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     

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     

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     

Nonisothermal bulk crystallization of high‐density polyethylene via a modified depolarized light microscopy technique: Further analysis

The quiescent nonisothermal bulk crystallization kinetics of high‐density polyethylene was investigated with a modified depolarized light microscopy technique, which allowed for studies at average cooling rates of approximately 5–2500 °C min^?1. All of the samples crystallized at a pseudoisothermal temperature (i.e., the plateau or crystallization temperature), despite the nonisothermal nature of the cooling conditions. The rate of the crystallization process increased monotonically with increasing the cooling rate and decreasing the crystallization temperature. Moreover, the apparent crystallinity content was a certain decreasing function with the cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1009–1022, 2002     

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     

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     

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     

Modification of properties of CaCO3‐polymerization‐filled polyethylene

CaCO₃–polyethylene (PE) compositions, containing an ultrahigh molecular polyethylene (UHMPE) interlayer between the filler surface and the PE matrix, were synthesized by two‐step polymerization of ethylene on a filler surface activated with a suitable catalyst. The properties of the compositions were studied depending on the molecular weight of the PE matrix and the thickness of the UHMPE intermediate layer at the filler particles. It was shown that the presence of UHMPE as an interlayer in chalk–UHMPE–PE compositions leads to an increase of plastic deformation of the materials as long as the M_w value of the PE matrix is higher than is the brittleness threshold for PE. Chalk–UHMPE–PE compositions exhibit a higher ability for plastic deformation compared to chalk–PE compositions based on a PE matrix of a molecular weight equal to the molecular weight of the total polymer phase (UHMPE–PE) in the first case. There is no improvment of the mechanical properties when the UHMPE is dispersed in the compositions and not as an interlayer between a filler and a matrix. This means that the method of polymerization filling allows one to incorporate the polymer interlayer with a desired nature and properties between a filler surface and polymer matrix in filled polyolefin compositions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 577–583, 2003     

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     

影响低密度聚乙烯光接枝的因素

研究了空气气氛中以二苯甲酮为光敏剂时影响低密度聚乙烯（LDPE）光接枝的工艺因素。结果表明：随光照时间的延长、反应温度的升高、紫外光光强的增加，LDPE的有效接枝率增加；与丙烯酰胺单体相比，LDPE接枝丙烯酸的有效接枝率高，当单体浓度为2mol/L时，有效接枝率达极大值。光接枝LDPE对水的接触角随有效接枝率的增加而降低，当接枝率达一定值时，接触角不再随接枝率的变化而变化。     

Application of ultraviolet photografting technology to acrylamide/polyethylene to improve the interfacial adhesion of polyethylene/unsaturated polyester resin composites

This study was divided into two sections. In the first part, we used ultraviolet (UV) rays in the wavelength range 300–400 nm to remove the hydrogen atom from polyethylene (PE) and worked with a hydrophilic monomer to complete the grafting action. In the second part, we used the best conditions derived from the previous film grafting and applied them to fibers to achieve excellent adhesion for application in composite materials. For the handling process of the PE film, we initially used acrylamide (AM) as the monomer and then added acetone and benzophenone (BP) to form a reactive solution for the advanced photografting process. In general, the optimum concentrations of the monomer solutions obtained from the photografting of PE films were 2 mol/L of AM and 0.2 mol/L of BP. The UV irradiation time was fixed at 30 min. The optimum grafting conditions achieved in the first part of this research were applied in the photografting process for the PE fiber bundles in the second part. The unsaturated polyester (UP) resins were spread over the outer surfaces of the modified fibers. This was done to strengthen and increase the interface between the UP resins and the modified PE fiber. During the curing experiment of the grafted fiber bundles in the resin coatings, the best material quality was obtained under the following conditions: hardener content = 0.85% (relative to the UP resin weight), oven temperature = 80°C, and time frame = 5 h. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modification of the polarity and adhesive properties of polyolefins through blending with maleic anhydride grafted Fischer–Tropsch paraffin wax

The modification of the polarity and adhesive properties of linear low‐density polyethylene, low‐density polyethylene, and isotactic polypropylene through blending with paraffin wax (Fischer–Tropsch synthesis), grafted by maleic anhydride, was investigated. Maleic anhydride grafted paraffin wax significantly increased the polar component of the total surface free energy of polyolefins. Modified polyolefins also had significantly higher adhesion to the polar substrate, a crosslinked, epoxy‐based resin. The conservation of the good mechanical properties of the blends was observed up to 10 wt % wax, except for isotactic polypropylene blends, for which there was a reduction in the stress and strain at break at wax concentrations higher than 5%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3069–3074, 2006     

Powder‐shape analysis and sintering behavior of high‐density polyethylene powders for rotational molding

The quality of rotational molded products is strongly affected by the sintering behavior of the powders used in the process. In turn, for a given material, the sintering behavior of polymer powders is dependent on the size and the shape of particles obtained in the milling apparatus. The quality of powders for rotational molding is usually determined by means of size distribution, dry flow, and bulk density tests. However, these tests do not provide insight into the relationship between the shape of powders, the milling conditions, and the sintering behavior during the rotational molding cycle. Nevertheless, the application of mathematical tools to powder analysis can significantly improve the efficiency of the grinding process, looking not only at the size but also at the shape of the powder. This can in turn result in a higher reliability of rotational molding and in better performances of the products obtained in processes dominated by the sintering behavior of polymer powders. In this work the grinding process of recycled high‐density polyethylene was analyzed using a quantitative approach to the shape and size of the powders. In particular, shape factors, capable of characterizing powders obtained in different milling conditions, were studied. Finally, the influence of the powders' shape and size on sintering behavior was studied by thermomechanical analysis. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 449–460, 2004     

Physical properties of polyethylene/silicate nanocomposite blown films

Maleated polyethylene/silicate nanocomposite and maleated polyethylene/SiO₂ blown films were prepared by melt extrusion. The silicate and SiO₂ significantly affected the physical properties of the films. The former films showed higher tensile strength than the latter films. This high reinforcement effect seemed to be attributable to the strong interaction between the matrix and silicate as well as the uniform dispersion of silicate layers in the polymer matrix. The addition of silicate beyond a certain content gave a worse Elmendorf tear strength than SiO₂. The silicate did not increase the falling dart impact strength at all. The worst Elmendorf strength apparently originated from the orientation of anisotropic silicate rather than the orientation of lamellae of the polymer matrix, and the silicate made the films more brittle. The well‐dispersed silicate layers in the polymer matrix gave almost the same optical properties as the pure polymer despite the increase in the silicate content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2131–2136, 2003     

Nonlinear viscoelastic model for the prediction of double yielding in a linear low‐density polyethylene film

Tensile testing and tensile creep experiments for linear low‐density polyethylene in a thin‐film form were examined and analyzed in terms of a nonlinear viscoelastic model. The proposed model, based on two distinct thermally activated rate processes (Eyring models), was proved to describe the double‐yield‐point tensile behavior of the material tested. The required model parameters were evaluated from the corresponding creep‐strain curves, and this revealed the relationship between the main aspects of the inelastic behavior of polymers, that is, the monotonic loading and creep response. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3519–3527, 2004     

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     

Photografting of methacrylic acid on low-density polyethylene film in presence of polyfunctional monomers

Photografting (λ > 300 nm) of methacrylic acid (MAA) on low-density polyethylene (PE) film (thickness = 30 and 60 μm), on which xanthone photoinitiator was coated earlier, was investigated at 60°C in the presence of polyfunctional monomers such as N,N′-methylenebisacrylamide (MBAAm) and trimethylol propane triacrylate (TMPTA). Addition of the polyfunctional monomers (0.01 and 0.1 wt %) to the grafting system largely accelerated the photografting, and the magnitude of the enhancement was larger for TMPTA than MBAAm. MBAAm component was incorporated into PE substrate and/or MAA-grafted chains through the grafting reaction. Double bonds of the introduced polyfunctional component seemed to act as a new site for the grafting initiation, leading to the promoted grafting. The polyfunctional monomer did not affect distribution of the grafted chains in the cross section of the resultant MAA-grafted film, which was measured by electron probe microanalysis. Wettability of the MAA-grafted PE film was not influenced by the addition of MBAAm, but water absorbency was reduced by using a higher concentration of MBAAm. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1635–1641, 1997     

Characteristics of methacrylic acid‐grafted polyethylene films prepared by photografting in the presence of polyfunctional monomers

Photografting of methacrylic acid (MAA) on low‐density polyethylene film (thickness = 30 μm), on which xanthone photoinitiator was coated earlier, in the presence of polyfunctional monomers such as N,N′‐methylenebisacrylamide, ethylene glycol dimethacrylate, and trimethylol propane triacrylate was examined at 60°C in water/acetone (3:1 v/v) mixture solvent. The photografting was retarded at the earlier stage of polymerization, and then accelerated when small amounts of the polyfunctional monomers (1–3 mol % of MAA monomer used) were added to the system. Addition of the polyfunctional monomers did not affect distribution of the grafted chains in the cross section of the resultant MAA‐grafted PE film, which was measured by electron probe microanalysis. The MAA‐grafted samples were subjected to adsorption of cupric ions at 25°C for 24 h in the system of pH = 5. The adsorption was considerably suppressed for the grafted samples prepared at the earlier stage of polymerization in the system with the polyfunctional monomers. The phenomenon was discussed in terms of the formation of crosslinked and branched structures in the MAA‐grafted chains depending on the polymerization stage in the system with polyfunctional monomers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1262–1268, 2006     

Synthesis and characterization of a terpolymer of limonene,styrene, and methyl methacrylate via a free‐radical route

The free‐radical terpolymerization of a monocyclic terpene, namely, limonene (Lim), with styrene (Sty) and methyl methacrylate (MMA) in xylene at 80 ± 0.1°C for 2 h, with benzoyl peroxide (BPO) as an initiator under an inert atmosphere of nitrogen was extensively studied. The kinetic expression was R_pα[BPO]^0.5[Sty]^1.0[MMA]^1.0[Lim]^?1.0, where R_p is the rate of polymerization. The overall energy of activation was calculated as 26 kJ/mol. R_p decreased as [Lim] increased. This was due to a penultimate unit effect. The Fourier transform infrared spectra of the terpolymer showed bands at 3025–3082, 1728, and 2851–2984 cm^?1 due to C? H stretching of phenyl (? C₆H₅) protons of Sty, ? OCH₃ of MMA, and trisubstituted olefinic protons of Lim, respectively. The ¹H‐NMR spectra showed peaks at 7.3–8.1, 3.9–4.4, and 5.0–5.5 δ due to the phenyl, methoxy, and trisubstituted olefinic protons of Sty, MMA and Lim, respectively. The values of the reactivity ratios r₁ (MMA; 0.33) and r₂ (Sty + Lim; 0.06) were calculated with the Kelen–T?udos method. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2343–2347, 2004