Hydroxyl index

Figure 4 Changes in (a) carbonyl index and (b) hydroxyl index versus irradiation time for polystyrene films. O-con-trol -2,4-DHBP -2H-4MBP -2H-4BB X-DHBP-F A-HMBP-F and D-HBBP-F.

Figure 6 (a) Carbonyl index (at 1740 cm and (b) hydroxyl index (at 3550 cm ) versus aging time for CTA films X-control O-DHBP D-HMEP A-HBBP -DHBP-F -HMBP-F and A-HBBP-F. 

The carbonyl index is not a standard technique, but is a widely used convenient measurement for comparing the relative extent and rate of oxidation in series of related polymer samples. The carbonyl index is determined using mid-infrared spectroscopy. The method is based on determining the absorbance ratio of a carbonyl (vC = 0) band generated as a consequence of oxidation normalised normally to the intensity of an absorption band in the polymer spectrum that is invariant with respect to polymer oxidation. (In an analogous manner, a hydroxyl index may be determined from a determination of the absorbance intensity of a vOH band normalised against an absorbance band that is invariant to the extent of oxidation.) In the text following, two examples of multi-technique studies of polymer oxidation will be discussed briefly each includes a measure of a carbonyl index. 

Phenotypic trait measures based solely on the urinary excretion of 6-hydroxychlorzoxazone have also been reported based on the amount of metabolite excreted in zero to eight hours (278), or a hydroxylation index approach (279), or estimating the elimination half-life of the metabolite (280). However, the validity of these approaches is highly questionable, so they have not been widely applied. 

Kimura M, Ieri I, Wada Y, Mamyia K (1999) Reliability of the omeprazole hydroxylation index and length of therapy. Br J Clin Pharmacol 47 115-119... 

Initial experiments were undertaken with morpholine, dicyclohexylamine and dibutylamine terminated GPTA systems as well as the diethylamine sample which has already been investigated in previous work (14,15). The effect of Microscal irradiation on the increase in hydroxyl index of these amine acrylates is illustrated by the data in Table I. This shows that the nature of the terminal amine functionality has a marked effect on the hydroxyl index profile during irradiation. The following order of increasing hydroxyl index was observed relative to amine functionality ... 

Table I. Hydroxyl Index Values during Irradiation in a Microscal Unit for OV Cured (5% w/w Benzophenone) GPT (12 thick) after Reaction with Various Amines...

Amine lOOh Hydroxyl Index Values 200h 300h... 

The effect of Microscal irradiation on the increase in hydroxyl index for these electron-beam cured amine acrylates is shown by the data in Table II. 

The rates of loss do not correlate with the rates of increase in the hydroxyl index for these systems or with the photoyellowing and uv phenomena. This indicates that the mechanism of oxidation of the amine functionality is complex. An additional feature of interest is the profile of this band loss as related to terminal amine structure. In the simple alkyl substituted systems namely diethyl, dimethyl and dibutyl there is an initial rapid loss followed by a slowing down of the rate of decrease on prolonged irradiation. However, with the oxygen containing systems namely morpholine, N-ethyl ethanolamine and N-methyl ethanolamine the rate of decrease is linear with irradiation time. Evidently, there must be two different mechanisms in operation here. The loss of these infra-red absorption bands may be due to a process of dealkylation via oxidation (see reactions later). The band situated at 2978 cm"l exhibited similar behaviour although the extent of the loss was less than that observed with the previous band and the order of rate loss was marginally different. 

The charactaization of aU these products comprised their structural assessment through FTIR and NMR spectroscopy, the determination of the amount of solid residue and PO homopolymer and the measurement of their viscosity and hydroxyl index. Figures 12.1 and 12.2 show the FTIR and H-NMR spectra of the oxypropylated SL. 

The two most relevant propraties of these polyols with regard to their use as polyurethane precursors are their viscosity and hydroxyl index. Values which simulate those associated with comma-cial counterparts were readily obtained by adjusting the key process parameters, notably the PO/L ratio. 

Fig. 39 Changes in carbonyl index (a) and hydroxyl index (b) measured on UHMWPE at different doses. The data were taken from [09Z2] (7 ( Cs)-irradiation dose rate 0.4 kGy.h ). ( , ) unstabilized material (O, ) UHMWPE - 0.25 % wt rosemary extract (A, k) UHMWPE - 0.50 % wt rosemary extract...

Fig. 15 Variations of a hydroxyl index and b carbonyl index for polypropylene exposed to weathering treatment on two opposite seasons, (black) summer, (grey) winter...

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