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Valorização de Resíduos Provenientes de Café Através da Sua Incorporação em Compósi- tos Poliméricos
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Com o intuito de combater o desperdício produzido pela indústria do café e atender ao
conceito de economia circular estudou-se, neste trabalho, a possibilidade de incorporar borras
de café, previamente usadas para extração da bebida, em diversas matrizes poliméricas.
Foram usados um polímero sintético, PP, e dois biopolímeros, PBS e PBAT, através dos
quais se produziu o grão de compósitos por um processo de extrusão e adição de 5%, 20% e
40% (p/p) de borras.
Para estudar o efeito de plastificantes naturais foram adicionados 5% e 10% (p/p) de
óleo de soja e glicerol ao compósito de base polimérica PBS e 20% de borras de café.
Os grãos de compósitos produzidos foram utilizados para injetar diversos corpos de
prova com a finalidade de avaliar as seguintes propriedades: densidade, índice de fluidez,
dureza, resistência à tração, resistência ao impacto, absorção de água, perda de massa no solo,
degradação por exposição a radiação UV e hidrofobicidade.
Verificou-se que com o aumento da percentagem de borras a densidade de compósitos
com PP e PBAT tende a aumentar, enquanto a de compósitos com PBS tende a diminuir.
O índice de fluidez de compósitos com PP diminuiu linearmente com o aumento da
quantidade de borras incorporadas, enquanto a adição deste resíduo a biopolímeros resultou
no efeito contrário, o que provocou um aumento deste índice.
A dureza de compósitos com bases poliméricas de maior rigidez sofreu um decréscimo
pela adição de borras e a de compósitos formados com bases flexíveis levou ao seu aumento.
Na sua generalidade, quanto maior a percentagem de borras incorporada nos compósi-
tos, menores as resistências à tração e ao impacto.
Propriedades como a absorção de água, a perda de massa no solo e a degradação por
UV apresentam valores superiores quanto maior a quantidade de borras presente nos compó-
sitos. Estas são intensificadas aquando da utilização de bases poliméricas biodegradáveis.
A hidrofobicidade de compósitos formados por PP e PBAT mostrou-se tanto maior
quanto maior a percentagem de borras de café utilizada.
Com a adição de plastificante aos compósitos era esperado que propriedades como o
índice de fluidez, a resistência à tração e ao impacto e hidrofobicidade aumentassem, tendo-
se verificado resultados contraditórios e por isso inconclusivos.
In order to combat the waste produced by the coffee industry and meet the concept of circular economy, this project studied the possibility of incorporating coffee grounds, previ- ously used for extraction of the beverage in various polymeric matrices. A synthetic polymer, PP, and two biopolymers, PBS and PBAT, were used, through which the composite grain was produced by an extrusion process and addition of 5%, 20% and 40% (w/w) of coffee grounds. To study the effect of natural plasticizers 5% and 10% (w/w) soybean oil and glycerol were added to the composite with PBS and 20% coffee grounds. The produced composite grains were used to inject several specimens in order to eval- uate the following properties: density, melt flow index, hardness, tensile strength, impact strength, water absorption, mass loss in soil, degradation by exposure to UV radiation and hydrophobicity. It was found that with increasing percentage of coffee grounds the density of composites with PP and PBAT tends to increase, while that of composites with PBS tends to decrease. The melt flow index of composites with PP decreased linearly with the increase of the amount of coffee grounds incorporated, while the addition of this residue to biopolymers re- sulted in the opposite effect, which caused an increase of this index. The hardness of composites with polymeric basis of greater rigidity suffered a decrease by the addition of coffee grounds, and the hardness of composites formed with flexible poly- meric basis led to its increase. In general, the higher the percentage of coffee grounds incorporated in the composites, the lower the tensile and impact strengths. Properties such as water absorption, mass loss in soil, and UV degradation present higher values the greater the amount of coffee grounds present in the composites. These are intensified when biodegradable polymeric bases are used. The hydrophobicity of composites formed by PP and PBAT proved to be higher, the higher the percentage of coffee grounds used. With the addition of plasticizer to the composites it was expected that properties such as flow index, tensile strength, impact strength and hydrophobicity would increase, but the results were contradictory and therefore inconclusive.
In order to combat the waste produced by the coffee industry and meet the concept of circular economy, this project studied the possibility of incorporating coffee grounds, previ- ously used for extraction of the beverage in various polymeric matrices. A synthetic polymer, PP, and two biopolymers, PBS and PBAT, were used, through which the composite grain was produced by an extrusion process and addition of 5%, 20% and 40% (w/w) of coffee grounds. To study the effect of natural plasticizers 5% and 10% (w/w) soybean oil and glycerol were added to the composite with PBS and 20% coffee grounds. The produced composite grains were used to inject several specimens in order to eval- uate the following properties: density, melt flow index, hardness, tensile strength, impact strength, water absorption, mass loss in soil, degradation by exposure to UV radiation and hydrophobicity. It was found that with increasing percentage of coffee grounds the density of composites with PP and PBAT tends to increase, while that of composites with PBS tends to decrease. The melt flow index of composites with PP decreased linearly with the increase of the amount of coffee grounds incorporated, while the addition of this residue to biopolymers re- sulted in the opposite effect, which caused an increase of this index. The hardness of composites with polymeric basis of greater rigidity suffered a decrease by the addition of coffee grounds, and the hardness of composites formed with flexible poly- meric basis led to its increase. In general, the higher the percentage of coffee grounds incorporated in the composites, the lower the tensile and impact strengths. Properties such as water absorption, mass loss in soil, and UV degradation present higher values the greater the amount of coffee grounds present in the composites. These are intensified when biodegradable polymeric bases are used. The hydrophobicity of composites formed by PP and PBAT proved to be higher, the higher the percentage of coffee grounds used. With the addition of plasticizer to the composites it was expected that properties such as flow index, tensile strength, impact strength and hydrophobicity would increase, but the results were contradictory and therefore inconclusive.
Descrição
Palavras-chave
Borras de Café Compósitos PP PBS PBAT Plastificantes