Evaluation of PHB/Clay nanocomposite by spin-lattice relaxation time

Abstract

Poly(3-hydroxybutyrate) (PHB) based on nanocomposites containing different amounts of a commercial organically modified clay (viscogel B7) were prepared employing solution intercalation method. Three solvents, such as: CHCl 3 , dimethylchloride (DMC) and tetrahydrofuran (THF) were used. The relationship among the processing conditions; molecular structure and intermolecular interaction, between both nanocomposite components, were investigated using a nuclear magnetic resonance (NMR), as a part of characterization methodology, which has been used by Tavares et al. It involves the hydrogen spin-lattice relaxation time, T 1 H, by solid state nuclear magnetic resonance, employing low field NMR. X ray diffraction was also employed because it is a conventional technique, generally used to obtain the first information on nanocomposite formation. Changes in PHB crystallinity were observed after the organophilic nanoclay had been incorporated in the polymer matrix. These changes, in the microstructure, were detected by the variation of hydrogen nuclear relaxation time values and by X ray, which showed an increase in the clay interlamelar space due to the intercalation of the polymer in the clay between lamellae. It was also observed, for both techniques, that the solvents affect directly the organization of the crystalline region, promoting a better intercalation, considering that they behave like a plasticizer.

Obtenção de nanocompósito de EVA/sílica e caracterização por ressonância magnética nuclear no estado sólido

“…Logo o estudo por RMN desses materiais deve ser realizado no estado sólido [15][16][17][18][19][20][21][22][23] . Para o estudo de materiais sólidos, a determinação dos tempos de relaxação spin-rede, com constante de tempo (T 1 H) e spin-rede no eixo rotatório, com constante de tempo T 1ρ H, especialmente este último propiciam a geração de informação pormenorizada sobre a relação da nanoestrutura (morfologia)/propriedades dos materiais híbridos, o que faz com que o uso da RMN no sólido seja bastante atrativo para o estudo e entendimento do comportamento da nanoestrutura em nanocompósitos poliméricos, visto que os tempos de relaxação geram respostas em nível molecular [15,[23][24][25][26][27][28][29][30][31][32][33][34][35] . …”

Inorganic-organic hybrids based on poly (ε-Caprolactone) and silica oxide and characterization by relaxometry applying low-field NMR

“…According to this result, at least two types of molecular organization structure occurred in this semicrystalline polymer (Table 3). One was derived from the amorphous phase, whose protons had shorter relaxation time, and the second one referred to the protons that are constricted in the crystalline and/or rigid phase, which had longer relaxation times 32 . The spin-lattice relaxation time measurements revealed that the PCL-silica oxide hybrids were heterogeneous, as expected.…”

“…Figure 6 shows the T 1 ρH curves with one fit, for PCL/Aerosil ® R972 and be attributed to the poor dispersion of unmodified silica oxide in the PCL matrix. However, for all hybrid ratios, the rigid domain, which has the highest relaxation parameter value, controls the relaxation process [31][32][33] . …”

Polyhydroxyalkanoates (PHAs) for food packaging

“…There have been a number of recent studies dealing with the characterisation of PHB-and PHBV-based nanocomposites using MMTs and LDHs prepared either by solution casting (Lim et al, 2003;Bruzaud and Bourmaud, 2007;Hsu et al, 2007;Bruno et al, 2008;Wu et al, 2008;Erceg et al, 2009Erceg et al, , 2010 or by melt intercalation (Maiti et al, 2007;Hablot et al, 2008;Sanchez-Garcia et al, 2008;Ohashi et al, 2009;Botana et al, 2010). The fabrication of PHB/MMT nanocomposites through solution casting was first described by Lim et al (2003); however, the mechanical and rheological properties of the modified films were not reported at that time.…”