Nanosilica-Toughened Epoxy Resins

Abstract

Surface-modified silica nanoparticles are available as concentrates in epoxy resins in industrial quantities for nearly 20 years. Meanwhile, they are used in many epoxy resin formulations for various applications like fiber-reinforced composites, adhesives or electronic components; even in space vehicles like satellites. Some of the drawbacks of “classic” epoxy toughening using elastomers as a second phase, like lower modulus or a loss in strength can be compensated by using nanosilica together with such tougheners. Apparently, there exists a synergy as toughness and fatigue performance are increased significantly. This work intends to provide an overview regarding the possibilities of nanotoughening with silica, the industrial applications of such epoxy resin formulations and the most recent research results.

Synergistic improvement of mechanical and thermal properties in epoxy composites via polyimide microspheres

“…For example, Ge et al achieved the significant enhancement of the toughness of epoxy resin by using epoxidized hydroxy‐terminated polybutadiene (EHTPB), while a dramatically sacrifice was brought in the tensile strength of epoxy/EHTPB composites, the initial decomposition temperature and glass transition temperature ( Tg ) of the modified epoxy resin also decreased with the increase of EHTPB content 13 . Different from flexible modifiers, inorganic fillers, such as nano SiO 2, clay, graphene, glass beads, and glass fiber, can make up for the loss of rigidity caused by flexible segments 14–17 . However, poor compatibility tends to affect their uniform dispersion and their interfacial adhesion with polymer matrix, which also has a negative impact on their heat resistance.…”

Polymer Adsorbents vs. Functionalized Oxides and Carbons: Particulate Morphology and Textural and SurfaceCharacteristics

“…Additionally, complex and hybrid systems with PVA/AC, fumed silica/PDMS, etc., are described here mainly concerning the morphological and textural characteristics. All these materials can be considered as representatives of various classes of simple and complex adsorbents and polymer fillers described in detail elsewhere [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 28 , 31 , 32 , 54 , 55 , 56 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 89 , 90 , 91 ]. Some details on the materials used here are given in the Supplementary Materials file.…”

“…and carbons (chars, activated carbons (AC), carbon blacks, carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nanocomposites (CNC), graphene, graphene oxides (GO), etc. ), are typically better-studied (as relatively rigid solids with stable characteristics) than those of polymer adsorbents [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. The latter may be characterized by lower stability of the textural characteristics than stable and rigid solids due to various effects of dispersion media, swelling, aging, freezing with liquids, heating, mechanical loading, as well as due to high fractality, strongly tortuous pores, and disordered texture of nonrigid polymers [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ].…”

“…Therefore, it is difficult to accurately describe their various blends using firm software [ 87 , 89 , 90 ]. There are (i) synthetic highly disperse oxides (fumed silica, alumina, titania, binary and ternary fumed oxides) composed of spherical-like nonporous nanoparticles (NPNP); (ii) natural nanostructured oxides (clays, zeolites) with a complex shape of pores; (iii) porous oxides (silica gels, ordered mesoporous silicas, complex oxides) mainly with cylindrical pores, but with certain deviations and surface roughness; (iv) carbons (chars, activated carbons, graphene, graphene oxide, exfoliated graphite, nanotubes, carbon blacks, fullerites), which can have not only slit-shaped pores but also spherical, cylindrical, wedge-shaped and other pores; (v) polymers (1D, 2D, 3D hydrophobic and hydrophilic, functionalized, synthetic and natural) with complicated and tortuous pore networks; (vi) metal–organic framework structures with complex pore shapes; (vii) complex and hybrid systems with components of different kinds or classes [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 28 , 32 ]. Composites and hybrids can have pores with a shape different from that characteristic for individual components because of the possible penetration of one component into pores of other components.…”

Mechanical Characterization of Core-Shell Rubber/Epoxy Polymers for Automotive Structural Adhesives as a Function of Operating Temperature

“…To overcome this brittleness and improve their automotive applicability, it is common to improve their toughness using the following methods: formulating epoxy adhesives with urethane or rubber-based additives, adding thermoplastic or inorganic filler particles, and cross-linking with synthesized epoxy that has a urethane or rubber molecular structure. Core-shell rubber (CSR) nanoparticles are among the most widely used additives for improving the toughness of epoxy polymers since their shells and cores are made of thermoplastic and rubber-based materials, respectively [ 23 , 24 , 30 , 31 , 32 , 33 , 34 , 35 ].…”