Differentiation of non-black fillers in rubber composites using linear discriminant analysis of principal components

In the compounding of rubber composites, different non-black fillers are used to improve the physical properties, reduce the formulation cost, and provide special characteristics. Designing a rubber composite for a specific application needs the careful selection and differentiation of fillers based on its effect on processibility and overall material properties of the vulcanizate. However, fillers are usually classified according to their effect on reinforcement or function without much consideration to other properties such as vulcanization characteristics and heat aging resistance. Analyses of multiple properties are tedious when done in a univariate way. To differentiate non-black fillers with consideration to the various properties of rubber composites, linear discriminant analysis (LDA) of principal components (PCs) was used. This paper examines how vulcanization and mechanical properties can differentiate aluminosilicate, bentonite, and silica fillers in rubber composites. Aluminosilicate and silica were effectively differentiated from bentonite using the vulcanization characteristics and mechanical properties of rubber composites before heat aging. Better differentiation among the 3 non-black fillers was achieved when the mechanical properties of rubber composites after heat aging were included in the PC analysis. LDA required at least 6 PCs to correctly classify the non-black filler in 30 rubber composites.