2020/05/01 by Matthew E. Curd, Curd, Matthew E., Neil F. Morrison +9
Chemistry · Engineering · #Advanced Materials and Mechanics #Applied Physics (physics.app-ph) #Cellular and Composite Structures #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Polydiacetylene-based materials and applications
paper · pdf · doi:10.48550/arxiv.2005.12862
openalex publication_date 2020/05/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Recently, hollow thermoplastic microspheres, such as Expancel made by\nNouryon, have emerged as an innovative filler material for use in\npolymer-matrix composites. The resulting all-polymer syntactic foam takes on\nexcellent damage tolerance properties, strong recoverability under large\nstrains, and favourable energy dissipation characteristics. Despite finding\nincreasing usage in various industries and applications, including in coatings,\nfilms, sealants, packaging, composites for microfluidics, medical ultrasonics\nand cementious composites, there is a near-complete absence of statistical\ngeometrical information for Expancel microspheres. Further, their mechanical\nproperties have not yet been reported. In this work we characterise the\ngeometrical quantities of two classes of Expancel thermoplastic microspheres\nusing X-ray computed tomography, focused ion beam and electron microscopy. We\nalso observe the spatial distribution of microspheres within a\npolyurethane-matrix syntactic foam. We show that the volume-weighted\npolydisperse shell diameter in both classes of microsphere follows a normal\ndistribution. Interestingly, polydispersity of the shell wall thickness is not\nobserved and in particular the shell thickness is not correlated to the shell\ndiameter. We employ the measured geometrical information in analytical\nmicromechanical techniques in the small strain regime to determine, for the\nfirst time, estimates of the Young's modulus and Poisson's ratio of the\nmicrosphere shell material. Our results contribute to potential future\nimprovements in the design and fabrication of syntactic foams that employ\nthermoplastic microspheres. Given the breadth of fields which utilise\nthermoplastic microspheres, we anticipate that our results, together with the\nmethods used, will be of use in a much broader context in future materials\nresearch.\n