Green composites obtained by PCL melt blending with Diatomaceous Earth

In recent years, the development of eco-friendly composites using biodegradable polymers and natural materials has gained significant attention to mitigate environmental pollution effects. Here, we explore diatomaceous earth (Diat) as a filler for polycaprolactone (PCL) to obtain composites useful for environmental applications. Both components are biocompatible materials with relevant adsorption capacities towards inorganic and organic pollutants. Diat, well known for its non-toxicity and eco-friendliness, possesses high absorption capacity, low thermal conductivity, and low density due to its high porosity. Derived from the amorphous silica cell walls of dead diatoms deposited on marine sediment, Diat is composed of silicon dioxide (>90%), alumina and trace iron oxides, with particle sizes ranging from 3 to 200 µm1 . Its unique structure makes Diat suitable for diverse applications, including drug delivery systems, environmental remediation, and polymer reinforcement2 . In this study, composites were prepared by blending different Diat amounts (5, 15 and 50 wt%) with molten PCL. We present here the promising viscoelastic and thermal properties of these composites. Dynamic Mechanical Analysis (DMA) was employed to assess the viscoelastic characteristics of PCL/Diat hybrids, while Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) were used to determine the thermal properties. Incorporating Diat within the polymeric matrix improved PCL elasticity at temperatures below its melting point, with a more evident effect in composites with higher Diat content. DSC results showed that Diat can act as a nucleating site for PCL crystallization, resulting in enhanced melting and crystallization enthalpies. On the other hand, the melting and crystallization temperatures of the polymer were slightly affected by the filler concentration. Notably, mixing with Diat generated relevant effects on the PCL thermal stability, as evidenced by TGA data, due to the filler’s barrier effect. 3 Overall, the results obtained by thermal analysis methods highlighted the interfacial compatibility between PCL and diatomaceous earth. Melt blending of PCL with Diat emerges as an easy and efficient strategy to obtain biocompatible composites with enhanced properties, compared to the pure polymer. Such composites hold promise for various applications, including air pollutant remediation in museum environments. References: [1] P.Aggrey et al., RSC Adv. 2021, 11, 31884–31922 [2] A. Semenkova et al., J. Radioanal. Nucl. Chem. 2020, 326, 293–301 [3] I. Zglobicka et al., Materials 2022, 15, 621