Determining Heatset Temperature by Near-Infrared Reflectance Spectroscopy

Abstract

Heat has a significant impact on the molecular structure of nylon 6 and 66, which in turn changes the yarns' physical and chemical properties and their morphological response to further processing. One of the major components of heatsetting is the temperature at which the yarn is heatset. Nylon 6 and 66 yams were heatset at different temperatures in a Suessen unit, and near infrared (NIRA) and x-ray diffraction analyses were then made on these samples. A regression modeled calibration curve was established by measuring the NIRA reflectance of yams heatset at known temperatures. This curve was in turn used to determine effectively the heatset temperature of nylon 6 and 66 yams. Correlation of the NIRA data with the x-ray diffraction data indicates that the NIRA regression models detect and measure crystalline perfection and growth with the increase in Suessen heatset temperature.Heatsetting is one of the most critical processes in carpet yarn manufacturing, and can greatly influence the quality and aesthetics of a carpet. Several studies related to carpet yarn manufacturing [1] have shown that small variations in temperature during the setting of the yarn can cause a streak in a carpet. A streak is a visual pattern parallel to the tufting direction caused by physical, optical, or dye differences in the yarn. Since the introduction of the continuous heatsetting process (e.g., Superba or Suessen), carpet yarns have become more susceptible to streakiness, due, in part, to two factors: first, the larger number of settings and controls in these dynamic processes can readily deviate from the standard by operator choice or by normal fluctuations of the systems; second, straighter yarn tufts produced by some of these systems present a more perfect background for yarn defects to appear in the carpets.Various techniques, such as x-ray diffraction and thermal methods of analysis, used to estimate the heat history of nylon or polyester yarns are not suitable for routine quality control because of the time required to perform the test. We have recently investigated the use of near infrared spectroscopy to measure the heat histories of Suessen set nylon carpet yarns. The Technicon InfraAlyzer 400TXTM used in this study was easy to operate and a fast instrument for accurately detecting heat history differences in nylon carpet yarns.

Measuring Nylon Carpet Yarn Heat History by Remote NIR Spectroscopy

“…For both the Suessen and Superba heat-set bobbin sets, we observed minor spectral differences in the 1300-1700 nm spectral region and major spectral differences in the 2000-2200 nm spectral region, as demonstrated in Figure 3. These spectral ranges are in good agreement with those observed previously for Superba and Suessen HST by bench-top measurements [2,3,13,16]. The number and frequency of consecutive wavelength areas that exhibit spectral differences in these regions indicate a high potential for successful development of PLS model (wavelength regions) NIR calibrations in addition to the standard MLR (specific wavelengths) NIR calibrations.…”

“…HST calibrations and between the SDDS obtained with the remote sampling system and those obtained by previous bench-top laboratory evaluations [2,3,13]. For Suessen heat-set yarns, remote sampling systems can be readily used to measure the Suessen HST directly on the sample surface with minimal deterioration of NIR predictive capability.…”

“…The heat history of nylon yarn is usually determined by detecting changes in fiber structure and morphological parameters. We and others [2,4] have shown that fiber crystallinity and crystalline perfection increase by increasing heat-set temperature (HST), and thus yarn heat history can be estimated by detecting changes in fiber crystallinity and crystallinity parameters. Infrared (midttt) spectroscopy has been used by various researchers [ 1,7] to study polymer crystallinity and crystalline structure.…”

Near-Infrared Spectroscopy for Anticounterfeiting Innovative Fibers

“…Many NIR instruments have been commercialized to identify the natural and synthetic fibers, such as cotton, rayon, nylon, polyester, and poly(vinyl alcohol) [2]. Ghosh and Roy [3] used homologs of cotton to develop a calibration equation for monitoring the sugar content in cotton; Gosh and Rodgers [4] and Tincher et al [5] investigated the heatset temperature of nylon carpet and its heat history using NIR spectroscopy. By using advanced diagnostic statistics and computer programs, Richard et al [6] and Jasper and Kovacs [7] demonstrated the qualitative classification of various natural and synthetic fibers to reveal subtle differences among NIR spectra in the set of samples.…”

Circularity in Practice: Review of Main Current Approaches and Strategic Propositions for an Efficient Circular Economy of Materials

“…Specifications about secondhand plastic flakes could take the form of ranges of properties, particularly mechanical (functional), rheological (processing-related), and visual (aspect) properties. If the latter is perfectly captured by color cameras, the other two, being related to crystallinity, molar masses, and additives, may all be expressed in infrared spectra [61][62][63].…”