Agradeço aos meus pais e minha irmã, pelo amor e incentivo de sempre, e que foram fundamentais para a conclusão de mais essa etapa.Agradeço à minha orientadora Profª. Drª. Lucia Mei, pela confiança, paciência e ensinamentos.Agradeço ao colega Ivanei Pinheiro, pela grande contribuição para este trabalho e conselhos.À Luana Pinheiro e Edy Merendino da Tetra Pak Brasil, por fornecerem o papel reciclado, material imprescindível neste trabalho.Ao Prof. Dr. Derval Rosa, por disponibilizar o equipamento de ensaio de dureza Shore D de seu laboratório, na UFABC Santo André.À equipe do LRAC, professores, e demais funcionários da Faculdade de Engenharia Química.Aos meus amigos do laboratório de Biomateriais, Larissa, Ívi, Karine e Guilherme, pela companhia, suporte, paciência, risadas e por tornarem os dias mais leves. Aos meus amigos de Unicamp, Patrícia, Mayara, Eiko e Ivander, pela ajuda e incentivo.À todos os meus amigos, pelo apoio e compreensão ao longo desse período.À CAPES pelo apoio financeiro.Palavras-chave: Polimerização in situ, poliestireno, embalagens longa vida, papel reciclado ABSTRACT Every day, millions of carton packages (CP) are consumed worldwide. Being derived from virgin cellulose, the paperboard that constitutes the major part of these packages has good mechanical properties. Currently, the recycling rate of these packages does not follow the rate of consumption; thus, the high volume of quality paper that is disposed, and not recovered, creates an environmental liability that could be inserted in many applications not explored yet. Studies of practical applications of the paper obtained from CP recycling, or in combination with other materials, are scarce. In this work, in situ polymerization of styrene, in absence of solvents, was carried out in recycled paper from carton packages through immersion process, in the presence of benzoyl peroxide as thermal initiator. The presence of polystyrene in the paperboard was confirmed by Fourier transform infrared spectroscopy. Mechanical (tensile and flexural), morphological and structural properties, Shore-D hardness, thermogravimetric analysis, and water uptake of the paper, as well as the composite, were evaluated for comparison. Results showed that the mechanical properties and hardness of the composite are superior to the utilized recycled paper. Thermal stability of the material was improved with the presence of polystyrene, with the maximum degradation temperature of the composite being higher than the paper. A significant decrease in water uptake of the composites confirmed the hydrophobic nature of polystyrene present in the final product. Possible applications of the material can be appropriate for indoor environment with low load demand.