Poly mass loss

The actual time required for poly-L-lactide implants to be completely absorbed is relatively long, and depends on polymer purity, processing conditions, implant site, and physical dimensions of the implant. For instance, 50—90 mg samples of radiolabeled poly-DL-lactide implanted in the abdominal walls of rats had an absorption time of 1.5 years with metaboHsm resulting primarily from respiratory excretion (24). In contrast, pure poly-L-lactide bone plates attached to sheep femora showed mechanical deterioration, but Httie evidence of significant mass loss even after four years (25). 

On heating in air at 10°C per min, poly(m-carborane-siloxane) shows typically only 4% mass loss at 450°C and 7% mass loss at 600°C (see Fig. 4). In comparison, siloxanes without carborane units, show an approximate 50% mass loss at 450°C. As a consequence of the relatively high boron and carbon content of these materials, pyrolysis is expected to generate ceramic residues of boron carbide/silicon carbide. 

Figure 8 Mass loss of poly(ether-ketone-carbaborane) relative to that of PEEK (dashed).

Figure 5 Fractional release of dextran ( ) and rhodamine ( ) from a disk of poly(MSA) as a function of the polymer mass loss. 

Fig. 15.1 Typical thermogravimetric mass loss of a sample of poly(ethylene), heated at a constant rate.

Figure 7. The self development of a thin film ( 0.2 /Ltm) of poly(p-t-butylphenyl methylsilane) upon irradiation at 248 nm (KrF excimer laser). Mass loss is proportional to the frequency change (Af) of the quartz crystal microbalance.

Metal oxide semiconductor chemical sensors in combination with MDA have been shown to be useful to estimate the oxidative stability of polypropylene during processing instead of traditional melt flow index analysis (50). An array of sensors was used to receive a detailed analysis of volatiles. At quality measurements of different poly(butylene adipate)s the use of indicator products has been proven better than analyses of the decrease in molecular weight or mass loss for early degradation detection. Adipic acid, quantified using gas chromatography, was then used as the indicator product [51]. 

Figure 7.11 shows the result of a semi-static Td,o-value determination of poly(4 methyl-1-pentene). Mass losses s. 0.05 %wt. can easily be recognised in line with the TGA balance resolution and sensitivity. The weight loss rate is practically zero between 30°C and 110°C. Between about 110°C and 267°C a small, but nearly constant weight loss rate is detected (0.003 %wt./°C). These mass losses might be caused by the evaporation of a small oligomers fraction (0.5 %wt. maximally). The mass loss rate increases strongly at temperatures > 267°C due to what is considered to be the overall thermal decomposition of the polymer sample. 

A polymer mass loss rate of 10 kgh /area and an activation energy of 21.1 kJ/mol for atomic oxygen-exposed poly(methyl methacrylate) was reported by Whitaker et al. The mass loss rate was found to be directly related to the exposure area and to be independent of sample thickness. 

FIGURE 42.2 The effect of poly(L-lactide) composition in polyglycolide on the time required for 50% mass loss implanted under the dorsal skin of rat. (From Miller, R.A., Brady, J.M., and Outright, D.E., 1977. /. Biomed. Mater. 

The coatings provided excellent protection to various substrates. P2 protected silver mirror was estimated to lose only 2.5 % of its initial solar reflectance when extrapolated to 1000 hours ashing time. For the poly(carborane siloxane) P2 coating, the mass loss rate of Kapton was reduced to half that of the best commercial coating. 

Theoretically the decomposition of the azido group in a linear PAA should have resulted in a mass loss of 33.7%. The PAA thus had a lower azido content. This may be due to the branched structure of poly(allyl chloride) (PAC), which resulted in lower chlorine content, and since poly(allyl azide) was prepared by azidation of PAC therefore the azido content will be decreased. 

Poly(lactic-co-glycolic) acid (PLGA) dichloromethane Infrared and Raman spectroscopy used to study cranposition and degradation of the copolymer films in a phosphate buffer solution. Mass loss, FTIR, Raman (Vey etal. 2011)... 

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