Compositional effects on degradation rate

Several studies have been conducted on biostable polyurethanes to elucidate the effects of hard segment chemistry on polyurethane degradation rate. Tang et al. [104,105] observed the effects of hard segment chemistry and hard segment content 

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Fig. 5.20. Effect of polymer composition (1 % in benzene) on degradation rate.

There are a vast number of other factors which may be expected to influence the rate of desquamation, for instance, by affecting the rate of proteolytic reactions. pH, water, and ion concentrations, and lipid composition may all be expected to be of importance. Experimental data in this area are very scarce, but some speculations can be made. For instance, the pH dependency of SCCE activity could be of importance. SCCE has optimal activity at pH 7 to 8, but close to half its maximal activity at pH 5.5.36,37 This implies that rather small variations in either direction of the pH of the extracellular space should have effects on the rate of SCCE-mediated protein degradation. In support of this, the rate of spontaneous cell dissociation observed in plantar stratum corneum in vitro showed a marked pH dependency, being highest at neutral to weakly alkaline pH and decreasing at lower pH values.10... 

Main applications of thermal analysis are (1) Soil and clay analysis (2) Determination of Glass transition (3) Compositional effects on glass transition (4) Heat capacity determination (5) Characterization of polymer blends (6) Study the effects of additives added to polymer (7) Polymer degradation analysis (8) Crystallinity and crystallization rate study and (9) Reaction kinetic studies. 

Figure 7.10 Effect of Lactic Acid (LA) and Glycolic Acid (GA) composition on degradation rate of poly(lactide-co-glycolic acid).

Effect of copolymer composition on degradation rates of biodegradable polymer nanofibers. Concluded that conductivity or dielectric constant of solution determined fiber morphology. 

The ESRI experiments described in our publications and summarized in this chapter led to spatially resolved information on the effect of treatment conditions, amount of stabilizer, and polymer composition on the degradation rate. In the heterophasic systems studied in our laboratory, ESRI has identified specific morphological domains where chemical processes are accelerated. The combination of ID and 2D spectral-spatial ESRI experiments led to mapping of the stabilizer consumption on two length scales within the sample depth on the scale of a few mm, and within morphological domains on the scale of a few gm. 

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