Piezoelectric property improvement of polyethylene ferroelectrets using postprocessing thermal‐pressure treatment. (19th September 2018)

• Record Type: Journal Article
• Authors: Hamdi, Ouassim; Mighri, Frej; Rodrigue, Denis
• Is Part Of: Polymers for advanced technologies. Volume 30:Number 1(2019)
• Page Start: 153
• Page End: 161
• Publication Date: 2018-09-19
• Subjects: cellular structure -- ferroelectrets -- optimization -- polyethylene -- posttreatment; Polymers -- Periodicals; 668.9
• DOI: 10.1002/pat.4453
• Languages: English
• ISSNs: 1042-7147

Abstract

Abstract : In this work, biaxially stretched polymer foams with well‐defined cellular structures were prepared from polyethylene via blown‐film extrusion and subjected to corona charging to produce a piezoelectric response. The charging parameters were first optimized in terms of charging voltage and needle distance, as well as the gas type and pressure to investigate their effect on the piezoelectric coefficient ( d 33 ). The results show that samples charged under nitrogen (N2 ) at 100 kPa had better d 33 coefficient than those charged under ambient air or N2 at 20 kPa. Moreover, 2 different thermal pressure treatments were imposed to obtain an optimized eye‐like cellular structure with different cell aspect ratios (AR). The results showed that when the cells were elongated in both the longitudinal and transverse directions (higher AR), higher d 33 coefficients were achieved. From all the samples produced, the best results were obtained for a longitudinal aspect ratio (AR‐L) of 7.1, a transversal aspect ratio (AR‐T) of 4.6, and a relative foam density of 0.52 leading to a d 33 coefficient of 935 pC/N. This coefficient was further increased using reverse charging and multilayered films, reaching a maximum of 2550 pC/N. This value is much higher than typical ones reported so far for any polyethylene and polypropylene ferroelectrets. These results could increase the use of polyethylene in piezoelectric applications as these materials are very attractive for the large‐scale production of electret‐based sensors and transducers due to their low cost and easy processing.