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ABSTRACT:The photo-oxidation and thermal initiation changes of commercial low density polyethylene (LDPE) films used in greenhouse covering, in the presence or absence of ultraviolet (UV) stabilizer, were monitored by infrared (IR) spectroscopy, by mechanical tests and by applying the grafting of acrylic acid onto the aged films. It was found that the resistance of PE films to UV irradiation and heat initiation as proved by tensile strength and elongation at break % was better for stabilized PE films compared with the unstabilized ones. A simple correlation was not observed between the fall in mechanical properties and the rate of film oxidation. On the other hand, an almost linear relation was obviously noticed between the degree of PE oxidation (CAO) measured by IR spectroscopy and the grafting level.

The zwitterionic homopolymer poly[2-(methacryloyloxy)ethyl-dimethyl-(3-sulfopropyl) ammonium hydroxide was coated onto the surface of commercial polyamide reverse osmosis (RO) membranes. Aqueous solutions of the polymer at different concentrations were applied to modify the polyamide membranes through an in situ surface coating procedure. After membrane modification, cross-flow filtration testing was used to test the antifouling potential of the modified membranes. The obtained data were compared with experimental data for unmodified membranes. Each test was done by cross-flow filtering tap water for 60 hours. Yeast extract was added as a nutrient source for the naturally occurring bacteria in tap water, to accelerate bacteria growth. Fourier transform infrared spectroscopy, contact angle, scanning electron microscopy, atomic force microscopy, and permeation tests were employed to characterize membrane properties. The results confirmed that modifying the membranes enhanced their antifouling properties and cleaning efficiency, the fouling resistance to bacteria improving due to the increased hydrophilicity of the membrane surface after coating. In addition, the water permeability and salt rejection improved. This in situ surface treatment approach for RO membranes could be very important for modifying membranes in their original module assemblies as it increases water production and reduces the salt content.

SYNOPSISTwo unsaturated polyester resins based on poly ( 1,2 propylene-maleate-phthalate) ( P E 1 ) , and poly (oxy-diethylene-maleate-phthalate) ( PE2 ) were used for the impregnation of oven-dried white pine wood samples in admixture with styrene (S) . Curing was affected by the initiator-heat technique by either using 0.1-0.2% by weight of benzoyl peroxide (Bz,O,) , or 1% by weight of methyl ethyl ketone peroxide (MEK) . It was found that the use of PEl/S mixture resulted in the formation of wood-plastic combinations (wpc) with higher percent retention and higher percent polymer loadings than those obtained by the impregnation of wood samples with P E 2 / S mixtures. The use of different swelling solvents including ethanol, acetone or chloroform, did not influence the percent retention or polymer loadings of wpc for either P E l / S or P E 2 / S mixtures. Physical tests performed on wpc showed that compression, hardness, static bending were generally enhanced, water absorption was decreased, and dimensional change was retarded to different extents for both polyesters used, but no permanent stabilization was attained.

A simple and inexpensive technique for preparation of membranes by chemically induced graft copolymerization of methacrylic acid (MAA) onto low-density polyethylene (PE) films using sodium bisulfite (SBS) initiator was developed. Several parameters affecting the grafting rate and yield, such as the concentration of aqueous monomer solutions (4-20%) and initiator (0.025-0.2 M/L), reaction temperature (50-70 C), and within reaction times ranging from 1 to 6 h were studied. The results show that grafted films with 20% up to 500% graft were obtained under the synthesis conditions mentioned. Some selective properties of the grafted films (membranes), such as ORDER REPRINTS swelling behavior and mechanical properties were investigated. Also, the films were characterized by infrared (IR) spectroscopy, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). Such prepared graft copolymers may be of great interest in some practical uses such as dialysis and ultrafiltration membranes and also for wastewater treatment from heavy and toxic metals.