Adhesion between rubbery polymers

One way of improving the adhesion between polymer and filler is to improve the level of wetting of the filler by the polymer. One approach, which has been used for many years, is to coat the filler with an additive that may be considered to have two active parts. One part is compatible with the filler, the other with the polymer. Probably the best known example is the coating of calcium carbonate with stearic acid. Such coated or activated whitings have been used particularly with hydrocarbon rubbers. It is generally believed that the polar end attaches itself to the filler particle whilst the aliphatic hydrocarbon end is compatible with the rubbery matrix. In a similar manner clays have been treated with amines. 

In effect, this theory postulates a chemical reaction between promoter, polymer, and mineral substrate as in the chemical bond theory but also suggests that the presence of a region of intermediate modulus between polymer and substrate which transfers stress from the high modulus surface to the relatively low modulus polymer. Adhesive technology has long recognized this principle in specially formulated primers for use when bonding rubbery polymers to metals. 

Many of the entries in this book dealing with the science of a(fliesion and Theories of adhesion are relevant to composition materials in general. There are a number of articles that discuss specific aspects of composite materials that come within the scope of this book. Toughened adhesives, particnlarly Epoxide adhesives and Toughened acryiics, consist of polymers with a rubbery phase dispersed as small spheres within a more glassy matrix. Appropriate adhesion between the phases is crucial for effective toughening. 

The more general phenomenon of adhesion between a rubbery polymer and a different surface is frequently studied by tests of the force required to peel a thin layer of polymer from a rigid substrate. 2,53 at different peel rates and different temperatures can be combined by reduced variables with shift factors given by the WLF equation, indicating that here as in friction the process is controlled by rates... 

Most adhesives are counterparts of the coating systans we have already discussed (Table 13.5). A plasticized rubbery polymer has low volatility, high viscosity, and low surface tension, and makes a good adhesive. Cellophane tapes and self-stick postage stamps are typical applications of such a pressure-sensitive adhesive. The material r ains permanently liquid but forms a strong bond between the surface and the cellophane backing when slight pressure is applied to cause flow. When the surface is paper, presumably both specific and mechanical adhesion may be involved. Water... 

It is concluded that IR spectroscopy provides information on qualitative as well quantitative analyses of rubbery materials, apart from their microstructures (that is, whether cis or trans, syndiotactic, atactic or isotactic). Different types of rubber blends (compatibilised or self-crosslinked) can be identified by the infrared spectroscopy. Synthesis, and degradation of polymers can also be followed by IR spectra. Mechanism of interaction between rubbers and fillers, can also be studied by IR-spectra. Different types of chemical reactions like the milling behaviour of rubbers, mechanism of adhesion and degradation can also be studied with the help of IR spectroscopy. The technique plays a great role in the product analysis under reverse engineering. 

This type of adhesive is generally useful in the temperature range where the material is either leathery or rubbery, ie, between the glass-transition temperature and the melt temperature. Hot-melt adhesives are based on thermoplastic polymers that may be compounded or uncompounded ethylene—vinyl acetate copolymers, paraffin waxes, polypropylene, phenoxy resins, styrene—butadiene copolymers, ethylene—ethyl acrylate copolymers, and low, and low density polypropylene are used in the compounded state polyesters, polyamides, and polyurethanes are used in the mostly uncompounded state. 

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