Foams fluorinated copolymers

Some of the fluorinated copolymers of ethylene such as ethylene-tetrafluoroethylene and ethylene-chlorotrifluoroethylene polymers can be fabricated into foams that are useful for wire insulation applications. These compositions are usually comprised of 40-60... 

Surfactants used as lubricants are added to polymer resins to improve the flow characteristics of the plastic during processing they also stabilise the cells of polyurethane foams during the foaming process. Surfactants are either nonionic (e.g. fatty amides and alcohols), cationic, anionic (dominating class e.g. alkylbenzene sulfonates), zwitterionic, hetero-element or polymeric (e.g. EO-PO block copolymers). Fluorinated anionic surfactants or super surfactants enable a variety of surfaces normally regarded as difficult to wet. These include PE and PP any product required to wet the surface of these polymers will benefit from inclusion of fluorosurfactants. Surfactants are frequently multicomponent formulations, based on petro- or oleochemicals. 

An alternative means of reducing the dielectric constant of polyimides is to have a low dielectric constant component dispersed as a second phase within the rigid polyimide matrix. Two key approaches have been pursued to this end. The first involves the preparation of polyimide block copolymers with highly fluorinated coblocks and the second involves the generation of a polyimide foam. The main drawback to the first approach is the solubility of highly fluorinated blocks in organic media which will permit copolymerization with polyimides. This led to the investigation of new semi-fluorinated polymers derived from polyfaryl ethers). 

Electrical applications -FEP m [FLUORINE COMPOUNDS, ORGANIC - PERFLUORINATED ETHYLENE-PROPYLENE COPOLYMERS] (Vol 11) -ofplastic foams [FOAMED PLASTICS] (Vol 11)... 

The second system investigated 101) (polystyrene macromonomer and perfluoro-alkyl acrylate) is also of great interest. The polymerization is carried out in trifluoro-benzene with AIBN as the initiator to a conversion of the order of 60 %. The graft copolymer formed is soluble in a number of solvents in which the poly(perfluoro-alkyl acrylate) backbone would be insoluble, e.g. in THF and diethyl ether. The easy formation of foams indicates the low surface energy which is characteristic of fluorinated polymers. Double-detection GPC (UV and refractive index) showed that the distribution of polystyrene branches within the sample was quite uniform. 

Polymeric materials such as nylon, polyethylene, neoprene, mbber, acrylonitrile-butadiene copolymer, polyvinyl chloride-acetate, and polyurethane foam burn or react violently with fluorine (Schmidt and Harper 1967). 

Reprinted with permission from L. Li, et al., CO2 foaming in thin Aims of block copolymer containing fluorinated blocks. Macromolecules, 39 (2006) 4746-4755. Copyright (2006) American Chemical Society. 

Figure 9.22 Scanning electron microscopy images of nanoporous films of PMMA-b-PFM A diblock copolymer (above) and PFMA-b-PMMA-b-PFMA triblock copolymer (below). Reproduced from C. Dutriez, et al., Nanocellular foaming of fluorine containing block copolymers in carbon dioxide the role of glass transition in carbon dioxide, RSC Advances, 2 (7) (2012) 2821 with permission of the Royal Society of Chemistry.

C. Dutiiez, et al., Nanocellular foaming of fluorine containing block copolymers in carbon dioxide the role of glass transition in carbon dioxide, RSC Advances 2 (7) (2012) 2821. 

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