Caracterização e comparação do desempenho mecânico entre compósitos de polipropileno contendo fibras de vidro longas, e de poliamida 6 contendo fibras de vidro curtas
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Dissertação
Data
2021
Autores
Moraes, E.
Orientador
Bonse, B. C.
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MORAES, E. Caracterização e comparação do desempenho mecânico entre compósitos de polipropileno contendo fibras de vidro longas, e de poliamida 6 contendo fibras de vidro curtas. São Bernardo do Campo, 2021. 221 f. Dissertação (Mestrado em Engenharia Mecânica) - Centro Universitário FEI, São Bernardo do Campo, 2021 Disponível em: https://doi.org/10.31414/EM.2021.D.131339.
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Palavras-chave
compósitos poliméricos,PP com fibras longas,PA6 com fibras curtas,fibra de vidro
Resumo
Atualmente a poliamida reforçada com fibras de vidro curtas (PA SGF) tem sido usada amplamente na indústria automotiva em peças técnicas. Com baixo custo em comparação à poliamida 6 (PA6), o polipropileno reforçado com fibras longas (PP LGF) tornou-se um potencial candidato para substituir peças metálicas. Estes dois compósitos, na forma de grânulos, contendo 30%, 40% e 50% de fibras em massa, foram injetados em corpos de prova, sendo alguns envelhecidos a 140°C por 500 h e 1000 h. Os corpos de prova, envelhecidos e não, foram submetidos a ensaios mecânicos estáticos e dinâmicos, térmicos, químicos e morfológicos. Um comparativo entre propriedades destes compósitos mostrou que com o aumento nos teores de fibras, houve um aumento linear nos módulos elásticos e nas resistências à tração e à flexão de ambos. A tenacidade e a resistência ao impacto também apresentaram aumento, mas não linearmente, enquanto a deformação na ruptura e a resistência à fadiga flexural diminuíram. O PP com 40% de fibras longas (PP 40 LGF) apresentou resistência ao impacto superior, módulo elástico em tração e resistência à flexão similar à da PA6 com 30% de fibras curtas (PA6 30 LGF). O compósito PP 50 LGF apresentou módulo elástico em tração igual ao do PA6 40 SGF, resistência à flexão superior ao compósito PA6 40 SGF e muito próximo à do PA6 50 SGF, e resistência ao impacto superior à do PA6 30 SGF. A estabilidade térmica, grau de cristalinidade e temperatura de fusão se mantiveram praticamente constantes com o aumento no teor de fibras. Após o envelhecimento térmico a 140 ºC por 500 e 1000 horas, ensaios de espectroscopia no infravermelho evidenciaram a degradação termo-oxidativa nas amostras de PP LGF e mesmo com o aumento no grau de cristalinidade apontado pelo DSC, teve redução de algumas propriedades. Para os compósitos PA6 SGF pode ter ocorrido uma transformação de fase ?? mais dúctil, para uma fase ?? menos dúctil e mais resistente, elevando algumas propriedades. O envelhecimento também prejudicou a adesão fibra/matriz, facilitando o arrancamento e o descolamento das fibras, observado por microscopia eletrônica de varredura, diminuindo a resistência e fragilizando ambos os compósitos, especialmente quando foram submetidos à fadiga por flexão. A similaridade entre várias propriedades mostrou que há grande potencial da substituição da PA6 SGF pelo PP LGF, entretanto ensaios adicionais são necessários, preferencialmente em uma peça real.
Currently, polyamide reinforced with short glass fibers (PA SGF) has been used extensively in the automotive industry in technical parts. Due to its lower cost compared to polyamide 6 (PA6), long fiber reinforced polypropylene (PP LGF) has become a potential candidate for replacing metal parts. Pellets of these two composites containing 30 wt%, 40 wt% and 50 wt% fibers, were injection molded into test specimens, some of which were aged at 140 ° C for 500 h and 1000 h. The aged and non-aged specimens were subjected to mechanical testing, both static and dynamic, as well as thermal, chemical, and morphological testing. A comparison between properties of these composites showed that with increasing fiber content, elastic moduli and tensile and flexural strength increased linearly. Toughness and impact strength also increased, however not linearly, while strain at break and flexural fatigue strength decreased. PP containing 40 wt% long fibers (PP 40 LGF) showed superior impact strength, and both tensile modulus and flexural strength similar to that of PA6 containing 30 wt% short fibers (PA6 30 LGF). The PP 50 LGF composite showed a tensile modulus equal to that of PA6 40 SGF, flexural strength superior to the PA6 40 SGF composite and very close to that of the PA6 50 SGF, and higher impact strength than that of PA6 30 SGF. Thermal stability, degree of crystallinity and melting temperature remained practically constant with the increase in fiber content. After thermal aging at 140 ºC for 500 and 1000 hours, infrared spectroscopy tests showed thermo-oxidative degradation in the samples of PP LGF and even with the increase in the degree of crystallinity indicated by DSC, some properties decreased. For PA6 SGF composites, a phase transition may have occurred of the more ductile ? phase to a stronger and less ductile ? phase, increasing some properties. Aging also impaired fiber/matrix bonding, facilitating fiber pullout and debonding, as observed by scanning electron microscopy, hence decreasing strength of both composites, especially when subjected to flexural fatigue. The similarity between several properties have shown there is great potential for the replacement of PA6 SGF by PP LGF, however additional tests are necessary, preferably on a real part.
Currently, polyamide reinforced with short glass fibers (PA SGF) has been used extensively in the automotive industry in technical parts. Due to its lower cost compared to polyamide 6 (PA6), long fiber reinforced polypropylene (PP LGF) has become a potential candidate for replacing metal parts. Pellets of these two composites containing 30 wt%, 40 wt% and 50 wt% fibers, were injection molded into test specimens, some of which were aged at 140 ° C for 500 h and 1000 h. The aged and non-aged specimens were subjected to mechanical testing, both static and dynamic, as well as thermal, chemical, and morphological testing. A comparison between properties of these composites showed that with increasing fiber content, elastic moduli and tensile and flexural strength increased linearly. Toughness and impact strength also increased, however not linearly, while strain at break and flexural fatigue strength decreased. PP containing 40 wt% long fibers (PP 40 LGF) showed superior impact strength, and both tensile modulus and flexural strength similar to that of PA6 containing 30 wt% short fibers (PA6 30 LGF). The PP 50 LGF composite showed a tensile modulus equal to that of PA6 40 SGF, flexural strength superior to the PA6 40 SGF composite and very close to that of the PA6 50 SGF, and higher impact strength than that of PA6 30 SGF. Thermal stability, degree of crystallinity and melting temperature remained practically constant with the increase in fiber content. After thermal aging at 140 ºC for 500 and 1000 hours, infrared spectroscopy tests showed thermo-oxidative degradation in the samples of PP LGF and even with the increase in the degree of crystallinity indicated by DSC, some properties decreased. For PA6 SGF composites, a phase transition may have occurred of the more ductile ? phase to a stronger and less ductile ? phase, increasing some properties. Aging also impaired fiber/matrix bonding, facilitating fiber pullout and debonding, as observed by scanning electron microscopy, hence decreasing strength of both composites, especially when subjected to flexural fatigue. The similarity between several properties have shown there is great potential for the replacement of PA6 SGF by PP LGF, however additional tests are necessary, preferably on a real part.