Pyrolysis-GC/MS and TGA as Tools for Characterizing Blends of SBR and NBR

2001 ◽  
Vol 74 (5) ◽  
pp. 803-813 ◽  
Author(s):  
Stephanie R. Shield ◽  
Ghebrehiwet N. Ghebremeskel ◽  
Cebron Hendrix
Keyword(s):  
Degradation Products ◽  
Specific Weight ◽  
Test Methods ◽  
Polymer Composition ◽  
Blend Composition ◽  
Peak Areas ◽  
The Individual ◽  
Blend Ratios ◽  
Analytical Tools ◽  
Technological Interest

Abstract There is increased technological interest to use blends of various dissimilar elastomers in applications for which service, material availability, or cost of a single elastomer do not provide the necessary processing, vulcanizate, or economic properties. Properties of polyblends are sensitive to variations in the amounts of the individual polymers used. Therefore, there is a need for developing a variety of analytical tools that will enable the compounder to monitor the consistency of blend compositions. In this study, the feasibility of using pyrolysis-GC/MS and thermogravimetric analysis (TGA) to estimate the blend composition of SBR/NBR blends was investigated. Pyrolysis-GC/MS degradation products that are characteristic of each polymer were identified. The GC/MS peak areas were used to determine the blend composition. The blend compositions were estimated by TGA from the linear correlation between the polymer composition and the temperature required to pyrolyze a sample to a specific “% weight loss.” The results obtained by pyrolysis-GC/MS and TGA were compared to calculated blend ratios of SBR/NBR in order to estimate the accuracy of the test methods presented in this study.

scholarly journals Bypassing Energy Barriers in Fiber-Polymer Torrefaction

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhuo Xu ◽  
Shreyas S. Kolapkar ◽  
Stas Zinchik ◽  
Ezra Bar-Ziv ◽  
Lucky Ewurum ◽  
...  
Keyword(s):  
Mass Loss ◽  
Synergistic Effects ◽  
Mass Loss Rate ◽  
Reactive Extrusion ◽  
Extrusion Process ◽  
Energy Barriers ◽  
Natural Energy ◽  
Plastic Wastes ◽  
The Individual ◽  
Blend Ratios

The amount of waste generation has been increasing with a significant amount being landfilled. These non-recyclable wastes contain large number of fiber and plastic wastes which can be treated with thermal processes to turn them into energy sources since they have high calorific values, are abundant and usually tipping fees are paid to handle them. This paper studied the torrefaction of non-recyclable paper (fiber) wastes, mixed plastic wastes (MPW) and their blends at different ratios in the temperature range of 250–400°C through thermogravimetric analysis (TGA). The solid residues after the experiments were analyzed by nuclear magnetic resonance (NMR) spectroscopy. Significant synergy between fiber and MPW were observed at the range 250–300°C, showing both increase in the reaction rate as well as the overall mass loss. At 250°C, the maximum mass loss rate was more than two times higher and the mass loss at the end of the experiments were also much higher compared to the expected results. In addition, synergy was weakened with an increase of temperature, disappearing at 400°C. The existence of such interactions between fiber and plastic wastes indicates that the natural energy barriers during the individual torrefaction in paper waste or plastic waste could be bypassed, and the torrefaction of fiber and plastic blend can be achieved at lower temperatures and/or shorter residence times. The MPW and fiber wastes were also compounded by extrusion (to produce pellets) at 220°C with different blend ratios. The fiber-MPW pellets from extrusion were characterized by IR spectroscopy, rheology, thermal analysis and flexural properties and showed significant chemical changes from the non-extruded blends at the same ratios. From IR characterization, it was found that there was significant increase in hydroxyl (OH) group on account of the carbonyl (C = O) and etheric (C-O-C) groups. The interaction between paper and MPW can be attributed to the plastic polymers acting as a hydrogen donor during the reactive extrusion process. Synergistic effects were also found from mechanical and rheological properties.

scholarly journals Differential Pulse Voltammetric Assay of Lercanidipine in Tablets

2002 ◽  
Vol 85 (6) ◽  
pp. 1247-1252 ◽  
Author(s):  
Alejandro Álvarez-Lueje ◽  
Sara Pujol ◽  
Luis J Núñez-Vergara ◽  
Juan A Squella
Keyword(s):  
Degradation Products ◽  
Differential Pulse ◽  
Pyridine Derivative ◽  
Liquid Chromatographic Method ◽  
Recovery Study ◽  
Curve Method ◽  
Ph Range ◽  
The Individual ◽  
Voltammetric Assay ◽  
Liquid Chromatographic

Abstract Lercanidipine in ethanol–0.04M Britton-Robinson buffer (20 + 80) gives an irreversible anodic response on a glassy carbon electrode in a broad pH range (2–12) that depends on pH. This signal can be attributed to oxidation of the 1,4-dihydropyridine ring to give the corresponding pyridine derivative. For analytical purposes, differential pulse voltammetry at pH 4 was selected. Under these conditions, good values of both within- and interday reproducibility were obtained, with coefficient of variation (CV) values of 1.56 and 1.70%, respectively, for 10 successive runs. For quantitation, the calibration curve method was used for lercanidipine concentrations ranging from 1 × 10−5 to 1 × 10−4M. The detection and quantitation limits were 1.39 × 10−5 and 1.49 × 10−5, respectively. A liquid chromatographic method with electrochemical detection was used for comparison. The voltammetric method showed good selectivity with respect to both excipients and degradation products. The recovery study exhibited a CV of 0.94% and an average recovery of 98.3%, and it was not necessary to treat the sample before the analysis. The method was successfully applied to the individual tablet assay of lercanidipine in commercial tablets.

Dynamic Behavior and Synchronization of an Automobile as a Complex System

2014 ◽  
Author(s):  
Claudia A. González-Cruz ◽  
Juan C. Jáuregui-Correa ◽  
Carlos S. López-Cajún ◽  
Mihir Sen
Keyword(s):  
Complex System ◽  
Wavelet Transforms ◽  
Cross Correlation ◽  
Correlation Coefficients ◽  
The Other ◽  
Accelerometer Data ◽  
Hilbert Transforms ◽  
The Road ◽  
The Individual ◽  
Analytical Tools

A complex system is composed of many interacting components, but the behavior of the system as a whole can be quite different from that of the individual components. An automobile is an example of a common mechanical system composed of a large number of individual components that are mechanically connected in some way and hence transmit vibrations to each other. This paper proposes a variety of inter-related analytical tools for the study of experimental data from such systems. In this work, experimental results of accelerometer data acquired at two locations in the automobile for two different kinds of tests are analyzed. One test is the response to impact on a stationary vehicle, and the other is the road-response to the vehicle being driven on a flat road at different speeds. Signals were processed via Fourier and wavelet transforms, cross-correlation coefficients were computed, and Hilbert transforms and Kuramoto order parameters were determined. A new parameter representing synchronization deficit is introduced. There is indeed some degree of synchronization that can be quantified between the accelerations measured at these two locations in the vehicle.

scholarly journals Biodegradability standards for carrier bags and plastic films in aquatic environments: a critical review

2018 ◽  
Vol 5 (5) ◽  
pp. 171792 ◽  
Author(s):  
Jesse P. Harrison ◽  
Carl Boardman ◽  
Kenneth O'Callaghan ◽  
Anne-Marie Delort ◽  
Jim Song
Keyword(s):  
Degradation Products ◽  
Toxicity Testing ◽  
Test Methods ◽  
Ecological Impacts ◽  
Aquatic Environments ◽  
Natural Ecosystems ◽  
Marine Habitats ◽  
Industry Standards ◽  
Plastic Bag ◽  
Chemical Conditions

Plastic litter is encountered in aquatic ecosystems across the globe, including polar environments and the deep sea. To mitigate the adverse societal and ecological impacts of this waste, there has been debate on whether ‘biodegradable' materials should be granted exemptions from plastic bag bans and levies. However, great care must be exercised when attempting to define this term, due to the broad and complex range of physical and chemical conditions encountered within natural ecosystems. Here, we review existing international industry standards and regional test methods for evaluating the biodegradability of plastics within aquatic environments (wastewater, unmanaged freshwater and marine habitats). We argue that current standards and test methods are insufficient in their ability to realistically predict the biodegradability of carrier bags in these environments, due to several shortcomings in experimental procedures and a paucity of information in the scientific literature. Moreover, existing biodegradability standards and test methods for aquatic environments do not involve toxicity testing or account for the potentially adverse ecological impacts of carrier bags, plastic additives, polymer degradation products or small (microscopic) plastic particles that can arise via fragmentation. Successfully addressing these knowledge gaps is a key requirement for developing new biodegradability standard(s) for lightweight carrier bags.

Feasibility studies for simultaneous immunochemical multianalyte drug assay by capillary electrophoresis with laser-induced fluorescence

1994 ◽  
Vol 40 (9) ◽  
pp. 1819-1822 ◽  
Author(s):  
F T Chen ◽  
R A Evangelista
Keyword(s):  
Capillary Electrophoresis ◽  
High Efficiency ◽  
Internal Standard ◽  
Feasibility Studies ◽  
Laser Induced Fluorescence ◽  
Resolving Power ◽  
Multiple Drug ◽  
Peak Areas ◽  
The Individual ◽  
Antigen Antibody

Abstract We present a method for the simultaneous quantification of multiple drug analytes in urine, based on combining immunochemical binding with capillary electrophoretic separation. Two fluorescent drug-cyanine (Cy) dye conjugates were prepared as competing species for the immunoassay. Morphine was derivatized with Cy5 (lambda max = 652 nm, epsilon = 215,000 mol-1cm-1 L), phencyclidine (PCP) with Cy5.5 (lambda max = 675 nm, epsilon = 200,000 mol-1cm-1L). The high-efficiency resolving power of the capillary electrophoresis system (20 microns x 27 cm column) separated the individual labeled drugs, and the antigen-antibody complexes were detected by laser-induced fluorescence (laser: 10 mW He-Ne at 632.8 nm) with Cy5 diacid as internal standard. Simultaneous competitive immunoassay of morphine and PCP in urine showed that the free labeled-drug peak areas were proportional to the concentrations of the drug species present in the urine sample. This immunoassay can be performed routinely and reproducibly in < 5 min with analytical detection limits of 4 nmol/L for PCP and 40 nmol/L for morphine.

Comparison of Standardized Test Methods for Determining the Permeability of the Surface Layer of Concrete

2015 ◽  
Vol 1122 ◽  
pp. 141-144
Author(s):  
Tereza Komárková ◽  
Monika Králíková ◽  
Dalibor Kocáb ◽  
Petr Misák ◽  
Tomáš Stavař
Keyword(s):  
Surface Layer ◽  
Water Permeability ◽  
Standardized Test ◽  
Test Methods ◽  
Standardized Assessment ◽  
Depth Of Penetration ◽  
The Individual ◽  
Durability Of Concrete

The durability of concrete can be assessed based on the quality of the surface layer of concrete, for which there are a few standardized assessment test methods. Usually, the quality of the surface layer of concrete is evaluated based on its air and water permeability. The aim of this experiment was to compare the outputs which provide some methods for determining the permeability of the surface layer of concrete (GWT, ISAT, TPT, the depth of penetration of water under pressure). The measured values using the individual methods of assessing the permeability of the surface layer of concrete very closely correspond.

scholarly journals Understanding and Kinetic Modeling of Complex Degradation Pathways in the Solid Dosage Form: The Case of Saxagliptin

Pharmaceutics ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 452 ◽  
Author(s):  
Robnik ◽  
Likozar ◽  
Wang ◽  
Stanić Ljubin ◽  
Časar
Keyword(s):  
Relative Humidity ◽  
Degradation Product ◽  
Degradation Products ◽  
Drug Product ◽  
Degradation Kinetics ◽  
Dosage Forms ◽  
Drug Substance ◽  
Polymer Composition ◽  
Solid Dosage Forms ◽  
Solid Dosage

Drug substance degradation kinetics in solid dosage forms is rarely mechanistically modeled due to several potential micro-environmental and manufacturing related effects that need to be integrated into rate laws. The aim of our work was to construct a model capable of predicting individual degradation product concentrations, taking into account also formulation composition parameters. A comprehensive study was done on active film-coated tablets, manufactured by layering of the drug substance, a primary amine compound saxagliptin, onto inert tablet cores. Formulation variables like polyethylene glycol (PEG) 6000 amount and film-coat polymer composition are incorporated into the model, and are connected to saxagliptin degradation, via formation of reactive impurities. Derived reaction equations are based on mechanisms supported by ab initio calculations of individual reaction activation energies. Alongside temperature, relative humidity, and reactant concentration, the drug substance impurity profile is dependent on micro-environmental pH, altered by formation of acidic PEG degradation products. A consequence of pH lowering, due to formation of formic acid, is lower formation of main saxagliptin degradation product epi-cyclic amidine, a better resistance of formulation to high relative humidity conditions, and satisfactory tablet appearance. Discovered insights enhance the understanding of degradational behavior of similarly composed solid dosage forms on overall drug product quality and may be adopted by pharmaceutical scientists for the design of a stable formulation.

Evaluating test methods by estimating total error

1994 ◽  
Vol 40 (3) ◽  
pp. 464-471 ◽  
Author(s):  
V M Chinchilli ◽  
W G Miller
Keyword(s):  
Coefficient Of Variation ◽  
Total Error ◽  
Test Methods ◽  
Repeated Measurements ◽  
Relative Bias ◽  
Test Method ◽  
Individual Subject ◽  
Common Procedure ◽  
The Individual ◽  
Upper Tolerance Limit

Abstract A common procedure for evaluating a test method by comparison with another, well-accepted method has been to use a repeated measurements design, in which several individual subjects' specimens are assayed with both methods. We propose the use of the intrasubject relative mean square error, which is a function of the intrasubject relative bias and the coefficient of variation of the test method, as a measure of total error. We construct for each individual subject a score that is based on how well an individual's estimate of total error compares with a maximum allowable value. If the individual's score is > 100%, then that individual's estimate of total error exceeds the maximum allowable value. We present a distribution-free statistical methodology for evaluating the sample of scores. This involves the construction of an upper tolerance limit to determine whether the test method yields values of the total error that are acceptable for most of the population with some level of confidence. Our definition of total error is very different from that defined in the National Cholesterol Education Program (NCEP) guidelines. The NCEP bound for total error has three main problems: (a) it incorrectly assumes that the standard error of the estimated relative bias is the test coefficient of variation; (b) it incorrectly assumes that the individual estimated relative biases follow gaussian distributions; (c) it is based on requiring the relative bias of the average individual in the population to lie within prescribed limits, whereas we believe it is more important to require the total error for most of the individuals in the population, say 95%, to lie within prescribed limits.

scholarly journals «Individual curriculum» as a way of planning by students of vocational and technical education of their employment

2021 ◽  
pp. 18-23
Author(s):  
Sergii Korol ◽  
Anna Zinchenko ◽  
Karina Hlushchenko
Keyword(s):  
Vocational Education ◽  
Test Methods ◽  
Curriculum Planning ◽  
Life Planning ◽  
Planning Methods ◽  
Professional Self ◽  
College Work ◽  
The Individual ◽  
Two Stages ◽  
Research Stage

The article deals with the problem of student’s employment in the specialty of graduation at vocational education institutions. Considering the plans of some students on relearning or developing new skills in courses or internships, they need awareness of right specialty to choose and job preferably to find after graduation. The paper considers the relevant issue of research and development of individual planning methods for vocational education students in terms of their employment. The emphasis is made on this factor impact for future employment, namely its impact on the individual professional orientation and career, which can be planned through an individual curriculum i.e. balanced life planning. An individual curriculum is a set of activities that help taking responsibility for the future by combining educational activities at school, college, work and in general throughout the career. It determines the sequence, form and pace of mastering the educational program components, own experience and other successful experiences, methods and activities necessary for achievement of the main planning goal. An individual plan is important as planning efficiently turns knowledge into skills. The study considered based upon the "Individual curriculum" method and auxiliary test methods: "Success motivation and failure fear (questionnaire by Rean A.O.)", a test to determine the motive for a profession choice – the method of professional self-determination by J. Holland. The research was implemented on the basis of the Sumy Chemical-Technological Center for Vocational Education, consisting of two stages of online testing with further explanation to students and their individual curricula development. The first research stage involved students’ participation in an online quest, tests performance and obtaining explanations based on the methods of comprehensive interpretation. The second research stage involved the method of "individual curriculum planning" based on a plan template according to the study year.

scholarly journals Learning analytics dashboard for twitter

2021 ◽  
Author(s):  
Anatoliy Gruzd ◽  
Nadia Conroy
Keyword(s):  
Learning Analytics ◽  
Online Survey ◽  
Qualitative Assessment ◽  
Named Entities ◽  
System Data ◽  
Twitter Users ◽  
The Individual ◽  
Intuitive Interface ◽  
Analytical Tools ◽  
Future Work

Designing a Learning Analytics Dashboard for Twitter-Facilitated Teaching Considering the increasing use of Twitter for both formal and informal learning, the primary goal of this project is to design a Learning Analytics (LA) dashboard to support instructors’ evaluation of Twitter-based teaching. To achieve this goal, we conducted an online survey involving 54 higher education instructors who have used Twitter in their past teaching. The main purpose was to identify why instructors use Twitter and what types of analytics they would consider valuable. The results of the survey evidence that instructors use Twitter to help students engage with class material, promote discussion, and build learning communities. Instructors expressed interest in analytical tools to help them quantitatively and qualitatively interpret Twitter data. Coupled with an in-depth literature review in this area, we relied on the survey data to prototype a Learning Analytics dashboard (https://dashboard.socialmediadata.org/educhat). Our online dashboard uses a simple, easy-to-read interface in accordance with previous successful dashboard implementations. Graphical visualizations allow instructors to monitor discussion patterns, such as the frequency and times of posting. Visual content breakdowns by number of retweets, original posts, and topics in the form of hashtags and named entities reveal the constituents of students’ posts. The dashboard provides additional analysis in the form of sentiment and subjectivity ranking as a way to contextually aid qualitative assessment. To support instructors’ awareness of class participation, we incorporated two visualizations that highlight the most active users and individuals who are most frequently mentioned in others’ tweets. Instructors can use the dashboard to gauge the participation at the individual- or classroom-level, and further discover what topics and links students discuss and share on Twitter. Three instructors piloted the LA dashboard over a 4-month semester in the Fall of 2017. Following their use, we conducted evaluation interviews with these instructors. Instructor evaluations confirmed that the proposed design is aligned with their pedagogical needs; they favored an intuitive interface that combined summative metrics for the entire class and personalized assessment of individual students. Based on instructors’ feedback, our future work will iteratively refine the design by integrating additional interactive features to adjust time scales of the output, investigate source data, collect data from lists of Twitter users (as opposed to a single hashtag), and further integrate the dashboard with other LMS (Learning Management System) data.

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