Controlled release from natural rubber

This report focuses on natural rubber as the controlled release substrate, and in the physical form of the commercially available sleeve stopper containing a septum and usually referred to as a rubber septum. Interest in this material developed because the rubber septum releases pheromone by only one mechanism (3), and therefore is amenable to systematic study. Also, in many empirical studies the rubber septum had proven to be efficacious for use in traps monitoring insect flight activity, and knowledge of its release characteristics would improve its usefulness. Research that contributes to an understanding of the factors controlling evaporation rates of insect pheromones from natural rubber septa is critically summarized here. 

Controlled Release of Insect Sex Pheromones from a Natural Rubber Substrate... 

Figure 18.14 Diffusion coefficient as a function of solute molecular weight in water (o) and in three polymers silicone rubber ( ), natural rubber ( ), and polystyrene (b). The regression lines through the measurements have slopes of -0.51 (water), -0.86 (silicone rubber), -1.90 (natural rubber), and -4.20 (polystyrene). Source adapted from RW Baker, Controlled Release of Biologically Active Agents, Wiley, New York, 1987.

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