nanoscale particles for polymer degradation

Accepted Manuscript Title: Nanoscale Particles for Polymer Degradation and Stabilization – Trends and Future Perspectives Authors: Annamalai Pratheep Kumar, Dilip Depan, Namrata Singh Tomer, Raj Pal Singh PII: S0079-6700(09)00011-2 DOI: doi:10.1016/j.progpolymsci.2009.01.002 Reference: JPPS 573 To appear in: Progress in Polymer Science Received date: 6-1-2008 Revised date: 13-1-2009 Accepted date: 14-1-2009 Please cite this article as: Kumar AP, Depan D, Tomer NS, Singh RP, Nanoscale Particles for Polymer Degradation and Stabilization – Trends and Future Perspectives, Progress in Polymer Science (2008), doi:10.1016/j.progpolymsci.2009.01.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 1 Nanoscale Particles for Polymer Degradation and Stabilization – Trends and Future Perspectives Annamalai Pratheep Kumar 1 , Dilip Depan 1 , Namrata Singh Tomer 2 and Raj Pal Singh 1 ∗ 1 Polymer Science and Engineering Division National Chemical Laboratory, Pune-411008, India E-mail: rp.singh@ncl.res.in Telephone: +91-20-25902091, Fax: +91-20-25902615 2 Department of Chemical & Biomolecular Engineering Clemson University, Clemson, SC 29634-0909, USA Abstract The field of nanoscience and nanotechnology is extending the applications of physics, chemistry, biology, engineering and technology into previously unapproached infinitesimal length scales. The polymer – nanoparticles / nanocomposites have been the exponentially growing field of research for developing the materials in last few decades and have been mainly focusing on the structure-property relationships and their development. Since the polymer-nanocomposites have been the staple of modern polymer industry, their durability under various environmental conditions and degradability after their service life are also essential fields of research. Thus, this article is intended to review the status of worldwide research in this aspect. Among various nanoparticulates, clay minerals and carbon nanotubes are more often used in enhancing physical, mechanical and thermal properties of polymers. In very few systems, the nanoparticulates have been incorporated into polymer as ‘nano-additives’ for both purposes: degradation and stabilization of polymers. The degradation and durability of polymers is reviewed in the presence of nanoparticles / nanocomposites under different environmental conditions. Nanoparticle -induced biodegradation of polymers is also discussed. ∗ Corresponding author 2 Key words: Polymer, nanoparticles, clay, carbon nanotubes, metal oxides, nanocomposites, degradation and stabilization. 3 Contents 1. Introduction 1.1. Definitions 1.2. Various classifications of polymeric nanomaterials 1.2.1. Nanoparticles 1.2.2. Nanocomposites 1.3. Growth and Significance 2. Preparation and processing of polymeric nanomaterials 2.1. Nanocomposites based on layers 2.2. Nanocomposites based on nanotubes 2.2.1. Carbon nanotubes 2.2.2. Cellulose whiskers 2.2.3. Inorganic nanotubes/nanofibers 2.3. Nanocomposites using nanoparticles 2.3.1. Synthesis of nanoparticles: Nucleation and growth 2.3.2. Preparation methods 2.4. Characterization of nanoparticulates and nanocomposites 3. Degradability and durability of Polymers: Overview 4. Degradation of polymeric nanomaterials 4.1. Photo-degradation and stabilization 4.1.1. Nanocomposites based on nanolayers 4.1.1.1.Polyolefins 4.1.1.2.Polyacrylates 4.1.1.3.Polyesters 4.1.1.4.Polycarbonates 4.1.1.5.Polyamides 4.1.2. Nanocomposites based on nanotubes / nanofibers 4.1.3. Nanocomposites based on nanoparticles 4.2. Thermal degradation and stabilization 4.2.1. Nanocomposites based on nanolayers 4.2.1.1.Polyolefins 4.2.1.2.Ethylene vinyl acetate copolymer 4.2.1.3.Polyacrylates 4.2.1.4.Polyesters 4.2.1.5.Polycarbonates 4.2.1.6.Polyamides and polyimides 4.2.1.6.1. Polyamides 4.2.1.6.2. Polyimides 4.2.1.7.Epoxy Polymers 4.2.1.8.Polyethers/ Polyurethanes/ Silicon rubbers 4.2.1.9.Miscellaneous 4.2.2. Nanocomposites based on nanotubes / nanofibers 4 4.2.3. Nanocomposites based on nanoparticles 4.3. Biodegradation and stabilization 4.3.1. Nanocomposites of biodegradable polymers 4.3.1.1.Biopolymers as matrix 4.3.1.2.Biopolymers as fillers 4.3.2. Nanocomposites of non-biodegradable polymers 4.4. Other factors 4.5. Advantages over conventional additives (stabilizers/ sensitizers) 5. Future perspectives 5.1. Road to new polymer-nanoparticulates systems 5.2. Importance for studying durability /degradability 5.3. Need of new stabilizing systems 6. Conclusions Acknowledgement Reference 5 Abbreviations µm Micrometre AAGR Average Annual Growth Rate AGU Anhydroglucose Unit ATH Aluminium trihydroxides BZD Benzidine CMC Critical Micelle Concentration CNT Carbon Nanotubes CVD Chemical Vapour Deposition DMA Dynamo Mechanical Analysis DNA Deoxyribose Nucleic Acid DP Degree of Polymerization DSC Differential Scanning Calorimetry EPDM Ethylene-Propylene Diene Monomer EVA Ethylene Vinyl Acetate Copolymer FTIR Fourier Transform Infra Red GPC Gel-Permeation Chromatography HAP Hydroxyapatite LDH Layered double Hydroxides LDPE Low Density Polyethylene LLDPE Linear Low Density Polyethylene MMT Montmorillonite MWCNT Multi-walled Carbon Nanotubes NC Nanocrystal nm Nanometre NMR Nuclear Magnetic Resonance NSP Nano scale particles OATP Organo Attapulgite OMMT Organically Modified Montmorillonite PBT Polybutylene Terphthalate PC Polycarbonate PE Polyethylene PLA Polylactic Acid PMMA Polymethyl Methacrylate PP Polypropylene PU Polyurethane PVD Physical Vapour Deposition SAXS Small Angle X-Ray Scattering SEM Scanning Electron Microscopy SPHERE Simulated photodegradation of high-energy radiant exposure SWCNT Single-walled Carbon Nanotubes TEM Transmission Electron Microscopy T g Glass Transition Temperature TGA Thermogravimetric Analysis TMDS Tetramethyl disiloxane USAXS Ultra Small X-Ray Scattering Spectroscopy 6 UV Ultraviolet WAXD Wide Angle X-Ray Diffraction XPS X-Ray Photo Electron Spectroscopy XRD X-Ray Diffraction 7 1. Introduction The field of nanoscience and nanotechnology which deals with materials and structures having dimensions that measure up to billionth of a meter (nanometer) is extending the applications of physics, chemistry, biology, engineering and technology into previously unapproached infinitesimal length scales. Now, at nanoscale one enters a world where physics and chemistry meet and develop novel properties of matter. In chemistry, this range of sizes has historically been associated with colloids, micelles, polymer molecules, phase-separated regions of block copolymers and similar structures. More recently, structures such as buckytubes, silicon nanorods, and compound semiconductor quantum dots have emerged as particularly interesting classes of nanostructures. In physics and electrical engineering, nanoscience is most often associated with quantum behavior, and the behavior of electrons and photons in nanoscale structures. Biology and biochemistry also have a deep interest in nanostructures as components of the cell; many of the most interesting structures in biology - from DNA and viruses to subcellular organelles and gap junctions can be considered as nanostructures [1-2]. Recently, Whitesides [3] discussed the reasons for the fascination and growth of this inter- / multi-disciplinary research. According to Braun et. al. [4], from 1980s, the growth of research papers dealing with the prefix called ‘nano’ is exponential. It is an earlier indication of explosive growth of research and fascination on nanoscience and nanotechnology. Not only in academia, in industries also, the impact of this field is significantly increasing such as in ceramics, chemical polishing agents, scratch-resistant coatings, stain-resistant trousers, cosmetics, sunscreens etc. Thus, synthesis of various nanoscale structures / particles has gained the interested for developing new nanomaterials and devices. For example, the 8 clusters, nanoparticles, nanowires, long molecules as nanotubes and polynucleotides, and functional supramolecular nanostructures are currently considered as potential building blocks for nanotechnology and nanoelectronic devices and circuits. On the other hand, synthetic polymeric materials are rapidly replacing more traditional inorganic materials, such as metals and natural polymeric materials (wood, fibers). As these synthetic materials are flammable, they require modifications to decrease their flammability through the addition of flame-retardant compounds. Environmental regulations have restricted the use of some halogenated flame-retardant additives, initiated a search for alternative flame-retardant additives. For this purpose, inorganic nanoparticles have become attractive since they can simultaneously improve both the physical, mechanical and flammability properties. Thus, polymer nanocomposites, in last few decades, have become worldwide research interest for developing polymeric materials with improved / desired properties by incorporation of these nanoscale materials into polymer matrix. Numerous research papers, patents and funding are generated out of this field. Most of the efforts were mainly focused on the structure- property relationships and their development. However, the usefulness of any materials depends on their durability in a particular environment in which they are used or their interaction with environmental factors [5]. Since the polymer-nanocomposites have been the staple of modern polymer industry, their durability under various environmental conditions and degradability after their service life are also essential parts of research. The clay mineral incorporated polymer nanocomposites have gained the fabulous attraction from the researchers. Recently, the durability of polymer nanocomposites based on layered silicates (clay minerals) under different environments (mainly under thermal 9 and photo-ageing) has been reviewed [6]. Thus, this article is intended to review the status of worldwide research in the aspect that the nanoparticulates can be incorporated into polymer as ‘nano-additives’ for both the purposes i.e. degradation and stabilization of polymers. 1.1. Definitions The terminologies very often applied in nanoscience and nanotechnologies are listed as follows; Nanoparticles: Although not specifically describing nanoparticles, the above-mentioned definitions imply a nanoparticle definition of particle less than 100 nm. Those particles having (one or more) dimensions of 100 nm or less and physical and chemical properties should also be to differ measurably than those of the bulk material can be called as ‘nanoparticules’ [7, 8]. Nanocomposites: The composite materials, that combine one or more separate components in order to improve performance properties, for which at least one dimension of the dispersed particles is in the nanometer range. Nanomaterials The development and use of nanoscale materials such as nanoparticles, nanocomposites, nanopowder, nanocrystals etc. Nanoscience Nanoscience is the study of phenomena and manipulation of materials at atomic, molecular and macromolecular scales, where properties differ significantly from those at larger scale. Nanotechnology Nanotechnology is the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications. Encompassing nanoscale science, engineering and technology, nanotechnology involves imaging, measuring, modeling, and manipulating matter at this length scale. Nanotechnologies are the design, characterization, production and application of structures, devices and systems by controlling shape and size at nanometer scale. Subdivisions of Nanoscience and Nanotechnology Nanobiotechnology The design, synthesis or application of materials or devices or technologies in the nanometer scale for basic understanding and / or treatment of disease Nanomedicine Application of nanotechnology for treatment, diagnosis, monitoring, and control of biological systems, which are needed at molecular level, has recently been referred to as "nanomedicine". Nanophotonics: A novel optical nanotechnology, utilizing local electromagnetic interactions between a few nanometric elements and an optical near [...]... involves dissolution of polymers in adequate solvent with nanoscale particles and evaporation of solvent or precipitation b) Melt mixing: In this method, the polymer is directly melt-mixed with nanoparticle c) In-situ polymerization: In this method, the nanoparticles are first dispersed in liquid monomer or monomer solution Polymerization is performed in presence of nanoscale particles d) Template synthesis:... nanocomposites is straightforward and as the nanocomposites contain no additional halogen, they are considered to be an environmentally friendly alternative In nanoscale particle filled polymer systems, the char formation, which insulates the base polymer from heat and forms a barrier, reduce the escape of volatile 15 gases from the polymer combustion, is explained to be responsible for improved flame retardancy... density of particles per particle volume (106-108 particles/ µm3), 4) Extensive interfacial area per volume of particles (103-104 m2/ml), 5) Short distances between particles (10-50 nm at φ ~1-8 vol%); and 6) Comparable size scales among the rigid nanoparticles inclusion, distance between particles, and the 12 relaxation volume of polymer chains The first two characteristics are not commonly observed for spherical... is a very important phenomenon, which affects the performance of all plastic materials in daily life In practice, any change of the polymer properties relative to the initial or desirable properties is called degradation In this sense, degradation is a generic term for any number of reactions that are possible in a polymer [73] The degradation of polymers involves several physical and /or chemical... quality of the polymeric materials (i.e., worsening of its mechanical, electrical or aesthetic properties) and finally to the loosening of its functionality [73-74] Table 3 gives list of environmental factors, which causes the polymer degradation [7583] Figure 8 shows the generally accepted pathways of degradation and stabilization where radical formation is initiating and vital step for polymer degradation. .. unit surface area For nucleation, the activation energy is at a critical size (r*) where the free energy ∆G reaches to a positive maximum (d∆G/dr = 0) Nuclei larger than the critical size will 27 further decrease their free energy for growth and form stable nuclei that grow to form particles Thus, the critical nuclei size (r*) can be r∗ = 2V γ 3 k B T ln( S ) For a given value of S, all particles with... Recently, a big window of opportunities has opened for polymer nanocomposites just to overcome the limitations of traditional micro-composites Although, the chemistry of clay minerals and composites based on some nano-scale particles are known for a several decades, the research and development of nanoscale- filled polymers has been skyrocketed in recent years, for numerous reasons First, unprecedented combinations... intercalate a polymer [21] Table 2 gives a glimpse of possible layered nanoparticles, which are potential candidates for preparing polymer nanocomposites Among these layered nanoparticles, clay minerals based on phyllosilicates have extensively been for last few decades, most probably because the starting clay materials are easily available and because their intercalation chemistry has been studied for a long... against degradation [84] To overcome the difficulties of evaporation and migration, the higher molecular weight or polymeric stabilizers can be introduced The polymeric stabilizers can be prepared by following three ways [73]; i) Grafting of stabilizer onto polymer 32 ii) Synthesis of polymerizable monomers anchored with stabilizer and homo/copolymerization iii) By using photo-rearranging polymers... and processing of polymeric materials as it is done mostly for preparing nanocomposites As we mentioned earlier, the nanoparticles are incorporated for their own primary functions The degradability and durability of polymers are discussed as primary and /or additional functions in the next section Figure 9, represents the various techniques available for following/ monitoring the degradation as well . D, Tomer NS, Singh RP, Nanoscale Particles for Polymer Degradation and Stabilization – Trends and Future Perspectives, Progress in Polymer Science (2008),. content, and all legal disclaimers that apply to the journal pertain. 1 Nanoscale Particles for Polymer Degradation and Stabilization – Trends and Future