Low-density polyethylene (LDPE) composites modified with a resin based on ethylene/methacrylic acid copolymer (surlyn) and/or citric acid were electron beam-irradiated and investigated by electron spin resonance (ESR) at room temperature. ESR studies were carried out directly after irradiation and after various time intervals up to 72 h postirradiation. The irradiated samples showed the ESR spectrum of seven lines that was assigned to the formation of allyl radical. The nature and yield of the allyl radical of the different LDPE samples were analyzed as a function of time after irradiation. Also, the radical concentration, decay, decay rate, and kinetics of radical decay were evaluated. Fourier transform infrared (FTIR) analysis at a series of different temperatures upon cooling from room temperature to -175 degrees C and the reverse heating to +125 degrees C\ was also carried out. The structural changes while cooling and heating of LDPE samples were investigated using FTIR spectrometry. The results showed that cooling of unirradiated LDPE samples to -175 degrees C results in a decrease of the intensities of IR bands. However, heating the samples from -175 degrees C up to +125 degrees C led to a consequence increase in the intensities of the IR bands. (c) 2007 Wiley Periodicals, Inc.