Artificial ageing of low density polyethylene film containing chemically bound UV - stabilizer

This paper deals with photostabilization of low density polyethylene films (LDPE) grafted with the UV-stabilizer 2-hydroxy-4-(3-methacryloxy-2-hydroxy-propoxy) benzophenone (HMB). The influence of grafting yield and the other grafting conditions upon photostabilization efficiency of LDPE films were then studied. The chemically bound monomer (HMB) was localized mainly near the surface of an LDPE film. The grafted LDPE film was exposed to an ultraviolet radiation source, and the degree of oxidation and other photooxidative changes were determined by transmission IR and ATR IR spectroscopy. Experimental results show that radiation grafting of a UV-stabilizer upon LDPE films is an efficient photostabilization method.     

Surface modification of polypropylene film by grafting with vinyl monomers for the attachment of chitosan

Polypropylene (PP) film activated by corona discharge treatment was grafted with methyl methacrylate (MMA) and acrylic acid (AA). The grafted PP was characterized by spectral, thermal analysis and swelling behavior which confirmed the occurrence of the grafting. The water vapor and oxygen permeability (OTR and WVTR) as well as the mechanical properties have been enhanced by grafting with both AA and MMA. The grafted PP was further immobilized with chitosan (CS) using ceric ammonium nitrate (CAN) as an initiator under ultraviolet radiation. The chitosan immobilized grafted film was characterized by FTIR, mechanical properties, thermal properties and swelling measurements. Scanning electron microscope (SEM) confirmed that the CS is bonded to the grafted PP film. The CS modified PP film has acquired enhanced antibacterial and antifungal properties.     

Distribution of acrylic acid grafted chains introduced into polyethylene film by simultaneous radiation grafting with water and ethanol as solvents

The graft copolymerization of acrylic acid onto low‐density polyethylene films by simultaneous γ‐ray irradiation was carried out. The effect of water and ethanol as grafting solvents on the distribution of grafted poly (acrylic acid) in the low‐density polyethylene films was studied with optical microscopy observations of dyed and sliced samples and attenuated total reflection/Fourier infrared spectroscopy analysis. When no vigorous homopolymerization occurred, both polyethylene and poly(acrylic acid) existed in the grafted layer, and the thickness of the grafted layer and the poly(acrylic acid) concentration in the grafted layer increased with an increasing degree of grafting, regardless of the grafting conditions, the former increasing faster than the latter. In comparison with water as the solvent, in the absence of the inhibitor, homopolymerization could be suppressed to a certain degree in the ethanol solvent system, whereas in the presence of the inhibitor, obvious homopolymerization occurred at a lower monomer concentration, and both the degree of grafting and the thickness of the grafted layer were lower. Such differences could be explained by the chain transfer and the relatively low solubility of poly(acrylic acid) in ethanol. In addition, an experimental scheme using optical microscopy to observe the dyed and sliced polymers was optimized. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1570–1577, 2007     

Chemically induced graft copolymerization of vinyl monomers onto cotton fibers

We investigated the chemically induced graft copolymerizations of acrylic acid (AA), acrylamide, crotonic acid, and itaconic acid (IA) onto cotton fibers. Benzoyl peroxide was used as an initiator. The effects of grafting temperature, grafting time, and monomer and initiator concentrations on the grafting yields were studied, and optimum grafting conditions were determined for the sample material. The maximum grafting yield value obtained was 23.8% for AA. Swelling tests, Fourier transform infrared spectroscopy, and scanning electron microscopy analyses of grafted and ungrafted fibers were also performed to characterize fiber properties. IA‐grafted fibers were measured as the most swollen fibers, with a swelling value of 510%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2343–2347, 2006     

Gas Separation Membranes Prepared by Styrene-Grafted Polytrimethylsilylpropyne

Abstract

Poly(1-trimethylsilyl-1-propyne) (PTMSP)—styrene (St) grafted films were obtained by a radiochemical method. St monomer vapors were absorbed by the PTMSP, and the grafting reaction was thereafter accomplished by Co⁶⁰ gamma irradiation in a nitrogen atmosphere. The films so grafted were tested for nitrogen—oxygen separation. The performances of the membranes were studied as functions of time and percent of grafting. The PTMSP—St grafted membranes showed an increased selectivity factor and better stability in comparison with pure PTMSP. The experimental data and some SEM observations confirmed that the grafting procedure changes the PTMSP matrix structure, filling the voids responsible for the PTMSP permeability change with time.     

HEMA‐grafted chitosan for dialysis membrane applications

Chitosan was graft copolymerized with HEMA (2‐Hydroxyethylmethacrylate) for the development of blood‐compatible dialysis membranes. The permeation characteristics of HEMA‐grafted chitosan films for four different solutes creatinine, urea, glucose, and albumin was studied in vitro at 37°C for assessment of the suitability as dialysis membranes. The grafted film CH‐12.5 composition (425% grafting) showed very high permeation to creatinine by reaching the equilibrium within 45 min. The compositions CH‐7.5 and CH‐12.5 showed excellent permeation to glucose when compared to virgin chitosan films. In the case of urea permeation, all the grafted compositions exhibited higher percent permeation than the virgin chitosan films. The copolymer films CH‐7.5 and CH‐12.5 showed enhanced permeability for the high molecular weight solute, albumin. The other grafted copolymer compositions followed almost the same trend as that of chitosan for the low molecular weight solutes as well as the high molecular weight solute. The copolymer films were also found to be highly blood compatible, noncytotoxic, and biodegradable. Hence, the need for developing blood‐compatible chitosan membranes with desirable permeability properties is achieved by the graft copolymerization of HEMA onto chitosan. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2960–2966, 2006     

A few physical properties of grafted polyethylene and nylon films

Methyl methacrylate, vinyl acetate, or N-vinylpyrrolidone was graft-copolymerized onto low-density polyethylene or nylon 6 film by simultaneous irradiation method. Higher extent of grafting was attained by liquid-phase grafting than by vapor-phase grafting. The relative change in the degree of crystallinity of backbone polymer caused by grafting was measured with differential scanning calorimetry. In polyethylene-g-vinylpyrrolidone, the degree of crystallinity decreased markedly with the extent of grafting. However, in other grafted films, especially in grafted nylon, the crystallinity decrease was limited, or substantially no decrease was observed in a few systems. Water vapor permeability of the grafted films changed uniformly with increasing extent of grafting, and particularly polyethylene- and nylon-g-vinylpyrrolidone films showed excellent permeability, and some were able to be used as dialyzer. The difference in grafting method, liquid-phase grafting or vapor-phase grafting, produced no difference in those properties. The grafting was found to bring about a change in the molecular orientation of the original film.     

Surface grafting polymerization of N‐vinyl‐2‐pyrrolidone onto a poly(ethylene terephthalate) nonwoven by plasma pretreatment and its antibacterial activities

The objective of this research was the surface grafting polymerization of biocompatible monomer N‐vinyl‐2‐pyrrolidone (NVP) onto a plasma‐treated nonwoven poly(ethylene terephthalate) (PET) substrate with ultraviolet (UV)‐induced methods. The effects of various parameters, such as the monomer concentration, reaction time, initiator (ammonium peroxodisulfate) concentration, and crosslinking agent (N,N′‐methylene bisacrylamide) concentration, on the grafting percentage were studied. The grafting efficiency of the modified nonwoven PET surfaces reached a maximum at 50 min of UV irradiation and with a 30 wt % aqueous NVP solution. After the plasma activation and/or grafting, the hydrophobic surface of the nonwoven was modified into a hydrophilic surface. NVP was successfully grafted onto nonwoven PET surfaces. The surface wettability showed that the water absorption of NVP‐grafted nonwoven PET (NVP‐g‐nonwoven PET) increased with increasing grafting time. NVP‐g‐nonwoven PET was verified by Fourier transform infrared spectra and scanning electron microscopy measurements. An antibacterial assessment using an anti‐Staphylococcus aureus test indicated that S. aureus was restrained from growing in NVP‐g‐nonwoven PET. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 803–809, 2006     

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     

Functionalization of LDPE and PP to Produce Grafted Membranes Used in Dialysis Processes. Part II

Abstract

Gamma radiation-induced grafting of N-vinyl pyrrolidone (NVP) monomers onto low-density polyethylene (LDPE) and polypropylene (PP) films was studied. The effect of monomer concentration, irradiation dose, and inhibitor concentration on the grafting percent was determined. The swelling behavior of the grafted membranes has been investigated, and it was shown that the modification of LDPE and PP films with hydrophilic monomers results in the growth of the water uptake percent. The permeability of high molecular weight materials such as creatinine and urea, through NVP-grafted membranes increased with increase in grafting percent. Thermal properties of the grafted membranes were studied by using thermo gravimetric analysis (TGA). The morphology of grafted membranes was investigated by using X-ray diffraction (XRD) and the scanning electron microscope (SEM). Structures of the grafted membranes were elucidated by spectroscopic analysis as FTIR, and their mechanical properties were also investigated.     

Grafting of acrylamide to nylon-6 by the electron-beam preirradiation technique. II. Kinetic aspects and film permeability

Single- and multilayered laminated nylon-6 films were grafted with acrylamide (AM) using the electron-beam preirradiation technique. Very high grafting yields were obtained within short time periods. Grafting onto single films was shown to proceed via “diffusion free” pseudo zero-order kinetics. Grafting onto multilayered films was diffusion controlled. SEM and EDAX measurements indicate uniform grafting of single-film membranes and asymmetric grafting of membranes prepared by grafting onto multilayered films. The permeability of grafted membranes to a number of permeants was found to increase with extent of grafting. The specific permeability to both water and solutes exceeded that of the dialysis grade cellophone at 500% graft. The selectivity of grafted films towards various solutes had also been found to be higher than that of cellophane.     

Control of biodegradability of poly(3‐hydroxybutyric acid) film with grafting acrylic acid and thermal remolding

Radiation‐induced graft polymerization of acrylic acid (AAc) on poly(3‐hydroxybutyric acid) (PHB) film was carried out and the resulting film was thermally‐remolded. The PHB films grafted with AAc (PHB‐g‐AAc) having a degree of grafting higher than 5% completely lost the enzymatic degradability. The enzymatic degradability of the grafted film was recovered by thermal remolding. The highest enzymatic degradation rate was observed at degree of grafting of 10% after thermal remolding. The PHB‐g‐AAc films and thermally‐remolded PHB‐g‐AAc films were characterized by contact angle and differential scanning calorimetry. The enzymatic degradability of PHB‐g‐AAc films was lost by the grafted AAc, which covered the surface of PHB film. The acceleration of enzymatic degradation in the remolded PHB‐g‐AAc films was mainly caused by decrease of crystallinity of PHB by dispread of grafted AAc during thermal remolding. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3856–3861, 2006     

Radiation-induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. IV. Studies on some physical properties and structural characterization by means of scanning electron microscopy

Binary mixtures of monomers, e.g., styrene and acrylamide in 1:1 methanol:water solution, were grafted onto cellulose acetate film by taking recourse to preirradiation grafting procedure. The surface modification of the films due to grafting was examined by means of scanning electron microscopy. The mechanical properties, e.g., tensile strength elongation at break, and elasticity as well as water vapor permeability of the grafted films, were investigated. In the case of ungrafted films or when acrylamide was grafted to a low extent, the film surfaces were smooth and hence were not modified to any significant extent. But when acrylamide was grafted appreciably, or when styrene was grafted singly or in binary mixture with acrylamide, the surfaces were found to be covered with fibrils. The pattern of the surface modification also changes with the increase of the extent of grafting. The observed properties of the grafted films were explained on the basis of the electron microscopic results.     

Surface modification of natural substrates by atom transfer radical polymerization

Surface modification of various solid polysaccharide substrates was conducted by grafting methyl acrylate (MA) and styrene via atom transfer radical polymerization (ATRP) to produce well‐defined polymer grafts. The hydroxyl groups on the surfaces of the substrates were reacted with 2‐bromoisobutyryl bromide followed by graft copolymerization under ATRP conditions. The studied substrates were filter paper, microcrystalline cellulose, Lyocell fibers, dialysis tubing, and chitosan films. The modified substrates were analyzed by FT‐IR, water contact angle measurements, TGA, and SEM. FT‐IR characterization of the grafted substrates showed significant differences between the different substrates in the amount of grafted polymer. Higher amounts of polymer seem to be possible to graft from native cellulose substrates than from regenerated cellulose substrates. To investigate whether the grafted polymers were “living” after a longer time period, a second layer of polystyrene was grafted from a filter paper modified with PMA one year ago. FT‐IR characterization of the filter paper showed a peak corresponding to styrene, indicating that a block copolymer had been formed on the surface. Graft copolymerization can be used to change and tailor the surface properties of the polysaccharide substrates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4155–4162, 2006     

Grafting of cellophane films using magnetron-enhanced plasma polymerization

The cellophane films were grafted with PAN for various time durations in magnetron enhanced air plasma. A magnetron-coupled plasma system was developed for the purpose. The rates of polymer deposition and etching were studied. The changes occurring in the angle of contact of water were studied. The attenuated total reflection—infrared spectroscopic studies confirmed the grafting of cellophane surface by polyacrylonitrile (PAN). The water vapor transmission rates through the grafted samples were also studied.     

Proton exchange membranes prepared by simultaneous radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) films. I. Effect of grafting conditions

The simultaneous radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP) films was studied at room temperature. The effects of grafting conditions (type of solvent, irradiation dose, dose rate, and monomer concentration) were investigated. The degree of grafting was found to be dependent on the investigated grafting conditions. The dependence of the initial rate of grafting on the dose rate and the monomer concentration was found to be of 0.5 and 1.3 orders, respectively. The results suggest that grafting proceeds by the so‐called front mechanism in which the grafting front starts at the surface of the film and moves internally toward the middle of the film by successive diffusion of styrene through the grafted layers. Some selected properties of the grafted films were evaluated in correlation with the degree of grafting. We found that the grafted FEP films possess good mechanical stability, which encourages their use for the preparation of proton exchange membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 220–227, 2000     

Thermal properties of proton-conducting radiation-grafted membranes

Proton-exchange membranes are required to exhibit chemical, mechanical, and thermal stability for fuel cell applications. The present investigation has been carried out to explore the thermal behavior of poly(ethylene-alt-tetrafluoroethylene) (ETFE)-based proton-conducting membranes, both uncrosslinked and crosslinked, prepared by radiation grafting and subsequent sulfonation. The influence of preparation steps (irradiation, grafting, sulfonation, crosslinking) on the thermal degradation, crystallinity, and melting behavior of membranes with varying degree of grafting was examined. ETFE base film and grafted films were studied as the reference materials. Furthermore, poly(tetrafluoroethylene-co-hexafluoropropylene)-based grafted films and membranes were investigated as well for comparison. Membrane preparation steps, degree of grafting, crosslinking, type of base polymer have considerable influence on the thermal properties of membranes. The crystallinity of the films decreases slightly by grafting, while a significant decrease was observed after sulfonation. For instance, crystallinity decreased from 37% (pristine ETFE) to 36% (uncrosslinked grafted film) and 23% (uncrosslinked ETFE-based membrane). On the other hand, the melting temperature of the base polymer was almost unaffected by irradiation and grafting. The crosslinked ETFE-based membranes exhibit a slightly higher melting temperature (262.5°C) than their corresponding grafted films (261.3°C) and the base film (260.6°C). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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

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

Surface modification of polythiophene and poly(3‐methyl thiophene) films by graft copolymerization

Polythiophene (PTH) and poly(3‐methyl thiophene) (PMT) films were electrochemically polymerized in an electrolyte solution of boron fluoride–ethyl ether. Ozone‐pretreated PTH and PMT films were subjected to UV‐light‐induced graft copolymerization with different monomers, including poly(ethylene glycol) monomethacrylate, acrylic acid, and glycidyl methacrylate. Surface grafting with the hydrophilic polymers gave rise to more hydrophilic PTH and PMT films. The structure and chemical composition of each copolymer surface were studied by X‐ray photoelectron spectroscopy. The surface grafting with the hydrophilic polymers resulted in a more hydrophilic PTH film. The dependence of the density of surface grafting and the conductivities of the grafted PTH and PMT films on the ozone pretreatment was also studied. A large amount of the grafted groups at the surface of the PTH and PMT films remained free for further surface modification and functionalization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and properties of polymerizable 1,8‐naphthalimide fluorescent dye grafted linear low‐density polyethylene

Light converting greenhouse films are novel plastic films for agriculture. In this study, 4‐methoxy‐N‐allyl‐1,8‐naphthalimide (MOANI) was grafted onto linear low‐density polyethylenes (LLDPE‐g‐MOANI) by melt reactive mixing. The effects of monomer concentration, chamber temperature, and reaction time on grafting degree were systematically studied. Evidence of the grafting reaction was determined by ¹HNMR, FTIR, UV–Vis, and fluorescence spectrometry. Dynamic rheological properties, isothermal crystallization kinetics, surface morphologies of LLDPE, LLDPE‐g‐MOANI, and blends of LLDPE and MOANI (LLDPE/MOANI) were also analyzed. In addition, mechanical and fluorescent properties of unpurified LLDPE‐g‐MOANI films were further studied after the UV condensation weathering and acceleration migration test, respectively. We demonstrated that the cross‐linking of LLDPE could be inhibited effectively by the graft of MOANI; the grafted MOANI acted as a nucleation agent to accelerate crystallization; the grafted MOANI effectively inhibited the aging process of LLDPE and the migration of free MOANI to the surface of the unpurified LLDPE‐g‐MOANI film. The modified LLDPE showed the potential application in long‐term light converting films. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42172.