Etching permanganate

Permanganic acid, a weaker acid than nitric acid, has been found to selectively remove the amorphous regions of polyolefins and many other crystalline polymers to reveal their internal lamellar organization. It was developed and has been applied by Olley and Bassett [328-330] and others [251, 252, 331] as a complementary method to chlorosulfonation. The original permanganate etching method involved the use of 

It has been known for more than 20 years that a wide array of polymers can be etched using potassium permanganate [331], although care must be taken to limit the effect of artifacts. The list includes linear and branched PE, PP, PS, poly (4-me thy lpentene-1), poly (butene-1), PVFz, PEEK, PET, and various copolymers such as EPDM terpolymers, and LCPs. The past decade has seen refinement of the method by many of the same researchers  

1% w/v KMn04 dissolved by eontinuous stirring in an acidie mixture of 10 volumes concentrated sulfuric acid, 4 volumes 85% ortho-phosphoric acid, 1 volume water, respectively, with the sample shaken for 2 h. (10 4 1 sulfuric acid, orthophosphoric acid, water.) 

Recovery of the etched specimens is typically by adding a small quantity of hydrogen peroxide to the chilled acid mixture. 

The standard two stage replica process was used with eellulose acetate, shadowed with tantalum/tungsten, followed by deposition of a earbon film and extraction of the replica (see Section 4.6.2). 

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Fig. 19 Transmission electron micrograph of a replicate of permanganic-etched polyethylene. Scale bar represents 0.5 pm. Courtesy of M. T. Conde Brana...

Fig. 20 Transmission electron micrograph of permanganic-etched linear polyethylene fraction crystallised at 130.4 °C for 27 days. Courtesy of D.C. Bassett. From [46] with permission from the Royal Society of London, UK...

Fig. 22 Transmission electron micrograph of permanganic-etched branched polyethylene crystallised at 120 °C for 1 min showing dominant S-shaped lamellae. From Patel and Bassett [54] with permission from Elsevier, UK...

The twisting lamellar structure of banded spherulites has been debated for decades without obtaining any satisfactory answer until recently. The nature of the isochiral (certain uniform handedness) lamellar twisting and the synchronic character of the twisting of a group of adjacent dominant lamellae both require an explanation. The permanganic etching technique provided... 

In the context of widespread research aimed at understanding the wear processes in order to improve the materials and so prolong the effectiveness of the implant, researchers have examined a number of PE hip cups worn on a cobalt chrome femoral head before and after implantation in the body (Olley et al, 1999). In early investigations the use of permanganic etching prior to light and electron microscopy was shown to allow sensitive discrimination between the quality of... 

More recently it has been possible to examine used hip cups which have been removed from the body. Electron microscopy of hip cup sections after permanganic etching reveals a layer of polymer, at least 10 pm thick extending inwards from the wear surface, which showed incipient cracking and appeared to have been embrittled by exposure to the body environment (Jordan et al, 2000). 

Fig. 1.9 AFM tapping mode images of a spherulitic texture in isotact polypropylene. The sample was crystallized to completion at 145°C and subjected to permanganic etching prior to examination. Image (a) shows topography while (b) contains phase information. Scale bars 5 iim.

Lamellae within adjacent bands of a banded spherulite of linear polyethylene crystallized at 125 C. The specimen was cut open after crystallization, and lamellae are revealed by permanganic etching of the cut surface. The electron micrograph is of a carbon replica of the etched cut surface (after 0. C. BassetO. Scale bar=f 0 fim. 

Figure 2. Electron micrographs of 50% (fig. 2a) and 10% (fig. 2b) blends of HOPE with LDPE quenched from 160 into iced acetone. Specimen prepared by permanganic etching followed by shadowing and...

Figure 4 (a) Polarized light micrograph of a syndiotactic polypropylene sample which contains 4wt.% 1-octene. The sample was isothermally crystallized at 132 C for 24 days, (b) Atomic force micrograph of the same sample as described in (a) after permanganic etching. 

Sectioning of bulk samples and permanganic etching very easily reveals the spherulitic morphology of PP. The lower magnification of Figure 4(a)... 

PERMANGANIC ETCHING AND ITS INSIGHTS INTO CRYSTALLINE POLYMERS... 

Permanganic etching is a technique, introduced from this laboratory, which allows systematic study with the electron microscope of the... 

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