Adhesion by Interdiffusion

The diffusion theory takes the view that polymers in contact may interdiffuse, so that the initial boundary is eventually removed. Such interdiffusion will occur only if the polymer chains are mobile (i.e. the temperature must be above the glass transition temperatures) and compatible. As most polymers, including those with very similar chemical structures such as polyethylene and polypropylene are incompatible, the theory is generally only applicable in bonding like linear 

Average roughness (l a)(Mni) Cleavage strength (Nm ) Coefficient of variation 

The free energy of mixing AGm is related to the enthalpy and entropy ASm of mixing by the Gibbs equation (38), where T is the absolute temperature. 

Diffusion at the interface between PVC and poly- -caprolactone has been demonstrated using energy dispersive X-ray analysis (EDX) [85,86]. These polymers are compatible in the melt at all ratios, but phase separation takes place on cooling. The technique permits the measurement of the concentration-distance curve for PVC in the interfacial region. The results of work at 70°C gave a diffusion coefficient of 1.59 X 10 m s  

Voyutskii [87] has shown some electron micrographs of the interfaces of poly-methylacrylate-PVC and polybutylmethacrylate-PVC prepared at 210-220°C. Mixing at the interface was much greater with the first pair. 

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