Preparation of micro-molded exfoliated clay nanocomposites by means of ultrasonic technology

Abstract

Ultrasound micro-molding technology has been tested as a new method to get polymer/clay nanocomposites. Biodegradable polylactide (PLA) and poly (nona-methylene azelate) (PE99) have been used as polymer matrices, whereas different silicate clays have been assayed. The new technology is able to get specimens without evidences of degradation during processing. Only the use of organo-modified clays could give rise to a slight molecular weight decrease when the poly (alkylene dicarboxylate) sample was considered. Ultrasonic micro-molding has revealed effective to get directly nanocomposites with the final form required for a selected application, a homogeneous clay distribution up to a load of 6 wt-% and more interestingly exfoliated structures without being necessary the use of a compatibilizer agent between the organic polymer and the inorganic silicate clay. Transmission electron micrographs and X-ray diffraction profiles revealed exfoliated structure when N757, C20A, C25A, and N848 clays were employed.; Crystallization behavior of exfoliated PLA nanocomposites was highly peculiar since clay particles had an antinucleating effect that decreased the overall crystallization rate respect to the neat polymer. In addition, the incorporation of layers into growing spherulites increased the crystal growth rate. A typical crystallization effect was on the contrary observed for nanocomposites derived from the poly (alkylene dicarboxylate) sample.Peer ReviewedPostprint (published version

MMT and LDH organo-modification with surfactants tailored for PLA nanocomposites

“…Interestingly the T cc values are slightly enhanced with respect to that of PLA matrix, contrary to data generally obtained (showing a decrease of T cc ) and invoking nucleation effects [23] mainly due to intercalated morphologies. Stronger interactions and consequently exfoliated morphologies accounted for a different behaviour, as here observed, and resulting in a delayed crystallization [24,25]. After annealing the T g values increased as result of increased amorphous rigid fraction owing to raised crystallinity.…”

Dispersion of Functionalized Silica Micro- and Nanoparticles into Poly(nonamethylene Azelate) by Ultrasonic Micro-Molding

“…PE99 samples could be processed under relatively mild conditions, as previously established [15]. Thus, a minimum irradiation time of 1.2 s, low amplitude of 24 μm, and a moderate molding force of 300 N were sufficient to guarantee a 100% molding efficiency.…”

“…Therefore, optimization of processing parameters to obtain minimally degraded samples is an essential step in applying the new micro-molding technology. In this sense, we have recently found that it is possible to establish appropriate conditions for biodegradable polymers that could be interesting for the production of biomedical devices such as polylactide (PLA) [13], poly(butylene succinate) (PBS) [14], and poly(nonamethylene azelate) (PE99) [15]. Degradation logically increases with irradiation time and amplitude, but a minimum period is necessary to ensure complete injection into the mold, as well as a minimum amount of vibration energy.…”

Desenvolvimento e caracterização de bionanocompósitos pelo método de extrusão

“…Uma possível explicação seria que as moléculas do glicerol se intercalaram entre as camadas da MMT evitando a interação entre a matriz polimérica e a MMT. Por outro lado, na curva B, que representa a menor concentração de MMT estudada, o pico teve uma leve diminuição que pode ser explicada por uma possível esfoliação das nanopartículas de MMT devido à baixa concentração da argila e pela inclusão de cadeias poliméricas entre as camadas das nanopartículas (DÍAZ et al, 2014;GÜNISTER et al, 2007).…”

“…Além disso, o pico de difração em 2θ = 10,2° refere-se a um alto grau de desacetilação da quitosana (≥ 85 %). Por outro lado, os reforçadores tais como a MMT mostraram o pico característico em 2θ = 7,2° o qual corresponde a um espaçamento entre as camadas lamelares de 12,6 Å (d001) (DÍAZ et al, 2014). E as fibras de bambu exibiram picos a 2θ = 22,0° e dois picos de difração sobrepostos a 2θ = 15,7° e 17,7°, respectivamente, os quais podem ser atribuídos à estrutura polimórfica da celulose I ou celulose nativa (CHANG et al, 2010;LU et al, 2014).…”