The use of smoke acid as an alternative coagulating agent for natural rubber sheetsÕ production Vanda S. Ferreira a , Ione N.C. Re ˆgo a , Floriano Pastore Jr. a, * , Mariana M. Mandai b , Leonardo S. Mendes b , Karin A.M. Santos b , Joel C. Rubim b , Paulo A.Z. Suarez b, * a Laborato ´rio de Tecnologia Quı ´mica (LATEQ), Instituto de Quı ´mica, Universidade de Brası ´lia, CP 4574, 70919-970, Brasilia-DF, Brazil b Laborato ´rio de Materiais e Combustı ´ veis (LMC), Instituto de Quı ´mica, Universidade de Brası ´lia, CP 4478, 70919-970, Brasilia-DF, Brazil Received 2 June 2003; received in revised form 7 June 2004; accepted 7 June 2004 Available online 7 August 2004 Abstract A comparative study of rubber sheets obtained using formic, acetic, and smoke acid as coagulants is shown for latex obtained from native Amazonian trees and also from commercial cultivated trees. The evaluation of both processes of coagulation was car- ried out by spectroscopic and physical–chemical analysis, showing no differences in the rubber sheets obtained. This new method of rubber sheet preparation was introduced into Amazonian rainforest rubber tapper communities, which are actually producing in large scale. The physical–mechanical properties were similar among a large sheets made by different rubber tapper communities using this new method. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Hevea brasiliensis; Natural rubber sheet; Smoke acid; Coagulating agent 1. Introduction In order to protect the Amazon Rainforest, the Bra- zilian government has created, in the last decades, several protected areas where the natives live by extract- ing oils, nuts, fruits, seeds, flavors, rubber, etc., without environmental damage. They also produce charcoal from logs collected from the soil and rivers. Concerning rubber production, traditionally the Amazonian rubber tapper collects the latex in small cans and leaves it standing until spontaneous coagulation is complete. After a few days, the forest men obtain a coagulum which is sold without further processing. This very low quality product can be used for manufacturing only after several purification steps. For this reason, the price of the coagulum is very low and sometimes has no economic interest. The Laboratory for Chemical Technology (LATEQ) at the University of Brası ´lia (UnB) has focused its efforts on developing clean and simple technologies in order to increase the aggregated value of the products commercially produced by the natives of the Amazon Rainforest living in protected areas. One of these pro- jects is known as TECBOR (alternative technology for Amazonian rubber production), which is developed in association with the Brazilian Institute for Environ- mental and Renewable Resources (IBAMA). The aim of this project is to develop new technologies to enable forest people to produce natural rubber with higher quality. Rubber sheet is an example of a high quality prod- uct. Usually, this raw material is produced by latex 0960-8524/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2004.06.008 * Corresponding authors. Tel.: +55 61 3072162; fax: +55 61 2734149 (P.A.Z. Suarez). E-mail addresses: lateq@unb.br (F. Pastore Jr.), psuarez@unb.br (P.A.Z. Suarez). Bioresource Technology 96 (2005) 605–609