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«“√ “√ √“™∫— ≥±‘ µ¬ ∂“π Usa Sangwatanaroj, et al. 137 ªï ∑’Ë ÛÚ ©∫— ∫∑’Ë Ò ¡.§.-¡’ .§. Úıı A t = the integrated area of the filament- sample diffracto- gram Infrared Analysis Each variety of silk filaments was analyzed for its basic chemi- cal structure and functional groups using the FTIR spectrometer (model Nicolet Nexus 670) with an ATR (attenuated total reflectance) technique and DTGS detector. The FTIR spectrum of each filament was recorded from 650 to 4000 cm -1 with the averaged 100 scans and a resolution of 4 cm -1 . Softening Point The softening temperature of each sample was determined using the melting apparatus (Sanyo Gallenkamp) by heating the sam- ple and observing it for its soften- ing point. Burning Test Silk filaments were tested for their burning behavior according to the AATCC test method 20. They were observed for their appear- ances near the flame and during burning and for their burning resi- due. Strength Silk tenacity was determined using a Lloyd tensile tester, model L500, according toASTMD2256. All varieties of silk filament were conditioned overnight before being tested. Each sample of ten inches long was clipped onto the machine and then stretched to breakage with a stretching rate of 300 mm per minute using a 100 N load cell. Resistance to Sunlight The silk filaments were tested for their resistance to sunlight by exposing them to imitation sunlight produced by a mercury/tungsten arc lamp in the light fastness tester Shirley (model M237A) for 25 hours, and then testing their tenac- ity, compared to that before the exposure. Dyeability Silk dyeability was deter- mined by first dyeing each silk fila- ment with an Acid Orange 253 at 2% weight of filament (owf), 2% owf of 98% sulfuric acid and 1 g/dm 3 of nonionic wetting agent, in a stainless steel container of the laboratory dyeing machine, Ahiba Polymat, at a liquor ratio of 1:30, at 100 ˚C for 45 minutes. The dyed filament was removed from the cylinder, air dried and measured for its color strength (K/S before wash- ing) at a wavelength of 520 nanometers using the Macbeth reflectance spectrophotometer (Color-Eye 7000). Then it was washed, dried, and measured for its color strength (K/S after washing). The percentage of dye fixation was calculated by multiplying 100 by the ratio of the K/S after washing over the K/S before washing. Resistance to Acid, Alkali, and Bleaching Agent Each variety of silk filament was tested for weight loss after exposure to 2% owf of 98% sulfuric acid in dyeing conditions (see the dyeability section), 2-3 g/dm 3 sodium carbonate in the degumming condition (see the degumming section), and 3 g/dm 3 of 50% hydrogen peroxide in the bleaching condition (pH 10, 95 º C, 45 minutes). Results and Discussion Appearance, Cross-Sectional and Longitudinal Views The silk variety known as Chul 4 was a yellow filament while other varieties of Chul 6, Chul 1 and the imported Chinese silk were white filaments. All filaments were inner layer filaments and they all looked shiny and clean. The SEM micrographs of these filaments showed a similar appearance de- scribed as follows. Each piece of raw silk was covered with sericin gluing two filaments together and showed an uneven surface. On the other hand, each degummed silk appeared as an individual filament with triangular cross-sectional shapes and a more even surface. Hand and machine reeled filaments showed a similar appearance under SEM analysis. Figures 1 and 2 show the scanning electron micrographs of the local silk Chul 4 and the imported Chinese silk, reeled by machinery.