Particle binder polymer

Packing microspheres more closely by using external force results in some sections in which the spheres touch each other and other sections in which there is an intervening layer of binder polymer. The first type is markedly weaker than the second, and syntactic foam failure starts there. The practical conclusion is obviously that, in order to obtain strong syntactic foams, the microspheres should be packed somewhat less densely, so that thin binder layers are present between all filler particles 7 8). 

A major alternative to direct flow membrane filtration is depth filtration, in which particles are removed throughout the filtration matrix rather than just at the membrane surface, by various mechanisms such as size exclusion, electrostatic, and hydrophobic interactions. Depth filters are typically composed of a bed of cellulose or polypropylene fibers together with an inorganic filter aid such as diatomaceous earth and a binder to form a filter sheet. The filter aid imparts the matrix very high surface areas and plays an important role in increasing both retention and the capacity. Depth filters can also have an electrostatic charge usually associated with the binder polymer. 

In the presence of a binder polymer such as PVA the electrostatic repulsion between the particles decreases to some extent [12]. However, no effect of PVA on the wet packing density was observed at maximum polyelectrolyte adsorption. On the contrary de Laat and Berks [82] observed that polyelectrolyte stabilised BaTiOs suspensions flocculated upon addition of PVA. 

An emulsion, according to its basic definition, is a suspension of one material in a liquid in which it is not soluble. The emulsion as a whole may be considered soluble in another liquid, but in the case of binders for aqueous tape casting, the line of distinction must be drawn between water-soluble binders and emulsion binders. Specifically, a water-soluble binder is a polymer that dissolves in water, and an emulsion binder is a collection of insoluble polymer particles, droplets, suspended in water. As pointed out by Doreau et al., the addition of emulsion binder to a slip is accompanied by an addition of water which is also in that emulsion. An 80 g addition of a 50% active emulsion only puts 40 g of binder (polymer) into the tape. Soluble binders may be added 100% active. The two binder families will be discussed separately in this chapter. Phenomena that are shared by both types of binder will be discussed later. 

Lehrle et al. [407] have studied controlled release of the volatile antioxidant butylated hydroxy-toluene (BHT) from cross-linked alginate matrix particles. TG-MS results demonstrate that controlled release can be successfully achieved (i.e. BHT is retained beyond its normal evolution temperature) polyisoprene rubber is more resistant to oxidation when protected in this way than by the equivalent concentration of unencapsulated antioxidant. Tsuneto et al. [386] have analysed evolved gases in a process for removing binder polymer (PBMA and LLDPE) from ceramics obtained by injection moulding. 

In a latex system there is essentially no soluble binder resin. The pigment particles must be dispersed with polymer particles. The polymer particles and pigment particles must stick together. Too much sticking and flocculation occurs. Pigment particles can induce charge destabilisation, particulariy some of the modem pigments which are surface treated. 

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