Monomer Penetration Research Articles

Surface graft polymerization of acrylamide onto poly(ethylene terephthalate) film by UV irradiation

AbstractTo improve the low water wettability of poly(ethylene terephthalate) (PET), graft polymerization of acrylamide (AAm) by UV irradiation was performed onto the surface of a PET film with the simultaneous irradiation method without using a photo sensitizer. The PET film immersed in a 10 wt % deaerated aqueous solution of AAm was found to become highly hydrophilic upon UV irradiation. Optical microscopy on cross sections of grafted films showed that localization of the graft polymerization was restricted to a thin surface region of the film. Both the low concentration of polymer radicals formed by UV irradiation and the monomer penetration limited to the film surface would be responsible for localization of the grafted layer to the film surface region. Pretreatment of the PET film with benzyl alcohol was effective for enhancement of the graft polymerization. Retention of high hydrophilicity of the surface even after rigorous extraction of homopolymer and a comparative study of polymerization without UV irradiation strongly suggested that UV irradiation of the PET film under immersion in the deaerated AAm aqueous solution would lead to formation of the true graft copolymer.

Viscoelastic behaviour of rubberwood-polymer composites

The dynamic storage modulus E' of rubberwood ( Hevea braziliensis) increased after the in situ polymerization of methylmethacrylate in the wood cellular structure. A significant linear relationship existed between the percentage increase in E' and polymer loading. A thermal scan of tan δ values between -120° and 200°C revealed that the damping pattern of rubberwood was affected to different extents by three different polymeric systems. Poly(styrene- co-acrylonitrile) caused the greatest change in the damping pattern, followed by polymethylmethacrylate-dioxane, and polymethylmethacrylate. This observed trend was attributed to the relative extent of monomer penetration and interaction with the wood cell-wall components.

Effect of water on vapor phase photografting on cellulose and its derivatives

AbstractEffect of water on vapor phase photografting on cellulose was investigated at 60°C. An activated grafting of methyl methacrylate by water contained in the sample was observed in the experiment. The effect of water was commonly recorded irrespective of the type of cellulose derivatives such as cellulose acetate (degree of substitution, DS = 0.18 and 0.33), cellulose nitrate (DS = 0.35 and 0.75), and carboxymethl cellulose (DS = 0.19 and 0.74). Organic solvents can also be used in place of water, indicating that the percent grafting decreases in the order, water > methanol > acetone > cyclohexane. From ESR studies, water in the sample was found to contribute to the decay of cellulose radicals rather than to the radical formation. The decay was accelerated by organic solvents, and the magnitude of the effect was in the order, water ≈ methanol > acetone > cyclohexane. Based on the above investigation, it was presumed that water contained in the sample cannot contribute directly to the formation of cellulose radicals which may initiate grafting, but mostly promotes the penetration of monomer into cellulose fibers. Such penetration could lead cellulose radicals to an effective initiation of grafting.

Some ways of polymerizing methyl methacrylate in sandstone

The paper compares results obtained in the polymerization of methyl methacrylate in sandstone using various initiation systems: benzoyl peroxide, redox systems, and radiation. Most attention is paid to initiation systems which permit polymerization at laboratory temperatures. The study showed that with redox polymerization it is difficult to find a compromise between the time needed for penetration of monomer into the stone and speed of polymerization. A serious defect is destruction of some of the samples during polymerization and this occurs also when using radiation. On the other hand no destruction of the stone samples occurred when the polymerization temperature was above 80°. Results obtained are compared with those previously reported in the literature.

Field Impregnation Techniques for Highway Concrete

The corrosion of reinforcing steel due to the penetration of deicing salts poses a considerable problem in bridge decks. One approach which has received much attention has been impregnation with a liquid monomer followed by polymerization to effectively seal the capallary pores against salt intrusion. The feasibility of impregnating a bridge deck to a depth of 4 in. or more under field conditions is demonstrated herein. Since the present deep impregnation techniques are costly in terms of energy, materials, and time, simplifications and improvement would be desirable. Herein, results of preliminary experiments with the use of a pressure-mat technique for mechanically assisting monomer or sealant penetration are described. It is shown that pressure mechanically applied to patterned rubber mats can effect uniform impregnation with a monomer such as methyl methacrylate or a sealant such as tar or linseed oil in reasonable times. Such an impregnation could conceivably be effected using rollers. /ASCE/

Effect of Moisture Content and Drying Method on the Penetration of Monomers into Concrete

Effect of Moisture Content and Drying Method on the Penetration of Monomers into Concrete

Impregnation and polymerization of vinylic monomers in porous media. I. Kinetics of impregnation

In this work, we have studied the mechanism and kinetics of penetration of monomers and of liquids of low molecular weight into porous media such as asbestos cements. Although the phenomenon is physically different from a molecular diffusion, the kinetics of impregnation are well represented by Fick's laws of diffusion. We observe an excellent agreement between the experiment and the theoretical equation as long as the degree of impregnation does not exceed 80%. If, in order to represent this, we use a simplified model introducing a flow governed by Poiseuille's law through a bundle of capillaries of the same diameter, we obtain a parabolic law which is verified up to only 55%. We have demonstrated the physicochemical parameters which influence the kinetics of impregnation. The results can be summarized by the following empirical equation: Where η represents the viscosity of the liquid, γ the surface tension, θ the angle of contact, γ the average radius, and ϵ the porosity; D* appears as a constant equal to 2.0 × 109 cm−2. The standard deviation of its determination is 0.14 × 109 cm−2.

Nylon 6/Graphite Fiber Composites by in Situ Polymerization

The in situ polymerization of caprolactam to Nylon 6 was investigated as a method for making graphite fiber composites. It was necessary to find a co-catalyst (using sodium caprolactam as catalyst) which could be mixed at about 100°C and where the final mixture had a long enough pot life to allow for mixing and application to the fibers. The temperature could then be raised to 200°C to initiate rapid polymerization. Co-catalysts tested were all esters as these had earlier been shown to have appropriate lifetimes. They were phenyl acetate, benzyl acetate, benzyl benzoate, t-butyl acetate and ∈-caprolactone. Benzyl derivatives gave brittle polymerizates, while the others gave tough materials. Phenyl was excluded as potentially reacting too rapidly. t-Butyl gave good polymers at 190°C but expanded into a foam when heated to 210° due to volatilization of the t-butanol. ∈-Caprolactone initiated well and produced no residues, so it was chosen as the major co-catalyst. Jigs were designed on which graphitic fiber could be wound at various tensions. These were put in tubes containing precatalyzed monomer at 100°C. The whole was degassed several times and then heated to 200°C for polymerization. Several samples of composites were made with fiber densities of 25 to 40 volume % using Thornel 50 S and 75 S fibers. The samples still had some voids due to lack of complete penetration of monomer. The samples varied widely in their tensile strengths and moduli due mainly to variations in fiber density, but also to some voids. The best samples achieved about 70% transfer of properties. This is a respectable figure when one considers that these are the first samples made at these fiber densities. Scanning electron microscope photographs show the best samples had excellent adhesion of matrix to fiber. This resulted in essentially no pull-out, and the areas examined showed multiple fracture of fibers at the fracture surface with extensive deformation of the matrix. Such composites should have high impact strength.