Enhanced mechanical properties of polyamide 6 fibers coated with a polyurethane thin film

Polyamide 6 (PA6) fibers were coated with polycarbonate‐based thermoplastic polyurethanes (CPUs) by dip‐coating method and cured at 100°C for 24 h. There were abrupt increases in tensile strength and elongation at break of the CPU‐coated PA6 fibers. This was due to the increase of crystallinity from the structural changes inside the fiber induced with the CPU coating. An interfacial interaction region of 10 μm was formed at the interface of each PA6 fiber and the CPU‐thin film coating. Interface stiffening occurred when the PA6 fiber was under mechanical stress and the CPU coating delayed the formation of microcracks on the same under loaded stress. All these factors resulted in the increase of strength and elongation of CPU‐coated PA6 fibers. CPUs showed good adhesion to PA6 fibers. Blending has been the key to the performance enhancement of PA6 fibers, but the present method of thin film CPU coating improved their performance without changing the inherent morphological properties. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Electrically conductive composites of polyurethane derived from castor oil with polypyrrole‐coated peach palm fibers

Electrically conducting fibers were prepared through in situ oxidative polymerization of pyrrole (Py) in the presence of peach palm fibers (PPF) using iron (III) chloride hexahydrate (FeCl₃·6H₂O) as oxidant. The polypyrrole (PPy) coated PPF displayed a PPy layer on the fibers surface, which was responsible for an electrical conductivity of (2.2 ± 0.3) × 10⁻¹ S cm⁻¹, similar to the neat PPy. Electrically conductive composites were prepared by dispersing various amounts of PPy‐coated PPF in a polyurethane matrix derived from castor oil. The polyurethane/PPy‐coated PPF composites (PU/PPF–PPy) exhibited an electrical conductivity higher than PU/PPy blends with similar filler content. This behavior is attributed to the higher aspect ratio of PPF–PPy when compared with PPy particles, inducing a denser conductive network formation in the PU matrix. Electromagnetic interference shielding effectiveness (EMI SE) value in the X‐band (8.2–12.4 GHz) found for PU/PPF–PPy composites containing 25 wt% of PPF–PPy were in the range −12 dB, which corresponds to 93.2% of attenuation, indicating that these composites are promising candidates for EMI shielding applications. POLYM. COMPOS., 38:2146–2155, 2017. © 2015 Society of Plastics Engineers     

Dielectric studies of composite paper reinforced with polypyrrole coated pulp fibers from wasted egg holders

Development of thin, flexible, light‐weight, renewable, low‐cost, and environmentally friendly electrode materials are highly feasible in era of modern disposable electronic technology. This article presents the synthesis and dielectric studies of polypyrrole (PPy) coated pulp fibers, directly collected from wasted egg holder's tray. PPy coated pulp fibers converted into compact sheet for the development of potential renewable and low‐cost electrode materials. The morphology, chemical structure, and thermal stability of naked and PPy coated pulp fibril sheets were investigated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA), respectively. PPy coated pulp fibers revealed better thermal stability and compactness of sheet morphology. Impedance measurements showed a high value of dielectric constant of 1.15 × 10⁶ at 0.5 Hz and conductivity of 7.45 × 10^?4 S/cm at room temperature for PPy coated pulp fibril sheet. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42422.     

Preparation of silver nanoparticle functionalized polyamide fibers with antimicrobial activity and electrical conductivity

In this work, silver nanoparticle functionalized polyamide 6 (PA6) fibers were prepared using the electroless plating method. The surface of PA6 fibers was modified by exploiting dopamine/CuSO₄/H₂O₂ system prior to electroless plating to enhance the bonding force between the fiber and the silver nanoparticles. It was found that both the formation rate and the chemical stability of polydopamine (PDA) coatings on the PA6 fiber surface were improved by the introduction of CuSO₄/H₂O₂. The results confirmed the successful deposition of silver nanoparticles on PA6 fiber surface and the average particle diameter of 223 nm. Compared with uncoated fibers, the silver plated PA6 fibers exhibited excellent antimicrobial activity to both Escherichia coli and Staphylococcus aureus (with an antimicrobial efficiency of 99.9% and 100%, respectively). The electrical resistance of the silver coated PA6 fibers reached 0.98 Ω over a length of 1 cm, indicating a good electrical conductivity. In particular, coating durability of the formed silver layer was investigated by subjecting the fibers to various mechanical deformations, and the results showed that the formed silver layer was maintained well after 50 times of cyclic stretching at a constant displacement of 10 mm. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47584.     

Structure and mechanical behaviors of thermoplastic polyurethane thin film coated polyamide 6 fibers part II. A solution coating method

Thermoplastic polyurethane thin film (TPU) coated PA6 fibers were prepared by dipping fibers into a TPU solution. The thickness of the thin film coating was 20 μ m. A series of polymer glycols which include polycarbonate, polyether and polyester were used for the preparation of the TPU. Both tensile strength and elongation at break of the TPU coated fibers increased although both magnitudes of the TPUs are much lower than for the original PA6 fibers. Also there was a significant improvement in the abrasion resistance TPU coated PA6 fibers. The PA6 fibers are prone to micro-cracks when under mechanical stress but the TPU thin film coating delayed the formation of the micro-cracks, thereby improving the mechanical properties of PA6 fibers. The theoretical investigation on the effect of interface interaction region using the viscous flow model described could clearly explain the effect of the same on the mechanical performance of TPU coated PA6 fibers.     

Mechanical,thermal, and microwave properties of conducting composites of polypyrrole/polypyrrole‐coated short nylon fibers with acrylonitrile butadiene rubber

Pyrrole was polymerized in the presence of anhydrous ferric chloride as oxidant and p‐toluene sulfonic acid as dopant. Polypyrrole‐coated short nylon fibers were prepared by polymerizing pyrrole in the presence of short nylon fibers. The resultant polypyrrole (PPy) and PPy‐coated nylon fiber (F‐PPy) were then used to prepare rubber composites based on acrylonitrile butadiene rubber (NBR). The cure pattern, direct current (DC) conductivity, mechanical properties, morphology, thermal degradation parameters, and microwave characteristics of the resulting composites were studied. PPy retarded the cure reaction while F‐PPy accelerated the cure reaction. Compared to PPy, F‐PPy was found to be more effective in enhancing the DC conductivity of NBR. The tensile strength and modulus values increased on adding PPy and F‐PPy to NBR, suggesting a reinforcement effect. Incorporation of PPy and F‐PPy improved the thermal stability of NBR. The absolute value of the dielectric permittivity, alternating current (AC) conductivity, and absorption coefficient of the conducting composites prepared were found to be much greater than the gum vulcanizate. PPy and F‐PPy were found to decrease the dielectric heating coefficient and skin depth significantly. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

New strategy towards flame retardancy through design,synthesis, characterization,and fire performance of a chain extender in polyamide 6 composites

A novel flame‐retardant chain extension agent (9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide)‐3,5‐triglycidyl isocyanurate defined as DOPO‐TGIC was synthesized, and its chemical structure was well characterized and confirmed. The effect of DOPO‐TGIC as a synergistic agent on the flame retardancy, rheology, thermal and mechanical properties of polyamide 6/aluminum diethylphosphinate (PA6/AlPi) composites were investigated in details. The results demonstrated that PA6/AlPi/DOPO‐TGIC composites (1.6 mm) successfully passed UL‐94 V‐0 rating with the limiting oxygen index value of 30.5% when the total loading amount of AlPi/DOPO‐TGIC was 10 wt%. In order to achieve the equal flame‐retardant level, the individual AlPi was required 14 wt%. The incorporated DOPO‐TGIC improved the complex viscosity of PA6/AlPi/DOPO‐TGIC composites due to the chain extending reaction between epoxide groups in DOPO‐TGIC and the terminal groups of PA6 matrix. The mechanical performance of PA6/AlPi/DOPO‐TGIC composites was also improved compared with that of PA6/AlPi composites. DOPO‐TGIC stimulated to the formation of more sufficient and compact char layer during combustion. The higher melt viscosity and compact char layer of PA6 composites effectively constrained the volatilization of flammable gases, thus the heat release was reduced. Consequently, the introduction of DOPO‐TGIC simultaneously enhanced the flame retardant and mechanical properties of PA6/AlPi/DOPO‐TGIC composites compared with that of PA6/AlPi composites. POLYM. ENG. SCI., 59:E206–E215, 2019. © 2018 Society of Plastics Engineers     

Polyamide‐6 composites reinforced with cellulose fibers and fabricated by extrusion: Effect of fiber bleaching on mechanical properties and stability

We prepared polyamide‐6 (PA‐6) composites using bleached and semibleached cellulose fibers from Eucalyptus species by processing in a corotating interpenetrating twin‐screw extruder. PA‐6 is a challenging matrix because of its high processing temperature, which overlaps the thermodegradation temperature of the fibers. The selection of the processing conditions for extrusion and the use of the lubricant ethylene bis (stearamide) permitted the production of composites with 20, 30, and 40 wt% of bleached fibers, which are lighter than the corresponding glass fiber composites. Composites with 30 wt% of bleached fibers yield the best mechanical properties and good fiber/matrix interaction, as demonstrated by mechanical tests and scanning electron microscopy. X‐ray photoelectron spectroscopy studies showed that the natural moisture in the fibers promotes the fiber/matrix interaction through the formation of ester bonds. We assessed the effect caused by the presence of lignin in the fibers. Composites containing 30 wt% of semibleached fibers maintained the flexural properties and showed small improvements in thermal stability when compared with bleached fiber composites; however, there is a slight decrease in the tensile properties. Through accelerated aging tests, we observed that increased lignin concentration in the fibers reduced the formation of carbonyl compounds on sample surfaces, indicating a stabilization effect. POLYM. COMPOS., 38:299–308, 2017. © 2015 Society of Plastics Engineers     

Enhanced mechanical properties of multilayer nano‐coated electrospun nylon 6 fibers via a layer‐by‐layer self‐assembly

We reported the mechanical properties of the polyelectrolyte multilayer nano‐coated electrospun fiber mats with different number of layers. Multilayer nano‐coatings composed of layers of PSS and PAH were successfully deposited onto electrospun nylon 6 fibers via layer‐by‐layer self‐assembly. Compared with pure nylon 6 fibers, the morphology of polyelectrolyte multilayer coated nylon 6 fibers was uniform and smooth. The mechanical properties of polyelectrolyte multilayer coated random and aligned nylon 6 fibers were remarkably enhanced. Moreover, it was found that the higher degree of alignment resulted in higher tensile strength, suggesting the combined effects of the alignment, the surface nanocoating and the formation of internal networks of polyelectrolytes on nylone 6 fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of polyamide 6 incorporation to the short glass fiber reinforced ABS composites: an interfacial approach

The properties of 30 wt% short glass fiber (SGF) reinforced acrylonitrile-butadiene-styrene (ABS) terpolymer and polyamide 6 (PA6) blends prepared with extrusion were studied using the interfacial adhesion approach. Work of adhesion and interlaminar shear strength values were calculated respectively from experimentally determined interfacial tensions and short beam flexural tests. The adhesion capacities of glass fibers with different surface treatments of organosilanes were evaluated. Among the different silanes tested, γ-aminopropyltrimethoxysilane (APS) was found to be the best coupling agent for the glass fibers, possibly, because of its chemical compatibility with PA6. Tensile test results indicated that increasing amount of PA6 in the polymer matrix improved the strength and stiffness of the composites due to a strong acid–base interaction at the interface. Incorporation of PA6 to the SGF reinforced ABS reduced the melt viscosity, broadened the fiber length distributions and increased the toughness of the composites. Fractographic analysis showed that the incorporation of PA6 enhanced the interactions between glass fibers and the polymeric matrix.     

表面改性超高相对分子质量聚乙烯纤维的热性能研究

采用铬酸刻蚀和化学气相沉积聚吡咯处理了超高相对分子质量聚乙烯(UHMWPE)纤维。用DSC、DMA、X-射线衍射及SEM分析了纤维的热力学性能、结晶情况及纤维的表观形貌。结果表明,铬酸处理及化学气相沉积聚吡咯处理后,纤维的耐热性均有所提高,纤维表面变得更加粗糙,其中化学气相沉积聚吡咯处理的纤维变化更明显。     

Durable flame‐retardant and antidroplet finishing of polyester fabrics with flexible polysiloxane and phytic acid through layer‐by‐layer assembly and sol–gel process

A three‐layer functional coating was prepared through layer‐by‐layer (LbL) assembly and a sol–gel process. The multilayered coating was composed of a phytic acid (PA) coating dipped between two layers of flexible polysiloxane coatings and was deposited on the polyester fabric by LbL assembly. Flammability tests indicated that the multilayer coating prevented droplet generation during combustion. The PA also absorbed the reactive free radicals to reduce the flame‐burning rate. After being soaked for only 20 min in PA solution, the fabric exhibited self‐extinguishing properties and antidroplet effect during the vertical flame test, while cone calorimetry confirmed that the coated fabric exhibited a 65% decrease in the peak heat release rate and reduced the total amount of smoke released by 72%. After washing the coated fabric 45 times, there was no significant decrease in the phosphorus content and the limiting oxygen index of coated fabrics. Thus, the coating synthesized in this study is an effective method of constructing durable, functional coatings on the surface of fabrics. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46414.     

Short glass fiber reinforced ABS and ABS/PA6 composites: Processing and characterization

In this study acrylonitrile‐butadiene‐styrene (ABS) terpolymer was reinforced with 3‐aminopropyltrimethoxysilane (APS)‐treated short glass fibers (SGFs). The effects of SGF concentration and extrusion process conditions, such as the screw speed and barrel temperature profile, on the mechanical properties of the composites were examined. Increasing the SGF concentration in the ABS matrix from 10 wt% to 30 wt% resulted in improved tensile strength, tensile modulus and flexural modulus, but drastically lowered the strain‐at‐break and the impact strength. The average fiber length decreased when the concentration of glass fibers increased. The increase in screw speed decreased the average fiber length, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength were affected negatively and the strain‐at‐break was affected positively. The increase in extrusion temperature decreased the fiber length degradation, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength increased. At higher temperatures the ABS matrix degraded and the mechanical strength of the composites decreased. To obtain a strong interaction at the interface, polyamide‐6 (PA6) at varying concentrations was introduced into the ABS/30 wt% SGF composite. The incorporation and increasing amount of PA6 in the composites broadened the fiber length distribution (FLD) owing to the low melt viscosity of PA6. Tensile strength, tensile modulus, flexural modulus, and impact strength values increased with an increase in the PA6 content of the ABS/PA6/SGF systems due to the improved adhesion at the interface, which was confirmed by the ratio of tensile strength to flexural strength as an adhesion parameter. These results were also supported by scanning electron micrographs of the ABS/PA6/SGF composites, which exhibited an improved adhesion between the SGFs and the ABS/PA6 matrix. POLYM. COMPOS. 26:745–755, 2005. © 2005 Society of Plastics Engineers     

Surface modification of carbon nanofibers via deposition of an ultrathin coating of plasma‐polymerized poly(acrylic acid) and its effect on the properties of polyamide 6/CNF nanocomposites

Carbon nanofibers (CNFs) were coated with an ultrathin layer of poly(acrylic acid) (PAA) via plasma polymerization. The effect of the plasma reactor parameters on the extent of the CNF modification was studied. SEM micrographs showed that surface roughness increased with the plasma treatment. The thickness of the ultrathin PAA layer deposited on the CNF was determined by STEM to be ca. 8 nm. Untreated and treated CNF were melt‐mixed with polyamide 6 (PA6) in a Brabender mixing chamber to obtain PA6/CNF nanocomposites. The effect of the plasma treatment on the dispersion and compatibility was examined and found to improve markedly. Fractured tensile specimens showed that the CNF seemed to be completely embedded in the polymer matrix, indicating high compatibility between the PA6 and the PAA‐coated CNF. Tensile stress and tensile modulus of PA6 nanocomposites with treated CNF were found to increase by 30 and 48%, respectively, when compared with those with untreated CNF. However, the increase in tensile stress and modulus with respect to pure PA6 was 52 and 88%, respectively. Finally, XRD showed that the CNF induce the formation of the α (alpha)‐crystalline phase in PA6. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

化学气相沉积PPy/UHMWPE纤维的研究

采用化学气相沉积制备了聚吡咯/超高相对分子质量聚乙烯(PPy/UHMWPE)纤维,测试了不同氧化剂浓度、不同沉积时间和温度下PPy/UHMWPE纤维的表面剪切强度,用扫描电镜、动态热机械分析仪、傅立叶变换红外光谱仪分析了PPy/UHMWPE纤维的表面形态、热机械性能和复合材料官能团的变化。结果表明:PPy均匀分布在UHMWPE纤维表面,UHMWPE纤维与PPy之间无化学键作用而是分子间作用力;随着氧化剂三氯化铁浓度的增加和吡咯沉积时间的延长,PPy/UHMWPE纤维表面剪切强度先增大后减小;随着处理温度的升高,PPy/UHMWPE纤维表面剪切强度先增大,当处理温度超过85℃时,其剪切强度则减小。     

A novel method to graft carbon nanotube onto carbon fiber by the use of a binder

A novel method is developed for grafting multiwall carbon nanotubes (MWNTs) onto the surface of polyacrylonitrile‐based high strength (T300GB) carbon fiber. Functionalized MWNTs were well dispersed in the PVA solution and the carbon fiber was dip‐coated in this solution. After heat treatment of the coated carbon fiber under a nitrogen atmosphere, MWNTs with carboxyl groups were grafted onto the functionalized carbon fiber via chemical interaction. The resulting materials were characterized by Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FESEM), Raman spectrum and mechanical testing. FESEM observations revealed uniform coverage of carbon nanotubes on carbon fiber. The carbon fiber grafted with MWNTs improved the tensile strength by 12% with respect to the pristine carbon fiber. These results are supportive of good interfacial bonding between the carbon nanotubes (CNTs) and carbon fiber. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of hydrothermal carbon coating on the properties of CF/ZrB2/SiBCN prepared by slurry injection

With the advantages of short production cycle and facility, slurry injection technology will help explore new possibilities for the preparation of high-performance fiber toughened ultra-high-temperature ceramic (UHTC). Here, hydrothermal carbon (HTC) coating with abundant functional groups is developed on the surface of the carbon fiber (CF) to optimize the slurry injection process and finally enhance the performance of CF/ZrB₂/SiBCN. The enhanced surface energy of HTC coated CF could efficiency promote the injection process, ultimately contributing to the formation of the compact and uniform ceramic green body. The denser matrix of the finally product combined with the HTC coating establish an isolation between oxygen and fiber. Even in a more aggressive oxidation environment, the HTC coating could act as a sacrifice layer to prevent the fibers from damage. The results identify a unique attraction during the construction of CF/ZrB₂/SiBCN with optimal properties and could be extended to other CF/UHTCs.     

Melamine polyphosphate/silicon‐modified phenolic resin flame retardant glass fiber reinforced polyamide‐6

The halogen‐free flame retardance of glass fiber reinforced polyamide‐6 (PA6) is an everlastingly challenge due to well‐known wick effect. In this research, a novel system composed of a nitrogen–phosphorous flame retardant, melamine polyphosphate combined with a macromolecular charring agent, silicon‐modified phenolic resin (SPR), was employed to flame‐retard glass fiber reinforced PA6. It exhibited obvious synergistic effect between the two components at a proper ratio range. The flame retardance of the composites can be remarkably improved due to the increased amount and improved thermal stability of the produced char. The flame resistance tests indicated that the synergism system with an optimized ratio achieved V0 (1.6 mm) rating of UL94, 25.2% of Limited Oxygen Index, and only 338.2 W/g of the heat release peak rate. The corresponding synergistic mechanisms were investigated by the characterizations including the thermal gravimetric analysis, carbonation test, and the char morphology observation. It confirmed that the introduced SPR could accelerate the carbonation of PA6 resin, which was in favor of the construction of denser and more continuous charring structure. In addition, the flame retardant materials also indicated the acceptable mechanical properties, showing the advantages in the overall performance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and characterization of graphene reinforced PA6 fiber

Here, we report the successful preparation of PA6/GO composite fibers through in situ polymerization and the melting spinning method. The results suggest that graphene has induced only minor changes on the relative viscosity yet exhibits significant effects on the crystallization characteristics. The SEM images of the fibers have shown several expended borders as a consequence of graphene addition. The maximum strength of the composite fibers (5.3 cN/dtex) has been reached 0.05 wt % graphene added to the system; the draw ratio was equaled to 3.8. Compared to the neat PA6 fiber, the fibers with graphene displayed superior creep resistance features; the creep rate constant was 0.38 at a 0.05 graphene concentration, with a draw ratio of 3.5. The approach employed in this research paves the way towards PA6/graphene nanocomposites have been prepared through in situ polymerization using caprolactam and graphene oxide/water pulp as starting materials. In situ polymerization approach facilitated a superior interaction between PA6 and graphene. Compared to graphene oxide powder, the graphene oxide in water pulp has prevented the agglomeration when added to the caprolactam melt, leading to its enhanced dispersion within the system. PA6/graphene as‐spun fiber has been produced by the mean of melt‐spinning strategy using a melt‐spinning machine, obtaining products with different draw ratios after drawing at 120 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45834.