Surface treatment thermoplastics

Plastic packagiag materials are thermoplastic, ie, reversibly fluid at high temperatures and soHd at ambient temperatures. These materials may be modified by copolymerization, additives ia the blead, aHoyiag, and surface treatment and coating. Properties of principal plastic packagiag materials are givea ia Table 1. 

Wu, S.Y, Schuler, A.M. and Keane, D.V., Adhesive bonding of thermoplastic composites 1. The effect of surface treatment on adhesive bonding. 9th Int. SAMPE Symp., Oct. 13-15, 1987. 

This technique involves the dispersion of a nanomaterial in a monomer (Fig. 4.8). This step requires a certain amount of time that depends on the polarity of the monomer molecules, the surface treatment of the nanomaterial, and the swelling temperature. For thermoplastics, the polymerization can be initiated either by the addition of an agent or by an increase in temperature. For thermosets such as epoxies or unsaturated polyesters, a curing agent or peroxide can be added in order to initiate the polymerization. Functionalized nanomaterials can improve their initial dispersion in the monomer and consequently in the composites. In the case of layered materials, such as clays or graphene, the most important step is the penetration of the monomer between the sheets, thus allowing the polymer chains to exfoliate the material. The... 

Filler surface treatments are of considerable use in thermoplastic applications and are often applied as part of the production process. The various methods used to apply such treatments are therefore covered in this article. 

A variety of methods are available for the production of glass beads. These generally involve the atomisation of molten glass or the melting of fine glass powder. A variety of surface treatments are used, mainly of the silane type. A wide p article size range is available, but the finer sizes (3 0 micron and below) are most used in thermoplastics. 

Particle/particle interactions induce aggregation, while matrix/filler interaction leads to the development of an interphase with properties different from those of both components. Both influence composite properties significantly. Secondary, van der Waals forces play a crucial role in the development of these interactions. Their modiflcation is achieved by surface treatment. Occasionally reactive treatment is also used, although its importance is smaller in thermoplastics than in thermoset matrices. In the following sections of this chapter attention is focused on interfacial interactions, their modification and on their effect on composite properties. 

The surface tension of two thermoplastics and three fillers are listed in Table 2. Large differences can be observed both in the dispersion, but especially in the polar component. The surface tension of the majority of polymers is in the same range, in fact between that of PP and PMMA. Those listed in Table 2 represent the most important particulate fillers, and also reinforcements used in practice, since clean glass fibers possess similar surface tensions to Si02. Surface treatment lowers the surface tension of fillers significantly (see Sect. 6.1). 

To further explore the influence of silica material properties (morphology, surface area, silanol concentration, and surface treatment) on the silica flame-retardant properties, various types of silicas (silica gel, fumed silicas, and fused silica) were investigated.50 51 Material properties of the various silicas are summarized in Table 8.6. These different types of silicas were added to polypropylene and polyethylene oxide to determine their flame-retardant effectiveness and mechanisms. Polypropylene was chosen as a non-char-forming thermoplastic, and polyethylene oxide was chosen as a polar slightly char-forming thermoplastic. Flammability properties were measured in the cone calorimeter and the mass loss rate was measured in the radiative gasification device in nitrogen to exclude any gas phase oxidation reactions. 

Sometimes primers can take the place of surface treatments. Two examples are with porous substrates and with certain plastic substrates. With weak porous substrates, such as wood, cement, or porous stone, the primer can be formulated to penetrate and bind weakly adhering material to provide a new, tightly anchored surface for the adhesive. Chlorinated polyolefin primers will increase the adhesion of coatings and adhesives to polypropylene and to thermoplastic olefins. The chlorine atoms in the outer surface of the primer increase surface energy and enhance adhesion of adhesives, sealants, and paints. 

As with metal substrates, the effects of plastic surface treatments decrease with time, so it is important to carry out the priming or bonding as soon as possible after surface preparation. The surface preparation methods suggested in App. F are recommended for conventional adhesive bonding. Greater care must be taken in cleaning thermoplastics than... 

Parts molded from polyetherimide can be assembled with all common thermoplastic assembly methods. Adhesives that are recommended include epoxy, urethane, and cyanoacrylate. However, service temperature must be taken into consideration in choosing an adhesive because PEI parts are generally used for high-temperature applications. Good adhesion can be effected by simple solvent wipe, but surface treatment by corona discharge, flame treatment, or chromic acid etch will provide the highest bond strengths. 

Reinforced thermoplastic parts are generally abraded and cleaned prior to adhesive bonding. However, special surface treatment such as used on the thermoplastic resin matrix may be necessary for optimum strength. Care must be taken so that the treatment chemicals do not wick into the composite material and cause degradation. It may not be a good idea to use chemical surface treatment without first verifying that the treatment does not degrade the substrate. 

A more vital application is to discern how reinforcement surface treatments improve adhesion to thermoplastic matrices. Since the nonreactive nature of thermoplastics normally precludes interfacial covalent bond formation, secondary bonding forces, such as London dispersion interactions and Lewis add/base interactions, may play a major role in these drcumstances. These secondary binding forces are subject to surface energetics analysis. 

When glass fibers are compounded in polyamides in high content, warping of the molded product can become a problem. Wollastonite exhibits better properties in this aspect." Wollastonite is a white mineral that consists essentially of calcium metasilicate. It is commonly used as an inorganic filler material of thermoplastic polymers for molding. The wollastonite fibers are treated with silane surface treatments by using y-aminopropyltri-ethoxysilane or y-glycidylpropylmethoxysilane. 

However, in both cases - thermoplastics and thermosets - the equipment and the processes need to be adapted to the nanosized fillers. The most crucial point in the production of polymer-nanofiller dispersions is the proper separation of the CNTs from each other, the deagglomeration of agglomerates, and their coupling to the polymeric matrix material. For this purpose, dispersion aids, stabilizers, and compatibilizers, used for other filler particles, need to be adapted in many cases specifically for nanosized fillers with their different surface treatments for the different matrix materials. This is a very complicated issue, and makes a close co-operation between the different scientific disciplines necessary [1]. 

Chem. Descrip. Reactive epoxy-functional siloxane oligomer in water Uses Adhesion promoter between inorg. materials (glass, minerals, metals) and org. polymers (thermosets, thermoplastics, elastomers) surface treatment aid for mins. reinforcement aid for glass fibers primer for glass and metals surface modifier for org. materials additive for water-borne polymers... 

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