Estudo do processamento e da degradação térmica do poli (Hidroxibutirato) e suas blenadas com poli (Caprolactona)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Aiming the development of high-performance biodegradable polymeric materials, the properties and the processing behavior of poly(3-hydroxibutyrate), PHB, and their blends with poly(ε-caprolactone), PCL, have been investigated. Two sample of PHB obtaneid from sugarcane and characterized by infrared spectroscopy and X-ray diffraction, with molecular weights of 2,4 x 105 g.mol 1, PHB(A) and 3,0 x 105 g.mol 1,PHB(B), were used. Differential scanning calorimetry (DSC) showed that the sample were different regarding the crystallinity degree, 49% for the PHB(A) and 60% for the PHB(B), the glass transition temperature (Tg), 2,0oC (A) and 4,4 oC (B), and the melting temperature, 178oC (A) and 171oC (B). The samples have been processed through high-pressure compacting,solid state extrusion, and injection molding. Cylindrical billets of PHB prepared by compaction at 200 MPa showed high shore hardness, 71,3 (0,9) D, and compression strength, 51,7 ( 1,0) MPa. The solid state processing was carried out by uniaxial compression, at temperature between the Tg and the melting point, through conical dies with extrusion draw ratio of 25 . It has produced extremely fragile materials with very high crystalline degrees (ca. 90%). Specimens of PHB(B) obtaneid by injection molding showed tensile strength, 24.53 (0,77) MPa, and modulus ,3.82 ( 0,06) GPa, compatible to diverse type of applications. A small decrease on the tensile strength, 21,88 ( 0,40) MPa, and modulus, 2,17 (0,25) GPa, and a high increase on the elongation at break, 86.7% (20,0) were noted for PHB(B)/PCL (70/30) blends prepared by injection molding. DSC analyses of this blend showed two Tgs, at 10,6oC for the PHB matrix, and at 62,9 oC for the PCL domains. The significant decrease on the Tg of PHB in the blend is possibly related to a partial miscibility of PCL in PHB. Thermal degradation studies of PHB were carried out by thermogravimetric methods, showing that the degradations occurs in only one step and that the presence of oxygen does not interfere in the degradation process.

ASSUNTO(S)

espectroscopia de infravermelho spectroscopy, infrared calorimetria microscopia eletronica polimeros extrusão em fase sólida degradação térmica processing phb calorimetry solid state extrusion thermal degradation electron microscopy phb pc processamento pcl

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