Sodium etching effect

Meier, J. F., and Petrie, E. M., The Effect of Ultraviolet Radiation on Sodium Etched Polytetrafluoroethylene Bonded to Polyurethane Elastomer, Journal of Applied Polymer Science, vol. 17,1973, pp. 1007-1017. 

Table 7.2 shows the effect of sodium etching on several fluoropolymers by Tetra-Etch on the surface composition and lap shear bond strength. In general, the data for various fluoropolymers indicate an increase in the adhesive bond strength with increasing fluorine and chlorine content. Kinetics of treatment is more favorable to perfluorinated PTFE than PVF that contains one fluorine per monomer unit according to the data in Table 7.2. 

Table 7.1. Effect of Sodium Etching on the Surface Compostiiton and Adhesion Bond Strength of Fluoropolymers ...

Fig 10.34) indicate that the PTFE surface is comprised of only carbon and fluorine. The energy shift can be curve-fitted by trial and error to determine the functional groups on the surface. The most simplified report that ESCA generates is the atomic composition of the surface elements with the exception of hydrogen. A helpful tool for investigating surface changes of a polymer is the ratio of other elements to carbon. Table 10.9 shows the effect of sodium etching on the surface composition of a few different fluo-ropolymers. 

Table 14.3 contains data that compares the results of plasma treatment and sodium etching for four fluo-ropolymers. Peel strengths of untreated and treated samples were measured by bonding them into T-peel specimen using the flexibilized epoxy adhesive Scotch-Weld 3553 (available from 3M Corp.). The laminates were cured for several hours at 70°C and peel tested at 12.5 cm/min pull rate. Polytetrafluoroethylene does not accept plasma treatment as well as PEA and FEP, as indicated by its relatively low peel strength. Sodium etching is the only effective method of modifying the surface of PTFE. 

Table 5.23 shows the effect of sodium etching for several fluoroplastics by Tetra-Etch (www.gore. com), on the surface composition and lap-shear... 

If embedding in a resin that is polymerized by UV light, such as Lowicryl and LR Gold, do not osmicate the samples. Any effect of the osmium on antigenicity can usually be eliminated by using sodium meia-periodate during etching to oxidize the unbound osmium (see step 7). 

Structure of the Oxidized Graphite. The oxidizing treatment with sodium hypochlorite produces two effects on the structure of graphite namely (i) etching of the microcrystals resulting in an increase of the number of steps (li) functionalization of the steps i.e. creation of carboxylic and other acidic groups at the extremities of basal planes. 

The etch rate of silicon in HF does not have a clear dependence on dopant concentration. Also, oxygen in silicon has little effect on the etch rate in HF [51]. However, the reactivity of silicon in HF solution may be significantly increased when active elements such as sodium are present in the silicon [112], Also, the etch rate of silicon has been found to increase with ion implantation, which produces an amorphous structure [113]. 

The enhanced diffusion demonstrated for metals is probably generally operative and has indeed been directly observed in an ionic crystal 133). A crystal of sodium nitrate, on which etch pits visible in a microscope had been produced, was exposed to ca. 8 x lO i ev/gm of y-rays, after which the etch pits were no longer visible, having presumably been filled by diffusion under the irradiation. It is somewhat surprising to find a detectable effect at so low a dose, but it may be that the etch pits, which are probably at the ends of dislocations, are particularly well situated for localization of the enhanced diffusion. 

Figure 13. Effect of complexing agent, versene, on passivation by sodium nitrite (A) etched iron in NaNOi solution (B) same as in A plus versene...

---