Inorganic barrier fillers

MarciniSin, A., Hricova, M., Ujhelyiova, A., et al. Effect of inorganic (nano)fillers on the UV barrier properties, photo and thermal degradation of polypropylene fibres. Fibres Text East Eur. 17, 29-35 (2009)... 

Flame retardants (qv) are incorporated into the formulations in amounts necessary to satisfy existing requirements. Reactive-type diols, such as A/ A/-bis(2-hydroxyethyl)aminomethylphosphonate (Fyrol 6), are preferred, but nonreactive phosphates (Fyrol CEF, Fyrol PCF) are also used. Often, the necessary results are achieved using mineral fillers, such as alumina trihydrate or melamine. Melamine melts away from the flame and forms both a nonflammable gaseous environment and a molten barrier that helps to isolate the combustible polyurethane foam from the flame. Alumina trihydrate releases water of hydration to cool the flame, forming a noncombustible inorganic protective char at the flame front. Flame-resistant upholstery fabric or liners are also used (27). 

Besides the coextruded laminate structure in Fig. 4b, cases c-f are also viable structures for some applications. Chapter 11(47) discusses the addition of inorganic fillers to EVOH copolymer to achieve large increases in barrier properties in some applications. The effects of different loadings of mica flake in several polymers other than EVOH was also recently reported to be effective (80). 

Keldax . [DuPont] Ethylene interpolymer composition with high load-ittgs of inorganic fillers thermoplastic sound barrier resins fv automotive, business madiines, industrial equip. 

In order to obtain a competitive product, the PHB performance can be greatly enhanced with the addition of nanometer-size inorganic fillers. This kind of materials are called nanocomposites and have an interesting characteristic The mechanical properties [42], the barrier properties [43], the thermal properties [44], and some others such as the flammability [45], water adsorption [46], and creep resistance [47] can be greatly enhanced with the addition of a small amount of filler (usually less than 10 wt%) [6,42-48]. 

In addition to particle breakup, the coalescence process may be affected as well. It has been speculated that exfoliated clay platelets or well-dispersed nanoparticles may hinder particle coalescence by acting as physical barriers [19,22]. Furthermore, it has been suggested that an immobilized layer, consisting of the inorganic nanoparticles and bound polymer, forms around the droplets of the dispersed phase [50]. The reduced mobility of the confined polymer chains that are bound to the fillers likely causes a decrease in the drainage rate of the thin film separating two droplets [44]. If this is the case, this phenomenon should be dependent on filler concentration this is shown in Figure 2.8, which shows the effect of nanoclay fillers on the dispersed particle size of a 70/30 maleated EPR/PP blend [19]. 

Favorable enthalpic contribuhons are necessary to overcome the entropic penalties due to the confinement of the polymer between the silicate sheets (Vaia and Giannelis 1997a,b, Balazs et al. 1998). However, this condition is respected only when polymer-clay interac-hons are more favorable than surfactant-clay interachons. This represents a challenge for PO/OLS nanocomposites because PO-clay interactions are as poor as the surfactant alkyl-clay interactions for this reason, the system is under "theta conditions" of mixing and the entropic barrier prevents any dispersion of the inorganic fillers. 

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