Color measurements are made of various kinds of flax retted by dew, water, or enzymes. Two sets of samples are analyzed under different conditions using different spectropho tometers and by reflectance in the visible and near infrared spectral regions. Sample set one consists of 55 samples of various flax types retted by traditional dew and water methods and various experimental enzyme retted samples. Means and standard deviations of CIELAB color values for each of the classes are displayed as spheroid plots. The enzyme retted fiber flax class forms a separate group that is substantially lighter and slightly yellower than dew retted flax. Water retted flax is intermediate between dew and enzyme retted flax, but tends to be closer to dew retted flax. Near infrared spectra vary with different cleaning methods to remove shives from fibers. A second set of 16 samples consists of dew, water, and spray enzyme retted samples, the latter samples also analyzed with regard to subsequent cleaning processes. CIELAB and Hunter Lab methods provide similar comparisons, although CIELAB values are higher within treatments. Enzyme retted fibers tend (P > 0.05) to be lighter and yellower than water retted ones. None of the flax fibers are as light as the cotton samples included for comparison. The Δ ECIELAB values are 8.8 between dew and water retted fibers, 13.6 between dew and enzyme retted fibers, and 4.9 between water and enzyme retted fibers. Factors that affect the color of enzymatically retted flax fibers are prior microbial activity, shive content, and fiber fineness. These color methods could form the basis for developing a color standard for short staple flax fibers.

The relationship between pore size and air permeability in two spunlaced fabrics and two spunbonded/meltblown/spunbonded (SMS) fabrics were investigated. Minimum, maximum and mean flow pore sizes were determined using liquid porosimetry. The influence of fabric weight and thickness on air permeability and pore sizes was also evaluated. For the spunlaced fabrics, air permeability was most highly correlated with mean flow pore size, while there was a significant correlation between air permeability and maximum pore size for the SMS fabrics. Liquid porosimetry is a useful technique in assessing pore sizes of nonwoven fabrics and can also aid in understanding the mechanism of air permeability.

The findings of earlier research on the influence of particular yarn and fabric structural variables on heat transfer and air flow through fabrics are used in explaining similarities and differences among measurements of air permeability and thermal transmittance of three medium-weight plain weave fabrics. Two fabrics constructed of staple polyester (PET) yarns exhibited higher air permeabilities and lower thermal transmittance values than the third fabric, which was composed of PET filament yarns. Bulk densities of the two staple yarn fabrics were approximately equal, but the fabrics differed in weight, thickness, fabric count, yarn tex, and yarn twist. The staple yarn fabric with the lowest fabric count, highest weight, and highest thickness exhibited the lowest thermal transmittance in both single and multiple layers; however, differences between its thermal transmittance values and those of the thinner, lighter weight staple yarn fabric were not statistically significant. There were significant differences in air permeability between each of the three fabrics. Measurements also were taken on multiple layers of the fabrics. Regression analysis revealed nonlinear declines in thermal transmittance and air permeability as fabric layers were increased. Differences in air permeability and thermal transmittance among the fabrics are explained on the basis of structural differences.

Twenty-seven samples representing variations of retted flax fibers are analyzed using a color spectrophotometer and CIELAB models. Variables included enzyme or dew retting, fiber or seed flax, enzyme and chelator concentrations, and sequential cleaning steps. In addition to differences in color with enzyme or dew retting, the variables involved in enzyme retting also contribute to differences in the lightness, redness-greenness, and yellowness-blueness of the resulting fibers. Dew retted fiber flax, as well as seed flax that has weathered during storage prior to enzyme retting, is significantly darker than non-weathered, enzyme retted fiber flax. Pairwise comparisons show that lower enzyme concentrations (0.05% v/v as commercially supplied) produce redder and yellower fiber samples than those retted with higher (0.3% v/v) enzyme levels. Higher chelator levels, ( i.e., 50 versus 25 mmol ethylenediaminetetraacetic acid) produce redder fibers. Fiber lightness significantly increases with additional cleaning steps. Results indicate that objective color measurements and color standards can define important fiber properties in order to tailor raw materials for specific industrial applications.

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