Manufacture of Syntactic Foams Using Starch as Binder: Post-Mold Processing

Abstract

Syntactic foam manufacturing method, 'post-mold processing', based on the buoyancy of hollow microspheres was studied for potential building material applications. The post-mold processing involves mixing starch particles and ceramic hollow microspheres in water. It was found starch particles tend to adhere to hollow microspheres, forming agglomerations, during mixing. It was also found that 'volume fraction of starch particles on a microsphere making a relative density of 1.0' (VFSMRD) is an indicator for mixture volume transitions. Both the maximum total volume expansion of mixture and a transition in formation, after phase separation, of mixture volume in water referred to as 'top phase' in a mixing container were taken place at a calculated VFSMRD.It was found that hollow microsphere size effect on attracting starch particles was relatively high but IBVMS effect was not significant. Also, no effect of water volume for a given diameter of cylindrical container was found. Starch-microsphere inter-distance was discussed and considered 1 Corresponding author 2 to be an important parameter affecting starch content in an agglomeration. A Simple Cubic cell model for the starch-microsphere inter-distance was adopted to quantitatively explain various effects on starch content in agglomeration such as hollow microsphere size, initial bulk volume of hollow microspheres (IBVMS) and water volume. Further, the following were found for manufactured syntactic foams: (a) volume fraction of starch in foam is of linear relation with starch content before mixing for a given experimental data range and (b) shrinkage is relatively high for small hollow microspheres with high starch content.

Pre-Mould Processing for Syntactic Foams: Modelling, Theory and Experiment

“…In this work, pre-mould gelatinisation was employed. More details are available in references [23][24][25][26].…”

“…A wide range of different types of syntactic foams can be made by selecting different materials and consolidating techniques for binder and hollow microspheres. The consolidating techniques include coating microspheres [10], rotational moulding [11], extrusion [12,13], pressure infiltration [14], and ones that use inorganic binder solution and firing [15], dry resin powder for sintering [16][17][18][19], compaction [20,21], liquid resin as binder [22] for in situ reaction injection moulding, and buoyancy [1,[23][24][25][26][27]. The last method (buoyancy) has recently been demonstrated to be capable of control of a wide range of binder contents at low costs, widening the applicability of syntactic foams.…”

“…However, it is dimensionally unstable during manufacturing, thereby limiting the applicability. For example, gelatinised starch binder tends to shrink significantly when it dries [25][26][27]. Islam and Kim [25] have studied relationships between various manufacturing parameters for starch binder and ceramic hollow microspheres.…”

Novel mechanical behaviour of perlite/sodium silicate composites

“…It is only recently that Shastri and Kim [21,22] studied some selected properties for mechanical behaviour of expanded perlite consolidated with starch for demonstration of a new manufacturing process based on the principle of buoyancy [23][24][25][26][27][28]. The new process appears to be capable of extending the limitation of perlite application, allowing us to manufacture novel perlite/sodium silicate composites.…”

A Model of Foam Density Prediction for Expanded Perlite Composites

“…However, their applications as the main constituent of composites have been limited due to relatively poor mechanical properties when manufactured with the conventional manufacturing methods. Recently Kim [9] and Shastri [10] studied some selected properties for mechanical behavior of perlite foam consolidated with starch for demonstration of a new manufacturing process based on the principle of flotation [11][12][13][14][15][16]. The new process appears to be capable of extending the limitation of perlite application, allowing us to manufacture samples for exploring novel mechanical behavior of consolidated expanded perlite particles.…”