SEM study of the morphologic change of high‐density polyethylene surface grafted with glycidyl methacrylate

Scanning electron microscopy (SEM) study of the morphologic change of high‐density polyethylene (HDPE) surface grafted with glycidyl methacrylate (GMA) was reported. Radiation‐induced grafting of GMA onto HDPE was carried out in acetone and dichloromethane solution, respectively. The effects of irradiation dose, atmosphere, and swelling time on grafting were investigated. Generally, the extent of grafting increased with irradiation dose, but for the grafting carried out in acetone solution, the extent of grafting initially increased with irradiation dose and then remained almost constant. The extent of grafting was higher in acetone solution than in dichloromethane solution at the same irradiation dose. The extent of grafting in nitrogen was higher than that in air. The successful grafting of GMA onto HDPE was confirmed by weighing and FTIR analysis. SEM investigations showed that the morphologies of the PE samples grafted in acetone solution were quite different to those grafted in dichloromethane. The grafting of GMA carried out in acetone was mainly on HDPE surface and that carried out in dichloromethane was mainly in the bulk of HDPE. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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     

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     

Solvothermal preparation of maleic anhydride grafted onto acrylonitrile-butadiene-styrene terpolymer (ABS)

The grafting copolymerization of maleic anhydride (MAH) onto acrylonitrile-butadiene-styrene terpolymer (ABS) was carried out through solvothermal process. Infrared (IR) spectra and ¹H NMR spectra confirmed that maleic anhydride was successfully grafted onto the ABS backbone. The influences, such as MAH concentration, the initiator's content, reaction temperature and time, comonomer, ABS concentration and different solvents, on the grafting copolymerization were also studied. Results indicated that the preparation of MAH grafted onto ABS through solvothermal method can be carried out in both good solvent and poor solvent, which is much different from the traditional solution grafting method, and high grafting degree can be obtained in good solvent.     

Photografting of N‐isopropylacrylamide and glycidyl methacrylate binary monomers on polyethylene film: Effect of mixed solvent consisting of water and organic solvent

Photografting (λ > 300 nm) of N‐isopropylacrylamide (NIPAAm) and glycidyl methacrylate (GMA) binary monomers (NIPAAm/GMA) on low‐density polyethylene film (thickness = 30 μm) was investigated at 60°C using mixed solvent consisting of water and an organic solvent such as acetone. Xanthone was used as a photoinitiator by coating it on the film surfaces. A maximum percentage of grafting was observed at a certain concentration of acetone in the mixed solvent, which was commonly observed for both ratios of NIPAAm/GMA, 8/2 and 7/3. Based on the photografting of NIPAAm/GMA on xanthone‐coated film, monomer reactivity ratios of NIPAAm (r₁) and GMA (r₂) were calculated using the Fineman–Ross method. The values were 0.31 ± 0.1 and 4.8 ± 0.2 for the water solvent system, while they were 0.96 ± 0.1 and 4.9 ± 0.1 for the mixed solvent system. NIPAAm/GMA‐grafted films with a homogeneous distribution of grafted chains were formed by photografting using water and mixed solvents. The NIPAAm/GMA‐grafted films exhibited temperature‐responsive characters, whereas the grafted films showed a reversible change in the degree of swelling between 0 and 50°C, respectively. Epoxy groups in the grafted poly(NIPAAm/GMA) chains could be aminated with ethylenediamine in N,N′‐dimethylformamide at 70°C for 3 h. Complexes of the aminated NIPAAm/GMA‐grafted chains with cupric ion exhibited catalytic activity for the decomposition of hydrogen peroxide at 20 to 50°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2469–2475, 2005     

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     

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     

Reconsideration on the mechanism of free-radical melt grafting of glycidyl methacrylate on polyolefin

The styrene (St) assisted melt grafting of glycidyl methacrylate (GMA) on polyolefin was carried out by Haake mixer, and the grafting mechanism was investigated and reconsidered. It was revealed that there is equilibrium of grafting of GMA and depolymerization of grafted PGMA chains in the GMA/polyolefin grafting process, which was affected by both of the temperature and GMA concentration. It was found that the depolymerization of PGMA grafted on polyolefin occurred at the temperature above ceiling temperature of PGMA and dominated the grafting process before the addition of styrene monomer, which induced the decrease in grafting ratio of GMA. Adding styrene as co-monomer could promote the equilibrium moving forward to form the St-GMA chains so that the grafting ratio was greatly improved. It is proved that either controlling the reacting temperature below the ceiling temperature or changing the feeding order of styrene and GMA is effective to attain high grafting ratio of GMA on polyolefin.     

Adhesion of polyethylene plates photografted with methacrylic acid and acrylic acid with enzymatically modified chitosan solutions and X‐ray photoelectron spectroscopy analysis of failed surfaces

An investigation was carried out on the application of dilute chitosan solutions modified by a tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenetylamine (dopamine) to the adhesion of low‐density polyethylene (LDPE) and high‐density polyethylene (HDPE) plates photografted with carboxyl‐group‐containing hydrophilic monomers, such as methacrylic acid (MAA) and acrylic acid (AA). In the case where photografting was carried out at lower monomer concentrations or at lower temperatures, the adhesive strength sharply increased with lower grafted amounts. A sharp increase in the adhesive strength was found to be due to the formation of shorter grafted polymer chains at lower monomer concentrations and/or the restriction of the location of grafting to the outer surface region at lower temperatures. In addition, the adhesive strength also sharply increased at even lower grafted amounts for photografting onto the HDPE plates and/or that of AA because the location of grafting was restricted to the outer surface region. For the AA‐grafted LDPE and HDPE plates, substrate breaking was observed. This was attributed to the coverage of the substrate surfaces with grafted poly(acrylic acid) chains at lower grafted amounts and a high water absorptivity of the grafted layer. X‐ray photoelectron spectroscopy (XPS) analysis of the grafted LDPE plates incubated in a dopamine solution containing tyrosinase suggested that the increase in the adhesive strength was caused by the penetration of enzymatically modified chitosan solutions in the grafted layers and the subsequent reaction of quinone derivatives enzymatically generated with grafted polymer chains. In addition, the surface analysis of the failed surfaces by XPS showed that as the adhesive strength increased, the location of failure was shifted from the interface between the layers mixed with enzymatically modified chitosan materials and grafted polymer chains to the inside the grafted layer containing enzymatically modified chitosan materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Estimation of surface properties of grafted layers formed on low- and high-density polyethylene plates by photografting of methacrylic acid and acrylic acid at different monomer concentrations and temperatures

An investigation was carried out on estimation of hydrophilicity, wettability and water-absorptivity, and surface analysis by X-ray photoelectron spectroscopy of the low- and high-density polyethylene (LDPE and HDPE) plates photografted with methacrylic acid (MAA) and acrylic acid (AA) at different monomer concentrations or temperatures. Wettability of the MAA-grafted LDPE and HDPE plates increased with grafted amounts, and became constant when the substrate surfaces were fully covered with the grafted polymer chains. On the other hand, for the AA-grafted LDPE and HDPE plates, wettability had the maximum value, and then gradually decreased against the grafted amount probably due to aggregation of grafted PAA chains, although the surfaces were covered with grafted PAA chains at lower grafted amounts compared with grafted PMAA chains. Water-absorptivity sharply increased at lower grafted amounts due to formation of shorter grafted polymer chains for photografting at lower monomer concentrations or due to restriction of the location of grafting to the outer surface region for photografting at lower temperatures. Therefore, for photograftings of AA or onto the HDPE plates, the substrate surfaces were covered with grafted polymer chains and the grafted layers formed possessed higher water-absorptivity at lower grafted amounts. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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     

Examination of the role of oxygen in the photografting of methacrylic acid on a polyethylene film with a mixed solvent consisting of water and organic solvents

The photografting of methacrylic acid (MAA) on a linear low‐density polyethylene film (thickness = 30 μm) under air and nitrogen atmospheres was investigated at 60°C in mixed solvents consisting of water and an organic solvent, with xanthone as a photoinitiator. The organic solvents used were acetone, methanol, tetrahydrofuran, and dioxane. A maximum percentage of grafting occurred at a certain concentration of the organic solvent in the mixed solvent. This was observed for the systems under both air and nitrogen. The grafting reaction under air exhibited an induction period, but the rate of grafting after the period was greater than that under nitrogen. The formation of poly(ethylene peroxide)s by photoirradiation seemed to be a factor for the accelerated photografting under air. On the basis of attenuated total reflection infrared spectroscopy and scanning electron microscopy of the grafted film, the MAA‐grafted chains of the sample prepared under air tended to penetrate more deeply inside the film than those of the sample prepared under nitrogen. The resulting grafted films exhibited a pH‐responsive character: the grafted films shrank in an acidic medium but swelled in alkaline medium. This was evaluated from measurements of dimensional changes in the grafted films. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 992–998, 2003     

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     

Grafting of branched polymers onto the surface of vapor grown carbon fiber and their electric properties

The grafting of branched polymers onto vapor grown carbon fiber (VGCF) surface and their electric properties of the composite prepared from the branched polymer-grafted VGCF were investigated. In the first step, the grafting of copolymers having pendant peroxy groups onto VGCF was achieved by the copolymerization of 1-(t-butylperoxy-i-propyl)-3-i-propenylbenzene (BPPB) with vinyl monomers initiated by the system consisting of Mo(CO)₆ and trichloroacetyl groups previously introduced onto the surface. In the second step, the postpolymerization of vinyl monomers was initiated by pendant peroxy groups of grafted poly(vinyl monomer-co-BPPB) on the surface to give branched vinyl polymer-grafted VGCF. The dispersibility of VGCF in THF was remarkably improved by grafting of branched polymers onto the surface. The electric resistance of composites prepared from the branched polymer-grafted VGCF suddenly increased when the composites were transferred into solvent vapors and suddenly decreased when they were transferred to dry air.     

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     

Grafting of dichlorodimethylsilane onto cellulose acetate as a model system in homogeneous media

Homogeneous graft copolymerization of dichlorodimethylsilane (DCDMS) onto cellulose acetate (CA) was carried out in acetone. The weight conversion, grafting percentage and grafting efficiency were determined as functions of the polymerization temperature and the concentrations of monomer and cellulose acetate. The IR and NMR data of the graft copolymers showed peaks characteristic of grafted chains. The order of the solvents used for increasing the grafting yield values was found as follows: cyclohexanone > ethyl acetate > dioxane, which is in accordance with their dielectric constants. Cellulose acetate previously oxidized by treatment with a mixture of oxalic acid and potassium dichromate when grafted with DCDMS gave low grafting yield values. The rate of copolymerization grafting of DCDMS onto CA was determined (R_p = 1.1 %min⁻¹). The activation energy of the reaction between DCDMS and CA was calculated (1.32 kJ mol⁻¹, 0.32 kcal mol⁻¹). The mechanism of graft copolymerization of DCDMS onto CA is discussed.     

Aliphatic ketones/water/alcohol as a new photoinitiating system for the photografting of methacrylic acid onto high-density polyethylene

The photografting of methacrylic acid (MAA) onto high-density polyethylene (HDPE) initiated by aliphatic ketones, butanone, pentanone, heptanone, etc. has been reported. When these ketones were used alone or just with ethanol, grafting did not occur. However, grafting took place when a proper butanone/water/ethanol mixed solvent was used. When the volume ratio of butanone was fixed, the grafting of MAA onto HDPE became easier with an increase in the volume ratio of water. The grafting of MAA onto HDPE became easier and faster with a decrease in the volume ratio of butanone. The grafting rate increased with the increase of monomer concentration. The nature of the alcohol also affected the self-initiation by aliphatic ketone; ethanol was found to be better than methanol. Possibly, hydrogen bond formed between aliphatic ketone and water increases the energy and lifetime of the excited state of the ketone, permitting it to act as a grafting and polymerisation initiator. FTIR characterization of the grafted samples proves the successful grafting of MAA onto HDPE. The water absorbency of the grafted samples increased almost linearly with the extent of grafting both in air and in water. The PE films grafted in the butanone/water/ethanol solvent adsorbed approximately 30-40 mass% water per p-MAA.     

Surface structures and adhesion enhancement of poly(tetrafluoroethylene) films after modification by graft copolymerization with glycidyl methacrylate

Surface modifications of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) film were carried out via near-UV light-induced graft copolymerization with glycidyl methacrylate (GMA). The structure and chemical composition of the copolymer surface and interface were studied by angle-resolved X-ray photoelectron spectroscopy (XPS). For PTFE substrate with a substantial amount of grafting, the grafted GMA polymer penetrates or becomes partially submerged beneath a thin surface layer of dense substrate chains to form a stratified surface microstructure. The concentration of the surface-grafted GMA polymer increases with the plasma pretreatment time, the near-UV light illumination time, and the monomer concentration. The GMA graft copolymerized PTFE surfaces adhere strongly to one another when brought into direct contact and cured (i) in the presence of a diamine alone or (ii) in the presence of an epoxy adhesive (epoxy resin plus diamine curing agent). In the presence of diamine alone, failure occurs in the interfacial region. For epoxy adhesive-promoted adhesion, the failure mode is cohesive, i.e. it takes place in the bulk of one of the delaminated PTFE films. The lap shear strengths in both cases increase with the amount of surface-grafted epoxide polymer. The development of the adhesion strength depends on the concentration of the surface graft, the microstructure of the graft copolymerized PTFE surface, the interfacial reactions, and the nature of the bonding agent.     

Crystalline morphology at the interface between polyethylene‐grafted glass and polyethylene

Adhesion measurements performed on a polyethylene (PE)‐grafted‐glass interface showed that the structure of the PE free chains (matrix) was an important parameter. The fracture energy was higher for interfaces prepared from a linear matrix, such as high‐density polyethylene (HDPE), than for those from a branched PE [low‐density polyethylene (LDPE)]. Therefore, the microstructure of the grafted PE/PE matrix interface or interphase was investigated as a function of the molar masses of the connectors and the structure (linear or branched) of the free PE matrix chains. As the grafted chains were linear, a cocrystalline structure with free chains of the HDPE matrix was generated. PE connecting chains led to a low capacity for cocrystallization with LDPE. Cocrystallization was studied with blends based on functionalized PE chains and PE matrices. These blends were assumed to be miscible, as substantiated by a single differential scanning calorimetry (DSC) peak. The DSC analyses were confirmed by wide‐angle X‐ray scattering, which revealed a crystalline orientation of the chains in the interphase, that is, in the vicinity of the glass surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 214–229, 2003