Dispersion, hybrid interconnection and heat dissipation properties of functionalized carbon nanotubes in epoxy composites for electrically conductive adhesives (ECAs)
Graphical abstract
Research highlights
► Functionalized MWNTs shows good dispersion in the epoxy matrix. ► Aggregation of MWNTs hindered the coalescence of LMPA fillers. ► Functionalized MWNTs endowed function of thermal radiation into the epoxy composite.
Introduction
Epoxy polymers are widely used as electrically conductive adhesives (ECAs) because of their high tensile strength and modulus, low shrinkage in cure, good chemical and corrosion resistance, high adhesion and dimensional stability. ECAs were developed for and are used for electronic devices. With the increasing needs for heat dissipation in microelectronic devices, however, thermal management has become an important element in the design of electronic products because improvement in heat dissipation properties can lead to an exponential increase in the reliability and life expectancy of the device [1], [2].
In recent years, nanosized fillers such as nanoparticles, nanotubes, clay and nanofibers have been considered as filler materials for epoxy to produce high performance composites with enhanced properties. Carbon nanotubes (CNTs) are excellent candidates for improvement of epoxy resins. CNTs have attracted much interest due to their novel structures, high strength (∼100 times stronger than steel) and modulus (about 1 TPa), high thermal conductivity (about twice as high as diamond), excellent electrical capacity (1000 times higher than copper), and thermal stability (3073 K in vacuum) [3], [4], [5], [6], [7], [8], [9].
Owing to their unique properties, CNTs are considered to be ideal candidates for applications as fillers in composite materials [10], [11], [12], [13], [14]. However, raw CNTs have a tendency to aggregate because of their large surface areas and strong intrinsic Van der Waals forces. The dispersion of CNTs is extremely important in order to fully realize improvement in epoxy based CNT composites [15]. Researchers have proposed several methods to enhance the dispersion of CNTs in polymer matrix, including high shear mixing, surfactants, acid oxidation and other chemical methods [16], [17], [18], [19]. Oxidative processing is extensively employed to treat the surfaces of CNTs. This method utilizes strong acids such as HNO3 and H2SO4, by which hydroxyl and carboxylic acid groups are created on the nanotubes. Yu et al. proposed that rational selection of the oxidation process and type of CNTs is important for applications involving CNT-related composite materials [20]. Datsyuk et al. compared the structural integrity of multi-walled carbon nanotubes (MWNTs) for different oxidation methods [21].
Some researchers recently reported that different amino groups on the surfaces of MWNTs have great effects on the thermal and mechanical properties of composites [22]. For example, Gojny et al. showed that the incorporation of CNTs into polymers resulted in an enhancement of electrical and thermal conductivity [23]. Chen et al. produced epoxy-based nanocomposites containing functionalized MWNTs with amino groups. The nanocomposites exhibit high tensile strengths, impact strengths, decomposition temperatures and glass transition temperatures [24]. Yang et al. reported that the addition of triethylenetetramine (TETA) functionalized MWNTs in the epoxy matrix contributes to the improvement of mechanical and heat dissipation properties of the composites [25].
In this study, we prepared three types of MWNTs: raw, acid treated and m-phenylenediamine-grafted. These were blended with DGEBF or DGEBA, which are widely used epoxies. The composites were investigated to determine the effects of functionalized MWNTs on dispersion and interconnection in electronic devices. Further, we evaluated the influence of functionalized MWNTs on the enhancement of mechanical and heat dissipation properties of MWNT/epoxy composite systems.
Section snippets
Materials
MWNTs were obtained from Hanhwa Nano Tech (Seoul, Korea). These nanotubes had specified diameters of 20 and 30 nm and the purity was greater than 95%. Nitric acid (HNO3, 69%), sulfuric acid (H2SO4, 95.0%), thionylchloride (SOCl2, +90%), N′N-dimethylformamide (DMF, 99%), and ethanol (EtOH, 95.0%) were purchased from Samchun Chemical. 1,3-phenylenediamine(m-phenylenediamine) was purchased from Aldrich Chemicals.
The composite used in this study consisted of a polymer binder, curing agent, a low
Surface functionalities on MWNTs
The surface chemical states of raw MWNTs, a-MWNTs and m-MWNTs were characterized by XPS. Wide scan spectra in the range of 0–1100 eV identify the surface elements present with a quantitative analysis shown in Fig. 2. Binding energies around 282, 531 and 400 eV are attributed to C1s, O1s and N1s, respectively. The intensity of the O1s peak of a-MWNTs dramatically increased compared with that of raw MWNTs. This indicates a great effect of H2SO4/HNO3 treatment on the MWNTs. A new peak at around 400
Conclusions
In the present work, the effects of functionalization of MWNTs on the dispersion of nanotubes, morphology of metallurgical interconnection, pull strength and thermal conductivity of epoxy composites with different kinds of MWNTs were investigated. Characteristics of raw MWNTs were compared with those of acid-treated MWNTs and m-phenlyenediamine grafted MWNTs. In the functionalization process, acid treatment of MWNTs was first executed to effectively generate carboxyl groups on their surfaces
Acknowledgement
This research was supported by the Seoul R&BD Program (No. PA090933).
References (40)
- et al.
Advances in the science and technology of carbon nanotube and their composites: a review
Compos Sci Technol
(2001) - et al.
Physics of carbon nanotubes
Carbon
(1995) - et al.
Elastic moduli of multi-walled carbon nanotubes and the effect of Van der Waals forces
Compos Sci Technol
(2003) - et al.
Mechanical and electrical properties of a MWNT/epoxy composite
Compos Sci Technol
(2002) - et al.
Influence of dispersion states of carbon nanotubes on physical properties of epoxy nanocomposites
Carbon
(2005) - et al.
Dispersion and thermal conductivity of carbon nanotube composites
Carbon
(2009) - et al.
Chemical oxidation of multiwalled carbon nanotubes
Carbon
(2008) - et al.
The reinforcement role of different amino-functionalized multi-walled carbon nanotubes in epoxy nanocomposites
Compos Sci Technol
(2007) - et al.
Evaluation and identification of electrical and thermal conduction mechanisms in carbon nanotube/epoxy composites
Polymer
(2006) - et al.
Mechanical and thermal properties of epoxy nanocomposites reinforced with amino-functionalized multi-walled carbon nanotubes
Mater Sci Eng A
(2008)
Effects of carbon nanotube functionalization on the mechanical and thermal properties of epoxy composites
Carbon
Synthesis of a novel siloxane-containing diamine for increasing flexibility of epoxy resins
Mater Sci Eng A
Effects of novel carboxylic acid-based reductants on the wetting characteristics of anisotropic conductive adhesive with low melting point alloy filler
Microelectron Reliab
Functionalisation effect on the thermo-mechanical behaviour of multi-wall carbon nanotube/epoxycomposites
Compos Sci Technol
Functionalized effect on carbon nanotube/epoxy nanocomposites
Mater Sci Eng A
Effects of surfactant treatment on mechanical and electrical properties of CNT/epoxy nanocomposites
Compos Appl Sci Manuf
Influence of different carbon nanotubes on the mechanical properties of epoxy matrix composites – a comparative study
Compos Sci Technol
Mechanical properties of surface-functionalized SWCNT/epoxy composites
Carbon
Magnetically processed carbon nanotube/epoxy nanocomposites: morphology, thermal, and mechanical properties
Polymer
Processing-structure-multi-functional property relationship in carbon nanotube/epoxy composites
Carbon
Cited by (33)
Vertical alignment of carbon nanotubes in photo-curable polymer for multi-functional hybrid materials
2023, Applied Surface ScienceCitation Excerpt :They have superior thermal conductivity, electrical conductivity, and mechanical strength to conventional materials [2,3], therefore, many studies incorporate CNTs with other materials to improve their thermal, electrical, and mechanical properties. The CNT–polymer composites were developed for conductive polymer [4,5], conductive adhesives [6], reinforced plastics [7–9], elastic sensors [10], etc. In many cases, CNT-polymer composites were made by randomly dispersing CNTs in pre-polymer solutions.
Synthesis of a comb-like silicone-epoxy co-polymer with high thermal stability and mechanical properties for ablative materials
2020, Reactive and Functional PolymersCitation Excerpt :Thus, by introducing silicone into epoxy resin, an epoxy resin matrix with high residual carbon, good heat resistance, and utility for ablation materials can be synthesized. The mechanism of synthesis is through the organic functional group carried by the silicone molecular chain reacts with the epoxy resin, such as the hydroxyl [11,12], alkoxy [13,14], amino [15], epoxy group [16], ethylene [17,18], silicon hydrogen bond [19], carboxyl group [20] on the silicone molecule, and the hydroxyl group [21,22] on the epoxy resin molecular chain and epoxy group to synthesis a highly branched silicone-epoxy co-polymer [23–27]. These reactions are used to improve the compatibility of silicone and epoxy resins in the new type of epoxy resin [28,29].
A review on epoxy-based electrically conductive adhesives
2020, International Journal of Adhesion and AdhesivesCitation Excerpt :To overcome this problem, CNT agglomerates must be broken down and thoroughly dispersed in the base matrix which usually then results in an increase in the performance of the adhesive or composite. Therefore, various methods for enhancing CNT dispersion in a matrix have been proposed by many researchers including the use of high shear mixing, ultrasonication, the use of surfactants, acid oxidation of CNTs and other chemical methods [63]. CNTs have the ability to impart electrical conductivity to many polymers by creating an effective conductive network with a low percolation threshold value due to their high aspect ratio.
Electrically conductive adhesives based on thermoplastic polyurethane filled with silver flakes and carbon nanotubes
2016, Composites Science and TechnologyElectrically conductive self-healing polymer composite coatings
2015, Progress in Organic CoatingsCitation Excerpt :Carbon nanotubes (CNTs) are ideal as conductive fillers due to their excellent electrical conductivity, nanoscopic size, and high aspect ratio, which facilitate the formation of a network allowing for electron transport along the CNTs. In addition to sufficient electrical conductivity, ECAs based on epoxy and CNTs demonstrate improved adhesion and mechanical properties (including strength) compared to pristine epoxy [20–24]. However, even with the additional reinforcement resulting from CNTs, the epoxy matrix is still prone to cracking which often leads to device failure.
Application of nitrogen-doped graphene nanosheets in electrically conductive adhesives
2014, CarbonCitation Excerpt :Compared with conventional tin–lead solders, ECAs are more environmentally friendly, and they have been widely applied to electronic packaging and other industrial technologies, such as liquid crystal display (LCD) and solar cells [1–3]. Common filler materials include silver [3–6] and carbon materials [7–11]. Silver particles, nanowires, or flakes have long been widely used as fillers for commercial ECAs due to their excellent electrical conductivity and stability [3,12].