Mechanical and Moisture Barrier Properties of Epoxy-Nanoclay and Hybrid Epoxy-Nanoclay Glass Fibre Composites: A Review

Epoxy clay nanocomposites have been proven to have improved mechanical, thermal and physical properties over pristine matrix. Thus, the fields of application of epoxy-clay nanocomposites along with their hybrid glass/carbon fibre reinforced composites have grown tremendously during the last few decades. The present review paper covers the research work performed on epoxy clay nanocomposites. It includes the influence of the processing techniques and parameters on the morphology of the nanocomposite, the methods of characterization and the effects of adding nanoclay on the mechanical and physical properties of composite. The improvements in the liquid barrier properties brought about by the addition of nanoclay platelets to epoxy resin are discussed. The variation of physical and mechanical properties with nanoclay type and content are reviewed along with the effects of moisture uptake on these properties. The advances in the development, characterization and applications of hybrid glass fibre reinforced epoxy-clay nanocomposites are discussed. Findings of the research work on the influence of nanoclay addition and exposure to water laden atmospheres on the behaviour of the hybrid glass fibre epoxy-nanoclay composites are presented. Finally, the potential health and environmental issues related to nanomaterials and their hybrid composites are reviewed.

PPG-Terminated Tetra-Carbamates as the Toughening Additive for Bis-A Epoxy Resin

We synthesized PPG-terminated tetra-carbamates as a new toughening additive for epoxy thermosets through facile addition reaction of hexamethylene diisocyanate (HDI) with poly(tetra-methylene glycols) (PTMG) and poly(propylene glycols) (PPG). The effects of prepared tetra-carbamates on the rheological behavior of neat epoxy resin were studied along with the various cured properties of their modified epoxy systems. Four carbamate groups (–NHCOO–) endow the prepared additives not only with good intramolecular interactions, but also with optimal intermolecular interactions with epoxy polymers. This results in the suitable miscibility of the additives with the epoxy matrix for the formation of the typical biphasic structure of microparticles dispersed in the epoxy matrix via polymerization-induced microphase separation. The impact strength and critical stress concentration factor (K_IC) of cured modified epoxy systems with the additives are significantly higher than those of unmodified epoxy systems, without sacrificing the processability (T_g) and flexural strength. The toughening mechanism is understood as a synergism combination among the phase separation mechanism, the in situ homogeneous toughening mechanism, and the particle cavitation mechanism.

Recent advances in colloidal nanocomposite designviaheterogeneous polymerization techniques

Recent advances in colloidal nanocomposite design by heterogeneous polymerization are reviewed, with a specific focus on encapsulation and particle-based stabilization for specific materials applications.

Polymer encapsulated gibbsite nanoparticles: efficient preparation of anisotropic composite latex particles by RAFT-based starved feed emulsion polymerization

Anisotropic polymer-inorganic composite latex particles were synthesized by using a RAFT-based encapsulation approach on cationic gibbsite platelets. By using the RAFT agent dibenzyl trithiocarbonate, a series of amphipatic living random RAFT copolymers with different combinations of acrylic acid and butyl acrylate units were synthesized. These RAFT copolymers were used as living stabilizers for the gibbsite platelets and chain extended to form a polymeric shell by starved feed emulsion polymerization. Cryo-TEM characterization of the resulting composite latexes demonstrates the formation of anisotropic composite latex particles with mostly one platelet per particle. Monomer feed composition, chain length, and hydrophilic-lipophilic balance of the RAFT copolymer were found to be important factors for the overall efficiency of the encapsulation. Good control over platelet orientation and high encapsulation efficiency were achieved via this route.