Influência da sequência de processamento nas propriedades de engenharia da blenda PP/SEBS contendo argila montmorilonita
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Tipo de produção
Dissertação
Data
2015
Autores
Torrecillas, H. V.
Orientador
Souza, Adriana Martinelli Catelli de
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Citação
TORRECILLAS, H. V. Influência da sequência de processamento nas propriedades de engenharia da blenda PP/SEBS contendo argila montmorilonita. 2015. 113 f. Dissertação (Mestrado em Engenharia Mecânica) - Centro Universitário da FEI, São Bernardo do Campo, 2015 Disponível em: . Acesso em: 14 maio 2015.
Texto completo (DOI)
Palavras-chave
Argila-Análise,Materiais nanoestruturados,Nanocompósitos
Resumo
Esta pesquisa cientifica investigou a influência da argila montmorilonita (MMT) em uma blenda polimérica tenacificada, constituída por uma matriz de polipropileno (PP) e uma fase dispersa de um elastômero termoplástico (TPE) a base de estireno, no caso, o SEBS. Foram estabelecidos dois grupos de nanocompósitos, para avaliar comparativamente o efeito do polipropileno graftizado com anidrido maleico (PPgMA) atuando como agente compatibilizante nas interações dos componentes da blenda com a argila. Outro grande enfoque estabelecido foi a investigação da influência da sequencia de mistura no estado fundido dos materiais no processamento do grânulo. Os compósitos foram processados na extrusora com rosca dupla corrotacional, mantendo-se fixa as concentrações dos componentes. Foram estabelecidas três diferentes sequências de mistura, sendo a extrusão realizada em única etapa (todos os materiais juntos) ou duas etapas, neste caso, a argila MMT foi misturada ao PP e depois ao SEBS ou a condição oposta, onde a argila MMT foi misturada inicialmente ao SEBS e depois ao PP. Os corpos de prova foram injetados e as propriedades mecânicas foram avaliadas por meio de ensaios de tração, impacto e flexão. Os resultados indicam uma influência significativa da argila MMT. Em geral, a argila promoveu um melhor balanço entre rigidez, expresso pelo incremento do modulo de elasticidade em tração e flexão, versus a tenacidade, expresso, pelo aumento da resistência ao impacto. Um desempenho ligeiramente superior foi observado para o grupo de compósito com PPgMA. A influência da sequência de processamento também afeta as propriedades mecânicas, sendo que os compósitos processados em única etapa obtiveram maior rigidez, porém compósitos processados em duas etapas apresentam maior resistência ao impacto. As propriedades térmicas foram analisadas por meio de ensaio DSC, TGA e HDT. O TGA indica que a presença da argila MMT promoveu uma retardância na temperatura de degradação térmica, porém acelerou significativamente a taxa deste processo de degradação. O DSC indicou que não houve alterações relevantes no nível de cristalinidade do PP presente nos nanocompósitos. A morfologia dos compósitos foi avaliada através da microscopia eletrônica de varredura (MEV) utilizando-se superfícies de fratura de corpos de prova provenientes dos ensaios de impacto. Evidenciou-se a fase elastomérica em forma de dispersão de gotas em uma matriz contínua e que o tamanho médio da gota foi reduzido com a incorporação da argila MMT, neste caso, a argila coibiu e ou limitou a coalescência das partículas. A sequência de mistura no estado fundido também afetou a variação do diâmetro médio das gotas, foi observado uma redução mais significativa na condição em que inicialmente a argila MMT foi misturada a fase dispersa (SEBS) e em seguida foi adicionada ao PP. Foi constatada também uma correlação significativa entre a variação do tamanho de gotas com o desempenho obtido no ensaio de impacto. O grau de intercalação da argila na matriz polimérica foi comprovado pelo ensaio de difração de raios X (DRX), indicando também, um maior nível de intercalação para o grupo de compósitos com PPgMA. As variações do índice de fluidez (IF) foram confirmadas em função da composição da pré-mistura no estado fundido para as variantes da fase dispersa (SEBS) e matriz (PP) conforme sequencia de processamento.
The aim of this scientific research is firstly to investigate the effect caused by a presence and the absence of montmorillonite nanoclay (MMT), over a referential blend made by Polypropylene (PP) and thermoplastic elastomers (TPE), by styrene base (SEBS). It was also established two groups of Nanocomposites in order to evaluate the effect of maleic anhydride grafted polypropylene (PPgMA) acting as a compatibilization agent to promote a better interaction between blend components and nanoclay. Another focus of this work is also to investigate the potential effect caused by different melt mixing sequence for pellet extrusion on nanocomposites. In this case, the nanocomposites have been prepared by melting blending in a co-rotating twin screw extruder under the same material concentration content. The melt-mixed occur on three different sequence as following: at once step (all material together) and two steps (nanoclay with PP matrix phase at firstly, and after with a disperse phase of SEBS) or (nanoclay with SEBS phase at firstly, and after, with a PP). The specimens were injected and the mechanical properties were evaluated through tensile, flexural and charpy impact strength tests. Results indicate a high significant effect of MMT over mechanical properties. In overall, Nanoclay promotes a better balance of stiffness, expressed by an increase of young and flexural modulus, versus the toughness, expressed by an increase of impact strength. A similar behavior but with slight superior performance was also observed on the composites group in a presence of PPgMA. The Different melt-mixture sequence also affects with a significance level the young’s and flexural module and impact strength. In summaries, nanocomposites melted at once step got the highest stiffness and a melt-mixture done at twice step got the highest performance for impact strength. The thermal properties were evaluated by differential scanning calorimetry (DSC), thermogravimetry (TGA) and heat deflection temperature analysis (HDT). The TGA results indicates that MMT reduce the degradation temperature zone, however, increase drastically the speed of degradation process rate. The DSC measurements don’t show any relevant changes for the PP crystallization rate. The morphology of nanocomposites were evaluated and checked via scanning electron microscopy (SEM), using surfaces of fractured Charpy impact test specimens. The morphological condition revealed the presence of elastomers phase in shape of a droplet-like dispersed phase over a continuous matrix and the mean of dropt diameter was reduced once the nanoclay was incorporated, in this case, the MMT restrict the coalescence of particles. Also the different melt-mixture sequence affected the change of medium dropped size, which was observed a strongest reduction for the sequence condition where the MMT was firstly melted with a dispersive phase (SEBS) and after with a PP. It was also detected a significant correlation between size drop variation with impact strength performance. An intercalated of the clay pallets in the polymer chain was confirmed by X-ray diffraction (XRD), showing a better intercalation level for the composite group in the presence of PPgMA. The changes of melt flow rate (MFR) was also detected due to the composition of pre-melting condition for the matrix phase (PP) e disperse phase (SEBS) according to melt mixture sequence.
The aim of this scientific research is firstly to investigate the effect caused by a presence and the absence of montmorillonite nanoclay (MMT), over a referential blend made by Polypropylene (PP) and thermoplastic elastomers (TPE), by styrene base (SEBS). It was also established two groups of Nanocomposites in order to evaluate the effect of maleic anhydride grafted polypropylene (PPgMA) acting as a compatibilization agent to promote a better interaction between blend components and nanoclay. Another focus of this work is also to investigate the potential effect caused by different melt mixing sequence for pellet extrusion on nanocomposites. In this case, the nanocomposites have been prepared by melting blending in a co-rotating twin screw extruder under the same material concentration content. The melt-mixed occur on three different sequence as following: at once step (all material together) and two steps (nanoclay with PP matrix phase at firstly, and after with a disperse phase of SEBS) or (nanoclay with SEBS phase at firstly, and after, with a PP). The specimens were injected and the mechanical properties were evaluated through tensile, flexural and charpy impact strength tests. Results indicate a high significant effect of MMT over mechanical properties. In overall, Nanoclay promotes a better balance of stiffness, expressed by an increase of young and flexural modulus, versus the toughness, expressed by an increase of impact strength. A similar behavior but with slight superior performance was also observed on the composites group in a presence of PPgMA. The Different melt-mixture sequence also affects with a significance level the young’s and flexural module and impact strength. In summaries, nanocomposites melted at once step got the highest stiffness and a melt-mixture done at twice step got the highest performance for impact strength. The thermal properties were evaluated by differential scanning calorimetry (DSC), thermogravimetry (TGA) and heat deflection temperature analysis (HDT). The TGA results indicates that MMT reduce the degradation temperature zone, however, increase drastically the speed of degradation process rate. The DSC measurements don’t show any relevant changes for the PP crystallization rate. The morphology of nanocomposites were evaluated and checked via scanning electron microscopy (SEM), using surfaces of fractured Charpy impact test specimens. The morphological condition revealed the presence of elastomers phase in shape of a droplet-like dispersed phase over a continuous matrix and the mean of dropt diameter was reduced once the nanoclay was incorporated, in this case, the MMT restrict the coalescence of particles. Also the different melt-mixture sequence affected the change of medium dropped size, which was observed a strongest reduction for the sequence condition where the MMT was firstly melted with a dispersive phase (SEBS) and after with a PP. It was also detected a significant correlation between size drop variation with impact strength performance. An intercalated of the clay pallets in the polymer chain was confirmed by X-ray diffraction (XRD), showing a better intercalation level for the composite group in the presence of PPgMA. The changes of melt flow rate (MFR) was also detected due to the composition of pre-melting condition for the matrix phase (PP) e disperse phase (SEBS) according to melt mixture sequence.