The Primary Assessment of Rheological Properties

The method of flowability determination has also been standardized in Romania with STAS 5991-68. According to the Polish standard P-61/C-8936 the re-actoplastics in accordance with this method are subdivided into 4 classes with a core length of up to 50 mm — poor press-material 50-80 mm — press-material with a low flowability, 80-120 mm — press-material with an average flowability 120-180 mm — press-material with a high plasticity. 

No functional relationship between the flowability index according to Rashig and the other indices of the viscous-plastic properties has yet been establkhed. The flowability index determined by this method serves as a preliminary assessment of the suitability of the material for processing. 

The hardening rate of an aminoplast is determined by the amount of time necessary for a complete hardening of the specimen in the form of a conical test core. The specimen is pressed under conditions specifically indicated in the standards on the aminoplast  

The time of hardening is assumed to be the time of seasoning of a pressed test core which, judging by its appearance, seems to be of proper quality. 

The test-core method is used in Britain according to BS 2782 in the USA according to ASTM D731-57 in the FRG according to DIN-53465. 

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