Surface modification chemical mechanisms

M.S. Sreekala, M.G. Kumaran, and S. Thomas, Oil palm fibers Morphology, chemical composition, surface modification, and mechanical properties. J. Appl. Polym. Sci. 66,821-835 (1997). 

Amylose brushes (a layer consisting of polymer chains dangling in a solvent with one end attached to a surface is frequently referred to as a polymer brush) on spherical and planar surfaces can have several advantageous uses, such as detoxification of surfaces etc. The modification of surfaces with thin polymer films is widely used to tailor surface properties such as wettability, biocompatibility, corrosion resistance, and friction [142-144]. The advantage of polymer brushes over other surface modification methods like self-assembled monolayers is their mechanical and chemical robustness, coupled with a high degree of synthetic flexibility towards the introduction of a variety of functional groups. 

Surface modification of LDPE film can also be brought about by chemical treatment [118] with an aqueous solution of ammoniacal ammonium persulphate in the presence of Ni+2 ions under variable reaction conditions. The investigation of treated surface showed the presence of polar groups (viz. carbonyl and hydroxyl) in the infrared (IR) spectroscopy, with characteristic bands at 1700, 1622 and 3450 cm-1. It is known that the persulphate ion attacks the double-bond-producing epoxy or diol group. However, the destructive oxidation of saturated hydrocarbons does not occur with persulphate alone, but requires the presence of the nickel (II) ion. The authors have proposed the following mechanism of chemical treatment ... 

A practical problem is that the sputtered chemical complexes often exhibit only a transitory existence. Traditional mass spectrometric techniques provide information on gross removal but little understanding of the mechanism involved. Data requirements in this area include gross removal rates, nature of ejected species, and changes to surface stoichiometry. In Sect. 6.5.1., the influence of surface chemistry on the nature of the sputtered species, and in particular on secondary ion fractions will be discussed. The role of surface chemistry and surface modification procedures on impurity control will be elucidated there. 

Chemical Surface Modification. In considering the interface, one must contemplate not only the possibility of moisture disrupting the bond but also the possibility of corrosion of the substrate. Corrosion can quickly deteriorate the bond by providing a weak boundary layer before the adhesive or sealant is applied. Corrosion can also occur after the joint is made and, thereby, affect its durability. Mechanical abrasion or solvent cleaning can provide adhesive joints that are strong in the dry condition. However, this is not always the case when joints are exposed to water or water vapor. Resistance to water is much improved if metal surfaces can be treated with a protective coating before being bonded. 

All electrodes react with their environment via the surfaces in ways which will determine their electrochemical performance. Properly selected surface modification can effectively enhance the electrode heterogeneous catalysis property, especially selectivity and activity. The bulk materials can be chosen to provide mechanical, chemical, electrical, and structural integrity. In this part, several surface modification methods will be introduced in terms of metal film deposition, metal ion implantation, electrochemical activation, organic surface coating, nanoparticle deposition, glucose oxidase (GOx) enzyme-modified electrode, and DNA-modified electrode. 

Surface modification of a polymer prior to metallization is widely used to improve adhesion. The most common surface modifications employed are electric discharge (corona and plasma) and, more recently, ion-beam treatments QJ- Several mechanisms have been proposed for the improved adhesion after such surface modifications (2). These include mechanical interlocking, the elimination of weak boundary layers, electrostatic attractions, and chemical bonding. All of these can play a role in adhesion depending on the surface modification used, metal/polymer system, type of metal deposition, and the extent of polymer preparation employed. However, for low power, short exposure modifications, the formation of new chemical species which can provide nucleation and chemical bonding sites for subsequent overlayers is considered to be of prime importance (3-51. 

The interface between plastic and wood fibres strongly influences the mechanical properties of a plastic/wood fibre composite. A means for evaluating the effectiveness of surface treatment on the wood fibres in the PVC/wood fibre composites is presented that investigated the adhesion between PVC and laminated wood veneers. Wood veneers were first treated with gamma-aminopropyltriethoxysilane, dichlorodiethylsilane, phthalic anhydride, and maleated PP for surface modification. The chemical modification made on the wood surfaces was then characterised by different complementary surface analytical techniques X-ray photoelectron spectroscopy and surface tension measurements. 63 refs. 

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