Innovative polyetherimide and diatomite based composites: influence of the diatomite kind and treatment

In this work innovative composites were developed, using as polymeric matrix polyetherimide (PEI), a high performance thermoplastic, and as natural filler two different kinds of diatomaceous earth, i.e. uncalcined and calcined. The uncalcined powder was amino-functionalised to improve its chemical compatibility with the matrix, whereas the calcined one was submitted to a purification treatment with HCl to remove possible contaminants. Mechanical tests and microstructural characterisation were carried out to evaluate the influence of the filler kind, of its content (i.e. 1–10 wt.%) and of its amino-functionalisation or purification in the case of uncalcined and calcined diatomite, respectively, on the composites performance. The collected results show an increase of Young's modulus with the filler content, particularly in the case of amino-functionalised diatomite, suggesting a good chemical compatibility between filler and matrix. This is substantiated by the scanning electron microscopy (SEM) observation of the fracture surface of samples after tensile test.