Physical combined polymers

In the design of preceramic polymers, achievement of the desired elemental composition in the ceramic obtained from them (SiC and Si3N4 in the present cases) is a major problem. For instance, in the case of polymers aimed at the production of SiC on pyrolysis, it is more usual than not to obtain solid residues after pyrolysis which, in addition to SiC, contain an excess either of free carbon or free silicon. In order to get close to the desired elemental composition, two approaches have been found useful in our research (1) The use of two comonomers in the appropriate ratio in preparation of the polymer, and (2) the use of chemical or physical combinations of two different polymers in the appropriate ratio. 

Polybrominated Diphenyl Ethers. PBDEs are used as additive flame retardants in thermoplastics. Additive flame retardants are physically combined with the polymer material being treated rather than chemically combined (as in reactive flame retardants). This means that there is a possibility that the flame retardant may diffuse out of the treated material to some extent. 

Bicomponent fibres are sjmthetic fibres composed of two firmly but separately combined polymers of different chemical and physical structures. The structure of the bieomponent depends on the shape of the spinnerette orifice (side-by-side, sheath eore, matrix - fibril and multi-fibrillary) and the type of spinning method. Due to the structural differences, the two components shrink differently on heat treatment and form crimp and greater bulk in the fibre. The first fully synthetic bicomponent was an acrylic (Sayelle, Orion 21). The use of sheath-core fibres composed of nylon 6,6 and nylon 6 (Heterofil, ICI) for floor coverings is described. 

The tetrachlorate is essentially inactive against the tested viruses. Methotrexate, the physical combination of tetrachloroplatinate, and the polymer aU exhibit good activity against HSV-1 and VZV, both DNA viruses whose genome replication occurs in the nucleus with some activity against vaccinia virus—a DNA virus with... 

Polymer composites consist of the physical combination of two or more materials of the same or different categories (one of which must be polymer), forming a multi-phasic system with superior properties to the individual components, which do not lose their own identity. The components of a composite are physically separable. Of these two phases, one is a continuous phase or matrix, which is the polymer, and the other is a dispersed phase... 

ControUed-release polymeric systems can be divided into two broad categories based on the concept of combining biologicaUy active substances with polymeric materials to achieve a desired release profile. These systems are either a physical combination in which the polymer acts as a rate-controUing device or a chemical combination in which the polymer acts as carrier for the agent. The choice of the... 

E. A. Neubauer, D. A. Thomas, and L. H. Sperling, Effect of Decrosslinking and Annealing on Interpenetrating Polymer Networks Prepared from Poly(ethyl acrylate)/poly-styrene Combinations, Polymer 19(2), 188 (1978). Decrosslinking of PEP/PS IPNs. Hydrolysis of Acrylic acid anhydride. Morphology and physical properties. 

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