Polycaprolactone rates

Polycaprolactones (see also Section 25.11), although available since 1969, have only recently been marketed for biodegradable purposes. Applications include degradable film, tree planting containers and slow-release matrices for pharmaceuticals, pesticides, herbieides and fertilisers. Its rate of biodegradability is said to be less than that of the polylactides. 

Chang, R. K., Price, J., and Whitworth, C. W., Control of drug release rate by use of mixtures of polycaprolactone and cellulose acetate butyrate polymers. Drug Dev. Ind. Pharm.,... 

Until recently, hot-melt extrusion had not received much attention in the pharmaceutical literature. Pellets comprising cellulose acetate phthalate were prepared using a rudimentary ram extruder in 1969 and studied for dissolution rates in relation to pellet geometry. More recently, production of matrices based on polyethylene and polycaprolactone were investigated using extruders of laboratory scale. Mank et al. reported in 1989 and 1990 on the extrusion of a number of thermoplastic polymers to produce sustained release pellets.A melt-extrusion process for manufacturing matrix drug delivery systems was reported by Sprockel and coworkers.As one can see, a review of the pharmaceutical scientific literature does not elucidate many applications for hot-melt extrusion in this field. 

Munk and co-woricers have been concerned with the above-stated problem for some time (38, 39). In this volume (40), their attention is focused on miscible blends of polycaprolactone and polyepichlorohydrin. These authors demonstrate that to a considerable degree the probe variation problem can be mitigated by scrupulous attention to experimental details in the IGC methodology. This concern for details is required at any rate, if the high data reproducibility needed for meaningful studies of interaction in miscible polymer blends is to be attained. These details center on modified methods for coating polymers onto solid supports, on improved methods for measuring carrier gas flow rates, and on enhanced, computer-based data analyses of elution traces. Also, corrections are made for contributions to retention times from uncoated support material. More than twenty volatile probes are used by Munk, and the probe-to-piobe variations in %23, while not entirely absent, are much less apparent than they would be under standard experimental protocols. 

Crystallization can take place whenever the polymer is at a T above T. At 25° C, polycaprolactone is above Tg and so it may crystallize. On the other hand, polyfethylene terephthalate) can be quenched to 25°C at various rates resulting in various degrees of crystallinity which will not change as long as the temperature does not exceed Tg. So this polymer will be more suitable for the biodegradabOity study. 

FIGURE 22.22 Variation of mean size of the particles obtained as a function of applied voltage and flow rate. (Adapted from Enayati, M., Ahmad, Z., Stride, E., and Edirisinghe, M., Size mapping of electric field-assisted production of polycaprolactone particles, J. R. Soc. Interface, 7(Suppl. 4), S398, figure 4, 2010, The... 

Authors have reported the thermal degradation behaviour of polycaprolactone (PCL) bio-nanocomposites [47, 77]. A study by Chrissafis et al. [46] investigated the thermal behaviour of modified and unmodified nanocomposites on PCL. They revealed that both unmodified montmorillonite and multiwalled carbon nanombes inhibited the thermal degradation of the bio-nanocomposites. On the other hand, organically modified montmorillonite and nanosilica increased the rate of degradation of PCL bio-nanocomposites (Fig. 9). 

Polycaprolactones possess good low-temperature impact strength for paintable body panels, good fuel and oil resistance, and hydrolytic stability for seals, gaskets, and belting. Polycaprolactones have fast crystallization rates, high crystallinity, and are generally easily processed into complex parts. 

PHB and other PHAs can also be blended with other biodegradable polymers. In Japan, the Ministry of International Trade and Industry s Biological Industry Institute in 1990 announced the development of blends of PHB and polycaprolactone (PCL). The blends can be processed with conventional equipment, and the ratio of the two polymers determines the rate of degradation. ... 

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