Polymers, degradable, degradation products

Protective Coatings. Some flame retardants function by forming a protective Hquid or char barrier. These minimize transpiration of polymer degradation products to the flame front and/or act as an insulating layer to reduce the heat transfer from the flame to the polymer. Phosphoms compounds that decompose to give phosphoric acid and intumescent systems are examples of this category (see Flame retardants, phosphorus flame retardants). 

The study by Determan et al. [224] focuses on the effects of polymer degradation products on the primary, secondary, and tertiary structure of TT, OVA, and lysozyme after incubation for 0 or 20 days in the presence of ester (lactic acid and glycolic acid) and anhydride [sebacic acid and l,6-bis(p-carboxyphenoxy)hexane] monomers. The structure and antigenicity or enzymatic activity of each protein in the presence of each monomer was quantified. SDS-PAGE, circular dichroism, and fluorescence spectroscopy were used to assess/evaluate the primary, secondary, and tertiary structures of the proteins, respectively. ELISA was used to measure changes in the antigenicity of TT and OVA and a fluorescence-based assay was used to determine the enzymatic activity of lysozyme. TT toxoid was found to be the most stable in the presence of anhydride monomers, while OVA was most stable in the... 

Determan, A. S., Wilson, J. H., Kipper, M. J., Wannemuehler, M. J., and Narasimhan, B. (2006), Protein stability in the presence of polymer degradation products Consequences for controlled release formulations, Biomaterials, 27, 3312-3320. 

The chemical structure of a polymer determines its flammability, or to be more specific, the chemical structure of the polymer degradation product dictates the... 

Several types of species can diffuse in and out of controlled drag delivery systems, including water, drag, water-soluble excipients (e.g., polymers, plasticizers, and/or fillers), acids, and bases from the environmental bulk fluid as well as polymer degradation products. Often, the polymeric material is chosen in such a way that drag diffusion through the macromolecular network is the rate-limiting step. In these cases, the systems... 

SPME for Analysis of Polymer Degradation Products and Additives... 

A brief list of ionization methods is given in Table 1. (One may quibble a bit about the dates given in the table, but we believe these are more or less accurate.) Up xmtil about 1970, the only ionization method in common use was electron impact (El). Field ionization (FI) was developed in the 1950s, but it was never very popular, and chemical ionization (Cl) was just getting started. These three methods (El, Cl, FI) depend upon vaporization of the sample by heating, which pretty much limits polymer applications to small, stable oligomers or to polymer degradation products (formed by pyrolysis or other methods). Field desorption (FD-MS), invented in 1969, was the first "desorption/ionization" method. FD- and FI-MS are often very useful (particularly for analysis of less polar polymers), but they have never been in widespread use. 

Fluid-loss studies were conducted using a gas pressured filter apparatus. The partially degraded polymer solutions were filtered through specific pore size filters (Millipore MF 0.05 to 5.0 jm using a gas pressure of 1(X) psi. In addition to insoluble residues, the 0.05 pm filter retained polymer degradation products with molecular weights greater than 3.0 x 10 d. 

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