Michael Santiago Cintrón

Cellulose polymorphy, crystallite size, and the Segal Crystallinity Index

The X-ray diffraction-based Segal Crystallinity Index (CI) was calculated for simulated different sizes of crystallites for cellulose Iβ and II. The Mercury software was used, and different crystallite sizes were based on different input peak widths at half of the maximum peak intensity (pwhm). The two cellulose polymorphs, Iβ and II, gave different CIs despite having the same pwhm values and perfect periodicity. The higher CIs for cellulose II were attributed to a greater distance between the major peaks that are closest to the recommended 2-θ value for assessing the amorphous content. That results in less peak overlap at the recommended 2-θ value. Patterns calculated with simulated preferred orientation had somewhat higher CIs for cellulose Iβ, whereas there was very little effect on the CIs for cellulose II.

Identification of cotton and cotton trash components by Fourier transform near-infrared spectroscopy

The high demand for cotton production worldwide has demonstrated the need for standardized classification of foreign matter present with cotton. Cotton trash can become comingled with fiber during the ginning and harvesting processes. The conventional instrumental method used to determine the amount of cotton trash present with cotton fiber, the high volume instrument (HVI), lacks specificity in the identification of individual trash components (leaf, etc.). Fourier transform near-infrared (FT-NIR) spectroscopy was investigated to distinguish the individual types of cotton trash from the fiber. In this study, the concept of monitoring differences in spectral bands of cotton and cotton trash by FT-NIR spectroscopy was demonstrated and provided a ‘proof of concept.’ A spectral library based on NIR spectral data and pre-processing methods was developed using cotton and cotton trash samples (hull, leaf, seed coat, and stem) yielding over 97% identification accuracy of cotton trash components in the prediction set.

Physical and combustion properties of nonwoven fabrics produced from conventional and naturally colored cottons

A comparative study was conducted to identify the effects of processing on physical and combustion properties of needlepunched (NP) and hydroentangled (H-E) nonwoven fabrics produced from fibers of white fiber cotton and a naturally colored brown fiber cotton. A significantly higher degree of flame retardancy (FR) in was observed in fabrics produced from brown cotton fibers compared with white fibers. Calorimetry revealed lower heat release capacity, lower peak heat release rate, and total heat release from brown fibers compared with white fibers. The ash content was also higher in brown fiber samples suggesting higher levels of inorganic elements in the brown fibers. Elemental analyses revealed brown cotton fibers had higher levels of known FR elements including phosphorous and magnesium. The H-E process reduced FR in brown fabrics, which also correlated with a reduction in phosphorous. However, brown H-E fabrics still maintained higher FR than white H-E fabrics. Water content analysis indicated higher water levels in brown fibers, particularly brown greige fibers, which correlated with increased FR. Processing parameters such as energy of H-E did not affect combustion of the two fabric types. Scouring of the brown fiber fabrics reduced, but did not remove coloration, while scouring and bleaching removed the brown color completely. Scouring alone, or scouring and bleaching, completely removed the higher FR properties of the brown fiber fabrics. The results indicate that the mechanism of FR in brown cotton fibers is dependent on multiple compositional factors that may include element content, water content, and compounds related to coloration.

A pilot-scale nonwoven roll goods manufacturing process reduces microbial burden to pharmacopeia acceptance levels for non-sterile hygiene applications

A total of seven source fiber types were selected for use in the manufacturing of nonwoven roll goods: polyester; polypropylene; rayon; greige cotton from two sources; mechanically cleaned greige cotton; and scoured and bleached cotton. The microbial burden of each source fiber was measured as a preliminary assessment of microbial contamination using heterotrophic spread plate counts. Greige cotton fibers exhibited the highest levels of total microbial contamination, which were reduced by both storage time and trash removal in the form of mechanical cleaning. Changes in microbial burden levels were measured at each step in the nonwoven manufacturing process. The hydroentanglement process resulted in the greatest overall reduction in microbial burden with no detectable levels of aerobic microbial contamination present on any of the final hydroentangled roll goods regardless of the source fiber. No detectable levels of aerobic microbial regrowth were observed on any fabrics despite storage time or ambient storage conditions. Analysis of suspended solids present in hydroentanglement effluents collected during fabric production revealed significantly less suspended solids from synthetic fibers compared to all cotton fiber types. The study provided insight and potential guidelines that could be incorporated into a nonwoven processing line to ensure specific sterility requirements are met for various converters in end-uses such as hygiene and medical applications.