THERMAL ANALYSIS OF SERICIN COCOON
1974 Volume 30 Issue 10 Pages T459-T464
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1974 Volume 30 Issue 10 Pages T459-T464
The thermal properties of sericin cocoon shells have been studied and discussed about their thermal structural changes from the results of calorimetric measurements (Rigaku Denki Differential Scanning Calorimeters; DSC), Thermal Mechanical Analysis and Dynamic Mechanical Loss Tangent (Tan δ). The obtained results were summarized as follows:
(1) When the cocoon shells were treated in humid atmosphere, the degree of solubility of sericin cocoon shells in water decreased markedly. And sericin cocoon (Sericin A) dried at the room temperature and sericin cocoon (Sericin B) dried in humid atmosphere (90 C for 2 hours) begin to dissolve in water, at 60°C and 80°C, respectively. But the difference in the solubility between sericin A and B was not recognized in boiling water.
(2) According to DSC curves of sericin treated with water of various temperatures for 30 min, the temperature of endothermic peaks shifts about 10 degrees to higher region. From the results of density measurements also suggest that this shift is mainly due to the structual change of sericin into more stable state.
(3) It is recognized in tan δ measurement that the sericin's main chain begins to move at above 160°C. And this temperature is similar to the degradation temperature appeared on DSC curves of fibrous sericin. Furthermore it is confirmed by the measurements of tan δ and change in the length of fibrous sericin that the endothermic peaks appeared in the range from 230-240°C were caused by breakings of the inter and intra-molecules' bondings of sericin.
(4) When the sericin was kept in an desiccator controlled at various humidities for a week, the bond breaking temperature shifts from 230°C to 260°C (260°C is for 96% RH). This fact shows the structure of sericin becomes more stable being kept in high R. H. When the treatment times is short, the structual changes do not occur.
(5) It is generally known that the bad reelability of cocoon occurs when mounted at high temperature and humidity. This is partly attributable to the increase of the crystallinity of sericin.
