Epoxy-Glass Microballoon Syntactic Foams: Rheological Optimization of the Processing Window

A V Ullas,Devendra Kumar,Prasun Kumar Roy

doi:10.1155/2019/9180302

Abstract

In this paper, we discuss the chemorheology of epoxy based syntactic foams containing glass microballoons of varying density, with an aim of establishing the effect of microballoon loading on its processability. The primary objective is to determine the maximum microballoon loading that disperses uniformly in the resin without the aid of any diluent. The viscosity and dynamic mechanical properties of epoxy formulations containing varying amounts of glass microballoons were established by parallel plate rheometry. Our studies reveal that solventless processing of formulations with microballoon loading > 60% poses practical difficulties due to prohibitively high viscosities, although a packing efficiency of 74% is theoretically allowed in the case of hexagonal close packing. The presence of microballoons does not alter the curing mechanism. The mechanical properties of syntactic foams were inversely proportional to the loading and type of glass microballoons.

Highlights

Syntactic foams are lightweight composite materials prepared by incorporating hollow microballoons of glass [1], polymer [2, 3], or metal [4] in a suitable matrix
The chemorheological behavior of cycloaliphatic epoxy containing different types of hollow glass microballoons is studied to arrive at the optimal conditions required for processing of syntactic foam formulations
It can be seen that the cycloaliphatic epoxy resin exhibits a viscosity of ∼ 1000 mPa.s at 30∘C (γ=̇ 0.1 s−1) and the inclusion of microballoons leads to a considerable increase in its viscosity, the extent of which is proportional to the microballoon loading

Summary

Introduction

Syntactic foams are lightweight composite materials prepared by incorporating hollow microballoons of glass [1], polymer [2, 3], or metal [4] in a suitable matrix. The inclusion of these hollow counterparts allows for significant weight savings, which is crucial for certain applications, especially marine [5, 6], aerospace [7, 8], and blast mitigation [9]. Epoxy has been extensively studied [15,16,17,18,19,20], in view of its excellent mechanical properties and low shrinkage [21, 22]

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Conclusion