Laske Polymer Nanoclay Composites

1. Auflage 2015
ISBN: 978-0-323-31272-1
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 194 Seiten

Reihe: Micro and Nano Technologies

There is a major lack of fundamental knowledge and understanding on the interaction between a filler and the polymer matrix. When it comes to nanoscale fillers, such as layered silicates, carbon nanotubes, graphene or cellulose nanofibers it is even more important to know accurate structure-property relationships as well as identifying the parameters influencing material behavior. The reason for the lack of knowledge on how to process nanocomposites and why there are so few applications is that several scientific fields are affected and a joint effort of those scientific communities involved is necessary - starting from the filler manufacturing or pre-processing over polymer chemistry to the polymer processing. In Polymer Nanoclay Composites, all involved scientific areas are viewed together for the first time, providing an all-embracing coverage of all stages of polymer clay nanocomposites processing from lab-scale to industrial scale - stages from the raw material over manufacturing of polymer clay nanocomposites to characterization and the final products. Readers will gain insight in the physical/chemical pre-processing of layered silicates and their incorporation into a polymer matrix using sophisticated technologies (such as advanced compounding) as well as in real-time quality control of the nanocomposite production and future prospects. The book also describes nanotoxicological and nanosafety aspects. - Covers the whole processing route with all aspects of the nanocomposites industry with particular focus on the processing of polymer clay nanocomposites - Includes quality control and nanosafety - Multidisciplinary approach from an industrial perspective

Autoren/Hrsg.

Laske, Stephan

Inhaltsverzeichnis

1;Front Cover;1
2;Polymer Nanoclay Composites;4
3;Copyright Page;5
4;Contents;6
5;Introduction;10
5.1;Acknowledgments;12
5.2;References;12
6;1 Processing of calcium montmorillonites for use in polymers;14
6.1;1.1 Introduction;14
6.2;1.2 Definitions;18
6.3;1.3 Morphology of montmorillonite which is important for use in the polymer industry;18
6.4;1.4 Introduction—the activation of calcium bentonites to achieve a high aspect ratio;21
6.4.1;1.4.1 Problems in determining the soda ash dosage for the deposit-specific optimized cation exchange;22
6.4.2;1.4.2 Chemical–mineralogical basis of the alkaline activation of bentonites and technical problems in the realization;22
6.4.3;1.4.3 Thixotropy and yield point of bentonite suspensions;23
6.4.4;1.4.4 Definitions of a chemical and technical degree of activation;25
6.4.5;1.4.5 Activation technique;26
6.4.6;1.4.6 Determination of the yield point;29
6.5;1.5 Criteria for the selection of calcium bentonites, their alkaline activation, and the achievable aspect ratio;35
6.6;1.6 Conclusions;38
6.7;References;38
7;2 Chemical/physical preprocessing of nanoclay particles;40
7.1;2.1 Introduction—montmorillonite;41
7.2;2.2 Activation;42
7.2.1;2.2.1 Activation by acids;42
7.2.2;2.2.2 Characterization of activated MMT;44
7.2.2.1;2.2.2.1 EDX spectroscopy;44
7.2.2.2;2.2.2.2 FTIR spectroscopy;44
7.2.2.3;2.2.2.3 Thermogravimetric analysis;45
7.2.2.4;2.2.2.4 Medium angle X-ray scattering;46
7.3;2.3 Metal cation exchange;47
7.3.1;2.3.1 Metal-(II)-cations;47
7.3.2;2.3.2 Metal-(III)-cation;49
7.3.3;2.3.3 Characterization of metal cation–exchanged montmorillonite;50
7.3.3.1;2.3.3.1 EDX spectroscopy;50
7.3.3.2;2.3.3.2 FTIR spectroscopy;50
7.3.3.3;2.3.3.3 Thermogravimetry;52
7.4;2.4 Organomodification;52
7.4.1;2.4.1 Amino acid as modification reagent;53
7.4.2;2.4.2 Characterization of organomodified montmorrilonite;57
7.4.2.1;2.4.2.1 FTIR spectroscopy;57
7.4.2.2;2.4.2.2 Thermogravimetric analysis;57
7.4.2.3;2.4.2.3 MAXS measurements;60
7.5;2.5 Conclusions;61
7.6;References;62
8;3 Processing of polymer–nanoclay composites;66
8.1;3.1 Nanoclay Processing Basics;67
8.1.1;3.1.1 “Melt mixing” (compounding);67
8.1.2;3.1.2 Characteristic process parameters;67
8.1.2.1;3.1.2.1 Residence time characteristics;67
8.1.2.2;3.1.2.2 Specific energy input;68
8.1.2.3;3.1.2.3 Case study: influence of induced shear energy on the properties of polyolefine nanocomposites [1];69
8.1.2.3.1;3.1.2.3.1 Materials;69
8.1.2.3.2;3.1.2.3.2 Production of nanocomposites;69
8.1.2.3.3;3.1.2.3.3 Specimen;70
8.1.2.3.4;3.1.2.3.4 Tests;70
8.1.3;3.1.3 Calculation of the shear energy for extrusion and compounding;71
8.1.4;3.1.4 Calculation of the shear energy for injection molding;71
8.1.5;3.1.5 Visualization of nanoclay dispersion;72
8.1.6;3.1.6 Influence of shearing on Young’s modulus and breaking strain;72
8.1.7;3.1.7 Influence on internal pressure creep time and longitudinal shrinkage;75
8.1.8;3.1.8 Conclusions;76
8.2;3.2 Advanced compounding;77
8.2.1;3.2.1 Case study: extrusion of PP nanocomposites by advanced compounding [2];77
8.2.1.1;3.2.1.1 Materials and methods;77
8.2.1.1.1;3.2.1.1.1 Materials;77
8.2.1.1.2;3.2.1.1.2 Process design;77
8.2.1.1.3;3.2.1.1.3 Extensional melt rheology;79
8.2.1.2;3.2.1.2 Results and discussion;80
8.3;3.3 Injection mold compounding;84
8.3.1;3.3.1 Case Study;86
8.3.1.1;3.3.1.1 Experimental;87
8.3.1.2;3.3.1.2 Results;89
8.4;3.4 Conclusions;102
8.5;References;103
9;4 Characterization of polymer nanocomposites based on layered silicates;106
9.1;4.1 Introduction;107
9.2;4.2 Offline characterization;107
9.2.1;4.2.1 Spectroscopic measurements;107
9.2.1.1;4.2.1.1 WAXS and TEM;107
9.2.1.2;4.2.1.2 Nuclear magnetic resonance;109
9.2.1.3;4.2.1.3 Infrared and Raman spectroscopy;109
9.2.2;4.2.2 Determination of physical properties;110
9.2.3;4.2.3 Rotational rheometry;111
9.2.4;4.2.4 Extensional rheometry;113
9.3;4.3 Inline And online characterization;114
9.3.1;4.3.1 Online extensional rheometry with the help of Rheotens equipment;114
9.3.2;4.3.2 Inline NIR investigations;117
9.3.2.1;4.3.2.1 Principal component analysis;119
9.3.2.2;4.3.2.2 Multiple linear regression;122
9.3.2.3;4.3.2.3 Principal component regression;122
9.3.2.4;4.3.2.4 Partial least squares;123
9.3.2.5;4.3.2.5 Diagnostic methods to assess the quality of the calculated model;124
9.3.2.6;4.3.2.6 Pretreatment methods;126
9.3.2.7;4.3.2.7 Mean centering;126
9.3.2.8;4.3.2.8 Variance scale;127
9.3.2.9;4.3.2.9 Path length correction;127
9.3.2.10;4.3.2.10 Smoothing and derivation;128
9.3.2.11;4.3.2.11 Baseline shift;129
9.3.2.12;4.3.2.12 Outliers;129
9.3.2.13;4.3.2.13 Euclidean distance;130
9.3.2.14;4.3.2.14 Mahalanobis distance;131
9.3.2.15;4.3.2.15 Outlier species and their potential effect on models;132
9.3.2.16;4.3.2.16 NIR works;132
9.4;4.4 Conclusions;135
9.5;References;135
10;5 Properties and applications of nanoclay composites;140
10.1;5.1 Introduction;140
10.2;5.2 Mechanical reinforcement capabilities of layered silicates;141
10.3;5.3 Effect of layered silicates on the rheological properties;144
10.4;5.4 The influence of layered silicates on barrier properties;146
10.5;5.5 The influence of layered silicates on tribology;149
10.6;5.6 Thermal conductivity of layered silicate polymer nanocomposites;150
10.7;5.7 Thermal stability of layered silicate polymer nanocomposites;151
10.8;5.8 Layered silicates for biodegradation application;153
10.9;5.9 Clays for drug delivery systems;155
10.10;5.10 Layered silicates as halogen-free FRs;156
10.10.1;5.10.1 Development of fire;156
10.10.2;5.10.2 Layered silicates as FR additives;161
10.11;5.11 Summary;162
10.12;References;163
11;6 Safety issues of silica nanomaterials in the frame of industrial use;170
11.1;6.1 Introduction;170
11.2;6.2 Safety assessment according to REACh and guidance;173
11.2.1;6.2.1 Exposure and toxicity assessment;173
11.2.1.1;6.2.1.1 Exposure routes;175
11.2.1.2;6.2.1.2 Safety data sheets;177
11.2.2;6.2.2 Standardization;177
11.3;6.3 Nano-silica use in applications;178
11.3.1;6.3.1 Workplace safety;179
11.3.2;6.3.2 Environmental safety on nano-silica;182
11.4;6.4 Conclusions;182
11.5;Acknowledgment;184
11.6;Abbreviations;184
11.7;References;185
12;Index;190

Leseproben

Introduction
Stephan Laske Using (in)organic fillers in a polymer matrix has a long history in polymer science and engineering in order to achieve desired mechanical, rheological, chemical, or thermal properties [1–3]. There is ample (published) experience on which properties of the filler and the filler–matrix interface influence the compound [4–6], but still a major lack of fundamental knowledge and understanding exists on the interaction between the filler and the polymer matrix as well as on the mode of operation. When it comes to nanoscale fillers, such as layered silicates, carbon nanotubes, graphene, or cellulose nanofibers, it is even more important to know accurate structure–property relationships as well as identifying the influencing parameters, e.g., at the filler–matrix interface as structural arrangements on the molecular level influence the mechanical behavior at the macro level [7–14]. It has already been shown [15,16] that using nanofillers in polymer matrices poses a number of challenges, which includes the modification of the filler (e.g., ionic exchange reactions), the processing of the composite material (e.g., high residence time and shear rate needed simultaneously), or the material characterization (e.g., under mechanical loading). Previous results with layered silicates illustrated that for improved mechanical properties a highly intercalated structure and for enhanced barrier or flame retardancy a highly exfoliated structure is needed [17,18]. This example demonstrates the importance of structural arrangements on the molecular level for the mechanical behavior at the macroscale level and the need for the determination of accurate structure–property relationships as well as identifying the influencing parameters, e.g., at the filler–matrix interface [19,20]. These mentioned circumstances are the reasons for the complexity in processing polymer nanocomposites and why there are still only few applications. Furthermore, not only one scientific field is affected and joint efforts of several scientific communities are necessary. Starting from the filler manufacturing or preprocessing (e.g., the fiber manufacturers or the mineralogist who provides the raw material) over the polymer chemistry adding, e.g., the correct surface modification and functionalization, to the polymer processing using adequate techniques and processes for achieving flawless materials, every step in this chain is just a part of the puzzle. Within this book for the first time, all involved scientific areas are working together providing an all-embracing look on processing of polymer nanocomposites bridging the gap from the raw material to the final composite. This book gives an impressive gain insight the physical/chemical preprocessing of layered silicates, their incorporation into a polymer matrix using sophisticated technologies (such as injection molding compounder or advanced compounding) as well as in-line, real-time quality control of nanocomposite production and prospects of nanocomposite materials. Finally, a nanotoxicological view on the new materials completes the book and covers all aspects of nanocomposite industry. This book concentrates on one special class of nanofillers, which attracted both academic and commercial interest for several years due to their availability and costs, layered silicates. The main advantage of nanofillers is their high specific surface area which allows to achieve or exceed certain levels of specific properties with only a very small amount of filler compared to conventional fillers. Montmorillonite, hectorite, and saponite are the most commonly used layered silicates. Their crystal structure consists of layers made up of two tetrahedral coordinated silicon atoms fused to an edge-shared octahedral sheet of either aluminum or magnesium hydroxide. The layer thickness can be estimated with 1 nm. The other two dimensions vary from 30 nm to several microns or larger. Normally these layers form stacks, with a gap (due to van der Waals forces) between the single layers (see Chapter 1). Two particular characteristics of layered silicates are helpful for satisfactory dispersion and forming of different structures (agglomerated, intercalated, and exfoliated) in the polymer matrix. On the one hand, the layered silicates have the ability to disperse into individual layers (swelling). On the other hand, the surface chemistry of the layered silicates can be changed via ion exchange reactions with organic and inorganic cations (see Chapter 2). The organomodified layered silicate can be incorporated inside the carrier polymer due to supportive thermodynamics, during the ultimate steps of processing, in methods such as extrusion (compounding) or injection molding, to generate nanocomposite materials. As mentioned before, layered silicate filled polymer nanocomposites are processable by most of the commonly used processing techniques in industrial scale (see Chapter 3). During the process, the structures which are responsible for the level of reinforcement are formed by physical bonding between the hydrophilic clay, the hydrophobic polymer matrix, and if nonpolar polymers are used, a compatibilizer [21,22]. To characterize the homogeneity respectively the properties of the material, a variety of methods are used. These methods comprise offline as well as inline methods and outrun often the commonly used practice and interpretations for the specific needs of nanocomposite evaluation (see Chapter 4). If implemented properly such polymer nanocomposite materials can display a property profile which exceeds that of conventional filled polymer systems in several ways. Such properties cover multiple aspects including strength, stiffness, thermal as well as oxidative stability, diffusion properties against gas molecules and flame retardancy [23,24]. This enhanced property profile, obtained only by the addition of comparably small amounts of silicate layers to the carrier polymer, is especially attractive for certain applications due to the fact that polymer layered silicates nanocomposites have a significantly improved weight to performance ratio [12,23,25,26] (see Chapter 5). Another aspect that separates organomodified layered silicates as filler for polymers from conventional filler systems is indeed the significant reduction or absence of property trade-offs. Conventional polymer blends or composites implement the necessity to trade-off desired performance, mechanical properties (especially toughness and elongation properties), cost and processability. Polymer nanocomposites offer a passage to bypass these limitations of conventional polymer filler systems and thereby giving the opportunity to shape material properties without taking compromises in the cost of property trade-offs [23,24,27]. Especially for commodity matrix polymers such as polypropylene (PP) or polyethylene (PE), the addition of nanofillers offers great potential in improvement of certain properties, e.g., Young’s modulus and barrier properties simultaneously. Thereby the low cost of commodity plastics as well as their huge field of applications and the tuning of the final property profile with nanoscaled fillers offers tremendous opportunities in the application of such nanocomposites. Besides the modification, processing, and application of nanocomposites, nanotoxicology is always a necessary and overall important topic. Regarding the environmental and human hazards, numerous potential exposure scenarios for nanofillers within polymers, e.g., during the manufacture and machining process or generated during usage/recycling for both workers and consumers need to be considered in comprehensive risk assessment (see Chapter 6). Acknowledgments
The editor wants to thank all the authors for the contribution of their excellent and forward-looking work as well as their collaboration and effort for the “pit-to-part” idea. Furthermore, this book would not exist in this quality, if not many reviewers spent their rare time for revising the single chapter. At that point the editor wants to thank Dr. Hans Kolb, Dr. Joerg Schausberger, DI Tobias Struklec, Dr. Ivica Duretek, Ali Gooneie, Lis, and Dr. Lisa Bregoli. June 2014 References
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