สำนักราชบัณฑิตยสภา

The Journal of the Royal Institute of Thailand √–∫∫∑ÿ ππ‘ ¬¡¿“¬„µâ √–∫Õ∫ª√–™“∏‘ ª‰µ¬·∫∫‰∑¬ Properties of Industrial Thai Silks Reeled by Hand and by Machine Vol. 32 No. 1 Jan.-Mar. 2007 136 Whiteness Each variety of silk filament was paralleled and tightly wrapped on a flat sheet and then was sub- jected to whiteness measurement according to the AATCC test method 110. The whiteness of the silk was measured using a Macbeth reflectance spectrophotometer (Color-Eye 7000). Denier Each filament was weighed and measured for its length and the fineness or denier was determined by multiplying 9,000 by the ratio of the filament weight in gram over the filament length in meter, ac- cording to ASTM D1425. Degumming Loss Each raw silk filament was conditioned, weighed and then degummed in a stainless steel con- tainer of the laboratory dyeing machine Ahiba Polymat using the same formulation as shown previously in the degumming section. It was then washed, dried and conditioned overnight before weighing it and calculating its percentage of the degumming weight loss, according to JIS L0844. Moisture Content The moisture content of the filaments was determined by first conditioning each sample over- night and then weighing it before and after drying at 105 º C in an infrared weighing balance (model AD-4715). Its moisture content (%) was calculated by multiplying 100 by the ratio of the different filament weights before and after drying over the filament weight before drying, according toASTM D2654. Relative Density The relative density of the fila- ments was measured based on Archimedes’ method 5 using a den- sity test kit (Sartorius YDK 01) according to ASTM D3800. First, a one-inch long sample was im- mersed in water for at least 13 hours at room temperature, then weighed, pressed to remove excess water, weighed, dried at 110 º C, and weighed again. The relative densi- ty was then calculated according to the following equations. V = M - S (1) B = W / V (2) Dr = (B/D t ) Ó 100 (3) Where V = the sample volume, M = the sample weight after re- moving excess water, S = the sam- ple weight when soaking wet, B = the sample bulk density, W = the sample weight after dry- ing at 110 ˚C, D r = relative den- sity, D t = theoretical density Birefringence Silk birefringence ( ∆ n) was determined using the Beckeline method. 5 It was calculated from the difference between the refractive indexes of a single filament in parallel and perpendicular direc- tions, compared with that of a chloronaphthaline and cetane mixture (refractive index = 1.55). Under a polarizing microscope, the refractive index of the mixture in which the Beckeline disappeared was taken as the refractive of the sample. Crystallinity Silk crystallinity was analyzed using an X-ray diffractometer (model D8 Advance Bruker). The Ni-filtered Cu-K α (1.54 Å) radia- tion was used at 40kV and 40 mA. Silk filaments were scanned be- tween 5 and 32 º (2 θ values) with a rate of 2 º per minute, compared with their amorphous silks. Amor- phous silks were prepared as re- ferences for each variety of silk by dissolving the degummed silks in solutions of ethanol, water, and calcium chloride at a ratio of 5:6:8, respectively and at a temperature of 50 º C for 60 minutes 5 . Then the non-dissolved portions were screened out and the dissolved amorphous samples were coagu- lated in water, dried and ground into a powder form. The percent- age crystallinity of the silk fila- ments was determined according to equation 4. % crystallinity = [1 - (A a /A t )] Ó 100 (4) where A a = the integrated area of the amorphous- sample diffracto- gram