Silk degradation discoloration

Coated silk was not tested at 150 °C because Parylene-C undergoes a markedly increased degradation when heated above 135°C. Because initial observations on the discoloration of silk fabric indicated a change in the nature of the degradation reaction at temperatures above 110°C, calculations were performed both including and excluding the 150 C data. 

COLOR DIFFERENCE. Silk discolors when exposed to heat and light. The color change is taken as one measure of the extent of degradation. The color difference of each treated sample was evaluated on a Diano Match-Scan spectrophotometer against a standard untreated silk sample. The color differences AE ab are reported in CIELAB color difference units (CDU) for Illuminant Da5, and were calculated by (21)... 

Two solutions were prepared for each historical silk sample. Nessler s reagent was added to one, and deionized-distilled water was added to the other, so that an independent measurement could be made of the amount of discoloration contributed to the solution by the silk and its degradation products and contaminants, if any. For these measurements, deionized-distilled water was used as the blank, and a separate absorbance measurement was made on the solution of water and Nessler s reagent. 

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