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Abstract: Correlation between transport properties and free volume has been widely evidenced by several authors. We are showing through a positron annihilation study in a high barrier polymer that transport properties can be improved by means of antiplasticizers addition. We also are verifying in this paper the influence of both free volume hole size and free fractional volume in diffusion of gases, finding a relationship with solubility too. [Copyright &y& Elsevier]

In order to modify the transport properties of the amorphous polyamide Trogamid-T™, several additives with structural characteristics that produce antiplasticization have been tested. Positron annihilation lifetime spectroscopy (PALS) has been used to determine both the size of free volume holes and the number of holes (free fractional free volume). Polyvinyl phenol (PVPh), 1,5 dihydroxy naphthalene (Ndiol) and a hexafluorinated Bisphenol A (HFBA) were chosen according to the results of a preliminary study based on density and PALS measurements with 15% of additive blends. Their blends with Trogamid show different behaviours: HFBA behaves clearly as a plasticizer while the polyvinyl phenol acts as an antiplasticizer. Ndiol has a more special effect: blend densities are greater than additive whereas the hole size decreases. [Copyright &y& Elsevier]