The growing use of polymer composites has resulted in increasing demand for nanomaterials, such as carbon nanotubes (CNTs), graphene and nanocellulose, as companies seek alternatives to carbon fiber and petroleum-based composite materials. Over the last few years, nanocomposite applications have gained a commercial footing, due in large part to the efforts of resin manufacturers, compounders and masterbatch producers, who now offer user-friendly products to industries such as aerospace and aviation, automotive, food, pharmaceutical and electronics packaging, electrical and electronic goods, and sporting goods. Although applications vary widely, they principally exploit properties such as gas barrier, reinforcement and flame retardancy.
The need for continuous improvement in material performance is significant for engineering applications, with research focusing on new advanced materials with increased resistance to damage under operating conditions. This focus is more demanding in the case of structural composite materials, which are increasingly used in aeronautical/aerospace and automotive applications, as well as in civil infrastructure.1
Carbon nanomaterials are very promising for next generation composite materials. A small percentage of graphene within a polymer matrix can significantly improve its strength and stiffness, and impart electrical conductivity to the polymer. Graphene-based polymer composites display superior mechanical, thermal, gas barrier, electrical and flame retardant properties. Carbon nanotubes display comparable mechanical properties, but graphene is superior in terms of thermal and electrical conductivity.2
In the automotive and aerospace markets, there is a need to develop multi-functional materials that offer structural enhancement, thermal conductivity and resistance to varied environments. The demand in the aerospace and automotive sectors for lightweight, strong and flexible manufactured parts will drive growth for nanocomposites.
Compared with conventional materials, fiber reinforced nanocomposites or particle reinforced nanocomposites exhibit low density, high strength to weight ratio and high stiffness to weight ratio, high toughness with improved creep resistance and wear resistance. Combining high stiffened nanoparticles to the low modulus polymer matrix, improves the load carrying capacity. The use of graphene in automotive composites could allow for 30%-50% decrease in structural weight.3
WHAT ARE NANOCOMPOSITES?
Nanocomposites are multicomponent solid materials where at least one of the phases has at least one of its dimensions in the nano range. They consist of an organic polymer and an inert nanoscale filler, the latter added to modify the physical characteristics of the former.
Because of this nanostructure, these materials frequently display unique properties. The incorporation of a small fraction of nanoparticles (1-10 wt.%) dispersed into polymer matrix (typically thermosetting epoxy) significantly improves the properties of polymers and allows for novel functionalities.
Nanocomposites differ from traditional plastic composites in that they provide these properties with minimal impact on article weight and they do so without major processing problems. In packaging for example, nanocomposites offer good clarity; a combination not possible using traditional composite approaches. Advantages of nanocomposites over traditional plastics include:
- Enhanced modulus and strength.
- Lighter (10% reduction in mass=6% improvement in fuel efficiency).
- Enhanced recyclability.
- Can use existing plastics factories to make nanocomposites allowing for versatile and scalable processing/manufacturing.
- Dimensional stability.
- Reduced CTE.
- Cost Savings/Cycle time reduction.
- Electrical conductivity (static dissipation, elimination of primer during electrostatic painting)
- Thermal conductivity (heat dissipation).
Table 1: Applications in polymer composites, by nanomaterials type and benefits thereof.
|
Nanomaterials
|
Benefits | Application |
| Carbon nanotubes |
• Exceptional mechanical and thermal properties. • Low density and high aspect ratios. • Improved flexural strength • Improved flexural modulus • Improved compression strength • Improved impact strength |
• Additives in polymers such as epoxies, polycarbonates, polyurethanes, polyethylenes, polyamides, polyamides, polystyrene etc. for sporting goods, automotive, aerospace and marine. • Shape memory elastomers. |
| Graphene |
• The addition of 5% graphene doubles the mechanical properties of TPO and PP, and a tensile modulus increase of 80 per cent has been observed when compounding 1 per cent (by weight) of graphene with PMMA. • Improvement in mechanical and electrical properties of graphene-based polymer composites are superior in comparison to that of clay or other carbon filler based polymer composites. • Better nanofiller than CNT in certain aspects such as thermal and electrical conductivity. |
• Thermoplastic compounds and masterbatches. • Conductive additives for electronics packaging polymers. • Conductive composites for 3D printing. • Composites for energy storage/energy harvesting.
|
| Nanocellulose |
• High E-modulus. • High tensile strength. • High density. • Biocompatible • Eco-friendly. |
• Strength enhancing additives for renewable and biodegradable composites. |
| Nanoclays |
• Improved mechanical properties (comparable improvements with conventional filler require 20% loading). • Raised Heat Distortion Temperature (HDT). • Nucleating effect. • Permeability reduction of gases and vapours. • Improved solvent resistance. • Improved surface properties (e.g. printability, smooth- ness). • Reduced shrinkage. • Improved flame retardancy. |
• Automotive composites. • Packaging composites. |
Source: Future Markets.
MARKETS FOR NANOCOMPOSITES
Main commercial nanocomposites applications are in lightweight gasoline tanks, packaging, plastic containers, more fuel efficient, aircraft and car parts, stronger wind turbines, medical implants and sports equipment.
Aerospace
Technology innovation in aerospace is increasingly focused on creating products to reduce costs (e.g. fuel efficiency, maintenance, and repair), and increase safety and comfort. A major trend is creating multifunctional composite materials to carry out tasks generally performed by several elements.
The embedding of carbon-based nanomaterials, such as CNTs and more recently graphene nanoplatelets, has been investigated as a possible solution for a large number of challenges related to aerospace structures. Nanomaterials are utilised in the aerospace industry for improved (or tailored) properties that improve their functional performance (e.g. mechanical or electrical properties) or that deliver multi-functional properties (e.g. lightweight conductive nanocomposites).
The bulk of R&D into aerospace applications of nanotechnology and nanomaterials at present focuses on structural reinforcement of composite materials. Nanomaterials will potentially allow for the development of lighter, high-performance, robust and cost-efficient, multi-functional aircraft. Current trends in airframes that nanomaterials impact include:
- Structural integration: Larger unitized ”one piece” airframe sections
- Automated manufacturing: Better precision, improved productivity, lower cost
- Multifunctional structures, including all-new functions
- Mechanical systems (e.g. Morphing structures)
- Electrical systems (e.g. De-icing / anti-icing)
- Functional surfaces (e.g. Ice phobic)
- Integrated sensors (e.g. Ice conditions)
- Integrated actuators (e.g. Morphing structures)
- Very accurate shape and surface requirements
- Improved platform efficiency from laminar flow and multifunctional structures
- Reduced fuel consumption
- Improved range
- Reduced noise.
Technology innovation in aerospace is increasingly focused on creating products, which are less expensive to operate (e.g. fuel efficiency, maintenance, and repair), and offering new and improved technologies that passengers prefer. The embedding of carbon-based nanomaterials, such as CNTs and more recently graphene nanoplatelets, has been investigated as a possible solution for many challenges related to aerospace structures. The current trend is creating multifunctional composite materials to carry out tasks generally performed by several elements.
There are opportunities for nanomaterials in carbon fiber replacement. However, the epoxy resins, ESD shielding and nanocoatings segments are the most likely to generate significant short-medium term revenues in the aerospace sector.
Companies
Avdome Aviation, USA
The company has an exclusive license for using Standard Graphene’s materials in FRP sandwich panel, FRP sheet and fabric.
GE Global Research, USA
The company is developing superhydrophobic anti-icing nanocoatings for application in the aviation and wind power industries.
Nanocomp Technologies, Inc., USA
The company’s proprietary product is the CTex™ CNT yarn and CNT mats. Main application markets are in aerospace and aviation markets for nanotube materials to save weight in a variety of complex systems, as well as to provide electrostatic discharge (ESD) and electromagnetic interference (EMI) shielding components.
Figure 1: CNT Yarns.
Versarien plc, UK
The company has a Memorandum of Understanding with CT Engineering to develop graphene-enhanced composite components for the aerospace industry.
Automotive
Global anthropogenic carbon dioxide (CO2) emissions recently reached a record high level of 35.7 billion tons per year. It is estimated that more than a quarter of all combined greenhouse gas emissions (GHG) are associated with road transport vehicles.4
By 2020, automotive market is expected to grow to 100 million new vehicles per year. By 2050, it is estimated there will be 2.5 billion vehicles in the world. The ecological impact of this is therefore considerable.5 Therefore reduction in automotive fuel consumption is a key industry trend and automotive lightweighting is an important part of this. The development of new lightweight composite materials is essential.
The most effective way to reduce fuel consumption and decrease CO2 emissions is to produce lighter vehicles, and lightweight vehicle production has increased considerably. Achieving these emission cuts necessitates stringent fuel efficiency standards for automobiles which have forced OEMs worldwide to further reduce their vehicles’ weight. However, vehicle safety is usually compromised by lightweighting. Therefore, there is a need to develop new materials to overcome safety issues.
Polymer nanocomposites offer attractive physical properties including toughness, strength, stiffness, dimensional stability, increased modulus, heat deflection temperature, enhanced thermal properties, barrier properties, and rust and dent resistance. The use of nanocomposites in automotive production requires less filler material than conventional materials while providing equivalent or improved performance characteristics.
The addition of minimal amounts of graphene and CNTs makes semi-finished parts electrically conductive, allowing for more efficient and environmentally friendly coating processes based on counter charged, solvent-free powder coating particles.
Commercial resin pre-impregnated fabrics and tapes utilizing CNTs and graphene have been developed to reduce the mass of vehicles without compromising strength or durability, while increasing fuel efficiency.
Companies
American Process, Inc., USA
American Process Inc. and Futuris Automotive have formed a partnership with researchers at Georgia Institute of Technology, Clark Atlanta University, Swinburne University of Technology, and the USDA’s Forest Products Laboratory to develop ultra-strong, lightweight automotive structural components reinforced with nanocellulose.
The company has developed a vehicle made with graphene in its bodywork.
Figure 2: BAC Mono-lightweight panels made with graphene composites.
Denso Corporation, Japan
The company is developing nanocellulose resin composites for automotive components.
Group NanoXplore, Canada
The company has agreed to a $10.4M project with Sustainable Development Technology Canada (SDTC) to support the commercialisation of lighter, more reliable and higher-efficiency components for electric motor systems using graphene-enhanced engineering plastics in place of metals.
Nitta, Japan
The company is utilizing CNTs to improve the impact resistance of carbon fiber-reinforced plastic, used in auto parts.
Construction
Cement is one of the most important building materials, and global production has increased significantly in recent years, especially in developing countries. As the scale of structures created with concrete has increased dramatically, the need for advanced materials has too. Market trends include high strength and strain concrete and cement products using new composite materials with superior properties to existing materials.
Nanomaterial-reinforced construction materials are utilized for increased flexural strength and toughness. Nanomaterials such as carbon nanotubes have already been incorporated into construction materials. Nanocellulose is being developed for composite and cement additives allowing for crack reduction and increased toughness and strength. Adding 0.5% to cement adds 20% to strength and allows 17% less cement in concrete. Foamed, cellular NFC-concrete hybrid materials allow for lightweight structures with increased crack reduction and strength
The emergence of nanotechnology applications in concrete and cement is relatively recent and most developments are still in at an early commercialization stage. Nanomaterials affect cement and concrete in different ways including their processing conditions, released CO2 emissions, service life and functionalities. Addition of nanoparticles is leading to stronger, more durable, self-healing, air purifying, fire resistant, easy to clean and quick compacting concrete. Nanomaterials currently being developed are nano silica (silica fume), nano Alumina (Al2O3), nanostructured metals, carbon nanotubes (CNTs), graphene and carbon nanofibers (CNFs).
The global concrete and cement market was valued US$457.2 billion in 2011. Widespread implementation of nanomaterials has yet to occur in the construction industry with one of the biggest problems in their use being dispersion in the matrix material.
Companies
Carbon Nanotube Engineered Surfaces LLC, USA
Producing concrete products incorporating nanotubes.
Eden Energy, Australia
The company’s CNTs find application in cement for ultra-high strength concrete.
The company produces foamed, cellular NFC-concrete hybrid materials for strength enhancement of cellular concrete.
Figure 3: Nanocrete cement.
Nycon, USA
The company has produced Nycon-G-Nano, a nanofiber incorporated into cement products.
ZOZ GmbH, Germany
The company produces FuturBeton C.1 nanostructured cement/concrete additives.
Packaging
The bio-based and -active packaging market is growing due to the need for:
- environmentally friendly products
- improving food quality and safety during transportation.
- replacing petroleum-based, glass, metal, wax/plastic coated products.
Consumer demand for more environmental friendly products has led to the development of nanocomposites derived from renewable sources with triggered biodegradability, but with the same mechanical properties as commonly used materials. Nanoparticles have proportionally larger surface area and significant aspect ratio than their micro-scale counterparts, which promotes the development of mechanical and barrier properties.
Nano-enabled polymers keep food secure during transportation, increase shelf life and protect from pathogens.
There is an increasing need of better polymer-based barrier materials for preventing permeation of gases and moistures into food and beverage products. Polyethylene Terephthalate (PET) is one of the most used polymers in packaging for especially beverages. However, a limitation of its use is inherent non-negligible permeability to gases and vapors, including oxygen, carbon dioxide and water.6
The current shelf life of beverages sold in PET bottles is commonly 4-6 months. The degradation of flavourings and other components is associated with the influx of O2 or the efflux of N2 and CO2. Therefore, the shelf life of beverages could be extended if the gas barrier properties of the PET is improved.
Nanomaterials have been used as additives to increase packaging strength and decrease the permeability of plastics in PET bottles and packaged goods. Their enhanced properties, such as UV protection, barrier to moisture, gases and volatile components, mechanical strength, significantly improve packaging materials.
Application areas in food packaging, both flexible and rigid include packaging for processed meats, cheese, confectionery, cereals and boil-in-the-bag foods; extrusion coatings for paperboard fruit juice and dairy products; and beer and carbonated drinks products.
Nano-enabled polymers keep food secure during transportation, increase shelf life and protect from pathogens. Nano titanium dioxide and nanosilver are widely used in food packaging applications. Nanopellets of clay in particular are widely used to improve gas barrier properties.
Nanoclays
Nanoclays are thin sheets of layered silicates in the order of 1 nm thick and 70–150 nm diameter. The incorporation of nanoclays into polymeric matrixes can increase strength, mechanical modulus, and toughness of the polymer while improving barrier and flame-retardant properties. Montmorillonite, kaolinite, and saponite are examples of nanoclays that have been used as fillers in food packaging. They attracted great interest in the food industry due to their cost effectiveness, the availability, simple processability, and significant improvement in performance. Montmorillonite clays are the most widely used in polymers because of their high surface area (700–800 m2/g) and large aspect ratio (50–1000), resulting in their use as effective reinforcement fillers due to high degree of interaction with polymer matrix.
Figure 4: Structure of polymer film with the addition of nanocomposites.
Nanocellulose
Nanocellulose-based packaging demonstrates strength and stiffness close to that of polyolefines, and can be seen as a low cost “green” substitute for application in food packaging and conservation. Bio-nanocomposites based on nanocellulose are 100% fully biodegradable and are a prime candidate to replace petroleum-based packaging. Some of the shortcomings of biopolymers, such as weak mechanical and barrier properties can be significantly enhanced by the use of nanocellulose-based materials.
Nanocellulose-based packaging demonstrates strength and stiffness close to that of polyolefines, and can be seen as a low cost “green” substitute for application in food packaging and conservation. Bio-nanocomposites based on nanocellulose are 100% fully biodegradable and are a prime candidate to replace petroleum-based packaging. Some of the shortcomings of biopolymers, such as weak mechanical and barrier properties can be significantly enhanced by the use of nanocellulose-based materials.
Companies
Table 2: Nanoclay composite application developers and products in packaging.
| Company | Product |
Target market
|
| BYK Additives |
Laponite
|
• Rheology modifier • Film forming agent |
| Cloisite | • Flame retardants | |
| Optigel | • Rheology modifier | |
|
Scona
|
• Thermoplastic additives | |
| CBC Co., Ltd. | Somasif | • Composites |
| Lucentite | ||
| Elementis Specialties, Inc. |
BENTONE®
|
• Rheology modifier • Composites |
| FCC, Inc. | Nanolin DK | • Composites |
|
Grupo Repol
|
Dinalon PA
|
• Packaging films • Automotive composites |
| Kunimine Industries Co., Ltd. |
Sumecton
|
• Rheology modifier |
|
Laviosa
|
Delitte
|
• Composites
|
| Minerals Technologies, Inc./ Nanocor |
Nanomer®
|
• Composites • Flame retardants |
| Mitsubishi Gas Chemical | Nylon-MXD6 | • Packaging films |
| NanoBioMatters Industries S.L |
O2Block®
|
• Packaging films
|
| Tolsa | PANGEL S9 | • Rheology modifier |
Source: Future Markets.
Sporting goods
There are numerous products in the sports & leisure sector incorporating nanomaterials. Products incorporating fillers such as carbon nanotubes, graphene and nanoclays include ski wax, tennis balls, gold balls, bicycle frames, tennis rackets, baseball bats, badminton rackets and hockey sticks.7
CNTs and graphene have been incorporated into sporting equipment to enhance durability, flexibility, impact resistance and fatigue strength.8 Epoxy reinforced CNTs take advantage of CNTs mechanical properties while reducing the weight of materials needed for a specified application. These epoxies are used in tennis racquets and other sporting goods to improve strength, toughness, durability, vibration damping and other mechanical properties.
Companies
Applied Graphene Materials, UK
The company supplies graphene for the development of mechanically enhanced fishing rods manufactured by Century Composites.
Cellutech AB, Sweden
Developed a prototype helmet made of wood that incorporates nanocellulose foam. The outer shell of the helmet is made of wood veneer and the strap of durable paper. The inside cushioning is made of Cellufoam™.
Figure 5: Nanocellulose bicycle helmet.
Spanish sports company Catlike has utilized graphene in reinforced cycling helmets.
Figure 5: Graphene cycling helmet.
Dassi, Japan
The company is developing bike frames incorporating graphene.
Figure 6: DASSI bike incorporating graphene.
Versarien, UK
The company has a Memorandum of Understanding with Bromley Technologies to collaborate on the development of graphene-enhanced sports products.
Yonex, Japan
The company’s sporting goods (golf clubs and badminton racquets) incorporate Applied Nanotech, Inc.’s CNTs.
Figure 7: Head’s Graphene XT Prestige tennis racquet.
Wind energy
The wind energy market has grown exponentially in the past two decades and there is a continuous effort to develop cost-effective materials with higher strength to mass ratios for wind blades. The major design drivers for modern wind turbine blades are the fatigue properties (life-time) and stiffness to weight ratios (tip deflection, tower clearance).
Compression strength and stability are also important in order to design against global and local buckling. CNT and graphene nanocomposites for wind blade materials have attracted significant interest due to their favourable mechanical, damping, electrical, thermal and barrier properties.
There are significant opportunities for greater growth as composites account for a smaller percentage (51kg) of the vehicle’s weight compared to steel (907kg) and aluminium (272 kg). Currently used composite materials are based on thermoset as well as thermoplastics include sheet molding compounds or bulk molding compounds (SMCs/BMCs), glass fiber mat thermoplastics (GMTs) and long fiber reinforced thermoplastic composites (LFRT), where the fiber component is glass fiber. These materials suffer from a number of drawbacks that opens up opportunities for the use of nanomaterials.
Companies
The company is seeking to increase blade performance by using an epoxy resin reinforced with carbon nanotubes.
Siemens Energy, Germany
The company has a number of R&D projects exploring nanomaterials for wind turbine blades.
REFERENCES
1 K. LOH, D. RYU, “MULTIFUNCTIONAL MATERIALS AND NANOTECHNOLOGY FOR ASSESSING AND MONITORING CIVIL INFRASTRUCTURES”, SENSOR TECHNOLOGIES FOR CIVIL INFRASTRUCTURES, 1; 295-326 (2014).
2 http://pubs.acs.org/doi/abs/10.1021/am502986j
3 http://wp.sunderland.ac.uk/igcauto/outcomes-and-impact/
4 http://www.epa.gov/climatechange/ghgemissions/sources/transportation.html
6 A. Arora, G. Padua, Journal of Food Science, 3 (2010) 43-49.
7 http://www.nanocyl.com/de/Products-Solutions/Sectors/Recreational
8 CNT Composites for High Performance Structural Applications: Development, Measurement, and Scale-up, http://www.nist.gov/cnst/upload/Carlson.pdf
