Adhesion of surface‐grafted low‐density polyethylene plates with enzymatically modified chitosan solutions

An investigation was undertaken on application of dilute chitosan solutions modified by tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenetylamine (dopamine) to adhesion of the low‐density polyethylene (LDPE) plates surface‐grafted with hydrophilic monomers. Tensile shear adhesive strength effectively increased with an increase in the grafted amount for methacrylic acid‐grafted and acrylic acid‐grafted LDPE (LDPE‐g‐PMAA and LDPE‐g‐PAA) plates. In particular, substrate breaking was observed at higher grafted amounts for LDPE‐g‐PAA plates. The increase in the amino group concentration of the chitosan solutions and molecular mass of the chitosan samples led to the increase in adhesive strength. Adhesive strength of the PE‐g‐PMAA plates prepared at lower monomer concentrations sharply increased at lower grafted amounts, which indicates that the formation of shorter grafted PMAA chains is an effective procedure to increase adhesive strength at lower grafted amounts. Infrared measurements showed that the reaction of quinone derivatives enzymatically generated from dopamine with carboxyl groups was an important factor to increase adhesive strength in addition to the formation of the grafted layers with a high water absorptivity. The above‐mentioned results suggested that enzymatically modified dilute chitosan solutions can be applied to an adhesive to bond polymer substrates. The emphasis is on the fact that water is used as a solvent for preparation of chitosan solutions and photografting without any organic solvents. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Adhesion of grafted polypropylene plates with enzymatically modified chitosan solutions and analysis of failed surfaces by X‐ray photoelectron spectroscopy

In this study, hydrophilic monomers were photografted onto the PP plates at different monomer concentrations and temperatures, and grafted PP plates were bonded with enzymatically modified chitosan solutions. Their adhesive strength properties were discussed in relation to the grafting conditions and hydrophilic properties such as wettability and water‐absorptivity. In addition, the location of failure was investigated by X‐ray photoelectron spectroscopy analysis of failed surfaces. Wettability of the grafted PP plates except for the PP grafted with acrylic acid (PP‐g‐PAA) plates remained constant above the grafted amounts at which the PP surfaces were fully covered with grafted polymer chains. On the other hand, wettability of the PP‐g‐PAA plates passed through the maximum value and then gradually decreased with the grafted amount probably because of the aggregation of grafted PAA chains. Water‐absorptivity of the grafted layers formed at lower monomer concentrations or temperatures sharply increased at lower grafted amounts. The adhesive strength increased with an increase in the grafted amount and substrate breaking was observed for PP‐g‐PAA plates because enzymatically modified chitosan solutions were successfully penetrated in the grafted layers and quinone derivatives reacted with carboxy groups of grafted PAA chains. Failure occurred in the layers composed of grafted PAA chains and components containing in enzymatically modified chitosan solutions and the location was shifted to the inside of grafted layer, as the grafted amount increased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1369‐1376, 2013     

Adhesion of ultrahigh molecular weight polyethylene plates photografted with hydrophilic monomers and evaluation of failure location by X‐ray photoelectron spectroscopy

In this study, methacrylic acid (MAA) and acrylic acid (AA) were photografted onto the ultrahigh molecular weight polyethylene (UHMWPE) plates at different monomer concentrations and temperatures, and the grafted UHMWPE plates were bonded with aqueous polyvinyl alcohol (PVA) solutions. The tensile shear adhesive strength of both grafted UHMWPE plates was also discussed in relation to wettability and water absorptivity. The location of failure was also estimated by X‐ray photoelectron spectroscopy (XPS). Wettability of the MAA‐grafted UHMWPE plates became constant, when the UHMWPE surface was fully covered with grafted PMAA chains. Conversely, wettability of the AA‐grafted UHMWPE plates passed through the maximum value and then gradually decreased against the grafted amount probably due to aggregation of grafted PAA chains. Water absorptivity of the grafted layers formed at lower monomer concentrations or temperatures sharply increased at lower grafted amounts. The adhesive strength increased with the grafted amount and substrate breaking was observed at higher grafted amounts, indicating that a main factor to increase the adhesive strength is the formation of a grafted layer by shorter grafted polymer chains and/or the restriction of the location of photografting to the outer surface region. In addition, surface analysis by XPS showed that failure occurred in the boundary between the layer composed of grafted polymer chains and PVA chains and the ungrafted layer at a low adhesive strength, and the location of failure was shifted to the grafted layer containing PVA chains at the grafted amount increased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40133.     

Autohesive properties of polyolefins photografted with hydrophilic monomers

In an attempt to provide polyolefins such as low‐ and high‐density polyethylene and polypropylene with autohesive properties, hydrophilic monomers such as methacrylic acid (MAA), acrylic acid (AA), and 2‐(dimethylamino)ethyl methacrylate (DMAEMA) were photografted onto their surfaces. The wettabilities of the grafted plates stayed constant above full coverage of the substrate surfaces with grafted polymer chains, except for the AA‐grafted plates. The amount of absorbed water for the grafted layers formed increased with an increase in the number of grafted polymer chains. The autohesive strength increased with an increase in the wettability and water absorptivity of the grafted plates as well as the temperature and load on heat pressing. For all grafted plates substrate breaking at autohesive strength measurements was observed for grafted amounts 2–3 times as much as those at adhesive strength measurements. The substrate breakings for the HDPE and PP plates photografted with AA and DMAEMA at adhesive strength measurements were observed at lower grafted amounts compared with those photografted with MAA. This study has made it clear that the photografting of hydrophilic monomers onto polyolefin materials can markedly enhance autohesivity without any adhesives as well as the adhesivity for high grafted amounts. Therefore, polyolefin materials with improved autohesivity and adhesivity can be widely applied in adhesive fields, including for novel uses. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2244–2252, 2003     

Improvement of autohesive and adhesive properties of polyethylene plates by photografting with glycidyl methacrylate

Glycidyl methacrylate (GMA) was photografted with the low‐ and high‐density polyethylene (LDPE and HDPE) plates to provide their surfaces with autohesive and adhesive properties. The chemical composition and wettability of the GMA‐grafted LDPE and HDPE (LDPE‐g‐PGMA and HDPE‐g‐PGMA) plates remained constant above full coverage of the surfaces with grafted PGMA chains. Autohesive strength obtained with 1,4‐dioxane as a good solvent of PGMA increased with an increase in the grafted amount and substrate breaking was observed at the grafted amount of 117 μmol/cm². The grafted amount at substrate breaking was decreased by increasing the temperature and load during heat pressing. Adhesive strength was effectively enhanced by use of multi‐functional amine compounds because of the increase in the reaction between primary or secondary amine groups and epoxy groups appended to the grafted PGMA chains. In addition, the decrease in the amine compound concentration and the increase in the number of amino groups in the amine compounds used led to the decrease in the grafted amounts at substrate breaking. Substrate breaking occurred at lower grafted amounts for the HDPE‐g‐PGMA plates than for the LDPE‐g‐PGMA plates because the location of the photografting was restricted to the outer surface region for the HDPE plate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 493–500, 2007     

Improvement in adhesive‐free adhesion by the use of electrostatic interactions between polymer chains grafted onto polyethylene plates

The tensile shear adhesive‐free adhesion properties induced by electrostatic interactions between poly(acrylic acid) (PAA) and poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) chains grafted onto polyethylene (PE) with low‐density (LDPE) or high‐density (HDPE) plates were studied. PAA‐ or PDMAEMA‐grafted PE plates were immersed in a HCl or NaOH solution or water for 24 h, and their electrostatic properties were changed before they were overlapped with each other and heat‐pressed. The breaking of the substrate between the two plates with water‐swollen grafted layers was observed in the low range of grafted amounts in comparison with immersion in the acidic and basic solutions. The ability of the two plates with grafted polymer chains swollen in water to strongly bond with each other was a result of electrostatic interactions formed by positively charged PDMAEMA and negatively charged PAA chains. The breaking of the substrate in the case of adhesive‐free adhesion between quaternized PDMAEMA‐grafted and PAA‐grafted PE plates immersed in the basic solution occurred with lower grafted amounts of PAA. This came from the strong attractive force between dissociated anionic PAA chains and quaternized cationic PDMAEMA chains in the basic solution. In addition, the adhesive‐free adhesion strength of HDPE plates with the same grafted polymer chains encountered the breaking of the substrate with lower grafted amounts than that of LDPE plates. It was concluded that the grafting of polymer chains onto HDPE plates with high crystallinity was considerably restricted to the outer surface regions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2632–2638, 2006     

Structure and adhesion properties of acrylic acid grafted high‐density polyethylene powders synthesized by a novel photografting method

A novel photografting, nonvapor, and nonliquid phase living graft polymerization was developed to functionalize high‐density polyethylene (HDPE) powder. The structure and adhesion properties of HDPE powder grafted with acrylic acid (AA) were studied by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), water contact angle, peel strength, and graft degree measurements. The result shows that HDPE powder can be grafted with AA via the method with a short reaction time and a high monomer conversion. The graft degree increases with the reaction time. Then, the hydrophilicity of the grafted HDPE powder increases also. The peel strength of HPDE/steel joint improved significantly when acrylic acid grafted HPDE powder was used as hot melt adhesive in place of ungrafted HDPE powder. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structure and adhesion properties of linear low‐density polyethylene powders grafted with acrylic acid via ultraviolet light

The structure and adhesion properties of linear low‐density polyethylene (LLDPE) powder grafted with acrylic acid (AA) via ultraviolet light (UV) were studied by Fourier transform infrared spectroscopy (FTIR), electron spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM), and water contact angle, peel strength, and graft degree measurements. The results show that the chemically inert LLDPE powder can be graft‐copolymerized with AA via this photografting method. The graft degree increases with the ultraviolet irradiation time. The hydrophilicity of the grafted LLDPE powder and the peel strength of high‐density polyethylene (HDPE)/steel joint with the grafted LLDPE powder used as hot‐melt adhesive are improved considerably, as compared to that with the ungrafted LLDPE powder. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2549–2553, 2006     

Application of chitosan solutions gelled by melB tyrosinase to water‐resistant adhesives

An investigation was undertaken on the application of dilute chitosan solutions gelled by melB tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenethylamine (dopamine). The tyrosinase‐catalyzed reaction with dopamine conferred water‐resistant adhesive properties to the semi‐dilute chitosan solutions. The viscosity of the chitosan solutions highly increased by the tyrosinase‐catalyzed quinone conversion and the subsequent nonenzymatic reactions of o‐quinones with amino groups of the chitosan chains. The viscosity of chitosan solutions highly increased in shorter reaction times by addition of melB tyrosinase. Therefore, in this study, the gelation of a chitosan solution was carried out without poly(ethylene glycol) (PEG), which was added for the gelation of chitosan solutions using mushroom tyrosinase. The highly viscous, gel‐like modified chitosan materials were allowed to spread onto the surfaces of the glass slides, which were tightly lapped together and were held under water. Tensile shear adhesive strength of over 400 kPa was observed for the modified chitosan samples. An increase in either amino group concentration of the chitosan solutions or molecular mass of the chitosan samples used effectively led to an increase in adhesive strength of the glass slides. Adhesive strength obtained by chitosan materials gelled enzymatically was higher than that obtained by a chitosan gel prepared with glutaraldehyde as a chemical crosslinking agent. In addition, the use of melB tyrosinase led to a sharp increase in adhesive strength in shorter reaction times without other additives such as PEG. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Improvement of gas barrier property of polyolefins by diamond‐like carbon deposition and photografting polymerization

The gas barrier properties of isotactic polypropylene (iPP) and high‐density polyethylene (HDPE) are both significantly improved by diamond‐like carbon (DLC) deposition and photografting polymerization using acrylic acid (AA) monomers. In fact, the gas barrier properties can be highly improved just by DLC or by AA‐photografting polymerization. The improvement observed by AA‐photografting polymerization is more pronounced than that by DLC deposition in our general experimental condition. In more detail, the oxygen barrier property of DLC‐deposited and AA‐grafted iPP is considerably improved by ～10 times when compared with that of neat iPP. As for HDPE, the oxygen barrier property is enhanced by nearly six times through DLC deposition and photografting polymerization. By observing the surfaces, 30 nm layer of DLC and 1.0 μm of AA‐grafted layer are firmly constructed on the polyolefins, which should contribute to the enhancement of the oxygen barrier property. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characteristics of acrylic acid and N-isopropylacrylamide binary monomers–grafted polyethylene film synthesized by photografting

Method for introducing grafted chains consisting of two types of monomer components, acrylic acid (AA) and N-isopropylacrylamide (NIPAAm), into low-density polyethylene (PE) film (thickness = 25 μm) was investigated by two photografting technique using xanthone photoinitiator at 60°C. In the first method (one-step method), AA and NIPAAm binary monomers were graftcopolymerized onto PE film. In the second method (two-step method), AA was first photografted onto PE film and then NIPAAm was further introduced into the AA-grafted PE film by a second-step photografting. Water absorbencies of the grafted films (one- and two-step samples) prepared by the one- and two-step methods, respectively, decreased in the order of AA-grafted film > one-step sample > two-step sample > NIPAAm-grafted film. The water absorbency steeply decreased at 20 to 40°C with increasing temperature when immersed in water at the temperatures (5–60°C) for 24 h. Thermosensitivity, which was defined as the ratio of water absorbencies of the grafted samples at 5 and 60°C, was higher for the one-step sample than the two-step one. The different extent of the water absorbency and the thermosensitivity between both samples is discussed in terms of location of grafted chains in the film substrate, which was determined by electron probe microanalysis and attenuated total reflection–infrared measurements, and monomer sequence distribution of the grafted chains. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2057–2064, 1998     

The effect of matrix composition on the properties of cellulosic fibers–polyethylene composites

The solution/precipitation method was used for the preparation of polyethylene (PE)/cellulosic fibers composites. Blends of modified linear low density PE [linear low density PE‐grafted maleic anhydride (LLDPE‐g‐MAH)] with low density PE (LDPE) were used as matrices for the aforementioned composites. Blends of LDPE with a copolymer of LDPE and acrylic acid (AA)/n‐butyl acrylate (n‐BA) [(AA/n‐BA)–LDPE] were also studied for the same purpose. The reinforcing effect of cellulosic fibers in terms of tensile strength is more enhanced when mixtures of the modified polar polymer with pure PE were used as matrices, as compared with that corresponding to matrices consisting of modified PE alone. Regarding the Izod impact strength, composites of LLDPE‐g‐MAH presented the best performance with an improvement of 135% in comparison with specimens consisting of LDPE matrix, whereas composites of (AA/n‐BA)‐LDPE matrix showed a modest improvement of their impact resistance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Lamination of high‐density polyethylene by bulk photografting and the mechanism of adhesion

The photolamination of high‐density polyethylene (HDPE) by bulk photografting is described, along with a discussion of the adhesion mechanism. HDPE can be photolaminated very easily with a thin poly(acrylic acid) layer, photopolymerized from acrylic acid, with very strong adhesion obtained after a short time of UV irradiation; the adhesion failure mode is polyethylene breakage. Thicker HDPE sheets require longer irradiation times for strong adhesion. Methacrylic acid or hydroxyethyl methacrylate provides no adhesion of HDPE at all after irradiation. When glycidyl acrylate is used alone between HDPE sheets, the peel strength of the photolaminated polyethylene is only approximately 320 N/m, but when glycidyl acrylate or hydroxyethyl methacrylate is grafted with acrylic acid, very good adhesion can be obtained. It is proposed that stronger adhesion is produced by a less branched grafted chain structure, which permits much more chain entanglement. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1097–1106, 2005     

Comparative ozonization of LDPE and HDPE and grafting of some monomers to elaborate new ion exchange membranes

A comparative study of the ozonization of low density polyethylene (LDPE) and high density polyethylene (HDPE) was carried out. A grafting study of acrylic acid (AA), N,N‐dimethylamino‐2‐ethylmethacrylate (MADAME) and vinyl phosphonic acid (VPA) on LDPE and HDPE was performed in mass and solution. The ozonized polyethylene and the grafting polymers were characterized by IR spectroscopy and elementary analysis. Ion exchange membranes were prepared from grafted copolymers and characterized by the exchange capacity and electrical resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4423–4429, 2006     

Polypropylene/polypropylene‐grafted acrylic acid blends for multilayer films: Preparation and characterization

Polypropylene (PP) was functionalized with acrylic acid (AA) and styrene (st) as a comonomer by means of a radical‐initiated melt‐grafting reaction. FTIR, ESCA, and ¹H‐NMR spectroscopies were used to characterize the formation of polypropylene grafted with acrylic acid (PP‐g‐AA) and polypropylene grafted with acrylic acid and styrene (PP‐g‐AAst). The content of AA grafted onto PP was determined by using volumetric titration. Blends of PP with 0–100 wt % of PP‐g‐AA were prepared by melt mixing. The effect of the modified polymer content on the surfaces of cast films was characterized through FTIR–ATR and ESCA analysis as well as contact‐angle, wetting‐tension, and ink‐adhesion measurements. The influence of the content of AA on the melting and crystallization temperature of PP was investigated by DSC. The contact angles of water on cast‐film surfaces of PP/PP‐g‐AA blends decreases with increasing modified polymer content and decreasing PP‐g‐AA molecular weight. A notorious improvement on wetting tension was observed with increasing modified polymer content and decreasing PP‐g‐AA molecular weight. From FTIR–ATR and ESCA spectra of the blends, a calculation was made of the carbonyl index on the films' surfaces. It was found that the higher the carbonyl index, the lower the contact‐angle value for the polypropylene blends. An increase in crystallization temperature of PP was observed when AA monomers were grafted into PP and with increasing PP‐g‐AA content in the blend, probably caused by a nucleation effect of AA monomers that would improve the crystallization capability of PP. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1497–1505, 2001     

聚酰胺胺树形分子对羧基化聚乙烯的表面修饰

通过紫外光接枝方法,以丙烯酸为单体对低密度聚乙烯薄膜进行表面改性,然后用聚酰胺胺(PAMAM)分子对羧基化的聚乙烯表面进行修饰,制备了表面固定PAMAM树形分子的低密度聚乙烯薄膜。通过接触角测量,衰减全反射红外光谱,扫描电镜等方法的表征,证明丙烯酸成功接枝到聚乙烯薄膜表面,聚酰胺胺树形分子通过与羧基的结合形成团簇结构,反映了接枝链在薄膜表面的聚集状态。     

Application of enzymatically gelled chitosan solutions to water‐resistant adhesives

An investigation was undertaken on the application of dilute chitosan solutions gelled by tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenethylamine (dopamine). The tyrosinase‐catalyzed reaction with dopamine conferred water‐resistant adhesive properties to the semidilute chitosan solutions. The viscosity of the chitosan solutions increased highly by the tyrosinase‐catalyzed reaction and the subsequent reactions between o‐quinone compounds and chitosan. These highly viscous, gel‐like modified chitosan materials were allowed to spread onto the surfaces of the glass slides, which were tightly lapped together and held them in water. Tensile shear adhesive strength of over 400 kPa was observed for the modified chitosan samples. The increase in the amino group concentration of the chitosan solutions and the molecular mass of the chitosan used effectively led to the increase in adhesive strength of the glass slides. In addition, in the case where the chitosan solution was gelled by the enzymatic reaction with dopamine in the presence of poly(ethylene glycol), adhesive strength sharply increased at shorter reaction times concomitantly with the increase in the viscosity of the chitosan solutions because the tyrosinase activity effectively was retained by poly(ethylene glycol). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1818–1827, 2007     

Photografting of acrylic acid on high density polyethylene powder in vapour phase

A photografting technique was explored as a means of functionalizing high density polyethylene (HDPE) powder. The graft copolymerization reaction of acrylic acid on HDPE powder and the surface structure of grafted HDPE powder were studied in terms of grafting degree and grafting efficiency, and by FTIR and ESCA. The results show that the surface of chemically inert HDPE powder pretreated by an acetone solution of benzophenone (BP) can be graft‐copolymerized with acrylic acid by photografting in the vapour phase. Thereby, the grafting degree is increased but the grafting efficiency is decreased with increasing reaction time. When the BP concentration in pretreatment solution is increased, the grafting degree is increased to a maximum, and is then reduced. The most suitable reaction temperature is 90 °C. Grafting degree can reach the quite high value of 10.6 wt% under the conditions of BP concentration 1.0 wt%, reaction time 1 h and temperature 90 °C. © 2000 Society of Chemical Industry     

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