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

Bryan B. Pajarito

doi:10.1515/secm-2019-0010

Abstract

Abstract 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 frombentonite 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.

Highlights

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
The minimum number of principal components (PCs) needed to represent the variation in the material properties of rubber composite depends on the type of data input
Pretreatment of material properties with principal component analysis (PCA) allows visualization of data patterns that are related to the type of nonblack filler

Summary

Introduction

Abstract: 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. The analyzed properties were vulcanization characteristics (minimum and maximum elastic torques, scorch and curing times, cure rate index) and mechanical properties (tensile stress at specified elongations, tensile strength, strain at break, hardness) before and after heat aging. Rubber compounders use these properties to compare and assess different product formulations. This paper evaluates how vulcanization characteristics and mechanical properties before and after heat aging of rubber composites differentiate and predict the type of non-black filler using LDA of PCs. This paper determines which specific set of material properties, e.g. vulcanization characteristics, mechanical properties, or combined, best discriminate between different types of nonblack filler in rubber composites

Materials

Compounding and vulcanization of rubber composites

Measurement of material properties

Data analysis

Results and discussion

Conclusion