Tannin–Phenol Formaldehyde Resins As Binders for Cellulosic Fibers: Mechanical Properties

A.S Hussein,K M Abdulla,K.I Ibrahim

doi:10.4236/nr.2011.22013

Abstract

In this study Eucalyptus tannin (T) was isolated from outer bark of Eucalyptus trees; as sodium phenoxide salt and used as extender or copolymer into phenol formaldehyde (PF) resin at five percent (10, 20, 30, 40 and 50)% W/W. Tan-nin-phenol formaldehyde (TPF) and tannin formaldehyde-phenol formaldehyde (TFPF) resins that synthesized in this study were evaluated as adhesive material for cellulosic fibers by study the mechanical properties of the composite sheets .The results show that the substituting of (PF) with tannin at (10 –50)% W/W give resins with mechanical properties comparable or near to those of pure (PF) , where the tensile strength at break (Tb) ranging from 15.15 Mpa to 22.27 Mpa as compared with 17.6 Mpa for pure (PF); while the impact strength properties (Im) of composites sheets increased with increased the (T) percents which were about 5.16 KJ/m2 for (TPF – 10%) and 7.21 KJ/m2 for (TPF - 50%) .On the other hand modification of (T) to tannin formaldehyde resin (TF) appear less performance at the results of this study , this effect probably to low penetration of (TFPF) resins between the small voids of cellulose fibers when soaked it in resin solutions. In general the results of this study indicate that the Eucalyptus tannin can be used for par-tial substitution of (PF) to produce resins with feasible mechanical properties and can be used in some applications of (PF) resins.

Highlights

Tannins are one of the natural products which are widely distributed in plant kingdom, they are composed of different phenolic compounds [1,2]
The results show that the substituting of (PF) with tannin at (10-50)% W/W give resins with mechanical properties comparable or near to those of pure (PF), where the tensile strength at break (Tb) ranging from 15.15 Mpa to 22.27 Mpa as compared with 17.6 Mpa for pure (PF); while the impact strength properties (Im) of composites sheets increased with increased the (T) percents which were about 5.16 KJ/m2 for (TPF-10%) and 7.21 KJ/m2 for (TPF-50%) .On the other hand modification of (T) to tannin formaldehyde resin (TF) appear less performance at the results of this study, this effect probably to low penetration of (TFPF) resins between the small voids of cellulose fibers when soaked it in resin solutions
The tensile strength of these composites showed in Figure 1 and Figure 2; it indicate that the tensile of the samples made by (10-30)% tannin or tannin formaldehyde decrease relative to that of the sample which made by pure phenol formaldehyde (PF) resin, where the tensile of the resins that contain tannin or tannin formaldehyde at all percent lower than of the pure PF except the resins that contain (40-50)% W/W tannin have tensile values higher than that of PF

Summary

Introduction

Tannins are one of the natural products which are widely distributed in plant kingdom, they are composed of different phenolic compounds [1,2]. Condensed tannins are polymeric phenolic compounds comprising from flavon-3-ol repeating units; Condensed tannins are known for their wide distribution in various softwood and hardwood, and it constitute about 90% of the total world production of commercial tannins [3]. Many studies show that the phenolic natural of tannin make it suitable for synthesis polymeric resins and adhesives; Hergert [4] stated that (30-50)% W/W tannin replacement of the amino and phenolic resins have been formulated into wood adhesives. Other studies deal with reaction of tannin (Wattle tannin) with formaldehyde to synthesis polymeric resins [6, 7]

Objectives

Results

Conclusion