Polymer autohesion

Diffusion theory of adhesion K W ALLEN Polymer/polymer autohesion, molecular weight dependence... 

Voyutskii first proposed that diffusion was the major driving force for polymer autohesion and heterohesion. Since the introduction of the reptation theory, there have been many publications devoted to selfdiffusion and inter-diffusion in polymer solutions and melts. Here, we... 

Consistent with the spirit of the 1950s and 1960s, the diffusion theory generally got an unsympathetic reaction among supporters of the adsorption theory, i.e., mainly workers in the West. But attitudes changed, and by 1970, the position could probably be summarized by saying that diffusion was generally accepted as a mechanism for adhesion between samples of the same polymer (autohesion) or between very similar polymers (Wake 1982), but it was not more broadly accepted, even for polymer-polymer adhesion. 

Voyutskii, S.S., Autohesion and Adhesion of High Polymers. John Wiley and Sons, New York, 1963. 

The mechanism governing the formation of interply bonds has been established as autohesion or self-diffusion [28], Autohesive bonding is controlled by two mechanisms (1) intimate contact between the interfacial surfaces, and (2) diffusion of the macromolecules across the interface. Figure 7.22 shows the phenomenon of autohesion for an amorphous thermoplastic polymer. At time zero, the two surfaces are pressed together. Providing the temperature is... 

Destructive mechanical tests commonly are used to characterize autohesion of polymers. In the mechanical tests, two polymer surfaces normally are pressed together at a given temperature for a specified length of time. The fracture stress or fracture energy of the interface then is measured using the appropriate test. 

The process by which a thermoplastic matrix composite consolidates to form a laminated structure has been attributed to autohesive bond formation at the ply interfaces. Autohesive bond formation is controlled by two mechanisms (1) intimate contact at the ply interfaces, and (2) diffusion of the polymer chains across the interface (healing). The rate of autohesive bond formation and hence the speed of the composite consolidation process is directly related to the temperature-pressure-time processing cycle. 

Consolidation and development of interlaminar bond strength for thermoplastic matrix composites have been modeled by two mechanisms intimate contact and autohesion. Intimate contact describes the process by which two irregular ply surfaces become smooth (Fig. 13.10). In areas in which the ply surfaces are in contact, autohesion occurs, and the long thermoplastic polymer chains diffuse across the ply boundaries. Filament winding with thermoplastic matrix materials is considered an on-line consolidation process in that local... 

Voyutskii, S.S. 1963. Autohesion and adhesion of high polymers. In Polymer reviews, 140. eds. Mark, H.F. and Immergut, E.H. New York John Wiley Sons. 

In the theory of diffusion it is postulated that high molecular weight polymer molecules interdiffuse w ith each other across the inter ce. The term autohesion is often applied to this process in the adhering of portions of the same plastic material together. Since molecules of the same material diffuse across the inteiface, makhtg the two layers one, the original joint disappears. Once the joint is completely healed, there is little chance that adhesive failure will occur at the original inteiface. 

For autohesion to occur, the polymer must he well above its glass transition temperature. It is the primary mechanism operating in the heat sealing of plastics and the coalescence of droplets from emulsions of the film-forming plastics such as S-BR rubber during drying. 

Voyuiskii, S. S. (1963). Autohesion asund Adhesion of High Polymers (S. Kaganoff, Translator), (Interscience), Wiley, New York. 

S. S. Voyutskii, Autohesion and Adhesion of High Polymers, Interscience, New York, 1963. —, Contact angle, wettability and adhesion, Adv. Chem. Ser. 43, Am. Chem. Soc.,... 

The self-adhesion (autohesion) of polymers is of considerable practical importance as many moulding operations involve the need for streams of merging polymer melt to self-adhere to form a strong bond necessary to the integrity of the moulded article. Mechanisms of polymer diffusion are discussed in Polymer diffusion reptation and interdigitation and theories that relate interfacial structure to strength in Polymer-polymer adhesion models. In the latter article, the vector percolation (VP) model was described, which is here applied to welding, and the practical consequences of its predictions are drawn out. - ... 

Autohesive tack differs from the other types in that it involves mutual diffusion of polymer molecules across the interface it is discussed elsewhere (see the articles on Diffusion theory of adhesion and Polymer diffusion replation and interdigitation). Adhesive tack between elastomeric materials and other, usually rigid, surfaces is considered in this article. 

Skewis [89] measured the tack of rubber to rubber and rubber to glass as a function of contact time and results are shown in Fig. 19. The two factors which might contribute to tack in this case are the development of intimate contact by viscous flow of the polymer, and diffusion of polymer segments across the interface. Diffusion will not occur between polymer and glass, and the low levels of tack which develop between styrene-butadiene rubber and butyl rubber indicate low levels of diffusion. Higher levels of autohesion develop with the like polymer pairs and this was attributed to diffusion across the interface. As both viscous flow and diffusion are controlled by the same friction constant, factors which change D... 

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