with the epoxy matrix. Fourier transform-infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were used to measure the change of surface composition of the fibers after treatment. Modified oil palm and jute fibers were used as reinforcements for epoxy matrix to fabricate hybrid composites by the hand lay-up technique. Tensile and morphological properties of hybrid composites were studied, and tensile properties of hybrid composites prepared from chemically treated oil palm/jute fibers were found to be better than those of untreated hybrid composites. SEM micrographs disclose that interfacial bonding between fiber and matrix significantly improved in the hybrid composites. Developed hybrid composites can be exploited as alternative materials for development of automotive and structural components instead of synthetic fiber–reinforced polymer composites.     

Thermoresponsive conductive polymer composite thin film and fiber mat: Crosslinked PEDOT:PSS and P(NIPAAm‐co‐NMA) composite

The thermoresponsive conductive composite (TCC) thin films and fiber mats, whose electrical property changed with temperature, were fabricated successfully. The thermocrosslinkable and thermoresponsive copolymer, poly(N‐isopropyl acrylamide‐co‐N‐methylolacrylamide) (PNN), was synthesized. The TCC thin film and fiber mat were fabricated by spin coating and electrospinning process of PEDOT:PSS/PNN solutions, respectively. After thermocrosslinking and doping by DMSO, the composite thin films and fiber mats were obtained. Fibrous structures of TCC fiber mats were observed by SEM. The surface resistance and conductivity of composites were measured. The thermoresponsivity and swelling ratio of TCCs were also studied. The thermoresponsive conductive property was analyzed by measuring the surface resistance of TCCs in water bath under various temperatures from 20 to 50 °C. With the increase of temperature, the TCCs shrank to be dense structure and showed lower surface resistance. The TCC fibers mat exhibited greater sensitivity to temperature than thin film owing to its fibrous structure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1078–1087     

Surface modification for nano‐lignocellulose fiber through vapor‐phase‐assisted surface polymerization

This study addresses the inherent issues surrounding surface modification methods of nanofibers and proposes an environmentally friendly and less toxic strategy for the surface modification of hydrophilic nanofiber. From the continuation of our previous work, which discussed the easy production of nanofiber (average size: 127 nm) from oil palm mesocarp fiber (OPMF), in this work, the surface of nanofibers (M‐IL‐OPMF) were modified through vapor‐phase‐assisted surface polymerization (VASP) to improve the affinity of interface between the polymer grafted M‐IL‐OPMF and non‐polar matrix. VASP of ε‐caprolactone was successfully proceeded from the [M‐IL‐OPMF] at 70 °C for 24 h and 72 h, and compositions were estimated to be 35.7% fiber/64.3% polymer and 27.8% fiber/72.2% polymer. To confirm the grafting of PCL, size‐exclusion chromatography (SEC) and Fourier transform infrared (FT‐IR) spectroscopy, thermogravimetry (TG), and dispersibility test in hydrophobic solvent were carried out. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2575–2580     

Design of thermal hybrid composites based on liquid crystal polymer and hexagonal boron nitride fiber network in polylactide matrix

Development of high thermally conductive and electrically insulative composites is of interest for electronic packaging industry. Advancements in smaller and more compact electronic devices required improvements in packing materials, including their weight, thermal conductivity, and electrical resistivity. In addition, with the increasing environmental awareness, the usage of green (bio‐based) alternatives was equally important. In the present study a hybrid based on fibers of highly concentrated hexagonal boron nitride (hBN) in liquid crystal polymer (LCP) matrix were fabricated. These hybrids were formed by arranging hBN platelets into LCP fiber form to reach high filler concentration and then randomly mix it in polylactide (PLA) matrix. With appropriate filler interaction within the hybrid, thermal conductivity similar to that of pure fiber could be achieved. Filler interaction may be tailored by optimizing the fibers aspect ratio. This study demonstrated the effect of random fillers in fibers shape in increasing the overall thermal conductivity of PLA polymeric hybrid using hBN and LCP fibers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 457–464     

Effect of thermal decomposition processes on the thermal properties of carbon fiber reinforced cement composites in high-temperature range

Thermal conductivity, specific heat capacity, thermal diffusivity and linear thermal expansion coefficient of two types of carbon fiber reinforced cement composites are measured in the temperature range up to 800°C. Thermal conductivity and thermal diffusivity are also determined for the specimens exposed to thermal load up to 800°C before the measurement. Differential thermal analysis (DTA), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) are utilized for the assessment of thermal decomposition processes taking place in the high temperature range under consideration. The high temperature thermal properties of the studied materials are found to be positively affected by the application of the high alumina cement and in the case of the Portland cement based composite also by using the autoclaving procedure in the production process. Also, the randomly distributed carbon fibers that can reduce the damage of the pore structure by the thermal decomposition processes are identified as a positive factor in this respect. A comparison of thermal conductivity vs. temperature curves obtained for the specimens pre-heated to different temperatures is found to be a useful tool in the identification of major dynamic effects in the specimens due to the thermal decomposition reactions. The results are in a good agreement with the DTA, MIP, SEM and XRD analyses. The character of the thermal conductivity measurements that in fact includes the effects of convection and radiation into the thermal conductivity coefficient can be beneficial for a simple assessment of the influence of the fire on a dividing structure.