Surface modification peroxide treatment

Moreno-Castilla, C. el al.. Activated carbon surface modifications by nitric acid, hydrogen peroxide, and aimnonium peroxydisulfate treatments, Langmuir, 11, 4386, 1995. 

Laser surface treatment can be used either below or beyond the ablation threshold of the surface. Laser treatment is more often used below the ablation threshold of the material, thus inducing efficient modification of the surface composition [12, 18]. Various laser parameters, such as the wavelength, the fluence (laser intensity), the nature of the environmental gas, or the pulse number, may be changed in order to modify the characteristics of the treated surface as the treatment induces the formation of polar chemical species (hydroxyls, carboxyls, peroxides, etc.). Therefore, the use of laser treatment below the ablation threshold induces adhesion improvement mainly through thermodynamic and chemical parameters. 

Native cellulose are commonly modified by physical, chemical, enzymic, or genetic means in order to obtain specific functional properties, and to improve some of the inherent properties that limit their utility in certain application. Physical/surface modification of cellulose are performed in order to clean the fiber surface, chemically modify the surface, stop the moisture absorption process, and increase the surface roughness. " Among the various pretreatment techniques, silylation, mercerization, peroxide, benzoylation, graft copolymerization, and bacterial cellulose treatment are the best methods for surface modification of natural fibers. 

For surface modification applications, thick grafting layers are unnecessary and even undesirable because they may change bulk physical properties of the polymer, such as crystallinity and tensile modulus. A two-step method can be used to minimize the formation of the homopolymer. The polymer is preirradiated in air to produce peroxide groups on the surface. Grafting is subsequently initiated thermally in contact with a monomer. Other methods such as corona discharge, ozone treatment, and plasma treatment have also been used to generate peroxide groups on polymer surfaces. 

The work carried out by Kalaprasad and Thomas [34] shows different chemical surface modifications such as alkali, acetic anhydride, stearic acid, permanganate, maleic anhydride, silane, and peroxides improving the interfacial adhesion and compatibility between the fiber and matrix. A polyethylene thermoplastic matrix with sisal and glass hybrid composites was developed. The results showed that in all treatments, tensile strength increased about 10-30% and peroxide treatment showed maximum tensile strength and Young s modulus [34]. 

The previously discussed principles of grafting-to and grafting-from can also be applied for the modification of polymer surfaces with polymer brushes. However, the binding of linkers and polymerization initiators to polymer surfaces is not as straightforward as it is for oxidic inorganic materials. Thus, dedicated pretreatments are usually necessary. These may include rather harsh reaction conditions due to the chemical inertness of many polymers (see Chapter 3). Alternatively, radiation treatment of polymers (to form radicals) followed by exposure to air may be used to form peroxides and hydroperoxides, which can be directly used as initiators for thermally or ultraviolet-induced graft polymerizations [16,17] (see Chapter 2). 

Modification of polyurethanes as a blood contacting material is achieved by coating the polymer surface with heparin as the most suitable biomolecule that avoids thrombogenesis. The immobilization needs a functionalized surface that may offer sites for the heparin bonding. It is observed that helium plasma treatment of polyacrylonitrile and polysulfone followed by exposure to air leads to peroxide species of the order of 10 nmol/cm which are available for decomposition... 

Modification of lignocellulosic materials surface by copolymerization with vinyl monomers has been reported. The polymerization reaction is initiated at the surface of the fibers by incorporation of peroxides or oxidation-reduction agents, or by treatment with gamma radiation or cold plasma [49]. These reactions form free radicals on the fibers, which initiates the free chain reaction with the vinyl monomers. Different types of properties can be conferred to the fibers using different vinyl monomers, such as increased hydrophilicity with poly(vinyl alcohol), increased hydrophobicity with polystyrene or polyvinylacetate, increased reactivity with polyvinylamine etc. 

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