Polypropylene reinforced with semi-chemical fibres of Leucaena collinsii: Thermal properties

The incorporation of reinforcements with lower thermal stability than the matrix is one of the main handicaps of wood fibre composites. This work studies the influence of the incorporation of increasing quantities of semichemical Leucaena collinsii derived fibres on thermal properties, such as degradation temperature, glass transition, crystallization and melting temperatures, thermal conductivity and thermal expansion coefficient. With that aim, materials were tested by means of differential scanning calorimetry, thermogravimetric analysis, thermal conductivity analysis, thermomechanical analysis and dynamic mechanical analysis. It has been established that the thermal degradation occurs in two different phases, corresponding to the reinforcement around 260 °C and the matrix at 350°C. It has not been observed any influence on thermal transitions by the addition of reinforcement. The crystalline phase of the polymer enhances from 56 to 63% when a 50%w/w of fibres was added. Thermal conductivity increased by 44% when the fibre content was enhanced from 0 to 50%w/w. The thermal expansion coefficient evolution establishes that the conductivity drops when increasing the reinforcement composition.