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Dive into the research topics where Joseph H. Flynn is active.

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Featured researches published by Joseph H. Flynn.


Rubber Chemistry and Technology | 1962

Degradation of Polymers

Leo A. Wall; Joseph H. Flynn

Abstract Recent literature pertaining to both the theoretical aspects and experimental results of the degradation of polymers by heat and radiation is reviewed and critically evaluated. Theories of random and chain thermal degradation of vinyl polymers and co-polymers are reviewed. The degradation of polymethacrylates, polyacrylates, poly-α-methylstyrene, polyolefins, polystyrene, other vinyl polymers, cellulose, polyesters, polyamides, dienes, natural rubber, and copolymers are discussed in the light of these theories. The thermodynamics and energetics of the degradation of these polymers is also reviewed. Chain scission, crosslinking, and gel formation and the kinetic mechanisms of these processes which take place during degradation of polymers by ionizing radiation and ultraviolet light are included. Degradative, rather than synthetic, effects are emphasized in the discussion.


Thermochimica Acta | 1974

Thermodynamic properties from differential scanning calorimetry by calorimetric methods

Joseph H. Flynn

Abstract Simple theory and techniques are explored and developed to utilize the dif- ferential scanning calorimeter for the determination of heat capacities, glass transition and enthalpies of transition between two thermodynamic states of substances. Effects due to the transition kinetics and thermal and electronic lags of the instrument are either corrected for or eliminated.


Thermochimica Acta | 1980

The effect of heating rate upon the coupling of complex reactions. I. Independent and competitive reactions

Joseph H. Flynn

Theoretical curves of the rate of conversion vs. temperature at constant heating rate for first-order reactions with activation energies of 80, 160, 240 and 320 kJ mole−1 are compared over a range of heating rates from 10−9 to 105 K s−1 for independent and competitive reactions. Independent reactions with different activation energies may be separated from one another by either increasing or decreasing the rate of heating. The spectrum of derivative peaks for two competing reactions at various heating rates has a dispersion effect in the region of change from low to high activation energy reactions. The practical range of heating rates in thermal analytical experiments and the application of these model cases to the understanding of the kinetics of complex systems at high and low temperatures are discussed.


Thermochimica Acta | 1976

Steady-state parameter-jump methods and relaxation methods in thermogravimetry☆

Joseph H. Flynn; Brian Dickens

Abstract We describe a technique for thermogravimetric analysis in which the magnitude of a rate-forcing variable such as temperature, pressure, gaseous flow-rate, gaseous composition, etc., is jumped by discrete steps. This method can be used to determine kinetic relationships between the rate of weight-loss and the jumped variable. The method avoids the disparate effects of separate experimental histories in methods in which two or more experiments are compared. The necessity for guessing the often complex rate vs. extent of reaction relationship in methods where the rate forcing variable is changed continuously in a single experiment is also avoided. The method is illustrated with examples from the oxidation of polystyrene. Techniques involving multiple jumps and more complex programming are proposed. The fruitful investigation of weight-loss kinetics by the measurement of relaxation times during jumps or of phase lags while the rate forcing variables are oscillated is predicted for diffusion limited reactions and reactions with gaseous atmospheres.


Thermochimica Acta | 1992

Thermal analysis kinetics — past, present and future

Joseph H. Flynn

Abstract The history of the Kinetics Committee of the International Confederation for Thermal Analysis (ICTA) is reviewed. Some of the authors opinions on the development of thermal analysis kinetics over the past thirty years are presented along with his thoughts about areas of future progress.


Thermochimica Acta | 1993

Analysis of DSC results by integration

Joseph H. Flynn

Abstract The integration of data from differential scanning calorimetry to obtain enthalpy vs. time or temperature curves can be performed easily and painlessly with modern thermoanalytical instruments interfaced with computers. This paper reviews old techniques and develops new ones for determining proper thermodynamic quantities and temperatures, and degrees of conversion from the integrated curves. Methods for using the isothermal baseline rather than the transient one for minimizing the displacement from it during a constant heating rate experiment and for calibrating the isothermal temperature are described. Integration avoids errors due to kinetics effects and changes in interfacial resistance in the determination of heat capacity. The thermodynamic or “fictive” glass transition temperature and change in specific heat at the glass transition are determined more easily and in a correct manner by the integration method. The analysis of both sharp and diffuse first order transitions are discussed. Thermodynamically correct temperatures and heats of transition and reaction are obtained through integration. Application of the lever rule to isothermal “tie lines” is used to obtain the correct “fraction reacted” during transitions, and methods for compensating for weight loss and heat of evaporation are discussed. Purity determination by the stepwise isothermal method is briefly reviewed.


Polymer | 1982

A collection of kinetic data for the diffusion of organic compounds in polyolefins

Joseph H. Flynn

Abstract A comprehensive collection of kinetic data on the diffusion of organic compounds in polyolefins is contained in tables for low density polyethylene, high density polyethylene, polyisobutylene, polypropylene, hydrogenated polybutadiene, poly(4-methylpentene-1), ethylene-propylene copolymers, and self-diffusion of polyolefins. Diffusion constants for over 250 polymer-migrant entries at temperatures from −30° to 190°C, activation energies and pre-exponential factors for the diffusion process and parameters for the concentration dependence of the diffusion constant are included. A special feature of this compilation is an extensive section of annotated references. This includes: (1) as complete a characterization of each polymer and migrant as is possible. (2) a description of the experimental methods used to determine the diffusion constants, and (3) the assumptions made, equations utilized and calculations performed to obtain the data in the tables. The tables exhibit remarkable consistencies, considering the great variations in diffusion constants which can be brought about by thermal, mechanical, and solvent action. These consistencies lend hope that useful correlations may be developed from these data.


Thermochimica Acta | 1996

Early papers by Takeo Ozawa and their continuing relevance

Joseph H. Flynn

Eight of the early scientific papers of Takeo Ozawa are listed and their citations in journals are discussed. Some of them are cited with greater and greater frequency as the years go by. They and others of his early works still merit further attention by the scientific community. Their important features are summarized and their relevancy to present day thermal analysis, theory and application is evaluated.


Thermochimica Acta | 1988

Lifetime prediction for polymers from thermal analytical experiments - problems and how to deal with some of them

Joseph H. Flynn

Abstract Heating polymeric materials to accelerate their deterioration often alters their physical and rheological properties, As a result, kinetics parameters and even the degradation mechanism may change in the extrapolation range from accelerated to use conditions. Therefore, predictions based on such extrapolations are invalid. Examples of change in kinetics with changing temperature are given for poly(methylmethacrylate), polystyrene, Polyurethane and poly(ether-ether-ketone). Error propagation during extrapolation is discussed. Some guidelines for successful extrapolation and prediction are presented.


Thermochimica Acta | 1995

Report on the ICTAC Kinetics Committee (August 1992 to September 1994)

Michael E. Brown; Rose Marie Flynn; Joseph H. Flynn

Abstract This report is a summary of the proceedings at the two most recent workshops of the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC), held at the 10th ICTAC Congress, University of Hertfordshire, UK on 28 August 1992 and at the 6th European Symposium on Thermal Analysis and Calorimetry (ESTAC), Grado, Italy on 13 September 1994. It includes the proceedings of a workshop on the kinetics of dehydration of a proposed lithium sulfate monohydrate standard, reports on the present status of Kinetics Committee working projects, and a summary of the discussion at a workshop on “New Directions for Thermal Analysis Chemical Kinetics”.

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Leo A. Wall

National Institute of Standards and Technology

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Brian Dickens

National Institute of Standards and Technology

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Sidney Straus

United States Department of Commerce

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William L. Morrow

National Institute of Standards and Technology

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Albert Hybl

University of Maryland

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Lee A. Dunlap

National Institute of Standards and Technology

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Robert Simha

National Institute of Standards and Technology

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S. Straus

National Institute of Standards and Technology

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E. Segal

University of Bucharest

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