Atomic force microscopy study of the photografting of glycidyl methacrylate onto HDPE and the microstructure of the grafted chains

This article presents an atomic force microscopy (AFM) study of the initial stage of the photografting of glycidyl methacrylate (GMA) onto high-density polyethylene (HDPE) surface and the microstructure of the grafted chains. The grafting was carried out in acetone, dichloromethane and tetrahydrofuran (THF), as well as without solvent. Granular structures were found on the surface of the samples grafted in the solvents. The height of the granules increased linearly with their diameter. Each granule was thought to be a single grafted chain with a highly branched (or superbranched) microstructure. The grafting density on HDPE was quite small when the grafting was carried out in the solvents. The grafted chains were more branched when grafting was carried out in THF than when the grafting was carried out in acetone and dichloromethane. The bulk (no solvent) grafting of GMA onto HDPE was much faster and more uniform than that carried out in the solvents. The thickness of the bulk grafted materials was a few nanometers after 30 s irradiation, and possibly, the grafting density was much higher and the grafted polymers were much less branched than those produced in solvent.     

Radiation‐induced grafting of glycidyl methacrylate onto high‐density polyethylene (HDPE) and radiation lamination of HDPE

Radiation‐induced grafting of glycidyl meth‐acrylate (GMA) onto high‐density polyethylene (HDPE) and the radiation lamination of HDPE by bulk grafting of GMA were reported. The effects of irradiation dose, monomer concentration, and atmosphere on grafting were investigated. The extent of grafting initially increased with irradiation dose and then remained almost constant. The extent of grafting was higher in 2M GMA than in 1M GMA at the same irradiation dose. The extent of grafting in nitrogen was higher than that in air. The grafted samples were characterized with FTIR spectrometry and thermogravimetric (TG) analysis. A carbonyl group was found on grafted HDPE samples, and the carbonyl index increased with the extent of grafting. TG analyses proved the existence of grafted materials on HDPE and the grafted GMA thermally decomposes at a temperature lower than that of HDPE. Strong adhesion could be obtained with radiation lamination of HDPE by bulk grafting of GMA. Benzophenone facilitates the grafting in a proper concentration range. The adhesion mechanism of the laminated samples was the entanglement of the grafted chains. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 772–779, 2005     

Photografting of methyl methacrylate onto high‐density polyethylene initiated by aliphatic ketones

The photografting of a water‐insoluble monomer methyl methacrylate (MMA) onto high‐density polyethylene (HDPE) initiated by an aliphatic ketone/water/alcohol initiating system has been reported. The aliphatic ketones, such as acetone, butanone, and cyclohexanone, could effectively initiate the grafting reaction when they were mixed with water and ethanol to form homogeneous aliphatic ketone/water/ethanol mixed solvents that could dissolve the water‐insoluble monomer. The nature of aliphatic ketone affected the grafting; at the same aliphatic ketone/water/ethanol volume ratio, the grafting system containing acetone or butanone always led to a higher extent of grafting than that containing cyclohexanone. Water also played a very important role in the grafting reaction; in the tested range, the rate of formation of grafted PMMA on HDPE increased with the increase of water : volume ratio. The grafting of MMA carried out in 5 acetone/40 water/55 ethanol mixed solvent led to the highest extent of grafting. ATR‐FTIR characterizations of the grafted samples proved the successful grafting of MMA onto HDPE. SEM investigations of the HDPE surfaces grafted in different aliphatic ketone/water/ethanol mixed solvents indicate the morphologies of grafted surfaces varied with the mixed solvents used. This study broadened the application fields of the aliphatic ketone/water/alcohol initiating system for photografting. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of acid and pH value on the photografting initiated by aliphatic ketones in aqueous solutions

The photografting of methacrylic acid (MAA) onto high‐density polyethylene (HDPE) initiated by aliphatic ketones (acetone, butanone, and cyclohexanone) in aqueous solutions with different pH values adjusted by adding different amount of mineral acids was reported. Acids significantly enhanced the photografting yield, and the extent of grafting generally increased with decreasing pH value. The effect of pH value on the grafting reactions varied with the acid used. The grafting of MAA onto HDPE surface was confirmed with FTIR and SEM characterizations. The water absorbency of the grafted p‐MAA varied with the extent of grafting. When the extent of grafting was less than 2000–3000 μg/cm², grafted p‐MAA absorbed about 25–30% water, whereas at higher extent of grafting, it absorbed about 50% water. The mechanism of the acid enhancement of the photografting of MAA initiated by aliphatic ketones in aqueous solutions is believed to be attributed to the change of the solubility of monomer in the solution and the conformation of grafted chains, both are favorable for accelerating grafting reactions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Radiation‐induced graft polymerization of glycidyl methacrylate onto PE/PP nonwoven fabric and its modification toward enhanced amidoximation

A nonwoven fabric made of polypropylene coated by polyethylene was used as the trunk polymer in the preparation of a highly efficient new adsorbent. Metal ion uptake capacity has been aimed to be increased by introducing double amidoxime groups per repeating unit of the chains grafted to trunk polymer. The base polymer was irradiated by electron beams with a dose of 200 kGy under N₂ atmosphere and glycidyl methacrylate (GMA) was grafted onto irradiated nonwoven fabric. Grafting conditions were optimized, and GMA‐grafted polymer was modified with 3,3′‐iminodipropionitrile in ethanol at 80°C. GMA grafting (150%) was determined to be the optimum degree given that higher extent of grafting rendered the materials brittle. Pendant nitrile groups were then amidoximated by using 6% hydroxylamine in methanol–water mixture (1 : 1). The all‐polymeric structures were characterized by using FTIR, SEM, and thermal analysis methods, confirming the grafting, modification, and amidoximation stages gravimetrically, spectroscopically, and visually. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Functionalization of high‐density polyethylene in the molten state by glycidyl methacrylate grafting

:This study concerns the melt‐free radical grafting of glycidyl methacrylate (GMA) onto high‐density polyethylene (HDPE). We studied the effect of two initiators (tert‐butyl cumyl peroxide and di‐tert‐butyl peroxide) onto HDPE. Crosslinking of polymer was observed in the presence of 0.3 wt % tert‐butyl cumyl peroxide but not with 0.3 wt % di‐tert‐butyl peroxide. The grafting was carried out in a Brabender batch mixer at 190 °C. The grafting yield of GMA onto HDPE (determined by infrared spectrometry) is weak (<1 wt % for an initial concentration in monomer of 6 wt %). Moreover, it was noted that the degree of grafting did not vary with the concentration and the nature of peroxide used. To increase the grafting yield of GMA, we added to the HDPE/peroxide/GMA system an electron‐donating monomer, such as styrene. Adding this comonomer multiplied the rate of grafted GMA 3‐ or 4‐fold, resulting in a ratio [styrene]_i/[GMA]_i = 1 mol/mol with [GMA]_i = 6 wt %. So, the copolymerization is favored compared with the homopolymerization. This kind of copolymer presenting reactive functions is very attractive in the field of compatibilizing immiscible polymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 581–590, 2001     

Solvothermal preparation and characterization of maleic anhydride grafting high density polyethylene copolymer

In this article, the grafting copolymerization of maleic anhydride (MAH) onto high density polyethylene (HDPE) was carried out through solvothermal process. Infrared spectra (IR) revealed that MAH had been successfully grafted onto the HDPE backbone. The influences of the reaction parameters on the grafting copolymerization, e.g., the concentration of the initiator, MAH and HDPE content, reaction time, reaction temperature, comonomer, and different solvents were also studied. Further studies found that MAH could be grafted onto HDPE in both good solvents and poor solvents, which was much different from the traditional solution grafting method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Grafting of glycidyl methacrylate onto high‐density polyethylene with reaction time in the batch mixer

The melt grafting of glycidyl methacrylate (GMA) onto high‐density polyethylene (HDPE) in the presence of free radical initiators was investigated in the batch mixer. The graft content was determined with the titration and FTIR spectroscopy. The graft content increased with the increase of peroxide and initially introduced GMA concentration. Increase of the grafted GMA content resulted in decrease of the melt index. Interestingly, there was a sudden drop of GMA grafting content with the reaction time. It is assumed that depolymerization of GMA have taken place over the ceiling temperature. The crystallinity of the prepared glycidyl methacrylate grafted high density polyethylene (HDPE‐g‐GMA) was determined by the measurement of the heat of fusion. GMA grafted site acted as defect and crystallinity of the HDPE‐g‐GMA decreased with the increase of grafting reaction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Radiation‐induced grafting of pentamethyl hindered amine light stabilizer 1,2,2,6,6‐pentamethyl‐4‐piperidinyl methacrylate onto polypropylene

The γ‐radiation‐induced grafting of 1,2,2,6,6‐pentamethyl‐4‐piperidinyl methacrylate (PMPM) onto polypropylene (PP) was investigated with a simultaneous irradiation technique. The effects of the solvent, dose, monomer concentration, and photoinitiator on the grafting were investigated. The grafting was easier in a benzene solution than in chloroform and acetone solutions. The grafting percentage first increased almost linearly with the irradiation dose until 20 kGy and then increased slowly or remained constant. The grafting percentage increased with the monomer concentration until 1.1 mol/L. The grafting percentage was higher when the proper amount of benzophenone was added. The grafted samples were characterized with Fourier transform infrared spectroscopy and thermogravimetric analysis. Carbonyl groups were found on grafted PP samples, and the carbonyl index increased with the grafting percentage. Thermogravimetric analyses proved the existence of grafted materials on PP, and grafted PMPM thermally decomposed at a lower temperature than PP. The radiation resistance of PP with grafted PMPM was better than that of pristine PP. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2157–2164, 2005     

Sulfonation of (glycidyl methacrylate) chains grafted onto nonwoven polypropylene fabric

Sulfonation of polyglycidyl methacrylate (PGMA) chains grafted onto nonwoven polypropylene fabric is investigated in detail. Sulfonation reaction consists in implantation of sulfonate groups via epoxy ring‐opening of PGMA chains grafted onto nonwoven polypropylene fabric by reaction between the GMA‐grafted sample and sodium hydrogensulfite in water–dimethylformamide solution. On the basis of analyses of IR spectra of the appropriate samples and data of backward titration, two simultaneous processes are demonstrated to take place during the sulfonation reaction. These processes are the implantation of sulfonate groups via opening of the GMA epoxy rings and hydrolysis of the GMA epoxy rings with α‐glycol groups formation. The main peculiarities of the sulfonation reaction in depending on the GMA grafting degree are reported. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Styrene‐assisted melt‐free radical grafting of glycidyl methacrylate onto isotactic poly(1‐butene)

The melt‐free radical grafting of glycidyl methacrylate (GMA) onto powered isotactic poly(1‐butene) (iPB‐1) using styrene (St) as a comonomer in a Haake mixer was studied. The effects of temperature, initial GMA, and peroxide concentration, as well as the addition of St comonomer, on the final grafting degree, grafting efficiency, and the melt flow rate of grafted polymer were studied. It was shown that the addition of St as a comonomer could significantly enhance the grafting degree of GMA on iPB‐1 and reduce the extent of degradation of iPB‐1 to some degree. It has been found that the grafting degree of dual‐monomer melt‐grafted iPB‐1 was about twice that of single‐monomer‐grafted iPB‐1 for the same monomer and peroxide concentrations. The grafting of GMA onto iPB‐1 remarkably accelerated the crystal form II → I transformation of iPB‐1. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Radiation‐induced grafting of styrene onto poly(tetrafluoroethylene) (PTFE) films. I. Effect of grafting conditions and properties of the grafted films

Radiation‐induced grafting of styrene onto poly(tetrafluoroethylene) (PTFE) films was studied by a simultaneous irradiation technique. Grafting was carried out using γ‐radiation from a ⁶⁰Co source at dose rates of 1.32–15.0 kGy h⁻¹ at room temperature. The effects of type of diluent, dose rate, irradiation dose, and the initial monomer concentration in the grafting solution on the degree of grafting were investigated. The degree of grafting was found to be strongly dependent upon the grafting conditions. The dependence of the initial rate of grafting on the dose rate and the initial monomer concentration in the grafting solution was found to be in the order of 0.6 and 1.7, respectively. The chemical structure and the crystallinity of the grafted PTFE films were studied by means of Fourier‐transform infrared, (FTIR), electron spectroscopy for chemical analysis (ESCA) and X‐ray diffractometry (XRD). © 2000 Society of Chemical Industry     

Surface modification of UHMWPE fibers by ozone treatment and UV grafting for adhesion improvement

In this study, the surface of ultra-high-molecular-weight-polyethylene (UHMWPE) fibers was modified by ozone pretreatment, followed by ultraviolet (UV) grafting, to enhance the interfacial properties of UHMWPE fibers/rubber composites. The fibers were first pretreated by ozone to introduce oxygen-functional groups. The graft polymerization of glycidyl methacrylate (GMA) onto the ozone-treated fibers was implemented by UV irradiation. The effects of time and GMA concentration on the grafting efficiency were investigated. The modified fibers were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). The XPS and FTIR results revealed that GMA was successfully grafted onto the fibers with epoxy groups. SEM images confirmed that a continuous layer of poly-(GMA) (PGMA) was grafted onto the fibers. The interfacial adhesion force of UHMWPE fibers with rubber matrix was characterized by H pullout testing, which showed that the maximum force the fibers/rubber composites increased by 79% over that of the untreated fibers.     

Surface modification of MWNTs with BA‐MMA‐GMA terpolymer by single‐step grafting technique

In this article, a facile strategy was developed to prepare BA‐MMA‐GMA/MWNTs (multiwalled carbon nanotubes) hybrid nanoparticles as nanofillers in rubber by single‐step grafting technique. First, a new macromolecular surface modifier butyl acrylate (BA)‐α‐methyl methacrylate(MMA)‐glycidyl methacrylate (GMA) terpolymer was synthesized via radical copolymerization. Afterward, this terpolymer modifier was covalently grafted onto the surface of crude MWNTs by single‐step grafting technique. The structure, surface properties, and thermal stability of modified MWNTs were systematically investigated by FTIR, TGA, and TEM. FTIR results showed that BA‐MMA‐GMA terpolymer was successfully grafted onto the surface of MWNTs. TGA indicated that the optimum mass fraction of macromolecular modifier coated on the surface of MWNTs was 9 wt %. TEM images revealed that an organic coating layer was formed and the modified MWNTs showed good dispersibility in acetone. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Radiation‐induced grafting of acrylic acid and sodium styrene sulfonate onto high‐density polyethylene membranes. I. Effect of grafting conditions

Radiation‐induced grafting of sodium styrene sulfonate and acrylic acid onto high‐density polyethylene (HDPE) membranes was studied by the preirradiation technique. Grafting was carried out using an electronic beam from a 2‐MeV accelerator at room temperature. The effects of the type of solvent, inhibitor concentration, preirradiation atmosphere, monomer concentration, and storage time of preirradiated HDPE membranes on the grafting yield were investigated. Easy control over the grafting yield was achieved by proper selection of the reaction conditions. IR spectroscopy analysis of the grafted membrane confirmed the existence of sulfonate and carboxylic acid groups in the grafted membranes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3401–3405, 2006     

Surface modification of cellulose filter paper by glycidyl methacrylate grafting for biomolecule immobilization: Influence of grafting parameters and urease immobilization

Graft copolymerization of glycidyl methacrylate (GMA) onto cellulose filter paper (CFP) was carried out by a free‐radical initiating process using ceric ammonium nitrate (CAN) as an initiator. Optimum conditions pertaining to different grafting percentages were evaluated as a function of monomer and initiator concentrations, polymerization time and temperature. CFP with various graft levels of GMA was characterized by fourier transform infrared (FTIR) spectroscopy and thermo gravimetric analysis (TGA). Surface morphology of ungrafted and grafted CFP was evaluated by scanning electron microscopy (SEM). Attenuated total reflectance (ATR)‐FTIR spectral analysis provided the evidence of grafting of GMA onto CFP. The maximum grafting of 102% was achieved by using 4 × 10^?3 molL^?1 CAN and 5% of GMA (w/v) monomer at 60°C in 25 min. The CFP‐g‐GMA surfaces with different graft levels were evaluated as a support for immobilization of biomolecules. Urease was selected as the model enzyme to be covalently coupled through the surface epoxy groups of the CFP‐g‐GMA discs. Immobilized discs were further studied for urea estimation and their reusability. Although the highest degree of urease immobilization was observed at 100% (162‐μg urease/disc) graft level, the urease immobilized on discs with 70% (105‐μg urease/disc) graft level gave the maximum activity of the enzyme. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Radiation‐modified copolymer for the extraction of metal ions from water

The modification of heavy‐duty polyethylene films was carried out through the graft copolymerization of acrylamide and vinyl acetate mixtures of different compositions with the simultaneous radiation method. The influence of the synthesis conditions (the irradiation dose, comonomer composition, and dilution) on the degree of grafting was investigated. The grafted samples were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and differential scanning calorimetry. The effect of the grafting degree on the thermal stability of the modified polymer was examined. The extraction of heavy and toxic metals such as cadmium, cobalt, copper, nickel, and lead by the modified heavy‐duty polyethylene was evaluated, and the metal‐ion uptake by the grafted and chemically treated samples seemed better than that of the grafted and untreated ones. Both the rate and amount of the metal‐ion uptake were affected by the temperature of the feed solution and the grafting degree. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Investigation of styrene‐assisted free‐radical grafting of glycidyl methacrylate onto high‐density polyethylene using response surface method

In this study, the free‐radical grafting of glycidyl methacrylate (GMA) onto high‐density polyethylene (HDPE) in the presence of styrene, as a comonomer, is investigated using a Brabender internal mixer. To optimize grafting level of GMA onto HDPE, response surface method (RSM) was exploited. Using RSM method of experimental design, it was possible to investigate the individual effects of various variables including dicumyl peroxide (DCP) concentration, GMA content, as well as reaction time, and their interactions on grafting efficiency. The fitted quadratic model obtained from statistical analysis is expressed by an approximating function to investigate the final torque as a responding variable over the experimental range of the independent variables. The grafting yield of GMA onto HDPE for the prepared samples was determined using titration/back‐titration technique and Fourier transform infrared spectroscopy (FTIR). According to the torque–time diagrams, increasing the DCP content led to an increase in GMA grafting yield. Also, it was found that the reaction time imparts minor effect on the final processing torque, and there exists an interaction between DCP and GMA content. The results of melt flow index (MFI) test showed that increasing the reaction time at constant DCP and GMA content enhances the MFI values of the samples, due to the more probability of chain scission phenomenon. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Study of compatibilization of HDPE–PET blends by adding grafted or statistical copolymers

The reactive compatibilization of blends of HDPE–PET [high‐density polyethylene–poly(ethylene terephthalate)] was investigated in this study. The compatibilizers used were two grafted copolymers prepared by reactive extrusion containing 1.20–2.30 wt % GMA such as HDPE‐g‐GMA and one statistical copolymer containing 1 wt % GMA such as Lotader AX8920. HDPE was successfully functionalized using a melt free‐radical grafting technique. Grafting was initiated in two ways: adding an initiator in the polymer–monomer mixture or activation by ozone of polymer. Ozonization of HDPE by the introduction of a peroxide lead to a better grafting yield and to better grafting efficiency of the samples. The effects of the three compatibilizers were evaluated by studying the morphology and the thermal and mechanical properties of HDPE–PET (70/30 wt %) blends. Significant improvements were observed, especially in morphology, elongation at break, and Charpy impact strength of the compatibilized blends. A more pronounced compatibilizing effect was obtained with the statistical copolymer, for which the elongation at break and the impact strength were increased by 100%, while the uncompatibilized blends showed a 60% decrease in the Young's modulus and the strength at break. We also were able to show that the grafting yield increase of 1.20–2.30 wt % of GMA did not affect the properties of the blends because the grafted copolymers possess very similar chemical structures. However, compatibilization of blends with grafted copolymers is an interesting method, particularly for recycled blends, because the synthesis of these compatibilizers is easy and cheap in comparison to statistical copolymer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2377–2386, 2001     

Photoinitiated surface grafting of synthetic fibers,I. Photoinitiated surface grafting of ultra high strength polyethylene fibers

Photoinitiated surface grafting of acrylic monomers has been carried out onto high strength polyethylene (HSPE) yarn by means of a continuous process. The grafting reaction is initiated by UV irradiation of the yarn after presoaking in an acetone solution of initiator and monomer. Four initiators, benzophenone (BP), 4-chlorobenzophenone (4-CBP), 2-hydroxy-2-cyclohexylacetophenone (HHA), and 2,2-dimethoxy-2-phenylacetophenone (DMPA), and two monomers, acrylic acid (AA) and acrylamide (AM), have been used. After short irradiation time (10 to 20 s) successful grafting is obtained, as shown by ESCA and IR-ATR spectra, dye adsorpotion from aqueous solution, and measurements of adhesion of single filaments to epoxy resin. Grafting efficiency of 74% has been reached for AA as monomer (26% is homopolymer). The tensile strength and modulus of the HSPE yarn are retained in the grafting process. The degree of surface grafting is mainly a function of structure and concentration of monomer and photoinitiator in the presoaking solution and of the irradiation conditions used. Increasing irradiation time gives increasing amounts of grafted polymer up to a certain limiting value. The reactivities of the four initiators have been compared showing the highest grafting yields of AA with BP and of AM with 4-CBP as photoinitiator. AA grafted HSPE yarn can be dyed to rather deep color by dipping in an aqueous solution of Crystal Violet. Increased dye absorption by a factor of up to seven has been measured for yarn grafted with AA to the maximum level obtained. The filaments of the grafted yarn show increased adhesion to epoxy resin by a factor of up to five compared with the ungrafted filaments.