Solvent etching

Surface prqiaiation of the joint area may be required to remove oxides, grease, moisture, etc. (prior to adhesive application) by mechanical, solvent, etching or degreasing processes to facilitate wetting. 

Electron Microscopy can be used for resolution of smaller objects the practical limit of resolution being a few angstrom units. Electron Microscopy has been used in the study of the morphology of crystalline polymers. The usual techniques of replication, heavy-metal shadowing, and solvent etching are widely used. The direct observation of thin specimens, like polymer single crystals, is also possible and permits the observation of the electron-diffraction pattern of some specimen area, which is invaluable for... 

The solvent-etched fracture surface of folly cured PEI modified epoxy with different composition is shown in Figure 3.8. For PEI content smaller than 10wt%, the PEI-rich phase is dispersed in a continuous epoxy-rich matrix [i.e., sea-island morphology is observed (a and b)]. Above 25 wt% PEI content, nodular structure was observed (e and f) where the epoxy-rich phase forms spherical nodules and the PEI rich phase forms the matrix. With PEI content between 15 wt% and 20 wt%, dual phase morphology, where sea-island morphology and epoxy nodular structure coexist, is present (c and d). Similar morphology was observed in PEI/BPACY blend [47],... 

Solvent etching—When there exists a large solubility difference in a particular solvent of the polymers being studied, e.g., PP/EP blends. 

Figure 3. Electron-micrograph of polystyrene-rubber blend by the solvent-etch-double replica method...

Figure 5.5. A bright-field image (transmission electron microscopy) of a polyester-urethane block copolymer film that was solvent-etched and stained by iodine. The dark domains are about 30-100 A in width. Some samples exhibited variations in domain size. (Koutsky et, al, 1970.)...

Solvent etch remove weak boundary layer M, P... 

Pores are created at nanolevels after removal of one or several blocks by solvent etching, hydrolysis, acid dissolution, thermal degradation, ozonolysis, or ultraviolet irradiation [49], Only porous thin films can be fabricated when neat BCPs are used whereas blends are more favorable to monoliths and bulk pieces. However, using the BCP method and these removal techniques, generally only films less than 20 pm were produced to induce a proper development of morphology and because of the difficult availability of the BCP and its removal. In addition, the intended applications as nan-olithographic templates or separation membranes require thin samples. 

The mildest form of treatment involves solvent etching, which relies on low melting point being more easily dissolved than the bulk of the material. In crystalline materials phase segregation can occur and hence this process can be very useful in outlining spherulite boundary layers and similar vulnerable areas. 

There are essentially two main etching techniques vapour etching for only a few seconds and controlled isothermal treatment with a liquid solvent for a considerably longer time (several hours). A solvent etching temperature (Td) is selected on the basis of the melting point of the segregated species (Tm) ... 

Beryllium Degrease with solvent Etch in a sodium hydroxide solution Heat the sodium hydroxide solution to 82°C 2.7°C (180°F 5°F)... 

Chromium Degrease with solvent Etch in hydrochloric acid solution Heat the solution to 93X 3 C (200 F 6 F)... 

Copper and copper alloys Degrease with solvent Etch with a solution of Immerse for 1-2 minutes at room temperature... 

Glass and quartz (non-optical) Degrease with solvent Etch in a solution of Parts by weight Distilled water Chromium trioxide 4 1 Immerse for 10-15 minutes at a temperature of 23 C rC(75 F 2 F) Rinse thoroughly with distilled water. Dry for 30 minutes at 98°C TC (209°F 2 F) Apply adhesive while glass or quartz is hot... 

Degrease with cold solvent Etch in a solution of ... 

Zinc Vapour degrease with solvent Etch in a solution of Parts by weight Distilled water 80 Cone, hydrochloric acid (s.g. 1.18) 20 Solution temperature 23°C (75°F) Immerse the metal for 2 to 4 minutes Rinse thoroughly in cold, running, distilled (or de-ionised) water Place in an oven, at66°C to71°C(150°Fto 160°F). Dryfor 20-30 minutes Apply the adhesive as soon as possible... 

Oscilloscope traces of photocurrent transients recorded with a 120 ym thick PTS crystal in sandwich conformation. The crystal had been prepared by one side solvent etching of a native TS-6 monomer crystal and subsequent thermal polymerization. Photocurrents were excited through a semitransparent Ag-contact by 1.06 ym pulses of a Nd-laser at a dose of about 10 photons cm 2. Carrier generation has... 

The problems of solvent etching described above are primarily associated with the selectivity of the solvent. In a one-component semi-crystalline polymer, for example, extraction of amorphous regions will generally be accompanied by some disruption of the remaining crystal population. One area where selectivity may not be a problem is that of polymer blends one... 

Figure 10.9 Examples of solvent-etched samples, as seen in the SEM (a) shows an elliptic crystal of linear polyethylene after dissolution of the surrounding matrix in decalin the crystal is shown sitting on a piece of filter paper (b) shows the gel/pore structure of a partially cured polyester resin the unreacted component was extracted by using dichloromethane.

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