Fractal Analysis and Radiographic Inspection of Microwave Welded HDPE Bars

• Published in: Imaging and Image Analysis Applications for Plastics pp. 217 - 223
• Main Authors: Staicovici, Stefan, Wu, Chung-Yuan, Benatar, Avraham, Bahman, Zoofan
• Format: Book Chapter
• Language: English
• Published: United States Elsevier Inc 1999; William Andrew Publishing/Plastics Design Library; Elsevier Science & Technology Books
• Subjects: Materials science; Plastics & polymers technology; Plastics & Rubber; Properties & Testing
• ISBN: 1884207812; 9781884207815
• DOI: 10.1016/B978-188420781-5.50027-9

Microwave welding uses microwave energy to generate heat in a conductive polymer gasket which is placed at the joint interface. The conductive polymer used throughout this work is polyaniline (PANI) doped with HCl. In order to assure structural compatibility at the interface, PANI and HDPE powder are initially mixed and a gasket is compression molded. The conductivity of the gasket placed at the interface controls the amount of heat produced. The welding parameters, which mostly affect the joint strength are heating time, power level, welding pressure, and percentage of conductive polymer in the gasket. The strength of a microwave welded joint depends on the amount of gasket remaining at the interface. As the amount of gasket remaining at the interface increases the joint strength decreases, while the disassembly capacity increases. The joint interface pattern is studied employing fractal geometry. The fractal dimension is calculated for a set of samples whose welding parameters are widely varied. The welding parameters chosen for analysis are percentage of conductive polymer (polyaniline), heating time, and power level. The box counting method is used to calculate the fractal dimension. As the fractal dimension approaches unity, maximum joint strength is obtained. Due to its electronic nature the conductive polymer is more X-ray absorbent than the surrounding HDPE. Therefore, X-ray radiography is performed on the welded joints. A pass/no pass test method can be set-up to control the joint quality depending on the relationship between the amount of squeeze out and joint strength.