Determination of the energy efficiency in mixing of PLA/cellulose biocomposites

In order to set up a method to determine the energy efficiency of a cellulose fibres reinforced PLA biocomposite compounding process in a batch mixer, it was necessary to study the energy balance of mixing in the case of pure PLA. The process consists in two steps: (1) melting and (2) mixing. In the melting phase, the polymer pellets has to melt and to reach the mixing set temperature; once this temperature is reached, the mixing phase starts. Energy efficiency of the melting phase is defined as the ratio between the theoretical energy consumed by the material to reach the mixing set temperature and the energy consumed the temperature is reached. It appears that melting efficiency increases with the missing temperature and decreases with rotor speed. Reinforced composites having different concentration regime were also studied. In the case of concentrated suspensions, it appears that the total energy input increases with the fibre content. Aspect ratio has no significant influence on energy consumption for diluted and semi-diluted suspensions but strongly increases the energy consumption in the case of concentrated suspensions.