Polypropylene Composites Reinforced with Biodegraded Sugarcane Bagasse Fibers: Static and Dynamic Mechanical Properties

Sandra Maria Da Luz,Antônio Pascoal Del'Arco Junior,Adilson Roberto Gonçalves,Sirlene Maria Da Costa,Silgia Aparecida Da Costa

doi:10.1590/1980-5373-mr-2015-0410

Abstract

The present work aimed to study sugarcane bagasse fibers pre-treated with fungi and using NaOH/ anthraquinone (AQ) in chemical pulping processes for applications in composite materials. Bagasse was decayed with 250 mg of Ceriporiopsis subvermispora inoculum in a 20 L bioreactor. After that, samples were submitted to similar conditions of decaying without inoculum charge. Decayed and undecayed fibers were treated with NaOH 12.5 wt%, 0.15 of AQ and a 12:1 (v/w) liquor:bagasse ratio at 160°C. Then, all obtained fibers were characterized according to their chemical composition. Dried biotreated (decayed) and control (undecayed) fibers were mixed through an extruder process with polypropylene. Later, composite granulates were injected directly in mold with cavities for tensile, flexural and shear tests. Composite materials with 10 and 20 wt% fibers were submitted to static mechanical standard tests and DMA (Dynamic Mechanical Analysis) to evaluate the effect of biotreatment. Biotreatment, cook time (pulping), and fiber content contributed to improvements in the mechanical properties of the composites. The interface between fiber and matrix was increased with the biotreatment and pulping of fibers. Furthermore, DMA results also showed that fiber incorporation into PP improved the modulus, mainly for biotreated fibers/PP composites. The Tg (tan δ data) from composites was dislocated at lower temperatures with respect to neat PP due to the influence of fibers on matrix.

Highlights

In recent years, there has been an increasing trend toward more efficient utilization of residual agroindustrial products such as sugarcane bagasse 1,2
The biodegradation of the lignocellulosic materials for white-rot fungi caused a certain softening of the material that can facilitate the subsequent pulping processes
Biotreated and control fibers (60 min) presented better results than that of other fibers, reaching a 48.2 and 92.5% increase for pulps biotreated with 10 and 20 wt% fiber, respectively, in relation to neat PP. These results show that the fiber content, biotreatment and time cooking for pulping contributed to improve the mechanical modulus, obtaining rigid composite materials

Summary

Introduction

There has been an increasing trend toward more efficient utilization of residual agroindustrial products such as sugarcane bagasse (generally known as “bagasse”) 1,2. Bagasse is the fibrous residue of sugarcane after crushing and the extraction of sugarcane juice and is one of the largest residual agriculture products in the world 4 Sugarcane bagasse is composed of three main macromolecular components: 50% cellulose, 25% polyoses and 25% lignin 5,6. Several processes and products have been reported that utilize bagasse as a raw material. These include the production of dissolving pulp, paper pulp, ethanol and the reinforcement of polymeric matrices . An initial pre-treatment with fungi was proposed, aiming to facilitate lignin and hemicellulose removal during chemical pulping, resulting in fibers with higher cellulose contents

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Conclusion