Melt production and characterization of nanocomposites based on hdpe and coated calcium carbonate

In the first part of this thesis the production of calcium carbonate particles up to a nanometric dimension and their coverage process with fatty acid was studied. Calcium carbonate was obtained through the precipitation method, a process that allows obtaining high purity, low particle size and narrow size distribution. Operative parameters were studied with a design of experiment (DOE) approach and a consequent analysis of variance (ANOVA) to identify their effect on the final size of particles and to identify which parameters are the most influential. Coating process was conducted after that precipitate calcium carbonate (PCC) production and the influence of the fatty acid concentration on the quality of the final coating was studied. An innovative coverage method with a water softening step was introduce to evaluate the effect of water hardness on the process. In the second part of the thesis, melt production of PCC-HDPE nanocomposites was performed to investigate the toughening mechanism and to evaluate the effect of coverage concentration on the final mechanical properties. HDPE was chosen as matrix because of its wide use in many application, easy processability, ductility at room temperature, no chemical reaction with the filler, no biodegradation. Melt mixing was preferred to other techniques as in-situ polymerization or solvent mixing because the process is industrially scalable (the absence of solvent is more sustainable from an economic and environmental point of view), allows chain orientation (useful for some application), can work with polymers unsoluble in most common solvents and assure a better dispersion and uniformity of the product. In addition to the melt mixing of covered PCCs with the polymer also a one step process of PCCs coverage directly in the polymer melt was investigated. In this last part, partially covered PCCs were used to study the composites final properties. Covered PCCs of commercial origin were used for excluding any variability due to PCCs laboratory production