HIPing

Pellets for use in the HIPing studies were formed in a two stage 

---

Fig. 19.4. Hot-isostatic pressing ("HIPing") the powder, in a thin steel preform, is heated and compressed by high-pressure argon.

Cameron, N.R. and Sherrington, D. C. High Internal Phase Emulsions (HIPEs)-Structure, Properties and Use in Polymer Preparation. Vol. 126, pp. 163-214. 

Lewis, R. G., et al. (1991). Preliminary results of the EPA House Dust Infant Pesticides Exposure Study (HIPES). Abstracts of the Papers of the American Chemical Society 201(89-Agro Part 1, April 14). 

A high internal phase liquid-liquid emulsion (HIPE) is one where the internal or dispersed phase droplets occupy >74% of the total volume of the emulsion. At this point the droplets contact each other and beyond this volume % the droplets are forced into distorted polyhedra. If for example styrene and divinylbenzene are employed as the continuous phase and water droplets dispersed in this oil phase using a suitable surfactant to form a HIPE, the comonomers can be polymerized to form a poly(styrene-divinylbenzene) polyHIPE. Typically the water droplets are... 

Siemer, D. D., Roy, D. M., Grutzeck, M. W., Cougar, M. L. D. Sheetz, B. E. 1997. PCT leach tests of hot isostatically pressed (HIPed) zeolitic concretes. Materials Research Society Symposium Proceedings, 465, 303-310. 

Polymer materials can easily be prepared from HIPEs if one or the other (or both) phases of the emulsion contain monomeric species. This process yields a range of products with widely differing properties. Additionally, as the concentrated emulsion acts as a scaffold or template, the microstructure of the resultant material is determined by the emulsion structure immediately prior to polymerisation. 

In this review, the structure, properties, stability and applications of highly concentrated emulsions will be discussed in the first section. Following this, the use of HIPEs to generate novel polymer materials will be the focus of the second part. 

These concentrated emulsions have been referred to by a number of different names in the literature, including high internal phase ratio emulsions (HIPREs) [1,3-7], gel-emulsions [8-14] and hydrocarbon gels [15,16], In this review, the term HIPE will be used throughout. 

In addition, Sebba and others [19,21-25] have detailed systems known as polyaphrons , which appear to be o/w HIPEs prepared with very low surfactant concentrations in each phase. Although it is stressed that polyaphrons differ from conventional concentrated emulsions, the present authors and others [7,16], believe that this is not the case. 

---