Effect of polyurethane sizing on carbon fibers surface and interfacial adhesion of fiber/polyamide 6 composites

Commercial epoxy sized carbon fibers (CFs) or unsized CFs have poor interfacial adhesion with polyamide 6 (PA6). Here, CFs are coated with polyurethane (PU) and their surface properties in terms of surface chemistry, contact angle, roughness, and morphology, are investigated. The results of Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy demonstrate PU sizing evidently increases the quantity of polar functional groups on the CFs surface. The surface energy of the PU sized fiber is calculated according to the Owens–Wendt method. Compared with unsized fibers, the contact angle of PU sized fibers is decreased while their total surface energy is increased, indicating superior wettability. Moreover, transverse fiber bundle tests are performed to determine the interfacial adhesion between the CFs and PA6 matrix. The transverse fiber bundle strength of unsized CF is measured to be 12.57 MPa. For PU sized CFs processed with sizing concentration of 1.2%, this value is increased to 24.35 MPa, showing an increase of more than 90%. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46111.     

Effects of the combination of solid lubricants and short carbon fibers on the sliding performance of poly(ether imide) matrix composites

Solid lubricants, that is, graphite flakes and poly(tetrafluoroethylene) powders, were incorporated with short carbon fibers into a poly(ether imide) matrix to improve the tribological performance. Wear tests were performed with a polymer pin against a mild steel counterpart at a constant sliding speed of 1 m/s under various temperatures and contact pressures. Composites filled with equilibrium contents of solid lubricants and short carbon fibers, that is, 10 vol % of each filler, exhibited the lowest wear rate and friction coefficient. The relatively lower concentration of solid lubricants adversely affected the wear resistance, whereas the friction coefficient did not vary significantly in comparison with the friction coefficient of the composites filled with only short carbon fibers. The improved tribological behavior was attributed to more continuous and effective friction films formed on the material pairs during sliding. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1428–1434, 2004     

Effect of calcium chloride on the surface properties of Kevlar fiber

In this study, we present a new approach to modify the surface of Kevlar‐29 fiber by the complexation. The surface of Kevlar‐29 fiber was treated by calcium chloride (CaCl₂) ethanol solution. The structure and morphology of the modified Kevlar‐29 fiber were characterized by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction instrument, atomic force microscopy, and scanning electron microscopy. The results showed that CaCl₂ treatment's method can cause changes of the chemical groups of Kevlar‐29 fiber. The amino‐groups of Kevlar‐29 fiber were freed and the contents of ‐C‐N‐ increased. The changes can improve the surface roughness of Kevlar‐29 fibers. This can increase the adhesive of Kevlar fiber/epoxy composites. From the ILSS and mechanical properties values, it can be concluded that treatment with 5 wt % CaCl₂ for 5 h is the optimum complexation condition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41358.     

Synthesis of hydrophilic to superhydrophobic SU8 surfaces

In published literature, it is widely reported that the plasma treatment and funtionalization with Octadecyltrichlorosilane (OTS) self‐assembled monolayer (SAM) can individually alter the wetting properties of SU8 surface. A combination of the two approaches gives better results and the synergism of the two approaches produces a superhydrophobic SU8 surface, which is presented in this work. We have investigated various composition of plasma for treatment of SU8 surfaces and permuted the treated SU8 surfaces with deposition of OTS SAM. In all such synergized experiments, we obtained water contact angle higher than 150°, which is much higher than the one that can be obtained with individual application of the two approaches. The combined approach presented in this work is suitable for bulk production of superhydrophobic surface, and is a mask‐less process, which makes it cost effective. The surface topography, wetting, and chemical properties of SU8 surfaces were characterized using the contact angle goniometry, atomic force microscopy, FTIR, Raman, and XPS spectra. The superhydrophobic SU8 surfaces were observed to be stable even after five months. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41934.     

Application of ultraviolet photografting technology to acrylamide/polyethylene to improve the interfacial adhesion of polyethylene/unsaturated polyester resin composites

This study was divided into two sections. In the first part, we used ultraviolet (UV) rays in the wavelength range 300–400 nm to remove the hydrogen atom from polyethylene (PE) and worked with a hydrophilic monomer to complete the grafting action. In the second part, we used the best conditions derived from the previous film grafting and applied them to fibers to achieve excellent adhesion for application in composite materials. For the handling process of the PE film, we initially used acrylamide (AM) as the monomer and then added acetone and benzophenone (BP) to form a reactive solution for the advanced photografting process. In general, the optimum concentrations of the monomer solutions obtained from the photografting of PE films were 2 mol/L of AM and 0.2 mol/L of BP. The UV irradiation time was fixed at 30 min. The optimum grafting conditions achieved in the first part of this research were applied in the photografting process for the PE fiber bundles in the second part. The unsaturated polyester (UP) resins were spread over the outer surfaces of the modified fibers. This was done to strengthen and increase the interface between the UP resins and the modified PE fiber. During the curing experiment of the grafted fiber bundles in the resin coatings, the best material quality was obtained under the following conditions: hardener content = 0.85% (relative to the UP resin weight), oven temperature = 80°C, and time frame = 5 h. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Soy‐filled polyethylene fibers for modified surface and hydrophilic characteristics

By adding soy flour (soy) to linear low‐density polyethylene (LLDPE), soy‐PE fibers with enhanced hydrophilic characteristics were developed. Blends containing only soy and LLDPE had limited draw‐down, and the resulting thick fibers showed poor mechanical properties. When monoglyceride was added as a compatibilizer, thin fibers with good properties could be successfully spun due to improved dispersion of soy agglomerates in the LLDPE melt. Fibers spun from a blend containing 23/7/70 wt % of soy‐monoglyceride‐LLDPE displayed a tensile modulus and strength of 615 ± 38 and 57 ± 8 MPa, respectively. At 30% less synthetic content, these fibers still displayed mechanical properties generally comparable to those of base polyethylene fibers. Contact angle measurements showed that the soy‐based fibers had a hydrophilic surface (contact angle of 33° ± 4°). Moisture absorption studies confirmed that soy‐PE fibers gained about 20 wt % moisture in 1 h, whereas neat LLDPE fibers did not absorb any significant amount (LLDPE is hydrophobic). This hydrophilic behavior of soy‐PE fibers mimics that of natural fibers. Presence small soy agglomerates on the fiber surface also provides a textured surface and a desired tactile feel to the soy‐PE fibers, which coupled with hydrophilic behavior indicates their potential use in disposable nonwovens. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46609.     

超疏水/亲水性结构表面流动沸腾传热实验研究

用激光烧蚀方法在抛光后的铜上制备出四种无需涂覆修饰即可获得超疏水/亲水性的规则微阵列结构表面。基于流动可视化与温度数据结果,分析了表面浸润性和过冷度对流动沸腾传热性能的影响,与经典汽化核心密度关联式进行了对比。结果表明：疏水表面可削弱单相对流传热,大幅强化沸腾传热,最大传热系数提高了75.5%,沸腾起始点提前3.5 K,且汽化核心数目较裸铜表面提高了5倍以上,但有较低的临界热通量。超亲水表面可增强单相对流传热、小幅度提升流动沸腾传热。对比亲水表面与疏水表面的气泡生长过程,发现疏水表面尾端气泡容易汇聚,生长周期较长;而亲水表面没有发生明显的气泡汇聚行为,气泡生长周期较短。     

Additive manufacturing of high-strength polyamide 6 composites reinforced with continuous carbon fiber prepreg

The additive manufacturing of continuous fiber reinforced thermoplastics (CFRTPs) paves way for the high-strength, light-weight components for variety of load-bearing applications. In this work, the continuous carbon fiber reinforced PA6 (CCF-PA6) composites was successfully printed from the prepreg filament. The prepreg filament was prepared in-house by impregnating the heat-and-acid treated 1 K carbon fiber bundle with the molten PA6. The tensile strength of the prepreg filament, which contained with 40 vol% CF, reached 984 MPa. The unidirectional CCF-PA6 specimens were subsequently 3D-printed with the prepreg filament, and the mechanical strength of those 3D-printed specimens were tunable by adjusting a set of printing parameters, such as layer thickness, hatch spacing and printing temperatures. The highest tensile strength of the specimen reached 555 MPa. Those specimens also exhibited outstanding mechanical strength at elevated temperatures, still reaching 184 MPa at 150°C. The mechanical strength of those specimens was dependent on the content of the fiber. This study can hopefully provide new insights for feedstock design and spur novel ideas in tailoring the mechanical properties of the 3D-printed CFRTPs.     

Enhancement of physical and mechanical properties of polyamide 66 fibers using polysiloxane-functionalized multi-walled carbon nanotubes

A polyamide 66/3-aminopropyl-terminated poly(dimethylsiloxane) (PA66/APDMS)-carboxylate multiwalled carbon nanotubes (CMWNTs) nanocomposite (PA66/APDMS-CMWNTs) was synthesized using a one-pot method, and the product was melt-spun into fibers. The glass transition temperature (T_g) of the PA66/APDMS-CMWNTs nanocomposite fiber is 68.0°C, which is 22% higher than that of the pure PA66 fiber. This result indicates that there is a strong interfacial interaction between APDMS-CMWNTs and the PA66. Furthermore, the crystallinity of PA66/APDMS-CMWNTs nanocomposite fiber reaches a maximum due to the addition of APDMS-CMWNTs. Additionally, the tensile strength and Young's modulus of PA66/APDMS-CMWNTs nanocomposite fiber are 167% and 631% higher, respectively, than that of the pure PA66 fiber. The strengthening mechanism was discussed using force balance-based expression, which demonstrates that the stress on the PA66 is more efficiently transferred to the APDMS-CMWNTs. These results argue that using APDMS-CMWNTs as a filler can enhance the physical-mechanical properties of PA66 with an elevated degree never being reported.     

Effect of silk fiber to the mechanical and thermal properties of its biodegradable composites

In recent years, natural fiber‐reinforced biodegradable thermoplastics are being recognized as an emerging new environmentally friendly material for industrial, commercial, and biomedical applications. Among different types of natural fibers, silk fiber is a common type of animal‐based fiber, has been used for biomedical engineering and surgical operation applications for many years because of its biocompatible and bioresorbable properties. On the basis of our previous study, a novel biodegradable biocomposite for biomedical applications was developed by mixing chopped silk fiber and polylactic acid (PLA) through the injection molding process. This article is aimed at studying the dynamic mechanical and thermal properties of the composite in relation to its biodegradation effect. At the beginning, it was found that the initial storage modulus of a silk fiber/PLA composite increased while its glass transition temperature decreased as compared with a pristine PLA sample. Besides, the coefficient of linear thermal expansions (CLTE) of the composite was reduced by 28%. This phenomenon was attributed to the fiber–matrix interaction that restricted the mobility of polymer chains adhered to the fiber surface, and consequently reduced the T_g and CLTE. It was found that the degraded composite exhibited lower initial storage modulus, loss modulus and tan delta (tan δ) but the T_g was higher than the silk fiber/PLA composite. This result was mainly due to the increase of crystallinity of the composite during its degradation process. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

辊式涂布法构建纸基牢固超疏水表面

采用辊式涂布的方法在纸基材料上构建超疏水表面,并对超疏水表面的牢固性、自清洁性和疏水性能进行评价。用γ-氨丙基三乙氧基硅烷和1H,1H,2H,2H-全氟辛基三乙氧基硅烷（POTS）对微米级和纳米级两种尺寸的TiO₂粒子进行疏水改性处理,然后将改性后的微/纳米TiO₂涂布在纸基材料表面。采用红外光谱（FTIR）对改性后的微/纳米TiO₂的化学组成进行了分析,采用扫描电镜（SEM）对涂布纸表面结构进行了表征,通过接触角、耐磨性和自洁净测试评价了涂层表面的超疏水性、牢固性和自清洁性。改性TiO₂的FTIR分析显示在1000～1500cm^-1之间出现多个C—F键的伸缩振动峰,表明POTS通过化学键与TiO₂表面发生了结合。涂布纸表面的SEM分析可以看出,纸基材料表面上均匀分布了微米和纳米尺寸的TiO₂颗粒,具备了类似荷叶表面微-纳结构的粗糙表面。涂层表面的水接触角为153°±1.5°,滚动角为3.5°±0.5°,水滴在涂层表面呈球形,极易滑落,涂层在水中浸泡7天后,接触角没有发生明显变化,表明纸张表面具备了优异的超疏水性能,且疏水稳定性较好。涂层表面经过10次循环磨损试验后,接触角仍能达到150°,滚动角为9°,表明机械摩擦没有对涂布纸表面的化学成分和粗糙结构造成明显的破坏,超疏水表面的牢固性较好。自洁净测试表明,涂布纸表面具有良好的自清洁和防污性能。该工艺过程操作简单,易于实现工业化生产,为在纸基表面构建综合性能优异的超疏水表面提供了一种新的便利途径。     

Plasma‐graft polymerization of a monomer with double bonds onto the surface of carbon fiber and its adhesion to a vinyl ester resin

Double bonds reactive with active radical species were introduced onto the surface of carbon yarn by the plasma‐graft polymerization of adipic acid divinyl ester and ethylene glycol dimethacrylate monomers to increase the adhesive strength in the interface between the carbon yarn and a vinyl ester resin. The degree of grafting increased with increasing polymerization time and polymerization temperature. The degree of grafting depended on both the solvent and the monomer species used in the polymerization, and a high degree was obtained with ethylene glycol dimethacrylate as the conjugated monomer and in a mixture of methyl isobutyrate and water. The grafted yarn, whose surface layer contained double bonds, was reacted with a vinyl ester resin containing benzoyl peroxide and N,N‐dimethylaniline. The pull‐out force of the yarn embedded in the resin increased with increasing degree of grafting. The failure in pulling out the yarn was cohesive. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2415–2419, 2003     

Coimmobilization of malic enzyme and alanine dehydrogenase on organic–inorganic hybrid gel fibers and the production of L‐alanine from malic acid using the fibers with coenzyme regeneration

Malic enzyme (EC 1.1.1.39) and alanine dehydrogenase (EC 1.4.1.1) were entrap‐immobilized on hybrid gel fibers of cellulose acetate (CA) and zirconium (Zr) alkoxide by air‐gap wet spinning. The production of L ‐alanine from malic acid with coenzyme regeneration was examined with the enzymes immobilized on the fibers. The productivity of L ‐alanine of the immobilized enzymes decreased to approximately one‐fifth of that of free enzymes, but the CA–Zr‐fiber‐immobilized enzymes retained a high level of productivity after repeated use. Reduced form of nicotinamide adenine dinucleotide (NADH) recycling also occurred effectively for the enzymes immobilized on the fiber. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Modified atmosphere packaging bags of peanuts with effect of inhibition of aflatoxin growth

In this article, packaging bags composited with selective barrier film and moisture absorbent nonwoven fabrics were prepared to design a kind of functional bags, which can inhibit the growth of aflatoxin of peanuts. The influences of the super‐absorbent fiber (SAF) and jute fiber on the internal relative humidity (RH) were investigated. It is found that jute nonwoven/selective barrier film composite bag can prevent the growth of aflatoxin B₁ of peanuts under the environment studied in this article because peanuts with higher moisture content can reduce O₂ content inside the bag by the aerobic respiration, achieving the modified atmosphere packaging (MAP) effect. In addition, a low RH micro‐environment can be achieved by using SAF as moisture absorbent. It is promising to design a packaging bag with the effect of inhibition of the growth of aflatoxin of peanuts, by selecting proper moisture absorbent and selective barrier film of the composite bag. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40190.     

Discontinuous carbon fiber/polyamide composites with microencapsulated paraffin for thermal energy storage

This work focuses on the development of multifunctional thermoplastic composites with thermal energy storage capability. A polyamide 12 (PA12) matrix was filled with a phase change material (PCM), constituted by paraffin microcapsules (T_melt = 43 °C), and reinforced with carbon fibers (CFs) of two different lengths (chopped/CF “long”[CFL] and milled/CF “short” [CFS]). DSC tests showed that the melting/crystallization enthalpy values increase with the PCM weight fraction up to 60 J/g. The enthalpy was 41–94% of the expected value and decreased with an increase in the fiber content, because the capsules were damaged by the increasing viscosity and shear stresses during compounding. Long CFs increased the elastic modulus (+316%), tensile strength (+26%), and thermal conductivity (+54%) with respect to neat PA12. Thermal imaging tests evidenced a slower cooling for the samples containing PCM, and once again the CFS-containing samples outperformed those with CFL, due to the higher effective PCM content. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47408.     

Effect of surface treatment on the physicomechanical and thermal properties of high‐density polyethylene/olive husk flour composites

In this study, a particular interest was focused on the recovery of lignocellulosic waste of olive husk flour (OHF) by its incorporation as filler in manufacturing composite materials based on high‐density polyethylene (HDPE) matrix with various filler contents (10, 20, and 30 wt %). The problem of incompatibility between the hydrophilic filler and the hydrophobic matrix was treated with two methods: the first method consists of using maleic anhydride‐grafted polyethylene (MAPE) as compatibilizer in HDPE/OHF composites. The second method, was focused on the chemical modification of OHF by vinyl‐triacetoxy‐silane (VTAS). Fourier transform infrared spectroscopy is used to analyze both grafting and silanization reactions involved. Scanning electron microscopy was used to show the morphology of the flour surface. Furthermore, the physicomechanical and thermal characteristics of the various composite samples were investigated as a function of filler contents and treatment types. The results showed that the properties of the composite materials are positively affected by the silanization treatment of OHF and also by MAPE addition. However, better mechanical and thermal properties with less moisture absorption were obtained for the composite materials compatibilized with MAPE. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Anisotropy of the elastic modulus for hybrid composites reinforced by short fibers and particles with respect to material porosity

Hybrid composites reinforced by short fibers and particles (HCRSFPs) have been widely used in many fields, and more and more scholars are paying attention to hybrid composites. In this study, the elastic moduli of HCRSFPs in arbitrarily chosen directions were investigated with respect to their porosities. A material model was built with the assumption of a compound of particles and polymer matrix containing voids as an effective matrix, and the HCRSFPs were treated as the compound of short fibers and the effective matrix. With consideration of the three‐dimensional spatial orientation distribution and the length distribution of the short fibers, the laminate analog approach and the Halpin–Tsai model were used to predict the elastic moduli of the HCRSFPs. Numerical examples and analyses showed that the fiber orientation distribution, reinforcement volume fraction, and porosity had great effects on the elastic moduli of the HCRSFPs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43708.     

Effect of rare earth elements surface treatment on tensile properties of aramid fiber‐reinforced epoxy composites

Solutions of rare earth modifier (RES) and epoxy chloropropane (ECP) grafting modification method were used for the surface treatment of aramid fiber. Tensile properties of both the aramid/epoxy composites and single fibers were tested. The effects of RES concentration on tensile properties of aramid/epoxy composites were investigated in detail to explore an optimum amount of rare earth elements in solution for modifying aramid fiber. The fracture surface morphologies of tensile specimens were observed and analyzed with the aid of SEM. The experimental results show that rare earth treatment is superior to ECP grafting treatment in promoting interfacial adhesion between the aramid fiber and epoxy matrix. Meanwhile, the tensile strengths of single fibers were almost not affected by RES treatment. The optimum performance is obtained when the content of rare earth elements is 0.5 wt %. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1037–1041, 2004     

Sustainable biocomposites from biobased polyamide 6,10 and biocarbon from pyrolyzed miscanthus fibers

The reinforcing effects of biocarbon of varying particle size ranges (crushed, <500, 500–426, 250–213, and <63 µm) on biobased polyamide 6,10 (PA 6,10) at 20 wt % loading were investigated for the resulting biocomposites. The heat deflection temperature and impact strength were observed to increase with reduction in particle size. Also, a 200% increase in the impact strength was observed in the biocomposite with biocarbon particles sized at <63 µm when compared to that with <500 µm. A 50% and 83% increase in the tensile and flexural moduli of the biocomposite with biocarbon particle size of <500 µm was observed, respectively, while the tensile strength was observed to remain unchanged. The flexural strength of the biocomposites was improved by 61% when compared to neat nylon. These results were due to good wetting, dispersion and increased surface area of the biocarbon within the nylon matrix. These results show the potential of biocarbon as reinforcing filler in nylon for applications especially in the automotive industry. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44221.     

Effects of fiber‐surface treatment on the properties of hybrid composites prepared from oil palm empty fruit bunch fibers,glass fibers,and recycled polypropylene

In this article, we report the effects of hybridization and fiber‐surface modification on the properties of hybrid composites prepared from recycled polypropylene (RPP), coupling agents, oil palm empty fruit bunch (EFB), and glass fibers through a twin‐screw extruder and an injection‐molding machine. The surface of the EFB fibers was modified with different concentrations (10–15 wt %) and temperatures (60–90°C) of alkali solutions. The structure and morphology of the fibers were observed with the help of Fourier transform infrared spectroscopy and scanning electron microscopy. Different types of composites were fabricated with untreated, alkali‐treated, and heat‐alkali‐treated fibers. Comparative analysis of the mechanical, structural, morphological, and thermal properties of the composites was carried out to reveal the effects of treatment and hybridization. The analysis results reveal that composites prepared from the alkali‐treated (in the presence of heat) fibers show improved mechanical, thermal, and morphological properties with a remarkably reduced water absorption. Additionally, the crystallinity of RPP also increased with the development of biaxial crystals. The improvement of various properties in relation to the structures and morphologies of the composites is discussed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43049.