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     

The study of melt grafting mechanism of acrylic acid and butyl acrylate onto low density polyethylene and its application as internal plasticizer

Melt grafting of acrylic acid (AA) and butyl acrylate (BA) (equal molar ratios) onto low‐density polyethylene (LDPE) was carried out in Haake internal mixter by free radical grafting copolymerization. The graft degree of AA and BA in the grafted LDPE (LDPE‐g‐(AA+BA)) was determined by FTIR. The influences of initiator on the graft degree of AA and BA, melt flow rate (MFR), and gel content were investigated, and the optimum conditions were obtained. The successive self‐nucleation/annealing (SSA) thermal fraction method was used to characterize the molecular structure and polydispersity of LDPE‐g‐(AA+BA) with various graft degrees. The effects of thermal fraction parameters on fraction of LDPE‐g‐(AA+BA) were investigated. On the basis of the results of SSA, the grafting reaction mechanism of AA and BA onto LDPE was proposed, i.e., grafting reaction preferentially occurred on the tertiary carbons of LDPE. The grafted LDPE possessed suitable reactivity and rheological property. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of phosphor coated with a polymer by emulsion polymerization and its application in low‐density polyethylene

The long‐afterglow phosphor SrAl₂O₄ : Eu²⁺, Dy³⁺ is liable to hydrolyze in water with deterioration of its luminescent properties. In this study, in situ emulsion polymerization was first used to prepare phosphor coated with poly(methyl methacrylate‐co‐butyl acrylate) [P(MMA‐co‐BA)] to improve water resistance. Fourier transform infrared spectra suggested that the polymer attached to the phosphor by chemical bonding. Observation by scanning electron microscopy (SEM) showed that a polymer layer formed on the surface of the phosphor. The resistance to water of the phosphor coated with the polymer layer was much better than that of the uncoated phosphor because the transparent polymer layer could suppress its hydrolysis process. Low‐density polyethylene (LDPE) plastics, doped with long‐afterglow phosphors, were manufactured with an extrusion technique. Through coating with P(MMA‐co‐BA), the compatibility of phosphor with the LDPE matrix was improved, as determined by SEM. The luminous LDPE plastics blended with the phosphor coated with polymer showed long and strong phosphorescence with little loss of persistence phosphorescence compared to the uncoated phosphor. The LDPE plastics still retained their mechanical properties through doping with 3% (mass fraction) of the phosphors. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Ozone‐induced grafting of a sulfoammonium zwitterionic polymer onto low‐density polyethylene film for improving hemocompatibility

Ozone‐induced grafting was developed to improve the hemocompatibility of biomaterials based on low‐density polyethylene (LDPE). An LDPE film was activated with ozone and graft‐polymerized with N,N′‐dimethyl(methacryloylethyl)ammonium propane sulfonate (DMAPS). The existence of sulfobetaine structures on the grafted film was confirmed by X‐ray photoelectron spectroscopy and attenuated total reflection/Fourier transform infrared (ATR–FTIR). More DMAPS was grafted onto the LDPE film as the DMAPS concentration increased, as determined by ATR–FTIR. Static contact‐angle measurements indicated that the DMAPS‐grafted LDPE film had a significant increase in hydrophilicity. The blood compatibility of the grafted film was preliminarily evaluated with a platelet‐rich‐plasma (PRP) adhesion study. No platelet adhesion was observed on the grafted film incubated with PRP at 37°C for 180 min. This new sulfoammonium zwitterionic‐structure‐grafted biomaterial might have potential for biomedical applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3697–3703, 2006     

Assessing biodegradability and mechanical,thermal, and morphological properties of an acrylic acid‐modified poly(3‐hydroxybutyric acid)/wood flours biocomposite

A poly(3‐hydroxybutyric acid) and wood flours (PHB/wood flours) composite and an acrylic acid‐grafted PHB/wood flours composite were characterized and their properties were examined and compared. Mechanical properties of PHB became significantly worse when it was blended with wood flours, due to the poor compatibility between the two phases. Much better dispersion and homogeneity of wood flours in the polymer matrix was obtained when PHB‐g‐acrylic acid (AA) was used in place of PHB in the composite. Improved mechanical and thermal properties of the PHB‐g‐AA/wood flours composite, notably an increase in tensile strength at breakpoint, evidenced its superiority to the PHB/wood flours composite. Furthermore, PHB‐g‐AA/wood flours composites were more easily processed because of their lower melt viscosity. Under soil and enzymatic environments, weight loss data indicated that both composites were more biodegradable with higher wood flours content. A reduction in tensile strength at break after exposure to soil and enzymatic environments was also observed in both blends, especially at high wood flours content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3565–3574, 2006     

Novel comb‐structured‐polymer‐grafted carbon black by surface‐initiated atom transfer radical polymerization and ring‐opening polymerization

Novel comb‐structured‐polymer‐grafted carbon black (CB) was synthesized with a combination of surface‐initiated atom transfer radical polymerization and ring‐opening polymerization. First, poly(2‐hydroxyethyl methacrylate) (PHEMA) was grafted onto the CB surface by surface‐initiated atom transfer radical polymerization. The prepared CB‐g‐PHEMA contained 35.6–71.8% PHEMA, with the percentage depending on the molar ratio of the reagents and the reaction temperature. Then, with PHEMA in CB‐g‐PHEMA as the macroinitiator, poly(?‐caprolactone) (PCL) was grown from the CB‐g‐PHEMA surface by ring‐opening polymerization in the presence of stannous octoate. CB‐g‐PHEMA and CB‐g‐(PHEMA‐g‐PCL) were characterized with Fourier transform infrared, ¹H‐NMR, thermogravimetric analysis, dynamic light scattering, and transmission electron microscopy. The resultant grafted CB had a shell of PHEMA‐g‐PCL. On the whole, the CB nanoparticles were oriented in dendritic lamellae formed by these shells. This hopefully will result in applications in gas sensor materials and nanoparticle patterns. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Improvement of conductive network quality in carbon black‐filled polymer blends

Heat treatment of polymer‐based composites is critical for the enhancement of both stability and long‐term service life, especially when the materials function under an inconstant temperature environment. The present article discusses the effect of heat‐treatment conditions on the electrically conductive properties of carbon black (CB)‐filled low‐density polyethylene (LDPE) and ethylene–vinyl acetate copolymer (EVA) composites, which are candidates for positive temperature coefficient (PTC) materials. It was found that the dispersion mode of CB particles changes as a function of the matrix morphology. When the composites are irradiated to form crosslinked networks in the matrix for the elimination of negative temperature coefficient (NTC) behavior, some of the produced free radicals are also entrapped for quite a long time after the irradiation treatment. These residual radicals further enhance the interaction between CB and the matrix and further induce the crosslinking of the matrix so that the composites' conductivity changes with time as a result of the continuous variation in the contacts between the conductive fillers. To improve the quality of the conduction paths in the composites, appropriate post‐heat treatment should be carried out, which speeds up the formation of the above‐mentioned two kinds of crosslinked structures within a limited time. Annealing at 75°C for more than 10 h is believed to be an effective way. After the treatment, a balanced performance characterized by reduced room‐temperature resistivity and improved PTC intensity was obtained. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2768–2775, 2002     

Mechanical properties,water‐swelling behavior,and morphology of water‐swellable rubber prepared using crosslinked sodium polyacrylate

A novel water‐swellable rubber (WSR) has been prepared by blending chlorobutadiene rubber (CR), reactive clay and other additives with crosslinked sodium polyacrylate (CSP), which was modified by interpenetrating polymer networks (IPNs) technology with crosslinked P(AA‐co‐BA). The structure of WSR was characterized by scanning electron microscopy (SEM). The mechanical properties, water‐swelling ratio by mass, and the percentage loss of CSP in the WSR were investigated. The results showed that the modified CSP grains can be dispersed well in the CR, and that it resulted in increase of mechanical properties and water‐swelling ratio and in decrease of percentage loss of CSP, compared with the unmodified one. When the percentage content of crosslinked P(AA‐co‐BA) used to modify CSP reached 30%, the tensile strength, elongation at break, and water‐swelling ratio of WSR exhibited maximum value, and percentage loss of CSP exhibited minimum value. When the content of CSP in WSR was 30 phr, the tensile strength, elongation at break, and water‐swelling ratio and percentage loss of CSP of the WSR containing CSP modified were 7.7 MPa, 1530, 438, and 2.5%, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1489–1496, 2006     

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     

Preparation and characterization of functionalized low density polyethylene matrix biocomposites

The incorporation of cellulosic fibers into polyethylene matrices was studied in this work, by dispersion of fluff pulp from maritime pine in a hot polymer solution, followed by co‐precipitation of the solid components by cooling at room temperature. The above method was found suitable for proper wetting and dispersion of fibers in the polymeric matrix, as compared with melt compounding. Unmodified low density polyethylene [LDPE], modified LDPE with maleic anhydride grafted linear low density polyethylene [M‐LLDPE] and a copolymer of acrylic acid and n‐butyl acrylate polyethylene [(AA/n‐BA)‐LDPE], were used as matrices for the preparation of fiber reinforced composites. The thermal properties of these composites were determined using differential scanning calorimetry and thermogravimetric analysis. The incorporation of cellulosic fibers results in a decrease of the crystallinity of the polymer matrix, as they act as inert material. In addition, the appropriate tests were run in order to determine the density and tensile properties of the composite specimens prepared by compression molding, with filler content ranging from 10 to 40% (w/w). Composites based on modified LDPE showed improved mechanical properties. The Takayanagi model, applied to predict the Young's modulus of composites, was in very good agreement with the experimental data obtained in this work. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Structural characterization of alpha methyl styrene‐butyl acrylate‐grafted polyetheretherketone films

Radiation‐induced graft copolymerization of alpha methyl styrene (AMS)‐butyl acrylate (BA) mixture onto poly(etheretherketone) (PEEK) was carried out to develop films of varying copolymer compositions. The characterization of films was carried out with fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), X‐ray diffraction analysis (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The presence of AMS and BA units within the film matrix was confirmed by FTIR. The intensity of the characteristic peaks for AMS and BA increased with the increasing grafted component in the films. The crystallinity of the films as observed from DSC and XRD decreased with the increasing graft levels. On the other hand, the melting temperature of the base polymer was almost unaffected by irradiation and the grafting process. The glass transition temperature (T_g) of the grafted film increased as compared to the virgin PEEK. Ungrafted film showed a stable thermogram up to ～500°C. However, the grafting introduced a new decomposition range in the copolymer, due to the presence of the AMS/BA. AFM images showed the formation of domains on the grafted PEEK film surface. The SEM also showed domain formation of the grafted component within the PEEK matrix. However, the fracture analysis did not show any prominent phase separation. Mechanical characterization of films in terms of tensile strength, elongation, and modulus was also carried out. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Novel microporous poly(vinylidene fluoride)‐graft‐poly(tert‐butyl acrylate) electrolytes for secondary lithium batteries

BACKGROUND: Much interest has recently been shown in improving the performance of lithium‐ion polymer batteries with gel polymer electrolytes (GPEs) due to a rapid expansion in industrial demand. Novel GPEs based on poly(vinylidene fluoride)‐graft‐poly(tert‐butyl acrylate) (PVDF‐g‐tBA) microporous mats are suggested in this study. RESULTS: Microfibrous polymer electrolytes were prepared using electrospinning and characterized for extent of grafting, morphology, crystallinity, electrochemical stability, ionic conductivity, interfacial resistance and cell cycleability. The degree of crystallinity was lower for tBA‐grafted PVDF mats than that of neat PVDF. The PVDF‐g‐tBA showed an improvement in the ionic conductivity, electrochemical stability, interfacial resistance and cyclic performance. CONCLUSION: The tBA‐grafted PVDF microporous electrolytes are promising candidates for enhancing the performance of lithium‐ion polymer batteries. Copyright © 2008 Society of Chemical Industry     

Partially miscible poly(lactic acid)‐ blend‐poly(propylene carbonate) filled with carbon black as conductive polymer composite

BACKGROUND: Conductive polymer composites (CPCs) can be obtained by filling polymer matrices with electrically conductive particles, and have a wide variety of potential applications. In the work reported, the biodegradable polymer poly(lactic acid) (PLA) as a partially miscible blend with poly(propylene carbonate) (PPC) was used as a polymer matrix. Carbon black (CB) was used as the conducting filler. RESULTS: Fourier transform infrared spectroscopy revealed interactions between matrix and CB filler; this interaction was stronger in PPC‐blend‐CB than in PLA‐blend‐CB composites. A rheology study showed that low‐viscosity PPC could improve the fluidity of the CPCs, but decrease that of CB. With increasing CB content, the enforcement effect, storage modulus and glass transition temperature increased, but the elongation at break decreased. CPCs exhibited the lowest electrical percolation thresholds of 1.39 vol.% CB when the content of PPC in PLA‐blend‐PPC was 40 wt%. The conductivity of CPCs containing 5.33 vol.% CB and 40 wt% PPC reached 1.57 S cm^?1. Scanning electron microscopy revealed that CB exhibits a preference for dispersion in the low‐viscosity phase (PPC) of the multiphase matrix. CONCLUSION: In the presence of CB, partially miscible PLA‐blend‐PPC could form multi‐percolation CPCs. Moreover, the combination of PLA and PPC with CB broadens novel application of both renewable polymers and CPCs. Copyright © 2008 Society of Chemical Industry     

PP/LDPE blends produced by reactive processing. I. Grafting efficiency and rheological and high‐elastic properties of [PP/LDPE]‐g‐IA melts

Itaconic acid (IA) was grafted onto polypropylene/low‐density polyethylene (PP/LDPE) blends. The ratio of polymeric components was varied from 100 : 0 to 0 : 100. The effect of the variation in the ratios of the components on grafting efficiency and concomitant side processes was studied. Grafting of IA (1 wt %) was initiated by 2,5‐dimethyl‐2,5‐di(tert‐butyl peroxy)‐hexane (0.3 wt %) and was carried out in an extruder reactor equipped with a dynamic mixer. An increase in the PP content of the blend led to a lower yield of the grafted product. With low concentrations of LDPE in the blend (up to 25 wt %), grafting efficiency was observed to increase, and this increase was greater in comparison with the additive rule. Between 25 and 99 wt % of LDPE in the blend, grafting efficiency rose monotonically with LDPE concentration. At or below an LDPE content of 25 wt %, the melt flow index (MFI) of [PP/LDPE]‐g‐IA would increase unlike with PP‐g‐IA systems. But a small quantity of PP (below 25 wt %) in the [PP/LDPE]‐g‐IA blends would result in a decreased MFI unlike with LDPE‐g‐IA. The dependence of swell index and melt strength on the ratio of polymeric components in [PP/LDPE]‐g‐IA blends also was investigated. ©2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5095–5104, 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     

Investigating nonlinear viscoelastic properties of molten carbon black/poly(ethylene‐co‐butyl acrylate) composites,using fourier transform rheometry and other test techniques

A series of molten carbon black (CB)/poly(ethylene‐co‐butyl acrylate) (EBA) composites were investigated through Fourier transform (FT) rheometry and other techniques. Filler loadings were above the critical percolation value, and consequently, strongly nonlinear viscoelastic properties were observed, with, in addition, an unusual complexity of carbon black effects when compared with other systems, for instance filled elastomers. FT rheometry appears particularly sensitive to such a complexity with typical variations of torque harmonics, as dynamic torsional strain is increased at constant frequency and temperature. How CB particles are distributed in the material appears as the key to understand experimental results. Indeed, in CB–EBA composites, filler particles concentrate in amorphous regions of the polymer, which are also butyl acrylate (BA)‐rich regions. At room temperature, such composites are basically dual‐phase systems: ethylene segments (PE)‐rich crystallites and CB‐rich amorphous BA regions. Solid‐state mechanical properties reflect this morphology. As temperature increases, crystallites melt down allowing a pseudofluid state to be eventually reached but the dual‐phase morphology is essentially kept. It follows that, under increasing (dynamic) strain, such complex dual‐phase molten systems exhibit a response that initially reflects a contribution from PE‐rich regions, easier to deform than CB‐rich amorphous BA regions, before the expected response of the filled BA phase is observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4071–4082, 2006     

Mechanical and thermal properties of LDPE‐cellulose acetate phthalate blends—Effect of maleic anhydride‐grafted LDPE compatibilizer

Biodegradable blends of LDPE and cellulose acetate phthalate have been prepared. Maleic anhydride‐grafted LDPE has been added as a compatibilizer to this blend. The elastic modulus and tensile strength has been considerably improved by adding LDPE‐g‐maleic anhydride compatibilizer. Scanning electron microscope micrographs reflected the observed results for the increase in mechanical properties of the blend. Further blend morphology exhibited a deformed matrix for the compatibilized blends. Thermogravimetric analysis studies showed two‐stage degradation for the blends. Differential scanning calorimetry thermograms showed a loss of crystallinity for the LDPE phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Interfacial behavior of epichlorohydrin–ethyleneoxide–allylglycidyl ether/fluorinated carbon black observed from mechanical and dielectrical properties

The purpose of this work was to study the effect of carbon black (CB) surface state on the interaction between CB and polymer matrix, as well as the polymer chain mobility. The mobility of polymer chain absorbed on the CB surface was estimated by using a dynamic mechanical analyzer and an impedance analyzer. The interaction parameter (B) and immobilized polymer layer thickness (ΔR) were estimated from the dynamic mechanical analysis. It was observed that values of B and ΔR decreased with increasing fluorine content on the CB surface. On the other hand, from the dielectric measurement, the Maxwell–Wagner–Sillars (MWS) relaxation peak, accompanied by migration of the charge carriers, accumulated at the interface between polymer and CB, observed at temperatures higher than the glass‐transition temperature (T_g) of the polymer matrix. The activation energy (E_{a MWS}), calculated from the relaxation frequency of MWS relaxation, was decreased with increasing surface fluorine content. Good agreement was found between the B and the ΔR values estimated from the dynamic mechanical analysis and the E_{a MWS} calculated from the MWS relaxation frequency estimated from dielectric measurement. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2928–2933, 2004     

Synthesis,effectiveness, and working mechanism of humic acid‐{sodium 2‐acrylamido‐2‐methylpropane sulfonate‐co‐N,N‐dimethyl acrylamide‐co‐acrylic acid} graft copolymer as high‐temperature fluid loss additive in oil well cementing

Monomers of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS®), N,N–dimethyl acrylamide (NNDMA) and acrylic acid (AA) were grafted on humic acid as backbone by aqueous free radical copolymerization in such a manner that a graft copolymer possessing lateral terpolymer chains was obtained. Molar ratios between AMPS®, NNDMA, and AA were found to be 1 : 1.54 : 0.02 and the ratio between backbone and graft chain was 20 : 80 wt %. The synthesized fluid loss additive (FLA) was characterized by size exclusion chromatography (SEC), charge titration, and Brookfield viscometry. Thermogravimetric and SEC analysis revealed stretched backbone worm architecture for the polymer whereby humic acid constitutes the backbone decorated with lateral graft chains. Grafting was confirmed by SEC data (R_g) and by ineffectiveness of a blend of AMPS®‐NNDMA‐AA copolymer with humic acid. Their performance as high temperature FLA was studied at 150°C by measuring static filtration properties of oil well cement slurries containing 35% bwoc of silica fume and 1.2% bwoc AMPS®‐co‐itaconic acid retarder. At this temperature, 1.0% bwoc graft copolymer achieves API fluid loss value of 40 mL, thus confirming high effectiveness. The graft copolymer viscosifies cement slurries less than other common synthetic FLAs. The working mechanism of the graft copolymer was found to rely on adsorption onto surface of hydrating cement, as was evidenced by adsorption and zeta potential measurements. Adsorption is hardly affected by temperature and results in constriction of the filter cake pores. The study provides insight into performance of cement additives under the harsh conditions of high temperature and high pressure. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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