In-line measurement of additive and pigment loadings in molten polymer systems by fiber optic spectroscopy

The purpose of this project is the further development of in-line spectroscopic measurements for molten polymer systems. There are two main focuses: development of an online technique for the determination of concentration of ultraviolet stabilizers and antioxidant additives in polypropylene at orders of magnitude higher than those previously studied, and the development of a practical on-line color measurement technique. The additive project is an extension of the work completed by Dr. Marion Hansen and graduate students at the Measurement and Control Engineering Center located at the University of Tennessee, Knoxville. The color measurement technique is novel in its approach. Quality control is one of the most important factors in plastics compounding. Compounding companies engage in the production of additive and color concentrates to be further diluted (or let-down ) by their customers. The end products are usually plastic pellets to be used in molding, film manufacturing, or fiber production. The end concentrations of additives and pigments in these end products are usually less than 1 % and more often in the 100-200 ppm region. These low concentrations mandate the knowledge of the actual concentrations of pigments and additives contained in the concentrate. Current quality control methods are predominantly off-line techniques. Most companies employ a method where a small sample is obtained from the production area and taken to a quality control analytic laboratory, where it is tested for additive concentration and/or color. Depending on the size and capacity of the facility, a large quantity of off specification material can be produced. Off-line techniques also have a given lag period before changes to the operating conditions can be made. The development of on-line measurement techniques not only provides a real time indication of the operating conditions, but is the fundamental element missing in the development of a real time, feed-back control system of the manufacturing process. The development of fiber optic cable allowed for traditional laboratory techniques to be applied in the production area of chemical processing facilities. The use of this type of cable has allowed the development of online techniques using near infrared (NIR), Fourier transform infrared (FTIR), ultraviolet (UV), and Raman spectroscopy. The additives objective of this project is to look at several of the most commonly used UVstabilizer and antioxidant additives in the polyolefin fiber industry. The objective is to determine a spectroscopic technique or combination of techniques to determine the amount of these additives contained in the sample. Research will also be conducted to investigate the effect of additive loading on the rheological properties of the polymer. These results are correlated back to the spectroscopic data to develop an on-line measurement of the viscosity or melt index of the material. The sample additives are compounded with an unmodified polypropylene resin. Research is focused at determining the best spectroscopic technique utilizing NIR or W methods as well as the optimal mathematical regression to provide the most accurate measurement of the additive concentration . The color objectives of this project are to look at several commonly used pigments in the plastics industry and also develop a spectroscopic technique to determine the pigment concentration. The actual measurement of color is impossible. It is the final customer that determines whether the material is the correct color for their product. There are several methods to determine color numbers currently that aid color matching. These numbers, however, are determined using a flat plaque and the final pigment loading, not the actual concentrated material. If the pigment is treated like another additive, it is possible to correlate the specification material to the color standard. Once the correct pigment loading is established, online measurement will indicate off specification material. This project will also investigate the different spectroscopic techniques currently available to determine the optimum method for measuring concentration, as well as the proper mathematical regression technique for the most accurate concentration measurements

Quantitative scattering of melanin solutions

The optical scattering coefficient of a dilute, well solubilised eumelanin solution has been accurately measured as a function of incident wavelength, and found to contribute less than 6% of the total optical attenuation between 210 and 325nm. At longer wavelengths (325nm to 800nm) the scattering was less than the minimum sensitivity of our instrument. This indicates that UV and visible optical density spectra can be interpreted as true absorption with a high degree of confidence. The scattering coefficient vs wavelength was found to be consistent with Rayleigh Theory for a particle radius of 38+-1nm.Comment: 23 pages, 5 figure

In-line monitoring of polymer processing using fiber-optic spectroscopy

This research was focused on developing fiber optic molecular spectroscopic techniques to provide information about chemical compositions and rheological properties (such as melt index and complex viscosity) of polymer melts in polymer processing. With the development of fiber optics, chemometrics, and the advent of powerful desk computers, in-line spectroscopic analyses have proven to be effective and non-destructive ways of providing real-time measurements of polymer melts, and have already found application in process monitoring. In this research, near infrared (NIR), ultraviolet-visible (UV-Vis), and Raman scattering spectroscopy have been applied to an in-line extrusion process for simultaneous measurements of compositions and rheological properties of flowing molten polymers. Fiber optic NIR and UV spectroscopic systems have been improved and applied to the in-line monitoring of polymer additives in polymer processing. A methodology is proposed for the feasibility of measuring the concentrations of multiple additives in polypropylene and polyethylene. It was found that the characteristics of absorption bands of polymer additives in NIR and UV spectroscopy depend on their chemical structures and chromophore groups. Slip agents and hindered amine light stabilizers with \u3eNH and -NH2 groups show strong NIR spectral bands. Thus, concentrations of additives with either of the above two groups can be determined by fiber-optic NIR spectroscopy. Conjugated unsaturated chromophores show strong and distinguished peak bands in the UV region. Thus, concentrations of additives with benzene rings or other kinds of conjugated groups in their chemical structures can be determined by the fiber-optic UV spectroscopy. In the prediction of rheology of polymer melts, polyethylene with erucamide and Armostat 310® and poly(ethylene vinyl acetate) (EVA) were studied. The effect of erucamide and Armostat 310® on the melt index of PE was investigated. Calibration models were built for the simultaneous measurements of concentrations of the above two additives and melt index of PE using NIR and UV spectroscopy, respectively. For the EVA copolymer system, a fiber-optic Raman scattering system was applied to the in-line monitoring of the concentration of vinyl acetate and rheological properties (melt index and complex viscosity) of EVA melts in an extrusion process. In the development of instrumentation, robust NIR transmission probes were applied to fiber-optic NIR spectroscopy system. A dual-beam fiber optic UV spectroscopic system was designed and evaluated, and the transmission efficiency of UV light was improved by UTK-designed UV probes for the determination polymer additives. For Raman scattering spectroscopy, a plane-polarized fiber optic Raman scattering spectroscopic system was applied to make simultaneous measurements of composition and rheological properties of poly(ethylene-vinyl acetate) (EVA) in extrusion

Visible and near infrared spectroscopy in soil science

This chapter provides a review on the state of soil visible–near infrared (vis–NIR) spectroscopy. Our intention is for the review to serve as a source of up-to date information on the past and current role of vis–NIR spectroscopy in soil science. It should also provide critical discussion on issues surrounding the use of vis–NIR for soil analysis and on future directions. To this end, we describe the fundamentals of visible and infrared diffuse reflectance spectroscopy and spectroscopic multivariate calibrations. A review of the past and current role of vis–NIR spectroscopy in soil analysis is provided, focusing on important soil attributes such as soil organic matter (SOM), minerals, texture, nutrients, water, pH, and heavy metals. We then discuss the performance and generalization capacity of vis–NIR calibrations, with particular attention on sample pre-tratments, co-variations in data sets, and mathematical data preprocessing. Field analyses and strategies for the practical use of vis–NIR are considered. We conclude that the technique is useful to measure soil water and mineral composition and to derive robust calibrations for SOM and clay content. Many studies show that we also can predict properties such as pH and nutrients, although their robustness may be questioned. For future work we recommend that research should focus on: (i) moving forward with more theoretical calibrations, (ii) better understanding of the complexity of soil and the physical basis for soil reflection, and (iii) applications and the use of spectra for soil mapping and monitoring, and for making inferences about soils quality, fertility and function. To do this, research in soil spectroscopy needs to be more collaborative and strategic. The development of the Global Soil Spectral Library might be a step in the right direction

Shining light on the storm: Using high-frequency optical water quality sensors to characterize and interpret storm nutrient and carbon dynamics among contrasting land uses

Elevated nutrient concentrations present significant challenges to surface water quality management globally, and dissolved organic matter mediates several key biogeochemical processes. Storm events often dominate riverine loads of nitrate, phosphorus, and dissolved organic matter, and are expected to increase in frequency and intensity in many regions due to climate change. The recent development of in situ optical sensors has revolutionized water quality monitoring and has highlighted the important role storms play in water quality. This dissertation focuses on improving the application of in situ optical water quality sensors and interpreting the high-frequency data they produce to better understand biogeochemical and watershed processes that are critical for resource management. We deployed in situ sensors to monitor water quality in three watersheds with contrasting land use / land cover, including agricultural, urban, and forested landscapes. The sensors measured absorbance of ultraviolet-visible light through the water column at 2.5 nanometer wavelength increments at 15-minute intervals for three years. These deployments provided a testbed to evaluate the sensors and improve models to predict concentrations of nitrate, three phosphorus fractions, and dissolved organic carbon using absorbance spectra and laboratory analyses through multivariate statistical techniques. In addition, an improved hysteresis calculation method was used to determine short-timescale storm dynamics for several parameters during 220 storm events. Goals of each dissertation chapter were to: (1) examine the influences of seasonality, storm size, and dominant land use / land cover on storm dissolved organic carbon and nitrate hysteresis and loads; (2) evaluate the utility of the sensors to determine total, dissolved, and soluble reactive phosphorus concentrations in streams draining different land use / land covers, and perform the first statistically robust validation technique applied to optical water quality sensor calibration models; and (3) analyze storm event dissolved organic matter quantity and character dynamics by calculating hysteresis indices for DOC concentration and spectral slope ratio, and develop a novel analytical framework that leverages these high frequency measurements to infer biogeochemical and watershed processes. Each chapter includes key lessons and future recommendations for using in situ optical sensors to monitor water quality

Characterization of Jet Fuel Combustion Emissions During a C-130 Aeromedical Evacuation Engines Running Onload

The purpose of this research was to characterize jet fuel combustion emissions (JFCE) in an occupational setting. Prior research demonstrated that aircraft emit hazardous species, especially at engine start-up and ground idle. Complaints of eye, nose, and throat irritation from occupational exposures near aircraft exist. In this study JFCE were tested during an aeromedical evacuation engines running patient onload (ERO) on a C-130 Hercules at the 179th Airlift Wing, Mansfield-Lahm Air National Guard. Ultrafine particles, VOC, formaldehyde, carbon monoxide (CO), sulfuric acid, and metals were sampled simultaneously in approximate crew and patient breathing zones. Testing methods were portable condensation particle counters (CPC), polycarbonate filters (PC) and thermophoretic samplers (TPS) for electron microscopy, MultiRae® gas monitors, EPA methods TO-17 and TO-11, and NIOSH methods N0600, N7908, N7300. Ultrafine particulate matter, VOC including EPA HAPs, formaldehyde, CO, and unburned jet fuel were detected. Particles were dominated by soot that was predominantly carbonaceous with trace oxygen, sulfur and few metals in concentrations up to 3.4E+06 particles/cc. Particle size distributions were varied with most sizes less than 100 nanometers (nm). Particle morphology was highly irregular. VOC were detected in ppb, and formaldehyde in ppm. Additive or synergistic effects are suspected and may intensify irritation. Health implications from inhaling nano-sized soot particles are inconclusive

Dynamics of Chemical Degradation in Water Using Photocatalytic Reactions in an Ultraviolet Light Emitting Diode Reactor

This work examined ultraviolet (UV) light emitting diodes (LED) and hydrogen peroxide in an advanced oxidation process in support of a USAF installation net zero water initiative. A UV LED reactor was used for degradation of soluble organic chemicals. There were linear relationships between input drive current, optical output power, and first order degradation rate constants. When drive current was varied, first order degradation rates depended on chemical identities and the drive current. When molar peroxide ratios were varied, kinetic profiles revealed peroxide-limited or radical-scavenged phenomena. Molar absorptivity helped explain the complexity of chemical removal profiles. Degradation kinetics were used to compare fit of molecular descriptors from published quantitative structure property relationship (QSPR) models. A novel QSPR model was built using zero point energy and molar absorptivity as predictors. Finally, a systems architecture was used to describe a net zero water program and proposed areas for UV LED reactor integration. Facility-level wastewater treatment was found to be the most feasible near-term application

Characterization of Commercial Pectin Preparations by Spectroscopic and Chromatographic Techniques.

Pectin has a long history as a food additive. However, elucidation of its fine structural and property relationships remains elusive. Recent research has focused on pectin\u27s ability to complex with divalent heavy metals to aid in characterizing it. Commercial pectins of unknown composition were obtained from local grocers. Purified pectin samples from orange peel, lemon peel, and apple pomace, each of low and high levels of methyl esterification and of unknown distribution pattern were also purchased. Instead of metal complexation, several highly absorbing dyes such as Ruthenium Red, Nile Blue, and Acridine Orange were used to complex with the pectins and their resulting UV-Vis spectral patterns were employed to determine if one can characterize the different pectins. Chemometric methods are also included to aid in distinguishing them apart