Elasticity of the polymers and composite forces of Van Der Wall

O objetivo do trabalho é estabelecer o vínculo entre as pesquisas teóricas e experimentais para melhor compreensão das diversas características da Engenharia e Ciência dos Materiais utilizando os seguintes polímeros e seus compósitos: Borracha termoplástica-Butadieno-estireno (SBS); Nanocompósito Borracha termoplástica-Bentonita modificada; Polipropileno puro (PP) e Nanocompósito Polipropileno intercalado.Todos os cálculos foram realizados usando o código VASP (Vienna Ab-initio Simulation Program), que é um pacote complexo para realizar simulações de dinâmica molecular quântica (MD) ab-initio usando pseudopotenciais e um conjunto de bases de ondas planas. Fizemos dois casos para os cálculos, primeiro consideramos os átomos de H livres e, segundo, consideramos todos os átomos livres para serem movidos. Os graus de liberalidade dos átomos C e H foram estudados como uma tentativa de compreender a redução da elasticidade da borracha. Este trabalho mostrou a ajuda de métodos computacionais para interpretar dados experimentais como Ressonância Magnética Nuclear (RMN), raios-X, ensaios mecânicos, e são importantes ferramentas para o estudo do processo molecular capaz de prever o comportamento do sistema. Finalmente, a energia mais alta na molécula de SBS que não foi relaxada é uma estimativa da instabilidade do estado.The objective of this work is to establish a link between theoretical and experimental researches to better understand the various characteristics of Materials Engineering and Science using the following polymers and their composites: Thermoplastic Butadiene-Styrene (SBS) Rubber; Nanocomposite Thermoplastic rubber-Bentonite modified; Pure Polypropylene (PP) and Nanocomposite Interpolated Polypropylene. All calculations were performed using the Vienna Ab-initio Simulation Program (VASP) code, which is a complex package to perform ab-initio quantum molecular dynamics (MD) simulations using pseudopotentials and a set of flat wave bases. We made two cases for the calculations, first we consider the H atoms free and, second, we consider all the atoms free to be moved. The degrees of liberality of atoms C and H were studied as an attempt to understand the reduction of rubber elasticity. This work showed the powerful help of computational methods to interpret experimental data such as Nuclear Magnetic Resonance (NMR), X-rays, mechanical tests, and are important tools for the study of the molecular process capable of predictingsystem behavior. Finally, the highest energy in the SBS molecule that has not been relaxed is an estimate of the state instability.Fil: Farias Guimarães, Tereza Cristina de. Universidade do Estado da Bahia; BrasilFil: Gil Rebaza, Arles Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Pachekoski, Wagner Maurício. Universidade Federal de Santa Catarina; Brasi

The influence of the industrial processing on the degradation of poly(hidroxybutyrate) - PHB

PHB was characterized after different industrial processes by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Melt Flow Index (MFI), Complex Dielectric Relaxation (CDR) and Size Exclusion Chromatography (SEC). Some properties of PHB were investigated before and after processing, in order to understand how temperature and other extrusion or injection conditions affect the polymer degradation. All the processed samples showed an increasing in the melt flow index, a decreasing of the dynamic crystallization temperature, and a reduction in the molar mass, suggesting some degradation. The molar mass reduction after processing, predicted when only thermal degradation is considered, was calculated in function of the kinetic parameters, such as constant thermal degradation and residence time during the industrial processing. It was found that the real molar mass reduction was higher than the theoretical value, indicating an important contribution of the shearing of polymeric chains during processing in the PHB degradation