Investigation of electron irradiation induced-changes in poly(vinylidene fluoride) films Mohamed Mahmoud Nasef a, *, Hamdani Saidi b , Khairul Zaman M. Dahlan c a Chemical Engineering Program, Universiti Teknology PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak, Malaysia b Membrane Research Unit, Universiti Teknologi Malaysia, Jalan Semarak, 54100 Kuala Lumpur, Malaysia c Radiation Processing Technical Division, Malaysian Institute for Nuclear Technology Research (MINT), Bangi, 43000 Kajang, Malaysia Received 9 June 2001; received in revised form 31 July 2001 Abstract The radiation-induced changes taking place in poly(vinylidene fluoride) (PVDF) films exposed to electron irradiation were investigated in correlation with the applied doses. Samples were irradiated in air at room temperature by a universal electron beam accelerator to doses in the range of 100–1200 kGy. Various properties of the irradiated PVDF films were studied using FTIR, dif- ferential scanning calorimetry (DSC) and universal mechanical tester. Unirradiated PVDF film was used as a reference. Electron irradiation was found to induce changes in physical, chemical, thermal, structural and mechanical properties of PVDF films and such changes vary depending on the irradiation dose. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: PVDF; Electron irradiation; Structural changes; Thermal properties; Mechanical properties 1. Introduction Fluoropolymers are well known for their excellent thermal and chemical stability and mechanical proper- ties [1]. Among them, poly(vinylidene fluoride) (PVDF) —(CF 2 -CH 2 ) n — has attracted considerable attention in many areas of research and industrial use [2]. This is due to its electrical properties, resistance to weathering, durability, biocompatibility and processibility [3]. Investigation of PVDF morphology and piezoelectric properties has become a subject for active research in the last 4 decades [4–7]. PVDF is a semicrystalline polymer, which has several crystalline phases known as a, b, g and d phases (or II, I, III and IV). The a (II) phase in which the polymer chains are in non-polar conformation (TGTG 0 ) is the most common phase appearing under normal circum- stances. The polar crystalline phase b (I), which has a zigzag (all-trans) confirmation is obtained by straining, stretching or quenching [3]. The intermediate polar confirmation g (III) results when the polymer is moder- ately stressed. The last phase d (IV) appears only under special crystallization temperature and pressure. Irradiation by ionizing radiation has been found to induce changes in the chemical structure and physical properties of polymers [8]. Such changes may be in the form of crosslinking, main chain session, or evolution of hydrogen depending upon the chemical as well as phy- sical nature of the polymer and the radiation. Radiation crosslinking and radiolysis of fluoropolymers have been reviewed in Refs. [1] and [9], respectively. The effect of electron radiation on the inherent proper- ties of the PVDF has been studied in various occasions [10–14]. However, some of the reported results, parti- cularly those related to crystallinity, crosslinking and melting temperature are contradictory and as a result further clarification studies are needed. The present work aims to investigate various changes taking place in the properties of PVDF films after exposing to electron radiation at different doses. 2. Experimental 2.1. Materials and electron irradiation The PVDF films were supplied by Goodfellow Cam- bridge (England). The film has a thickness of 0.08 mm and density of 1.76 gm/cm 3 . The irradiation experiments were 0141-3910/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0141-3910(01)00206-3 Polymer Degradation and Stability 75 (2002) 85–92 www.elsevier.com/locate/polydegstab * Corresponding author. Tel.: +60-5-3721131; fax: +60-5- 3721111.