Grafting modification of Kevlar fiber using horseradish peroxidase

Summary Horseradish peroxidase catalyzed grafting of acrylamide (AM) onto Kevlar fibers in mixed solvents of dioxane and water was studied. The factors affecting the grafting reaction, such as solvents composition, reaction time, temperature, pH of reaction media, concentration of acrylamide and hydrogen peroxide were examined. The modified fiber was characterized with IR, scanning electron microscopy (SEM), elemental analysis, XPS, contact angle measurement and the grafting yield. The O/C ratio and N/C ratio on the surface increased after treatment and the surface of the Kevlar fiber became rougher. The contact angle decreased from 80 to 45 after grafting, indicating the wettability of the fiber increased after modification. All the results suggested that AM have been grafted onto the Kevlar surface through HRP-mediated radical initiated grafting reaction. And the probably mechanism of HRP catalyzed grafting of AM onto Kevlar surface was proposed.     

Enzyme‐mediated grafting of acrylamide to ultrahigh molecular weight polyethylene fiber: A novel radical initiation system

The enzyme‐mediated grafting of acrylamide (AM) to ultrahigh molecular weight polyethylene (UHMWPE) fibers using horseradish peroxidase (HRP) was demonstrated. To optimize the reaction condition, the concentrations of monomer, H₂O₂, the initiator, and time were varied. The grafting results were discussed and a reaction mechanism was proposed. Function groups and structural change of the graft copolymer were determined by FTIR spectroscopic and scanning electron microscopy micrographs for proof of grafting and the results were discussed. Results show that the surface of treated fiber becomes rougher than the untreated surface. Compared to unmodified fiber, modified fiber surface had significantly increased the interfacial shear strength, and carbonyl‐stretching regions in the IR spectra. The interfacial shear strength of the UHMWPE fiber increased, clearly indicating that enzymatic‐grafted acrylamide could significantly increase the hydrophilicity of the surfaces of UHMWPE fibers. Moreover, the hydrophilicity of treated fiber depends on the monomer concentration, the initiator concentration, and oxidizing agent concentration as well as the time of the reaction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1011–1016, 2005     

Grafting modification of electrospun polystyrene fibrous membranes via an entrapped initiator in an acrylic acid aqueous solution

Ultrafine electrospun polymer fibers, with their large specific surface areas, have not found wide applications partly because the fiber surfaces usually carry an insufficient quantity of active groups. The electrospinning and surface‐grafting copolymerization of polystyrene fibrous membranes were carried out via the embedded radical initiator approach. The results from X‐ray photoelectron spectroscopy show that the initiator added to the polystyrene dope was deliberately expelled onto the fiber surfaces. The microstructure and hydrophilicity of the grafted membranes were investigated with Fourier transform infrared spectroscopy, scanning electron microscopy, and water contact angle and water uptake capacity measurements. An increase in the initiator dosages led to decreases in the grafting rate, water uptake, and hydrophilicity of the grafted membranes; the opposite was true for increases in the neutralization of acrylic acid (AA). However, the grafting, water uptake, and hydrophilicity of the grafted membranes presented nonlinear relationships with the concentration of AA. The initiator emigration technique will provide a facile and feasible platform for the surface‐grafting modification of electrospun membranes. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Grafted carbon fibers and their physicochemical properties. I. Grafting of methacrylic acid onto carbon fibers

A simple, reproducible method for grafting different carbon fibers (modified and unmodified, high‐modulus, and high‐tensile) with methacrylic acid is presented. The grafted carbon fibers were characterized by wetting measurements and electrokinetic studies. Scanning electron microscopy micrographs showed grafted polymer chains on all carbon fiber surfaces. The success of the grafting procedure depends on a suitable modification of the fiber surface. The amount and size of the grafted polymer chains on modified carbon fibers depend on the amount of initiator used. Contact angle measurements indicate an increase of the contact angle versus water and a decrease versus diiodomethane. The surface polarity calculated from the surface tensions obtained from contact angle values decreases for all systems under investigation. Zeta (ζ) potential measurements confirmed these results. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1175–1185, 1999     

Grafting of maleic anhydride onto polypropylene: Synthesis and characterization

Isotactic polypropylene was grafted with maleic anhydride using benzoyl peroxide as an initiator and toluene as a solvent. Effects of various parameters such as monomer and initiator concentration, reaction time, and reaction temperature on percentage grafting were studied. Effect of various solvents on extent of grafting was also studied. The maximum extent of grafting achieved was 5.3%. The graft copolymers were characterized by i.r., thermal, viscometric, and contact angle studies. Improved thermal stability and decreased intrinsic viscosity and critical surface tension were observed for graft copolymers. © 1994 John Wiley & Sons, Inc.     

Grafting of polystyrene and poly(p‐chlorostyrene) from the surface of ramie fiber via RAFT polymerization

Reversible addition‐fragmentation chain transfer (RAFT) radical polymerization was used for controlled grafting of styrene and p‐chlorostyrene from the surface of ramie fiber. The hydroxyl groups in ramie fiber were first converted to thiocarbonylthio groups as the RAFT chain transfer agent then used to mediate the RAFT polymerization of styrene, and p‐chlorostyrene in tetrahydrofuran using azobis (isobutyronitrile) as initiator at 60°C. The grafted copolymers were analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry, and contact angle measurements. The results confirmed that grafting occurred on the surface of the ramie fiber, substantially increasing the water contact angle from 75.31° to 147° for polystyrene grafted ramie fiber (cell‐PS) and 135° for poly(p‐chlorostyrene) (cell‐PSCl), and improving the hydrophobicity of the grafted fiber. The homopolymers formed in the polymerization were analyzed by size exclusion chromatography to estimate the molecular weights and polydispersity indices (PDIs) of chains grafted from the surface of the ramie fiber, as well as showed narrow chain length distributions with a PDI of 1.32–1.70. These materials possess potential applications in many advanced technologies. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Functionalization of industrial polypropylene films via the swift‐heavy‐ion‐induced grafting of glycidyl methacrylate

Swift‐silver‐ion irradiation was explored as a means of forming chemically active sites on the surface of biaxially oriented polypropylene films. The active species, formed in air, was used to induce the graft copolymerization of glycidyl methacrylate in an aqueous solution. The surface structure, crystallinity, morphology, and hydrophilicity of the grafted samples were characterized with Fourier transform infrared, UV, wide‐angle X‐ray diffraction, scanning electron microscopy, and contact‐angle measurements. Glycidyl methacrylate could be grafted onto biaxially oriented polypropylene after swift‐heavy‐ion irradiation without an additional initiator. The contact angle of the modified films decreased with the grafting percentage of glycidyl methacrylate on the polypropylene. The swift silver ions induced significant grafting only in small regions (i.e., the latent tracks) of the polymer. Furthermore, as the fluence of swift heavy ions increased beyond an optimum value, the overlapping of the latent tracks reduced the grafting yield. The observed findings could be very useful in developing an initiator‐free grafting system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Peroxide-initiated grafting of acrylamide on to polyethylene surfaces

Acrylamide has been grafted onto the surface of a polyethlene film with the aid of a peroxide initiator (tert-butyl peroxyneodecanoate). The peroxide was first swollen into the film from cyclohexane solution; the film was then dried under reduced pressure at room temperature. Excess initiator, adsorbed on the surface, was washed off with acetone. The grafting reaction was carried out by placing the film in a boiling solution of the monomer in water. After grafting, the film was extracted with water to remove monomers and homopolymer. The grafted films were characterized by infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), gravimetric measurements, and contact angle measurements. The graft yield was found to increase with reaction time up to about 5–15 min and thereafter level off. The presence of air was found to retard the grafting reaction. Increase in monomer concentration gave an almost continuous increase in graft yield, but high concentrations were not necessary to cover the surface of the film with polyacrylamide. This grafting has been found to function, but the process requires further development to reduce the total grafting time before it can be used commercially.     

Radiation‐induced graft copolymerization of MMA monomer onto UHMWPE: Adhesion improvement

Graft copolymerization of methyl methacrylate monomer onto ultra high molecular weight polyethylene (UHMWPE) and acid‐etched UHMWPE was conducted using preirradiation method in air in the presence of a Mohr salt and sulfuric acid to improve adhesion to the bone cement. The grafted samples were characterized by Fourier transform infrared (FTIR) spectroscopy, gravimetric method, goniometry, and interfacial bonding strength measurements. The FTIR results showed the presence of ether, carbonyl, and hydroxyl groups for grafted films. The gravimetric results showed that the chromic acid etching and graft copolymerization had a synergetic effect so, the irradiated, then chromic acid etched at room temperature and grafted sample (Rad etch25) had the highest grafting degree. The interfacial bonding strength between UHMWPE and poly methyl methacrylate bone cement was considerably improved by graft copolymerization and chromic acid etching. The surface morphology was studied by scanning electron microscopy. The substitution of polar groups into the backbone of UHMWPE by chromic acid etching and graft copolymerization changed its contact angles with water and methylene iodide and increased its surface energy, as evidenced by contact angle measurements. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

紫外辐射接枝改性UHMWPE纤维表面的研究

采用紫外辐射接枝方法对超高相对分子质量聚乙烯(UHMWPE)纤维表面进行改性。探讨了单体种类及浓度、引发剂、抗氧剂、接枝方法等对UHMWPE纤维表面处理效果的影响,测试了以其作为增强材料的复合材料的层间剪切强度。结果表明:在有氧开放体系下,气相接枝效果好于液相接枝;丙烯酰胺单体的接枝效果优于其它单体;接枝率随接枝单体浓度和接枝时间的增加而增加。采用丙烯酰胺为接枝单体,在光强度为86μW/cm~2条件下,对UHMWPE纤维进行紫外辐射接枝改性,按照一定铺层方式制备的环氧基复合材料的层间剪切强度从未处理的14.59MPa提高到17.36MPa。     

Development of biodegradable composites with treated and compatibilized lignocellulosic fibers

The aliphatic polyester Bionolle 3020 was combined with lignocellulosic fibers, namely, flax, hemp, and wood, to produce biodegradable composite materials. The effect of two fiber surface treatments, acetylation and propionylation, and the addition of maleic anhydride (MA)‐grafted Bionolle 3001 as a compatibilizer on the fiber/matrix interfacial adhesion was studied. The compatibilizer was synthesized through a MA grafting reaction in the presence of dicumyl peroxide as an initiator. The composites' mechanical properties, water absorption, fracture morphology (scanning electron microscopy), and biodegradation were evaluated. Both the fiber treatments and the compatibilizer incorporation significantly improved the composites' tensile strength, whereas an important reduction in the water absorption was found with the addition of treated fibers. Moreover, fiber incorporation into the matrix increased its biodegradation rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4703–4710, 2006     

Surface modification of acrylonitrile copolymer membranes by grafting acrylamide. I. Initiation by ceric ions

Surface modification of membranes of an acrylonitrile copolymer (PAN) containing 5.5% methyl methacrylate (MMA) and 4.0% sodium methylpropylenesulfonate by grafting acrylamide (AAm) with cetric ammonium nitrate as initiator in the aqueous medium has been studied. Results showed that the extent of grafting was varied with some parameters, such as dimethyl formamide and Tween-20 amount in the reaction solution, concentration of AAm, and reaction time. The grafted copolymer was verified by infrared spectra and X-ray photoelectron spectroscopy. Both of these methods also showed that the ester group of MMA unit on the surface of PAN membranes may be partially hydrolyzed into carboxyl group in the copolymerization condition. Surface and pore structures of PAN membranes after grafting were viewed under a scanning electron microscope (SEM). From SEM photos we know that AAm homopolymer branches were grafted onto the surface of the membrane and the morphology of membrane did not change. Results of contact angle of isooctane on the membrane under water showed that the wettability of the modified membrane was improved. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1521–1529, 1997     

Interfacial bond property of UHMWPE composite

The ultrahigh molecular weight polyethylene (UHMWPE)/hydrocarbon (PCH) composite was prepared by selecting a PCH resin as the matrix, which has the similar structure to UHMWPE fiber. The interfacial bond property between the PCH resin and UHMWPE fiber was investigated by macromechanics, micromechanics, and contact angle. The results show that the PCH resin has good wettability with the UHMWPE fiber surface. The UHMWPE/PCH composite has excellent transverse tensile strength, interlaminar shear strength, and the pull-out strength together with the outstanding interfacial bond property.     

Grafting of poly (methyl acrylate) onto sulfite pulp fibers and its effect on water absorbance

To prepare super water absorbent hydrogels of wood cellulose fibers, poly (methyl acrylate) (PMA) was copolymerized onto softwood sulfite pulp fibers using free radical initiator followed by alkaline hydrolysis. Ceric ammonium nitrate (CAN) was used as the free radical initiator. Effects of various parameters such as fiber concentration, monomer/pulp (M/pulp) ratio, CAN concentration, and reaction time on the grafting yield and on other grafting parameters were investigated. The graft conversion was the same from low to medium fiber concentration. The amount of initiator required was found to be independent of fiber concentration to achieve maximum grafting yield. Different fiber fractions (classified based on their length) have no effect on the grafting yield. The evidence of graft copolymerization was determined by using ATR‐IR spectroscopy. The X‐ray diffraction (XRD) analysis shows that grafting takes place both in amorphous and crystalline regions of cellulose fibers and the decrease in crystallinity of the grafted fibers with an increase in grafting yield was confirmed. The surface morphology of the PMA‐g‐cellulose was characterized by scanning electron microscopy (SEM). The water retention value of the hydrolyzed grafted pulp was determined based on a centrifugation technique. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

聚丙烯纤维接枝苯乙烯的研究

采用化学接枝法以苯乙烯(St)为接枝单体、过氧化苯甲酰(BPO)为引发剂,1,2-二乙烯苯(DVB)为交联剂、甲醇和正辛醇为溶剂,对聚丙烯(PP)纤维进行接枝改性。研究了原料配比和反应条件对其接枝的影响。结果表明,PP纤维上接枝St,适宜的原料配比和操作条件为:St质量与PP体积比(St/PP)为4,BPO质量与St体积比(BPO/St)为0.025,DVB与St体积比(DVB/St)为0.025,溶剂与St体积比为5,浸渍24～30h,在85℃恒温水浴中反应6～8h。在较佳条件下可得到导入率为110%-160%的接枝纤维。     

Synthesis and Characterization of Polypropylene Grafted by Acrylamide

Polypropylene (PP) was grafted with acrylamide using benzoyl peroxide (BP) as an initiator by melt mixture. Effects of various parameters such as monomer and initiator concentration, reaction time, and reaction temperature on degree of grafting were studied. The graft copolymers were characterized by irradiation (IR), electron spectroscopy for chemical analysis (ESCA), wide-angle x- ray diffraction (WAXD), DSC, and contact angle studies.     

Reinforcement of polypropylene using sisal fibers grafted with poly(methyl methacrylate)

Sisal fiber (SF) surface modification was carried out by grafting with methyl methacrylate (MMA) using cerium and ammonium nitrate as initiator. The effects of reaction time, monomer, and initiator concentration on the grafting parameters were systematically investigated. The results showed that MMA was successfully grafted onto the sisal fiber surface. The PMMA‐grafted sisal fibers were melt blended with polypropylene (PP) and then injection molded. The PP/SF composites were characterized by means of thermal analysis, mechanical testing, wide‐angle X‐ray diffraction, and SEM examination. PMMA grafted onto the surface of SF enhanced the intermolecular interaction between the reinforcing SF and PP matrix, improved the dispersion of SF in the PP matrix, and promoted the formation of β‐crystalline PP. These enhanced the thermal stability and mechanical properties of PP/SF composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1055–1064, 2003     

Preparation and characterization of poly(2‐acrylamido‐2‐methylpropane‐sulfonic acid) grafted chitosan using potassium persulfate as redox initiator

A grafted material based on chitosan and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) has been successfully prepared in homogenous solution using potassium persulfate as a redox initiator. The grafted copolymer was precipitated during the reaction polymerization. The effects of the reaction temperature and chitosan–potassium persulfate contact time as well as concentrations of AMPS, potassium persulfate, and acetic acid on grafting yield were investigated. The percentage of grafting is gradually increased with the increasing of the AMPS concentration. The extent of grafting can be controlled by setting the appropriate reaction conditions. The maximum percentage of grafting was about 180% under the optimum conditions (1% v/v acetic acid, 50°C reaction temperature, 10 min chitosan–potassium persulfate mixing period, 0.37 mmol of potassium persulfate, and 28.96 mmol AMPS). The grafted chitosan was insoluble in the acid of the grafting. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2314–2318, 2000     

聚丙烯/三元乙丙橡胶共混材料表面紫外光接枝聚丙烯酰胺的研究

采用紫外光接枝方法,在聚丙烯（PP）/三元乙丙橡胶（EPDM）共混板材表面接枝聚丙烯酰胺（PAAM）。用衰减全反射傅立叶变换红外光谱、X射线光电子能谱、接触角测试仪和扫描电子显微镜对接枝改性PP板表面进行了表征,并讨论EPDM含量、辐照时间、单体及引发剂用量对接枝量和接触角的影响。结果表明,在共混板材表面成功接枝了PAAM,当EPDM的含量为共混板材的20%时,改性PP板表面接枝量达到0.75 mg/cm^2;接触角从102.5°下降到72.5°;表面自由能从16.6 mN/m增大到48.7 mN/m。     

Functionalization of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) films via surface‐initiated atom transfer radical polymerization: Comparison with the conventional free‐radical grafting procedure

We modified hydrophobic poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBHV) films with hydrophilic chains to control their surface properties. We designed and investigated surface‐initiated atom transfer radical polymerization (SI‐ATRP) to modify the PHBHV films by grafting poly(2‐hydroxyethyl methacrylate) (PHEMA) from the surface. This method consisted of two steps. In the first step, amino functions were formed on the surface by aminolysis; this was followed by the immobilization of an atom transfer radical polymerization initiator, 2‐bromoisobutyryl bromide. In the second step, the PHEMA chains were grafted to the substrate by a polymerization process initiated by the surface‐bound initiator. The SI‐ATRP technique was expected to favor a polymerization process with a controlled manner. The experimental results demonstrate that the grafting density was controlled by the reaction conditions in the first step. The grafted films were analyzed by Fourier transform infrared spectroscopy, contact angle testing, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy. The results show that grafted chains under the SI‐ATRP method were preferentially located on the surface for surface grafting and in the bulk for conventional free‐radical polymerization initiated by benzoyl peroxide. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011