Radiation Physics and Chemistry 68 (2003) 865–872 Effect of ionizing radiation on physicochemical and mechanical properties of commercial multilayer coextruded flexible plastics packaging materials Antonios E. Goulas a, *, Kyriakos A. Riganakos b , Michael G. Kontominas b a Department of Materials Science and Technology, University of Ioannina, Ioannina GR-45110, Greece b Laboratory of Food Chemistry and Technology, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece Received 4 July 2002; accepted 5 March 2003 Abstract The effect of gamma radiation (doses: 5, 10 and 30 kGy) on mechanical properties, gas and water vapour permeability and overall migration values into distilled water, 3% aqueous acetic acid and iso-octane was studied for a series of commercial multilayer flexible packaging materials based on coextruded polypropylene (PP), ethylene vinyl alcohol (EVOH), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polyamide (PA) and Ionomer. The results showed that radiation doses of 5 and 10 kGy induced no statistically significant differences (p > 0:05) in all polymer properties examined. A dose of 30 kGy induced differences (po0:05) in the mechanical properties of PA/LDPE, LDPE/EVOH/LDPE and LDPE/PA/Ionomer films. In addition, the same dose induced differences (po0:05) in the overall migration from Ionomer/EVOH/LDPE and LDPE/PA/Ionomer films into 3% acetic acid and iso-octane and in the overall migration from PP/EVOH/LDPE-LLDPE into iso-octane. Differences recorded, are discussed in relation to food irradiation applications of respective packaging materials. r 2003 Elsevier Ltd. All rights reserved. Keywords: Multilayer packaging materials; Physicochemical properties; Gamma radiation 1. Introduction Multilayer coextruded flexible packaging materials are a significant development of modern packaging technology. Their use finds ever-increasing applications in food, pharmaceutical, medicinal, cosmetics and electronics packaging because such materials combine a number of desirable properties (barrier to gases and water vapour, mechanical strength, machinability and relatively low cost) that no single material possesses (Osborn and Jenkins, 1992; Robertson, 1993; Twede and Goddard, 1998; Defosse, 1999). There are large number of possible combinations of single materials in a coextrudate. Most coextruded multilayer structures are based on polyolefins [poly- ethylene (PE) and polypropylene (PP)]. Polyolefins have a low cost, are versatile and easy to process. Low-density polyethylene (LDPE) and linear low-density polyethy- lene (LLDPE) are valued for their toughness and sealability properties. When oxygen, aroma, or flavour protection is necessary, high barrier materials such as ethylene vinyl alcohol (EVOH), polyvinylidene chloride (PVDC) or aluminium applied through vacuum coating processes are used (Osborn and Jenkins, 1992; Robert- son, 1993; Twede and Goddard, 1998). The number of layers in a multilayer structure range from 3 to 13 but most commercial multilayer packaging materials include 3, 5 and 7 layer structures (Twede and Goddard, 1998; Defosse, 1999; Toensmeier, 2000). Special adhesives (generally polyesters, copolymers of ethylene, polyurethanes or acrylics) known as ‘‘tie’’ layers are used to ‘‘glue’’ individual layers into a single ARTICLE IN PRESS *Corresponding author. Tel.: +326510-97390; fax: +3265 10-98795. E-mail address: aegoulas@cc.uoi.gr (A.E. Goulas). 0969-806X/03/$ - see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0969-806X(03)00298-6