Optimization of the preparation process of biodegradable masterbatches and characterization of their rheological and application properties

Using glycerin as a plasticizer, polylactic acid (PLA) and titanium dioxide (TiO2) were blended and granulated using a twin-screw extruder to obtain a biodegradable white color masterbatch. The rheological properties of the masterbatch were characterized by a torque rheometer and a melt flow rate (MFR) tester. The dyeing force of the sample was characterized by measuring its whiteness index, lightness index, and yellowness index using a color meter, while the opacifying ability of the sample was characterized by measuring its light transmittance with a haze meter. Temperature sensors were set up in each zone of the extruder screws to measure their temperatures in real time. By using quadratic orthogonal rotation combination design, and in conjunction with a response surface methodology (RSM), the effects of processing conditions, such as screw shear speed, processing temperature, and glycerin content, on the opacifying ability of white PLA masterbatch were studied. In addition, Design-Expert software was used to simulate the relationship between various processing conditions and the opacifying ability of white PLA masterbatch. The experimental results showed that, when the glycerin content was 1%, the whiteness index of the masterbatch was highest and its color was brightest. When the glycerin content was 3.22%, the light transmittance of the masterbatch was lowest and its opacifying ability was strongest. This paper was the first to use response surface methodology to study optimization of the preparation process for biodegradable masterbatches.