Permeability of Plastic Films to Methyl Bromide: A Comparative Laboratory Study

Abstract: The permeability of plastic Ðlms to the fumigant methyl bromide (MB)was measured by two di†erent methods, in order to facilitate the selection ofÐlms which are impermeable to the gas. Polyethylene-based Ðlms are highly per-meable to MB, as evidenced by both methods. In contrast, multilayer coextrudedÐlms which have a layer of barrier material such as polyamide (PA) or ethylene-vinyl alcohol copolymer (EVOH) were signiÐcantly less permeable to MB, asreNected by the parameters permeability rate, time to 90% concentration (TC90,by the di†usion method) and lag-time values (by the variable-volume method). AsigniÐcant correlation was found between the permeability rate assessed by thedi†usion method and that obtained with the variable-volume method. Per-meability of all Ðlms increased with temperature as evidenced by all testedparameters. This increase was more pronounced with polyethylene Ðlms, the per-meabilities of which increased Ðve- to six-fold when the temperature wasincreased from 20iC to 60iC. The e†ect of temperature on barrier-Ðlm per-meability was less signiÐcant. Permeability of Ðlms to MB was a†ected by addi-tional factors such as additives, the length of the monomer side-chain, and thethickness and density of polyethylene Ðlms. 1998 SCI(Pestic. Sci., 53, 141E148 (1998)Key words: ethylene-vinyl alcohol; polyamide; fumigation; barrier Ðlms; methylbromide