Thermal Analysis of Polymeric Materials E-Book

• Herausgeber: Wiley-VCH GmbH
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 1244

Veröffentlichungsjahr: 2022

Beschreibung

This book delivers a detailed understanding of the thermal behaviour of the polymeric materials which aid in efficient analysis of polymeric thermal properties. It covers the most widely applied principles which are used in method development to substantiate what happens on heating of polymers and their key application areas in materials science. This book supplies the reader with well-chosen information in the field. The power of thermal analytical techniques in polymer science is demonstrated by reporting recent developments in (i) latest advancement in techniques, such as modulated temperature DSC and Fast Scanning calorimetry, (ii) studying the crucial thermal phenomena glass transition, crystallization behaviour, curing kinetics, and (iii) investigating polymeric materials that have gained interest over the last decade. The book also includes the recent hyphenated techniques and their applications.

Leseprobe

Thermal Analysis of Polymeric Materials

Methods and Developments

Volume 1

Edited byKrzysztof PielichowskiKinga Pielichowska

Thermal Analysis of Polymeric Materials

Methods and Developments

Volume 2

Edited byKrzysztof PielichowskiKinga Pielichowska

Editors

Prof. Krzysztof PielichowskiCracow University of TechnologyDepartment of Polymer Chemistry and Technologyul. Warszawska 2431‐155 CracowPoland

Prof. Kinga PielichowskaAGH University of Science and TechnologyDepartment of Biomaterials and CompositesAl. Mickiewicza 3030‐059 CracowPoland

Cover Image: © Jasmin Merdan/Getty Images

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Print ISBN: 978‐3‐527‐35187‐9ePDF ISBN: 978‐3‐527‐82868‐5ePub ISBN: 978‐3‐527‐82870‐8oBook ISBN: 978‐3‐527‐82869‐2

Preface

Thermal analysis (TA) is a group of techniques which are based on simultaneous measurement of the temperature and a physical property of the sample, and these techniques allow to characterize the thermal properties of materials and the thermal effects occurring during chemical reactions and physical processes. As such, thermal analysis methods find broad use in all fields of materials science, chemical engineering and technology, as well as physical chemistry and soft matter physics. One of the important classes of materials that has received increasing attention in recent years are polymeric materials, including pristine polymers, polymer composites, nanocomposites and biocomposites, organic–inorganic hybrids, blends, and interpenetrating polymer networks. Thermal analysis methods substantially contribute to the better understanding of fundamental issues related to glass transition, crystallization, oxidation, and kinetics of decomposition and curing. Evaluation of the thermal properties of polymeric materials, such as degradation behavior, thermal stability, and phase transitions, is of primary importance for numerous applications that have to meet the strict requirements of, e.g. aviation industry.

This book describes recent developments in the area of thermal analysis of polymeric materials, arranged in four parts, focused on methods, fundamentals, materials, and applications. To start with methods, thermal analysis methods have been described in a historical perspective, and on examples of thermogravimetry, differential scanning calorimetry, and thermomechanical analysis, specific features of TA techniques are discussed, as well as their classification provided. Important issues of instrument calibration and sample preparation, as well as the role of various factors on the course of thermal analysis profiles, are also outlined. In the second chapter, the modulated temperature differential scanning calorimetry (MT–DSC) technique developed in the 1990s has been described. The unique feature of this method is that by applying a periodic modulation with a small amplitude to the temperature scan, one can separate the total heat into two types of heat flow, namely the reversing heat flow (sensitive to periodic temperature modulation) and the nonreversing heat flow (insensitive to periodic temperature modulation). Such separation can provide additional information, e.g. on polymer glass transition, enthalpy relaxations, and melting/recrystallization effects. Chapter 3 is devoted to the fast scanning calorimetry (FSC), in which micromachined sensors are applied that enable ultra‐high scanning rates and very high sensitivity. Under these conditions, the kinetics of crystallization and melting processes in rapidly crystallizing materials can be studied, as well as atypical gelation effects, to name a few. The combination of FSC with a structural characterization technique, e.g. WAXD or AFM, allows a deep insight into the various processes (bio)macromolecules undergo. Chapter 4 deals with hyphenated thermal analysis techniques, which link the advantages of thermal analysis methods, such as TG or DSC, with IR spectroscopy features. Such coupled thermoanalytical techniques are useful tools in studying online various thermally induced chemical reactions, such as polymerization and crosslinking.

On the fundamentals, the connection between relaxation phenomena and glass transition in (polymeric) glasses is discussed in Chapter 5. The main α relaxation contribution to the vitrification and physical aging processes, also in a relatively narrow range around the calorimetric Tg, is presented; moreover, secondary mechanism in non‐equilibrium dynamics is discussed, too. Chapter 6 is devoted to polymer crystallization, including crystal nucleation (also studied by the FSC technique), growth, crystallization in polymer blends, and crystallization in industrial processing by, e.g. extrusion and injection molding. Within this technologically important topic, discussion on flow‐induced crystallization has been provided. In Chapter 7, principles and models associated with the polymer curing kinetics are presented. By using isoconversional and model‐fitting approaches to perform kinetic analysis, it is possible to determine kinetic parameters in the mixed kinetic‐diffusion regime and get an in‐depth look into the complex process of cross‐linking polymerization. The heat capacity of polymeric materials is one of the most important quantities that characterize the thermodynamic properties in advanced thermal analysis, and it has been thoroughly discussed in Chapter 8. Calorimetric techniques, such as DSC, MT–DSC, and FSC, and advanced thermal analysis make it possible to separate reversible and irreversible processes in the entire temperature range for the determination of thermodynamic and apparent heat capacities of polymeric systems. The thermo(oxidative) stability of polymeric materials, understood as the ability of a material to preserve its properties, especially mechanical properties, at elevated temperature and in an oxidative environment, is the subject of Chapter 9. The main concepts of the thermo(oxidative) behavior of polymers, good experimental practice, current testing procedures involving the use of hyphenated techniques and protocols for the determination of the oxidation induction time and thermo(oxidative) characteristics of different polymeric materials, including pristine polymers, blends, and composites, have been critically presented.

In the field of materials, the application of thermal analysis methods, particularly DSC and MT‐DSC, for the investigation of the properties of liquid crystalline polymers, has been presented in Chapter 10. DSC is a useful tool to determine, e.g. the liquid crystalline transitions of mesogenic diepoxides‐containing compositions and curing conditions of liquid crystalline polymer networks, modified by various fillers, crosslinked in magnetic field. In Chapter 11, thermal analysis of polymer nanocomposites and hybrid materials has been described. The influence of nanofillers and inorganic components on thermal degradation behavior, glass transition region, and thermomechanical properties has been discussed, along with the presentation of current challenges and future research directions. Chapter 12 titled “Biocomposites and Biomaterials” focuses on the application of thermal analysis techniques, such as TG, DSC, and DMA, to study the properties of biomaterials, including thermal stability, purity, and phase transitions. Useful information on the curing parameters of bone cements that contain phase‐change materials, as well as on the determination of the water content in hydrogel biomaterials, is also given. Thermal analysis methods for the characterization of polymer additives are presented in Chapter 13, which contains a wealth of valuable information on the application of TA methods for the characterization of additives that are widely used in the fabrication and processing of polymeric materials. Thermal stability and decomposition behavior of flame retardants, (nano)fillers, pigments, stabilizers, antioxidants, processing aids, etc. need to be checked before they are admixed to the polymer matrices, and thermal analysis techniques are indispensable tools in that respect.

In the Application part, thermal analysis in polymers recycling has been discussed in Chapter 14. Circular economy strategy and protection of the environment require proper characterization, identification, and quality control of the recycled polymers, as well as development of more efficient mechanical and chemical recycling routes of polymer wastes; in both these areas, TA and coupled thermoanalytical methods are vastly used. Chapter 15 deals with application of thermal analysis methods for life‐time predictions; such predictions are of primary importance to foresee the durability of polymers employed in structural applications and to plan the environmentally safe disposal of polymer wastes after their lifetime. In Chapter 16 application of thermal analysis methods – (modulated temperature) differential scanning calorimetry, thermogravimetry alone or coupled with spectroscopic techniques for evolved gas analysis, as well as dynamic mechanical analysis, for the characterization of organic and polymeric materials used in electrolytes and batteries, photovoltaic and solar cells, and as phase‐change materials for thermal energy storage, has been discussed. Thermal analysis of pharmaceutical glasses stabilized by polymers is presented in Chapter 17, which outlines the role of thermal analysis techniques in studying drug–polymer interactions that govern the dissolution behavior and storage stability. The influence of the thermal history on the product performance and the stabilization effect of the amorphous drugs by the polymers are discussed, too. In Chapter 18 titled “Thermal Analysis in Aerospace and Automotive Sectors” coupled techniques, such as TGA–MS, TGA–FTIR, and TGA–GC/MS, are shown to be versatile thermoanalytical tools that produce quantitative and qualitative information on volatile products released during thermal decomposition of advanced polymeric materials used in aerospace and automotive sectors. Finally, in Chapter 19, the application of thermal analysis methods for the characterization of textiles and fibers has been described. Textiles used, for example, in firefighting, aerospace and metallurgy/mining industries need to meet strict thermal stability requirements; polymer products can be evaluated by TA techniques, such as TG, TG–FTIR, TG–MS, and DSC.

We hope that this book will be a valuable source of information in the growing field of thermal analysis of polymeric materials. Thermal analysis techniques are an important group of methods that are widely used for characterization of the thermal properties of polymer materials. As pristine polymers have already been thermally characterized over the past five decades, most of the research interest in polymeric materials goes nowadays to advanced materials, such as polymer (nano)composites and organic–inorganic materials. However, because of the size and nature of novel bio‐ and nanoadditives, new effects have been observed that need careful examination by using both classical thermal analysis methods and new ones, such as recently developed fast scanning calorimetry. Knowledge on these effects and how to study them properly by using thermal analysis methods, especially the new ones, is distributed and fragmented in numerous scientific publications (some of them very recent), and there is no single source available that covers the most essential information; thus, with this book, the reader will benefit by having access to well‐chosen information on the recent developments in the field, provided by renowned experts.

This book is aimed at a wide audience of researchers working in the area of polymeric materials, especially in the rapidly growing field of polymer (nano)composites, biocomposites, and hybrid materials. Those who are introductory and advanced readers will have up‐to‐date knowledge of recent developments in the thermal analysis of polymeric materials. It will be relevant to readers from academia (postgraduate and Ph.D. students, and postdoc researchers, as well as lecturers preparing their teaching materials), and to engineers and technologists, as well as analytical chemists working in polymer, materials science, and relevant industrial sectors.

We are grateful to all contributors for the time and care that they have taken in preparing chapters, and to Wiley team for continuous support and smooth collaboration during the editing period.

Kraków, 14 February 2022

Krzysztof Pielichowski

Kinga Pielichowska

Part IMethods

1Thermoanalytical Methods: Fundamental Principles and Features

Nobuyoshi Koga

Hiroshima University, Graduate School of Humanities and Social Sciences, Department of Science Education, Division of Educational Sciences, 1‐1‐1 Kagamiyama, Higashi‐Hiroshima, 739‐8524, Japan

1.1 Introduction

Thermally induced transformations accompanied by the thermal energy exchanges in materials are natural phenomena, which have supported the history of human beings and the current development of our society. We human beings started to use fire in primitive times, which was sometimes natural secret and threats. The effective use of fire significantly improved primitive lives and brought ancient civilizations, as typically seen for the attempts at doing pottery, smelting metal, and producing glass [1]. The primitive concept of “heat” was thus created and has long been inquired to achieve the current scientific definition as a form of energy based on thermodynamics. Another important concept is “temperature,” which might be initially created based on daily lives as a wind‐chill factor. As in “heat,” the theoretical definition of “temperature” and the clearly separated recognition of “temperature” from “heat” required a long duration of transition from philosophical to scientific. The inventions of thermometers and definitions of temperature scales in the seventeenth and eighteenth centuries significantly contributed to the establishment of the theoretical definitions of “heat” and “temperature” through the systematization of thermodynamics [2]. Thus, we acquired the theoretical basis and practical tool for thermometry and calorimetry in the nineteenth century [3].

The thermometric measurement applied to clay minerals by Le Chaterier in 1887 [4, 5] is widely recognized as the beginning of our technique, that is, “Thermal Analysis (TA).” An important concept of differential measurement was introduced by Roberts‐Austen in 1899 establishing one TA method [6, 7], that is, differential thermal analysis (DTA). A measurement for the changes in property of sample substance, other than as appeared in thermometric curve, was invented by Honda in 1915 [8] using a thermobalance for recording the changes in sample mass during controlled temperature change, that is, thermogravimetry (TG). According to the International Confederation for TA and Calorimetry (ICTAC), “TA” is defined as “A group of techniques in which a property of a sample is monitored against time or temperature while the temperature of the sample, in a specified atmosphere, is programmed (1991).” [9] A TG instrument that fulfilled the ICTAC definition in 1991 had already been developed in 1920s by modifying Honda's thermobalance, as illustrated in Figure 1.1[10], and distributed commercially in Japan. The Honda's thermobalance modified by Saito was composed of (i) temperature control system using a variable resistor, (ii) atmospheric gas control system by flowing gases, (iii) detection system for the change in sample mass (sample property) using an analytical balance, (iv) temperature measurement and recording system using a thermocouple and pyrometer, and (v) recording system for the change in sample mass (sample property) by reading the tilt of the analytical balance. The modern thermoanalytical instruments have been achieved by dramatic improvements of the controlling and measuring systems of (i)–(v), as well as the inventions of new thermoanalytical techniques subjected to changes in different sample properties, which induced by various temperature alteration modes.

Figure 1.1 Schematic of Honda's thermobalance modified by Saito [10].

The modern thermoanalytical techniques revealed various novel findings of materials with regard to the temperature–heat–physical property relationship, as will be described for the polymeric materials in this book. The further progress of “TA” is necessary to reveal comprehensively the multidisciplinary nature of materials for realizing the ideal functionality of materials that enables sustainable development of our society by overcoming current challenges. As an introduction, fundamental principles and practices of TA are discussed in this chapter for finding the way for better TA measurements.

1.2 Classification of Thermoanalytical Techniques

1.2.1 Changes in Sample Property Subjected to Measurement

The current definition of TA is “Thermal Analysis (TA) is the study of the relationship between a sample property and its temperature as the sample is heated or cooled in a controlled manner (2014).” [11] According to the definition, any analytical techniques that measure and track the changes in a sample property with responding to controlled temperature change can be classified into TA. Traditionally, the classification of TA techniques is made with regard to the physical property or quantity subjected to the measurement during the controlled changes in sample temperature. The major TA techniques are summarized in Table 1.1. Other TA techniques that measure magnetic properties (Thermomagnetometry), optical properties (Thermoptometry), acoustic properties (Thermoacoustimetry), electrical properties (Thermoelectrometry), and structural properties (Thermodiffractomentry, Thermospectrometry) are usually listed as the family of TA. These primarily classified techniques are in many cases further classified into different special techniques of the practical uses. For example, differential scanning calorimetry (DSC) is further classified into the power compensation DSC and heat‐flux DSC because of the different principles of measurement. In thermomechanometry, the different load application modes lead to special techniques to measure different aspects of the mechanical properties of sample. Under applying negligible force, changes in the sample dimension are measured against temperature (Thermodilatometry, TD). Under applying a static force or dynamic force, the deformation of the sample is measured as the function of sample temperature or at a constant temperature as the function of force (static force thermomechanical analysis [sf‐TMA] or dynamic force thermomechanical analysis [df‐TMA]). When modulated force was applied, moduli (stress/strain) are determined (modulated force thermomechanical analysis [mf-TMA] or dynamic thermomechanical analysis [DTMA]). In all thermoanalytical techniques, sample temperature and the specific physical property of sample are measured simultaneously as a function of time. As in thermomechanometry, when the changes of sample property are measured in relation to the sample temperature and the other additional parameter, the additional parameter should be simultaneously measured as a function of time.

Table 1.1 Classification of major thermoanalytical techniques in view of physical property to be measured.

Physical property

Measurement parameter

Sensor/detector

Technique

Data

Invention

Temperature

Sample temperature

Thermometer

Thermometry or heating/cooling curve analysis

(Time,

T

)

1887 Le Chatelier [

4

,

5

]

Temperature difference between sample and reference (Δ

T

SR

 = 

T

S

 − 

T

R

)

Thermometer

Differential thermal analysis (DTA)

(Time,

T

, Δ

T

SR

)

1899 Roberts‐Austen [

6

,

7

]

Mass of condensed phase

Mass change (Δ

m

), derivative mass change (d

m

/d

t

)

Balance

Thermogravimetry (TG) Derivative thermogravimetry (DTG)

(Time,

T

, Δ

m

) (Time,

T

, d

m

/d

t

)

1915 Honda

[8]

Amount of exchanged gas

Pressure (

P

) or concentration (

c

)

Manometer, thermal conductivity meter, or concentration meter

Thermomanometry; exchanged gas detection (EGD)

(Time,

T

,

P,

or Δ

P

) or (time,

T

,

c,

or Δ

c

)

Eighteenth century, for example: Wedgwood [

12

,

13

]

Amount and nature of evolved gas

Spectrum

Mass spectrometer (MS) Gas chromatography (GC)

Evolved gas analysis (EGA)

(Time,

T

, MS) (Time,

T

, GC)

Enthalpy

(a) Difference in the electrical power supplied to sample and reference (Δ

p

SR

 = 

p

S

 − 

p

R

)

(b) Δ

T

SR

 = 

T

S

 − 

T

R

(a) Thermometer and ammeter

(b) Thermometer

Differential scanning calorimetry (DSC)    

(a) Power compensation DSC

(b) Heat‐flux DSC

(a) (Time,

T

, Δ

p

SR

 → d

h

/d

t

)

(b) (Time,

T

, Δ

T

SR

 → d

q

/d

t

)

(a) 1963 Perkin Elmer Corp

[14]

.

(b) 1940–1970s (Quantitative DTA) [

15

,

16

]; 1978 Du Pont Instrument

Dimension and mechanical properties

(a) Under negligible load: length change (Δ

L

)

(b) Under constant load: Δ

L

(c) Under applying periodically varying stress/strain: moduli (storage/loss)

Linear variable displacement transducer (LVDT)

Thermomechanometry    

(a) Thermodilatometery (TD)

(b) Thermomechanical analysis (TMA)

(c) Dynamic thermomechanical analysis (DTMA or DMA)

(a) (Time,

T

, Δ

L

)

(b) (Time,

T

,

F

, Δ

L

)

(c) (Time,

T

,

F

, Δ

L

 → moduli (storage/loss))

Combinations of more than one TA techniques enabling simultaneous measurements are also used to characterize the thermal events from different viewpoints. Simultaneous measurements of TG and DTA or DSC are commonly used (TG–DTA or TG–DSC), enabling the characterization of the thermal events of the sample in views of mass change and thermal effect. When the outlet gas from the TG–DTA instrument was introduced into EGA instrument such as mass spectrometer [17–19] and Fourier transform infrared (FTIR) spectrophotometer [20–22], simultaneous and combined measurements of TG/DTA–EGA are realized (see Chapter 4). Combination of differential scanning calorimetry with X‐ray diffractometry (DSC–XRD) reveals the relation between the thermal event of the sample with its structural change [23–28]. If microscopic views of the sample during the TG or DSC measurement are recorded, the relation of the thermal event and the morphological change of the sample are clearly evidenced (TG–thermomicroscopy or DSC–thermomicroscopy) [29]. Any other simultaneous measurements of different physical properties of the sample enabled by combining different TA techniques could invent new faces of TA.

1.2.2 Temperature Program Modes

Another standpoint of classification of TA techniques is the temperature program modes. Modern TA instruments rig sophisticated software and equipment to realize a variety of temperature alteration profiles for the TA measurement. This provides us TA information of the thermal event subjected to study from different viewpoints [30], even if the changes in the same physical property are measured using the same instrument. Figure 1.2 shows examples of TG–derivative thermogravimetry (DTG) measurements for the thermal decomposition of sodium hydrogen carbonate using different temperature program modes [31]. Classical measurement to trace a thermal event at a constant temperature (isothermal mode, Figure 1.2a) is still a necessary method to reveal the transformation behavior as a function of time, in which the sample is initially heated linearly at a large heating rate (β) to the desired temperature and kept at the temperature for observing time‐dependent change in a physical property. Measurements under linearly increasing or decreasing temperatures at β are the most common method in TA (linear nonisothermal mode, Figure 1.2b). In these traditional temperature program modes, the controlled temperature at a time (T(t)) in each program section is expressed by

(1.1)