Helson M. Da Costa Journal of Engineering Research and Application www.ijera.com ISSN : 2248-9622, Vol. 8, Issue 9 (Part -III) Sep 2018, pp 15-27 www.ijera.com DOI: 10.9790/9622-0809031527 15 | Page An Empirical Method For Determination Of Kinetic Models And Kinetic Parameters Associated To Thermo-OxidativeDegradation Of Recycled Polypropylene (PP) Helson M. Da Costa *,** , Valéria D. Ramos ** , Leonardo L. Esteves * , Mônica C. De Andrade * *Instituto Politécnico do Rio de Janeiro (IPRJ), Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, Rio de Janeiro (RJ), Brasil. ** Universidade Estácio de Sá (UNESA), Nova Friburgo, Rio de Janeiro (RJ), Brasil. Corresponding Author; Helson M. Da Costa ABSTRACT The kinetics of thermo-oxidative degradation of polypropylene recycled (PP rec.) was investigated using thermogravimetric (TG) analysis in air atmosphere. An empirical methodology was developed and it is the result of isoconversional methods (Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall methods) combined with Coats-Redfern method, one-sample t test and IKP method. It was observed that the kinetic mechanism of the PP rec. degradation is dependent of the heating rate used. In lower heating rates, the diffusion mechanism is ruling and D i -type equations can be used. Otherwise, in higher heating ratesthe reaction rate is proportional to concentration of fraction remaining of reactant(s) raised to a power and F i -type equations becomes as important as D i -type equations. PP rec. sample was also submitted to eight extrusion cycles prior to TG analysis (PP rec. / 8), and it was noted that the mechanochemical degradation combined with thermo-oxidation produced an expressive reduction in the activation energy values. In addition, there was also a simplification of kinetic mechanism with only F i -type equations being adequate for description of the process. Keywords-Polypropylene, recycling, thermal analysis, degradation, kinetics --------------------------------------------------------------------------------------------------------------------------------------- Date Of Submission:05-09-2018 Date Of Acceptance: 21-09-2018 --------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION One major problem associated with the applications of polymers is their instability to weathering. Organic materials are susceptible to attack by atmospheric oxygen and, in the case of synthetic organic polymers, oxidation degradation is often accelerated by environmental, biological and physical factors, e.g., sunlight, ozone, heat, radiation, mechanical stress, traces of transition metals ions, water, pollutants and micro-organisms [1-7]. In any of these situations, the oxidative processes lead to irreversible deterioration of the useful properties (e.g. mechanical properties: tensile, flexural and impact strengths; surface appearance: gloss, texture and color) of polymer artefacts and are reflected in poor performance or catastrophic failures. The extent of oxidative degradation, however, is not the same in all polymers: it depends on intrinsic chemical structure (the nature, number, and relative position of the chemical groups along the chain; magnitude of intramolecular forces – primary valence bonds – plus intermolecular forces – secondary valence bonds; crystallinity versus amorphicity; backbone rigidity; branch versus linear structures; crosslinking; etc.) and susceptibility to external influences during lifetime of the polymer product. Among polymeric materials, polyolefins always receive considerable attention because possess high mechanical strength, low density, flexibility at low temperatures, high impact strength, good electrical insulation properties, etc. However, as in most other polymers, polyolefins are also susceptible to oxidative degradation and understanding about the mechanisms of the process has been the subject of intensive research over decades [3-7]. Once that thermal stability of polymer compounds is the most important factor for polymer applications, the extraction of the maximum relevant information from non-isothermal data, obtained by thermal analysis (TA) techniques, as well as the modelling of the kinetic process become critical tasks. Nevertheless, the problem of the validity and applicability of mathematical models in kinetic analysis of TA data is still considered a very controversial topic. Several authors have pointed out that the decomposition of a solid is a heterogeneous process and, therefore, the description of which with homogeneous equations is a meaningless exercise. In addition, a single thermogravimetric analysis, for example, is considered unable to distinguish RESEARCH ARTICLE OPEN ACCESS