Polymer processing surface property modification

Electron beam-initiated modification of polymers is a relatively new technique with certain advantages over conventional processes. Absence of catalyst residue, complete control of the temperature, a solvent-free system, and a source of an enormous amount of radicals and ions are some of the reasons why this technique has gained commercial importance in recent years. The modification of polyethylene (PE) for heat-shrinkable products using this technique has been recently reported [30,31]. Such modification is expected to alter the surface properties of PE and lead to improved adhesion and dyeability. 

Organic surfaces are encountered in a wide range of situations where interfacial properties impact a material s performance characteristics. For example, a polymer s interfacial characteristics determine chemical and physical properties such as permeability, wettability, adhesion, friction, wear, and biocompatibility. " However, polymers frequently lack the optimum surface properties for these applications. Consequently, surface modification techniques have become increasingly desirable in technological applications of polymers. - These processes are capable of tuning the properties of... 

The same authors developed a process of encapsulation of polymers swelled by halogenated solvents in which ozone is greatly soluble but not monomers to be grafted. After ozonization of polymers swelled in solvents, mixtures of mono unsaturated or di unsaturated monomers are added to the activated polymers. Then, grafting is operated by UV irradiation. Grafting is mainly located at the surface of the starting polymer what prevents the modification of its intrinsic properties. This process permits to produce hydrophilic polysiloxanes used in medical applications (contact lenses, tubes, catheters, etc.). 

Abstract Polyolefins such as polyethylene, polypropylene and their copolymers have excellent bulk physical/chemical properties, are inexpensive and easy to process. Yet they have not gained considerable importance as speciality materials due to their inert surface. Polyethylene in particular holds a unique status due to its excellent manufacturer- and user-friendly properties. Thus, special surface properties, which polyethylene does not possess, such as printability, hydrophilicity, roughness, lubricity, selective permeability and adhesion of micro-organisms, underscore the need for tailoring the surface of this valuable commodity polymer. The present article reviews some of the existing and emerging techniques of surface modification and characterisation of polyethylene. 

Polymer surfaces are modified to obtain the desired surface properties without altering the bulk properties (J ). One of the most desired properties is adhesion between polymers and other materials such as polymers, metals or ceramics (2). There are many techniques for polymer surface modification, but they can be divided into two major categories. One is a dry process in which the polymers are modified with vapor-phase reactive species that are... 

While the covalent bonding of polymers on oxide surfaces requires certain reaction conditions adapted for the particular reaction system, for example highly purified non-aqueous solvents or thermally activated surface groups, surface modification with polyelectrolytes can be carried out in aqueous environment [31-46]. Numerous parameters can be adjusted to control the conformation of the polyelectrolyte molecules, e.g. their charge density and the charge density of the metal oxide surface. In other words, the adsorption process and the surface properties of the final product can be influenced in many different ways. This diversity is a challenge for academic research to develop novel hybrid materials for technical applications. 

Surface modification is broadly used in controlling the surface properties of fillers in rubber, synthetic polymers and other materials (see Chapter IX). The surfactant adsorption layers that make surfaces hydrophobic are used to prevent caking in hygroscopic powders (fertilizers), as anticorrosive agents and in numerous other processes. 

Modifications of the surface properties ofman-made fibers play a dominant role in several end-uses. Via a variety of application processes it is possible to treat manmade fibers with fluorine gas. The electronegativity of flouorine is 4.0eV the highest of all elements. In particular, the siuface activity of yams can be increased considerably by incorporating fluorine atoms. As part of this investigation some polymers and fiber types for diverse end-uses were tested (Table 17.1). All end-use applications for these yams have important surface function requirements, e.g., for tire yams the adhesion to mbber is very important while for tarpaulins it is the adhesion to PVC. Textile and medical applications with different end-use characteristics were also considered. The modifications attempted to this investigations did not influence other properties such as tenacity, elongation, or shrinkage. 

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