Synthesis by interfacial polycondensation of polyamide capsules with various sizes. Characteristics and properties.

摘要

Polyamide capsules are synthetized by interfacial polycondensation in an inverse dispersion (water in oil). Four processes are developped to obtain capsules of various sizes (plane films: diameter=infinity; millicapsules: (diameter=1-5mm; minicapsules: diameter=100-300 mu m; microcapsules: diameter=1-10 mu m). Capsules have been characterized by various techniques: their size by granulometry, their weight composition by gravimetry and their structure and the thickness of the membrane by microscopy investigations (SEM). The dry polyamide represents only 6 to 10% of the total mass of the capsules, the rest is water. All capsules are hollow particules. The membrane presents a disymetric structure, smooth for the aqueous phase, heterogenous for the organic phase and alveolar for the cross section. The membrane thickness depends on the reaction conditions and on the capsule size. The capsules properties are studied on the minicapsules. Capsules are permeable: 80% of the initial encapsulated poly(ethylenimine) (Mw= 70 000g/mol) are released out in 3 months. Capsules are breakable: they are all destroyed after 5mn of ultrasonic irradiation (power 80W). [References: 6]