Tannin as substitute of phenols in the formulation of phenolic resins for the processing of composites reinforced with material from renewable source

Author(s)

Vilmar Barbosa Junior

• Document type: Master's Dissertation
• Press: São Carlos. , gráficos, ilustrações, tabelas.
• Institution: Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT)
• Defense date: 2007-03-23

Examining board members

Elisabete Frollini; Alcides Lopes Leão; Holmer Savastano Junior

• Advisor: Elisabete Frollini
• Field of knowledge: Engineering - Materials and Metallurgical Engineering
• Indexed in: Banco de Dados Bibliográficos da USP-DEDALUS; Biblioteca Digital de Teses e Dissertações - USP
• Location: Universidade de São Paulo. Biblioteca do Instituto de Química de São Carlos; IQSC/T1912

Abstract

In the present work, tannin (macromolecule obtained from natural source) was used as substitute of phenol in the formulation of phenolic matrix composites, due to the presence of phenolic rings in its structure. The tanninphenolic matrix composites (50% w/w of tannin) presented mechanical properties better than those of phenolic matrix composites showing that substitution of material obtained in large scale from non-renewable source (phenol) can be done by material obtained from natural source (tannin) without compromising the properties of the composite. The tanninphenolic matrix composites reinforced by different reinforcing agents (fibers and particules) were characterized by different techniques: Izod impact strength, thermogravimetry (TG), differential scanning calorymetry (DSC), infrared spectroscopy (IV), dynamic-mechanical analysis (DMA) and scanning electron microscopy (SEM). The Izod impact strength showed an improvement of mechanical properties due to the incorporation of natural fibres (jute and coir) in the phenolic and tanninphenolic matrices and also the better reinforcement of these matrices by jute fibres, when compared to coir fibres. The barks of Acacia Mimosa (high content of tannin) were also used as reinforcing agents of the tanninphenolic matrices in the forms of fibres and particules. The presence of these reinforcing agents in the matrix led to differences in the properties of the composites, highlighted by its lower water uptake. The presence of tannins in both reinforcing agents and matrix enhanced the fiber/matrix interactions, lowering the voids that increase water uptake. The coir fibres were treated by ultrasound, in order to evaluate the influence of this treatment in the properties of the fibres and, therefore, the composites reinforced with them. Besides chemical composition, all the fibres were characterized by the following techniques: X-ray diffraction, tensile strengh, infrared spectroscopy (IV), and scanning electron microscopy (SEM). The results revealed that the ultrasound is a promising treatment of fibres for the processing of composites, because it modifies the morphology of the surface of fibres without leading them to chemical degradation. The separation of fiber beams allows enhancement of the fiber/matrix interactions, leading to composites with lower water absorption capacity. Other treatments, such as mercerization, for example, improved the impregnation of the fibres by the pre-polymer, leading to composites with better properties, at expenses of partial degradation of lignocellullosic fibres. In the present work, composites were prepared using material obtained from renewable source, according to the purpose of this work. The obtained composites presents potential for non-structural applications, such as, internal panels of cars, for example. (AU)