Thermal properties and morphology of high-density polyethylene filled with coffee dregs

Composites of high-density polyethylene (HDPE) and coffee dregs (COFD) were elaborated using four different types (integral, extracted, major size, and minor size) of COFD. The aim was to study the effects of particle size and soluble extraction over the properties of the HDPE. Four blends were made at the proportion of 90–10 % polymer-filler. The materials were evaluated through optical and scanning electron microscopy, differential scanning calorimetry and thermogravimetry/derivative thermogravimetry. The results showed that the integral COFD has a performance similar to the minor size one, and superior to the extracted. The composites degraded in two steps. The first one was in a temperature lower than the neat HDPE, but higher than the processing temperature of the polymer. The melting temperature and the degree of crystallinity of the composites resulted similar to the neat HDPE ones. In general, extraction and particle size of the COFD have little influence on the behavior of the HDPE. The results show that COFD can be used as filler in polymeric composites.