Compósitos polímero-madeira preparados por polimerização in situ de metil metacrilato usando aditivos bifuncionais

Abstract

ResumoO presente trabalho teve por objetivo a confecção de compósitos polímero-madeira por meio de polimerização in situ de metil metacrilato (MMA), utilizando ácido metacrílico (MAA) e glicidil metacrilato (GMA) como agentes de ligação e reticulação. Amostras de madeira de guapuruvu foram impregnadas em um sistema de vácuo e pressão e polimerizadas em estufa a 90°C por 10h, usando 1,5% de peroxido de benzoíla como catalisador. Os compósitos foram caracterizados por meio de testes de absorção de água e estabilidade dimensional, molhabilidade, ATR-IR, TGA, MEV e WPG. Os espectros de ATR-IR mostraram incrementos nas bandas a 1746, 1460, e 1145 cm -1 , referentes as estruturas químicas dos polímeros dentro da madeira, confirmado posteriormente pelas imagens de MEV. A termogravimetria apontou reações químicas entre os copolímeros e a parede celular da madeira nos compósitos com GMA e MAA. Os compósitos preparados com MMA apresentaram incrementos acima de 50% nas propriedades higroscópicas e de estabilidade dimensional, entretanto a adição de GMA e MAA resultou em maiores incrementos nas mesmas propriedades, entre 66-90%. Palavras-chave: polimerização por radicais livres, Schizolobium parahyba, catálise térmica, reticulantes, agentes de ligação. AbstractWe prepared wood/polymer composites by in situ polymerization of methyl methacrylate (MMA) using glycidyl methacrylate (GMA) and methacrylic acid (MAA) as cross-linkers and coupling agents. The guapuruvu wood samples were impregnated in a vacuum/pressure system and polymerized at 90 °C for 10 h, using benzoyl peroxide at 1.5 wt % as catalyst. We characterized the composites through water uptake, dimensional stability tests, wettability, ATR-FTIR spectroscopy, TGA, SEM, and WPG. ATR-FTIR spectra showed an increase of the peaks at 1746, 1460, and 1145 cm -1 , corresponding to the chemical structures of the polymers into the pores and capillaries of the wood. This was further confirmed in the SEM images. TGA curves showed evidences for a chemical interaction between the copolymer and the wood cell wall in the composites with GMA and MAA. Hygroscopicity and dimensional stability properties of the composites prepared with MMA improved by 50%. Nevertheless, the addition of GMA and MAA resulted in additional increases for hydrophobicity and dimensional stability of the samples, ~ 66 -90%.

Solution Copolymerizations of N‐Vinyl‐2‐Pyrrolidone with Acrylic Acid, Methacrylic Acid and Vinyl Acetate for Applications in Hair Cosmetics

“…On the other hand, the copolymerization of NVP with VA can lead to reduction of the thermal stability of the final product, as also observed in the present work. [33] The DSC curves of the obtained copolymers are shown in Figure 11. The DSC curve of the copolymer P(VP-co-VA) is not presented because it produced large amounts of volatiles and could not be analyzed accurately.…”

“…The band positioned at 1.450 cm -1 is related to the -CH 3 bond present in the acid, while band in the region 1.200-1.300 cm -1 is characteristic of the axial straining of the CO bond of carboxylic acids. [33] The presence of the characteristic PMAA signals in the spectrum of the copolymer indicates the incorporation of MAA into de PVP chains.…”