Polymer Testing (Aug 2021)
Quantifying damping coefficient and attenuation at different frequencies for graphene modified polyurethane by drop ball test
Abstract
In this study, polyurethane (PU) was modified by direct mixing of carboxyl functionalised graphene (GNP–COOH) referred to as f-GNP, without using any solvent, during in-situ polymerization. In a further attempt, the neat PU was modified with f-GNP and a hydrophobic silica-based solution (SG) during in-situ polymerization. The damping coefficient and attenuation capacity of neat polyurethane (PU), f-GNP based PU nanocomposite (PU + f-GNP), and f-GNP and hydrophobic silica-based solution PU nanocomposite (PU + f-GNP + SG), together with polytetrafluoroethylene (PTFE), high-density polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), polyethylene terephthalate (PET), polyvinyl chloride (PVC) and NYLON have been obtained by the drop ball tests under controlled and consistent conditions. The results show that among the tested materials, polyurethane modified with carboxyl functionalised graphene and silica-based Sol-Gel (PU + f-GNP + SG) displays the greatest attenuations and PTFE the least.The attenuation of the various materials has been identified with the SVD-QR method. This experimental modal analysis method has been used to analyse the free response signal of the system during the drop ball test and identify the modal parameters such as damping ratio and frequency of the modes of deformation of the system. The drop ball test results show that the damping coefficient of polyurethane modified with 0.5 wt% carboxyl functionalised graphene (PU + f-GNP) increased by 37% at frequency range 200–300 Hz, by 34% at frequency range 500–600 Hz and by 32% at frequency range 700–1000 Hz. The developed nanocomposite materials have great potential for protecting leading edge erosion (LEE) of wind turbine.
