Permanganic etchants

Olley RH, Hodge AM, Bassett DC (1979) A permanganic etchant for polyolefines. J Polym Sci 17 627-643... 

As far as true liquid chemical etchants are concerned, by far the most successful reagent has been the so-called permanganic etchant, which is particularly well suited to the study of lamellae in semi-crystalline materials. Although, in principle, lamellar morphologies may be studied by SEM it has been demonstrated that for reasons of resolution, replication and examination in the TEM is the more complex but more profitable route. This is not to say that SEM examination of surfaces etched using the permanganic reagent is not of use in many circumstances [79, 80]. Indeed, in some situations it is the only way forward, particularly in multi-component systems where subsequent replication may be a problem (for example, in the study of blends, films or fibres). 

Olley RH, Bassett DC. An improved permanganic etchant for polyolefins. Polymer 1982 23(12) 1707-10. 

Many types of chemical treatment are used in industry. Chromic, permanganic, sulphuric, and chlorosul-phonic acids are often used as the oxidants. It has been shown that the adhesion of polyethylene to substrates, such as cellophane, steel, aluminium, and epoxy adhesives, improves upon pretreatment with any of the etchants mentioned previously. 

An alternative method is to use mixtures of concentrated sulfuric acid and potassium permanganate, giving contrast between crystals and amorphous domain that turns out to be applicable to many different polymers, e.g. polyethylene, polypropylene, poly(but-l-ene), polystyrene and poly(aryl ether ketone)s. The strong etchant degrades the amorphous phase more quickly than the crystals and the resulting topography is revealed by heavy metal shadowing. Replicates are prepared which are examined in the electron microscope. 

Although several specific etchants have been devised [179-182], by far the most successful polymeric etching technique is permanganic etching [143, 183]. Initially reported in 1979, this approach to the study of polymer... 

Permanganic etching is frequently used to prepare surfaces for SEM examinations, notably of semicrystalline polymers and their blends and composites. In this case the etchant attacks the polymers destmctively and progressively removes the outer skin of the polymer, such that the loosely packed amorphous phase is preferentially etched out of the sample. This technique is especially useful for exposing the internal structural details of semicrystalline polymers. 

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