Polymer powders, treatment

Here we would like to emphasize that treatment with XeFj fluorinates the polymer surfaces, with the depth and degree of fluorination depending upon the reaction conditions. We never observed the formation of a perfluorinated surface layer after treatment with XeF,. Results of XPS analysis of XeFj-treated polyethylene film —(—CHj—CHj—) — showed that the maximum degree of fluorination corresponded to the composition —(—CF2—CH2—) —. After that, visible destruction of the polymer surface, i.e., cleavage of C—C bonds in the polymer macromolecule, would start. These results differ from those of the fluorination of polymer powders it was reported by Lagow and Margrave in the early 1970s that polymer powders were fully converted into perfluorinated polymers under the action of a F /N mixture. ... 

Finally, the HDPE slurry from the third reactor is sent to the decanter (4) and the polymer is separated from the dispersing medium. The polymer containing the remaining hexane is dried in a fluidized bed dryer (5) and catalyst/cocatalyst residuals are removed in the powder treatment vessel (7). 

From X-ray diffraction, it is known that semicrystalline polythiophene powder consists of completely co-planar molecules [64], in contrast to the oligomers with chain length of and above three. The crystallinity of powders of chemically coupled polythiophene prepared by monomer oxidation with iodine, increases from 35% as synthesized up to 56% after annealing at 753 K for 30 minutes [65]. At the same time the residual iodine content decreased from 3.17% as synthesized to 0.13% after the heat treatment. Whereas annealing at 753 K leads to a first degradation of the polymer, heat treatment at 673 K results in polythiophene with chains of approximately 1200 thiophene units. Electrochemically polymerized polythiophene gives a completely different X-ray diffraction pattern [66],... 

In Fig. 3.33, comparative information is presented on the adhesive strength of polymer powder coatings formed on aluminum substrates by the electrostatic method under an external field of 2.5-3 kV/cm (the charge density in the layer was q/m 3 10 C/kg) and thermal treatment of a similar thickness poured layer of uncharged particles [52]. 

The pure polymer powder derived from biotransformation can be processed via heat-moisture treatment to form a type-3 amylase resistant starch with a degree of resistance of > 90% (RS3). 

After the microbial fermentation, the EPS is recovered from the culture broth by first removing the cellular biomass via centrifugation or filtration. Then, the polymer in the clarified medium is precipitated by using a suitable organic solvent like ethanol, acetone, or methanol. The polymer pellet can be dried by lyophilization or heat treatment to obtain crude polymer powders. For applications requiring higher levels of purity, the... 

Product from melt or suspension treatment is obtained directly as emmb or powder. Polymer recovered from solution treatment is obtained by precipitative cooling or spray drying. Polymer with now stable end groups may be washed and dried to remove impurities, especially acids or their precursors, prior to finishing operations. 

Heat treatment at 400 °C of pure polymer specimens and composites containing 0.16 and 0.34 of calcite has shown [221] that the base polymer was sublimated without residue the specimen with Vf = 0.16 left a powder, and the specimen with Vf = 0.34 a brittle skeleton. Electron microscopy confirms that the latter consists of large crystalline inclusions interconnected by systems of small particles. 

The Vinyloop process is based on the selective dissolution of PVC used in composites applications like cable insulation, flooring, tarpaulins, blisters, etc. After removal of insoluble parts like metals, rubber or other polymers, the PVC is reprecipitated with all additives by introduction of a non-solvent component whieh will form with the seleetive solvent an azeotropie mixture. By using typical conditions, the process is able to reeover a pure PVC eompound powder ready for use without any additional treatment like melt filtration or a new pelletisation (speeific characteristics of the powder are average diameter of 400 microns and bulk density above 600 kg/ eub.m). All the solvents used are eompletely reeyeled and reused. PVC compounds recovered in the Vinyloop process can be reused in a closed-loop recycling scheme... 

The anodes of these two graphite samples were fabricated from a slurried mixture which contains 92 wt% of active graphite powder and 8wt% polyvinylidene difluoride (PVDF) polymer binder (Kureha 9130) and using 1 -methyl-2-pyrrolidinone (NMP) (Aldrich, >99%) as the solvent. After getting the homogenous slurry, the electrode laminates were coated on Cu current collector foil using a doctor blade in the laboratory-made laminate-coater. The laminates were then dried first at 75°C in air for 3 hrs and then the final heat treatment was carried out in a vacuum oven at 75 C for 10 hrs. Finally, the laminates were calendared to about 35% porosity in a dry room. 

In the X-ray powder diffraction patterns of the composites, the disappearance of the broad band centered at 22 °20, typical of amorphous silica, indicates that the zeolitisation of the mineral fraction of the parent composite was complete. In no diffraction pattern any sign of crystallised chitosan could be found. The two methods in which the silica-polymer beads were extracted from the aluminate solution after impregnation (methods A and C) allowed the formation of the expected zeolite X, with traces of gismondine in the case of the method C. The method B, in which excess aluminate solution was present during the hydrothermal treatment, resulted in the formation of zeolite A. 

For preparing this polymer the starting material used is paradibromobenzene, paradibromobenzene on treatment with activated copper powder at high temperatures, forms parapolyphenylene as under ... 

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