Effects of nanoparticles SiO2 on the performance of nanocomposites
Introduction
Epoxy resins are used in a variety of applications since their properties, such as thermal stability, mechanical response, low density and electrical resistance, can be varied considerably. The important factors influencing their performance are the molecular architecture, curing conditions and the ratio of the epoxy resin and the curing agent(s). The use of an additional phase (e.g. inorganic fillers) to strengthen the properties of epoxy resins has been a common practice. Developments in the synthesis of nanometer-sized particles have made it possible to process nanocomposites. Nanoparticles can fill up the weak microregions of resins to boost the interaction forces at the polymer–filler interfaces. A dramatic increase in the interfacial area between fillers and polymer can significantly improve the properties of the polymer [1]. The reinforcement efficiency is reported to show strong dependence on dispersion of nanoparticles. Well-dispersed nanoparticles can effectively enhance the comprehensive properties of nanocomposites, which are unique and different from any other current composites with typical filler amounts of less than 5 wt.% [2], [3].
Both macroscopic and microscopic measurements are normally performed for a newly synthesized composite to achieve an overall understanding. The positron annihilation lifetime spectroscopy (PALS) technique has been widely used in the study of polymeric systems at the molecular level in the recent years. This technique utilizes the interactions between the positrons and the electrons from the host material. Although there has been an observed increase of the number of papers concerning PLAS applications in the study of microstructure of polymers and polymeric blends [8], [9], little attention has still been addressed to the effect of nanoparticles on nanocomposites [4].
In this paper, an epoxy resin (CYD-128) is processed with various amounts of nanometer-sized SiO2 particles. The SiO2 nanoparticles have shown a positive effect on the mechanical and thermal properties of the nanocomposites. The positron annihilation lifetime spectroscopy technique was applied to probe the microstructure of the nanocomposites.
Section snippets
Materials
The CYD-128 epoxy resin and curing agents were used for this investigation. The CYD-128 obtained from YueYang Chemical is a diglycidyl ether of bisphenol A resin with an average molecular weight of 385 g/mol. Aromatic hardener (JHB-590) with an acid value of 660–685 mgKOH/g was produced by Dalian-Jinshi Chemical Industry. Nanoparticles SiO2 of mean diameter 15 nm, purchased from Mingri Nanomaterial, have a density of 0.22 g/cm3 and a surface area of 160±20 cm2/g. Hydroxide group content on the
Dispersion of nanoparticles
The dispersion of nanometer-sized particles in the polymer matrix is reported to have a significant impact on the mechanical properties of nanocomposites [5]. As the nanoparticles have a strong tendency to agglomerate, homogeneous dispersion of the nanoparticles in the polymer has been considered as a difficult process. A good dispersion may be achieved by surface modification of the nanoparticles under an appropriate processing condition [6]. In this work, three different approaches have been
Conclusions
The studies on the morphology and mechanical properties show that the introduction of SiO2 nanoparticles in the CYD-128 matrix polymer has dramatic effects on nanocomposites. Uniform dispersion of nanoparticles is critical to the morphological structure of nanocomposites, which in turn affects the impact strength of the SiO2/CYD-128. Much more interfacial surfaces can be generated between polymer and nanoparticles, which assists in absorbing the stress. The free volume parameters (τ3 and I3) of
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