INCREASING THE FUSION POINT AND ENTHALPY OF FUSION OF POLYAMIDES BY TREATMENT IN WATER

摘要

The present invention relates to a method for increasing at least one of the following two parameters of a polyamide: (i) its melting temperature and (ii) its melting enthalpy ΔHf in which: • this polyamide is contacted with solid state with water or steam at a temperature close to its crystallization temperature Tc for a time sufficient to effect this increase, and then the water (or water vapor) is separated from the The polyamide may be a homopolyamide or a copolyamide. It may be a mixture of polyamide and at least one other polymer, the polyamide forming the matrix and the other polymer (s) forming the dispersed phase. Advantageously, the polyamide is in divided form such as powder or granules. The granules thus treated can then be milled to make powders. The present invention also relates to a method of manufacturing polyamide articles by agglomeration of polyamide powders by melting using radiation, the powders having been treated according to the method mentioned above. or resulting from a grinding of granules treated according to the process mentioned above. As an example of radiation can be cited that provided by a laser beam (the method is called "laser sintering"). We can also mention the process in which a mask is placed between the powder layer and the radiation source, the powder particles protected from radiation by the mask are not agglomerated.