Study of flame‐resistant acrylic fibers reinforced by poly(vinyl alcohol)

Acrylic fibers [polyacrylonitrile (PAN) fibers] have excellent flame‐retardant properties after they are modified by hydrazine hydrate and metal ions; however, their widespread applications are restricted because of poor mechanical properties. To improve the mechanical properties of these modified PAN fibers, poly(vinyl alcohol) (PVA) was added to the spinning solution of PAN as an effective reinforcing agent. The structure of the fibers before and after modification was studied by Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive spectroscopy, and wide‐angle X‐ray diffraction. The mechanical properties and flame resistance of the fibers after treatment were also tested by a single‐fiber tensile tester and a limiting oxygen index (LOI) analyzer, respectively. We found that the LOI of the modified fibers was reduced from 54.7 to 29.1 after the introduction of 50 wt % PVA; however, the tensile strength was dramatically improved from about 1.50 cN/dtex to more than 4.00 cN/dtex. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43006.     

Surface chemical modification of natural cellulose fibers

Simple esterification and etherification reactions were applied to steam‐exploded Flax (Linum usitatissimum) with the aim of changing the surface properties through modification of fiber surface chemistry. Native and chemically modified cellulose fibers were characterized in terms of thermal stability, surface chemistry, morphology, and crystal structure. Independent of the substituent nature, chemically modified fibers exhibited a thermal stability comparable to that of native cellulose. Introduction of the desired chemical groups at the fiber surface was demonstrated by TOF‐SIMS analysis, whereas FTIR showed that the substitution reaction involved only a small fraction of the cellulose hydroxyls. No change of the native crystalline structure of cellulose fibers was caused by chemical modification, except in the case where ether substitution was carried out in water‐isopropanol medium. Cellulose fibers with unchanged structure and morphology and carrying at the surface the desired chemical groups were obtained for reinforcing applications in polymer composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 38–45, 2002     

Synthesis and properties of click coupled graphene oxide sheets with three‐dimensional macromolecules

A facile click chemistry approach to the functionalization of three‐dimensional hyperbranched polyurethane (HPU) to graphene oxide (GO) nanosheets is presented. HPU‐functionalized GO samples of various compositions were synthesized by reacting alkyne‐functionalized HPU with azide‐functionalized GO sheets. The morphological characterization of the HPU‐functionalized GO was performed using transmission electron microscopy and its chemical characterization was carried out using Fourier transform‐infrared spectroscopy, nuclear magnetic resonance spectroscopy, and X‐ray photoelectron spectroscopy. The graphene sheet surfaces were highly functionalized, leading to improved solubility in organic solvents, and consequently, enhanced mechanical, thermal, and thermoresponsive and photothermal shape memory properties. The strategy reported herein provides a very efficient method for regulating composite properties and producing high performance materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43358.     

Morphological and mechanical behavior of chemically treated jute‐PHBV bio‐nanocomposites reinforced with silane grafted halloysite nanotubes

In this study, at first, thin films of poly(3‐hydroxybutyrate‐co?3‐hydroxyvalerate) (PHBV) nanocomposites were prepared by adding 1–3 wt % grafted halloysite nanotubes (G‐HNTs). Jute‐PHBV bio‐nanocomposites were then fabricated using these films and chemically treated jute fibers in a compression mold machine. The effect of treatment and modification on jute fiber and halloysite nanotubes (HNTs), and the change in their morphology was investigated using Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM). Flexural and thermomechanical properties were determined using a three‐point bend test and dynamic mechanical analysis (DMA). The results showed separation of fiber bundles with rough fiber surfaces, and grafting of silane coupling agents on fibers and HNTs after the chemical treatment. As a result, a strong bonding was established between the PHBV, G‐HNTs and jute fibers that lead to significant improvements in flexural and thermomechanical properties of jute‐PHBV bio‐nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43994.     

Mechanical,morphological, and thermal properties of chemically treated pine needles reinforced thermosetting composites

Natural fibers are widely used as reinforcement in composites. Pine needles are one of the major biowaste generated by Pinus roxburgii plant. This species is found abundantly in the forests of Himachal Pradesh. In this work, composites of urea–resorcinol–formaldehyde resin‐reinforced with Pine needles fibers were prepared. Fibers were chemically modified to improve their compatibility with matrix. These fibers were mercerized with NaOH solution and acetylated to increase their hydrophobic character. The chemically modified fibers were characterized with Fourier transform infrared spectra, ¹³C‐nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy. The composites were prepared with treated and untreated fibers containing 30% fibers by weight using compression molding technique. The morphology of the materials thus obtained was evaluated by scanning electron microscopy. The chemical modifications of fibers improve fiber–matrix adhesion and also have markedly effect on mechanical properties of composites. Moreover, the thermal resistance of these composites was improved on chemical modification. These results indicate that chemically modified fibers exhibit better compatibility with the polymer matrix than that of untreated fiber. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci, 2013     

Synthesis of click‐coupled graphene sheets with hyperbranched polyurethane: Effective exfoliation and enhancement of nanocomposite properties

Graphene oxide (GO) was functionalized with hyperbranched polyurethane (HBPU) via click coupling between azide‐functionalized HBPU and alkynyl‐decorated GO. HBPU‐functionalized GO composites of various compositions were prepared. The azide‐containing HBPU was characterized using Fourier‐transform infrared (FT‐IR) spectroscopy and ¹H‐nuclear magnetic resonance spectroscopy. The HBPU‐functionalized GO composites were characterized using transmission electron microscopy and FT‐IR spectroscopy. The functionalized GO showed excellent dispersion in the HBPU matrix, giving composites with enhanced mechanical and thermal properties. The material properties were effectively regulated by click‐coupled exfoliation of GO with HBPU, enabling the production of high‐performance materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44631.     

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.     

Bamboo fiber reinforced polypropylene composites and their mechanical,thermal, and morphological properties

Short bamboo fiber reinforced polypropylene composites were prepared by incorporation of various loadings of chemically modified bamboo fibers. Maleic anhydride grafted polypropylene (MA‐g‐PP) was used as compatibilizer to improve fiber–matrix adhesion. The effects of bamboo fiber loading and modification of the resin on the physical, mechanical, thermal, and morphological properties of the bamboo reinforced modified PP composites were studied. Scanning electron microscopy studies of the composites were carried out on the interface and fractured surfaces. Thermogravimetric analysis and IR spectroscopy were also carried out. At 50% volume fraction of the extracted bamboo fiber in the composites, considerable increase in mechanical properties like impact, flexural, tensile, and thermal behavior like heat deflection temperature were observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fabrication of a poly(N‐vinyl‐2‐pyrrolidone) modified macroporous polypropylene membrane via one‐pot reversible‐addition fragmentation chain‐transfer polymerization and click chemistry

In this study, a macroporous polypropylene membrane (MPPM) was grafted with hydrophilic poly(N‐vinyl‐2‐pyrrolidone) (PNVP) based on a one‐pot reversible‐addition fragmentation chain transfer (RAFT) polymerization and click chemistry. First, we prepared the clickable membrane by bromination and following S_N2 nucleophilic substitution reaction; then, click chemistry and RAFT polymerization were performed in one‐pot to graft PNVP to the MPPM surface. The surface characterizations, including attenuated total reflectance/Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and field‐emission scanning electron microscopy, illustrated that PNVP was really grafted onto the MPPM surface. The permeation and antifouling characteristics of the MPPMs were measured by the filtration of a bovine serum albumin dispersion; this showed that in contrast to the nascent membrane, the grafted membrane efficiently obstructed protein molecules because of the compactly grafted polymer chains. The hydrophilicity and antifouling properties of MPPM were greatly ameliorated after modification. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42649.     

A comparative study of characteristics of polytetrafluoroethylene fibers manufactured by various processes

A series of polytetrafluoroethylene (PTFE) fibers were manufactured by three processing methods including extrusion process, split‐sheet process and split‐film process. The influence of processing methods on fiber properties were systematically studied using four PTFE powders with various molecular weights (3.86 × 10⁷, 4.71 × 10⁷, 4.92 × 10⁷ and 5.11 × 10⁷, respectively). Morphology, crystallinity, tensile behavior and friction properties of PTFE fibers were compared by scanning electron micrograph, X‐ray diffraction pattern, strength‐elongation curves and friction coefficients, respectively. The results showed that the in terms of flat filaments, mechanical properties became weak with the increase of molecular weight of PTFE powders at first, but were improved dramatically with further enhancement of molecular weight. In the case of both round filaments and split‐film fibers, fiber properties were improved with growth of molecular weight. Based on characteristics and friction coefficients, potential applications of three types of PTFE samples were analyzed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43553.     

Carboxymethylcellulose (CMC) as a model compound of cellulose fibers and polyamideamine epichlorohydrin (PAE)–CMC interactions as a model of PAE–fibers interactions of PAE‐based wet strength papers

Carboxymethylcellulose (CMC) is a cellulose derivative obtained by the carboxymethylation of some hydroxyl groups in the cellulose macromolecules. In this article, we use CMC as a model compound of cellulose fibers to study polyamineamide epichlorohydrin (PAE)–fibers interactions during the preparation of PAE‐based wet strength papers. The main advantages of the use of CMC to replace cellulose fibers are its water‐soluble character and the homogeneous reaction medium during mixing with PAE resin. Based on ¹³C cross‐polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) and Fourier transformed infra‐red (FTIR) spectroscopy, we prove the formation of ester bonds in PAE–CMC films boosted by a thermal posttreatment at 105°C for 24 h. These ester bonds are derived from a thermally induced reaction between carboxyl groups in the CMC structure and azetidinium ions (AZR) in the PAE resin. PAE‐based handsheets were prepared from 100% Eucalyptus fibers. After preparation, some samples were thermally posttreated (TP) at 130°C for 10 min and stored under controlled conditions (25°C and 50% relative humidity or RH). For lowest PAE dosage, storage of the not thermally posttreated (NTP) PAE‐based handsheets does not allow them to reach the tensile strength values of TP PAE‐based handsheets (at 130°C for 10 min), but the difference in terms of breaking length remains low. For the highest PAE addition level, NTP and TP PAE‐based handsheets exhibit close values of the breaking length from 30 days of storage under controlled conditions (25°C and 50% RH). When a thermal posttreatment is applied, the wet strength development of PAE‐based papers is a combined effect of homo‐ and co‐cross‐linking mechanisms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42144.     

Bleached extruder chemi‐mechanical pulp fiber‐PLA composites: Comparison of mechanical,thermal, and rheological properties with those of wood flour‐PLA bio‐composites

An environmentally friendly bleached extruder chemi‐mechanical pulp fiber or wood flour was melt compounded with poly(lactic acid) (PLA) into a biocomposite and hot compression molded. The mechanical, thermal, and rheological properties were determined. The chemical composition, scanning electron microscopy, and Fourier transform infrared spectroscopy results showed that the hemicellulose in the pulp fiber raw material was almost completely removed after the pulp treatment. The mechanical tests indicated that the pulp fiber increased the tensile and flexural moduli and decreased the tensile, flexural, and impact strengths of the biocomposites. However, pulp fiber strongly reinforced the PLA matrix because the mechanical properties of pulp fiber‐PLA composites (especially the tensile and flexural strengths) were better than those of wood flour‐PLA composites. Differential scanning calorimetry analysis confirmed that both pulp fiber and wood flour accelerated the cold crystallization rate and increased the degree of crystallinity of PLA, and that this effect was greater with 40% pulp fiber. The addition of pulp fiber and wood flour modified the rheological behavior because the composite viscosity increased in the presence of fibers and decreased as the test frequency increased. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44241.     

Surface modification of UHMWPE fibers by means of polyethylene wax grafted maleic anhydride treatment

A novel surface modification method for ultrahigh molecular weight polyethylene (UHMWPE) fibers to improve the adhesion with epoxy matrix was demonstrated. Polyethylene wax grafted maleic anhydride (PEW‐g‐MAH) was deposited on the UHMWPE fibers surface by coating method. The changes of surface chemical composition, crystalline structure, mechanical properties of fiber and composite, wettability, surface topography of fibers and adhesion between fiber and epoxy resin before and after finishing were studied, respectively. The Fourier transform infrared spectroscopy spectra proved that some polar groups (MAH) were introduced onto the fiber surface after finishing. The X‐ray diffraction spectra indicated that crystallinity of the fiber was the same before and after finishing. Tensile testing results showed that mechanical properties of the fiber did not change significantly and the tensile strength of 9 wt % PEW‐g‐MAH treated fiber reinforced composite showed about 10.75% enhancement. The water contact angle of the fibers decreased after finishing. A single‐fiber pull out test was applied to evaluate the adhesion of UHMWPE fibers with the epoxy matrix. After treatment with 9 wt % PEW‐g‐MAH, a pull‐out force of 1.304 MPa which is 53.59% higher than that of pristine UNMWPE fibers was achieved. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46555.     

Functionally modified,melt‐electrospun thermoplastic polyurethane mats for wound‐dressing applications

The electrospinning of a polymer melt is an interesting process for medical applications because it eliminates the cytotoxic effects of solvents in the electrospinning solution. Wound dressings made from thermoplastic polyurethane (TPU), particularly as a porous structured electrospun membrane, are currently the focus of scientific and commercial interest. In this study, we developed a functionalized fibrillar structure as a novel antibacterial wound‐dressing material with the melt‐electrospinning of TPU. The surface of the fibers was modified with poly(ethylene glycol) (PEG) and silver nanoparticles (nAg's) to improve their wettability and antimicrobial properties. TPU was processed into a porous, fibrous network of beadless fibers in the micrometer range (4.89 ± 0.94 μm). The X‐ray photoelectron spectroscopy results and scanning electron microscopy images confirmed the successful incorporation of nAg's onto the surface of the fiber structure. An antibacterial test indicated that the PEG‐modified nAg‐loaded TPU melt‐electrospun structure had excellent antibacterial effects against both a Gram‐positive Staphylococcus aureus strain and Gram‐negative Escherichia coli compared to unmodified and PEG‐modified TPU fiber mats. Moreover, modification with nAg's and PEG increased the water‐absorption ability in comparison to unmodified TPU. The cell viability and proliferation on the unmodified and modified TPU fiber mats were investigated with a mouse fibroblast cell line (L929). The results demonstrate that the PEG‐modified nAg‐loaded TPU mats had no cytotoxic effect on the fibroblast cells. Therefore, the melt‐electrospun TPU fiber mats modified with PEG and nAg have the potential to be used as antibacterial, humidity‐managing wound dressings. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40132.     

Melamine formaldehyde/polyvinyl alcohol composite fiber: Structures and properties controlled by reaction‐induced phase separation

Melamine?formaldehyde resin (MF)/polyvinyl alcohol (PVA) composite fibers with different phase structures and properties were prepared through reaction induced phase separation by wet spinning. Raman spectroscopy, rotary viscometer, and miscibility index were used to characterize the MF resins with different reaction degrees (RD). The phase structures of composite spinning dopes and composite fibers were observed by optical microscope (OM) and scanning electron microscope (SEM). Mechanical properties, flame retardant properties, and thermal stability of the composite fibers were also tested. Results show that the composite fibers made from MF resins with different RD have different phase structures and properties; when the miscibility index (MI) of MF resin is 1.60, the obtained MF/PVA composite fiber shows a sea‐island phase structure, which endues the fiber with the best comprehensive properties: the breaking strength, breaking elongation, rupture work and limiting oxygen index (LOI) are 4.29 cN/dtex, 13.55%, 8.46 × 10^?5 J/dtex and 43.1%, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42918.     

Method for the synthesis of para‐aramid nanofibers

The synthesis and electrospinning of novel N‐substituted aramid nanofibers (ANFs) prepared from basic dispersions of commercial microscale Kevlar fibers are herein reported. The functionalized ANFs were characterized via Fourier transform infrared spectroscopy, ¹³C solid‐state nuclear magnetic resonance spectroscopy, and X‐ray diffraction to confirm proper N‐substitution of the side groups and to determine changes to the polymer crystallinity and stability. These analyses suggested that the electrospun ANFs consisted of numerous crystalline domains in the transverse fiber direction with large amorphous regions that were void of defects commonly found in commercial Kevlar fibers. A semi‐empirical study of the variations in the solubility parameter due to various side chain moieties was conducted to facilitate solvent selection and to elucidate the enhanced solubility effects with selected organic solvents. These initial findings suggest a promising route for obtaining a new class of nanofibers with ultrahigh strength and stiffness. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44082.     

Water uptake,chemical characterization,and tensile behavior of modified banana–plantain fiber and their polyester composites

Banana–plantain fibers (BPFs) were treated with acetic anhydride (AA), epichlorohydrin (EP), and an acetic anhydride–epichlorohydrin blend (AA_EP). Natural fiber–polyester composites (PCs) were fabricated using untreated and treated BPF by the hand lay‐up technique. Modified BPF Raman and Infrared spectroscopy (ATR‐FTIR) analysis revealed losses of lignin and hemicelluloses and new chemical bonds that confirmed the replacement of part of the raw fiber hydroxyl groups, which gave rise to a degree of hydrophobicity in the treated fibers. This change altered their water sorption isotherms, swelling behavior in water, impedance spectroscopy, and XRD analysis. Assays of water absorption and tensile resistance for untreated BPF (U) and modified BPF polyester composites demonstrated a remarkable reduction in water intake, whereas tensile strength was maintained (P < 0.05) for the modified BPF polyester composites. POLYM. COMPOS., 37:2960–2973, 2016. © 2015 Society of Plastics Engineers     

Click‐coupling of anthraquinone dyes with β‐cyclodextrin: formation of polymeric superstructures

Two novel cyclodextrin‐modified anthraquinone dyes were synthesized and investigated for their complexation behaviour and formation of superstructures. Therefore, 1‐fluoro‐4‐N‐(propargylamino)anthraquinone and 1,4‐bis(propargyloxy)anthraquinone were prepared via nucleophilic aromatic displacement and subsequently covalently ‘click‐coupled’ in a copper(I)‐catalysed azide–alkyne cycloaddition with β‐cyclodextrin monoazide. Both the propargyl‐modified precursor and the click‐coupled anthraquinone dyes were evaluated as hosts and guests, respectively, in β‐cyclodextrin interactions. The anthraquinone dye bearing two cyclodextrins, 1,4‐bis((1‐β‐cyclodextrin‐1H‐1,2,3‐triazol‐5‐yl)methoxy)anthraquinone, enables the reversible formation of supramolecular crosslinked poly[(N,N‐dimethyl acrylamide)‐co‐(N‐(ferrocenoylmethyl)acrylamide)] ( 11 ), whereas the monofunctionalized compound 1‐fluoro‐4‐(((1‐β‐cyclodextrin‐1H‐1,2,3‐triazol‐5‐yl)methyl)amino)anthraquinone can be supramolecularly linked to 11 resulting in coloured polymers. These features of β‐cyclodextrin‐linked anthraquinone dyes can be verified with either ¹H ¹H NMR rotating frame nuclear Overhauser effect spectroscopy or the naked eye. © 2016 Society of Chemical Industry     

Sago starch and its acrylamide modified products as coating material on handsheets made from recycled pulp fibers

This study was carried out to determine the suitability of sago starch as a paper additive. The basic properties (i.e., pH, viscosity, and solid content) of the 5% weight over volume basis of unmodified and modified sago starch (sago starch blended with acrylamide, sago starch grafted with acrylamide in an acidic and adjusted to alkaline conditions) were determined. The starches were then used to coat laboratory handsheets made from recycled pulp fibers. The incorporation of acrylamide into sago starch through grafting significantly reduced the viscosity of the solution. Generally, coating the handsheets with unmodified sago starch significantly improved some properties as compared to the uncoated handsheets. Among the three types of sago starch modification methods, blending gave superior performance when coated on the handsheets, except for smoothness and air permeance, due to insufficient curing shown by the micrographs. FTIR spectra showed that the interactions between the blended acrylamide–starch solutions and the pulp fiber were weak. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 154–158, 2004     

Surface modification of polyimide fibers by novel alkaline–solvent hydrolysis to form high‐performance fiber‐reinforced composites

We modified polyimide (PI) fibers by a novel hydrolysis approach and fabricated PI‐fiber‐reinforced novolac resin (NR) composites with enhanced mechanical properties. We first used an alkaline–solvent mixture containing potassium hydroxide liquor and dimethylacetamide (DMAc) for the surface modification of the PI fibers. The results indicate that the surface roughness and structure of the PI fibers were controlled by the hydrolysis time and the content of DMAc. With the optimized hydrolysis conditions, the tensile modulus of modified PI fibers improved 15% without compromises in the fracture stress, fracture strain, or thermal stability. The interfacial shear strength between the modified PI fibers and NR increased 57%; this indicated a highly enhanced interfacial adhesion. Finally, the tensile and flexural strengths of the composites increased 72 and 53%, respectively. This research provides an effective method for the surface modification of PI fibers and expands their applications for high‐performance composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46595.