Papers as functional green materials BLOCH Jean-Francis 1, a , ALI Imtiaz 1,2,b , PASSAS Raphael 1,c and ROLLAND DU ROSCOAT Sabine 3,4,5,d 1 G-INP, 461 rue de la Papeterie - CS 10065 - 38402 Saint-Martin d'Hères Cedex, France 2 Faculty of Materials Science and Engineering, Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi (23640), Khyber Pakhtunkhwa, Pakistan 3 Univ. Grenoble Alpes, 3SR, F-38041 Grenoble 4 CNRS, 3SR, F-38041 Grenoble 5 European Synchrotron Radiation Facility, F 38043 Grenoble a Jean-Francis.Bloch@pagora.grenoble-inp.fr, b imtiazali@giki.edu.pk, c Raphael.Passas@pagora.grenoble-inp.fr, d sabine.rollandduroscoat@3sr-grenoble.fr Keywords: 3D, microstructure, natural fibers, paper, mechanical and optical properties, recycling Abstract. Paper is constituted of natural fibers and represents a perfect example of structural multifunctional materials. Indeed, its fibrous structure is engineered to fit the different end use properties: both optical and mechanical properties are usually required. These requirements may lead to contradictory needs in terms of structure. The influence of the structure on the physical properties is classically tackled based on standard methods such as the estimation of the porosity. However, this macroscopic property is not sufficient in terms of optimization of the fibrous network. For example, fluid transport has to be controlled either in the bulk of the material or only at its surface in the case of health or printing applications. Consequently, the characterization at the macro-level of the structure has to be complemented with an experimental measurement at the fiber level. The X-ray synchrotron micro-tomography, an imaging technique, is based on X-ray transmission. It allows the structure to be analyzed in 3D. It was carried in a large instrument (ESRF, France). The characterization of samples containing different recycled fibers was carried out. In particular, the influence of the number of cycles of drying-pulping is studied. Both qualitative and quantitative characterizations are obtained. The use of recycled fibers may also be included in the elaboration of materials, taking into account the modification of the fibers in terms of morphology and mechanical properties, essentially flexibility. Mechanical properties (tensile and deformation) constitute the main examples of the analysis showing the effect of the recycling of natural fibers: the decrease in mechanical resistance of the fibrous network is explained in terms of the increase of the global porosity, essentially in the bulk of the materials. The profile of porosity in the thickness direction is found to be essential to understand the evolution of physical properties. Introduction Materials constituted of natural ligno-cellulosic fibers are developing nowadays due to the increasing stress on environmental aspects. The design of multi-scale materials is based on the structural properties at the fiber level. The objective is to reach multifunctional optical and mechanical macroscopic properties. A trend is to elaborate the fibrous structures using not only virgin fibers but also recycled fibers. Howard and Bichard in their work described the basic effects of recycling on macroscopic pulp properties [1]. Hubbe et al. reviewed the effect of papermaking and recycling on fiber properties [2]. However, the lack of characterization of the fibrous structure at the microscopic level impeded optimization. It is therefore necessary (i) to characterize the obtained structures at different scales, namely the micro-level and the macro-level, (ii) to evaluate the influence of the fiber properties on the physical properties of the fibrous structure. Advanced Materials Research Vol. 747 (2013) pp 715-718 © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.747.715 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 88.180.142.49-05/06/13,23:03:48)