Mica-Filled Composites

In order to keep all the advantages of the mica-filled composites it is necessary to so adjust the manufacturing process as to minimize its crushing. Pressing may be the appropriate technique, as it follows from the data of Table 18. 

Mica provides similar benefits in a wide range of thermoplastic and thermoset composites including polyolefins, polyamides and styrenics. It is also reported that surface coated mica further increases tensile strength, flexural strength and modulus, and heat deflection temperature. The automobile industry is the main user of mica-filled composites, either with polypropylene or nylon as polymer matrix. Up to 40% mica loadings are used, sometimes in association with calcium carbonate, to produce various injection... 

Table 17 contains data on the strength of mica-filled PP compositions. 

In summary, the model systems discussed in this part were zero-shear suspensions of disk-shaped particles in Newtonian liquids, mica-filled polymeric composites, LCPs and colloidal suspensions. The TCP model offers a good understanding of the flow behavior of exfoliated CPNCs. In the case of intercalated systems similar behavior is expected but is complicated by stress-induced changes in the degree of the dispersion and aspect ratio, as well as other possible modifications, such as the thermal decomposition of intercalant. 

Figure 21.1 Complex dynamic viscosity as a function of shear rate (100 °C, 1 Hz) for the mica-filled NR composites.

Polypropylene composites have many advantages over metal such as corrosion resistance, low weight, easily molded complicated shapes, and low cost. A 1979 article (1), compared the cost of polypropylene composites versus steel sheet at equal stiffness (Table 14.1). Mica-filled (40 wt%) polypropylene was the only composite with a relative cost less than that of steel (0.98) for a part with stiffness equal to steel. The relative thickness of the composite was 2.88 and the relative weight was 0.45. Cost calculations were based on mica at 0.18/ lb and polypropylene at 0.31/lb. The relative cost of a 40% glass-filled polypropylene composite was 2.48 and its relative weight was 0.49. The relative cost of a 40 wt% filled talc/polypropylene composite was 1.32 and the relative weight was 0.61. 

RE Godlewski. Organosilicon chemical in mica filled polyolefins. 38th Annual Conference, Reinforced Plastics/Composites Institute, Houston, TX The Society of the Plastics Industry, Inc., 1983, Session 13-E. 

Fig. 5.69 SEM of a mica filled plastic bottle (A) and a mica-glass fiber composite (B) both show the platy shape of mica. Although the mica fracture surfaces do not appear resin coated there is good adhesion of these particles with the matrix. The mica is aligned with the oriented pol)mier (A).

Tablets. 50% Mica Filled High Density Polyethylene Composites. ...

A number of examples of reinforced or filled polymer systems are shown in Table 6. As a general rule, as the thermal conductivity or the amount of the non-polymeric phase increases, so does the thermal conductivity of the composite. Examples listed in Table 6 include glass-reinforced polycarbonate and pol3Kethylene terephthalate), and mica-filled epoxy resins. On the other hand, plasticizers... 

The choice of material for use as inhibitor depends mainly upon the type of propellant, that is, DB, CMDB, Composite and Fuel-rich and also on the ingredients in their formulations. For double-base propellants, cellulosic materials such a cellulose acetate, ethyl cellulose and different filled or unfilled flexible polyesters are used while fuel or binder material filled with inert substances such as asbestos, mica, silica, etc. in fine powder form is used for composite propellants. Since nitroglycerine is present in CMDB propellants also as in DB propellants, the materials used for DB propellants may also be used with minor modifications for the inhibition of CMDB propellants. 

Ruotsala et al. (1964) reported a partial analysis of a chamosite which contained 18.7% MgO and only 9.70% FeO. This is enough Mg to fill approximately half the octahedral positions and Fe2+ to fill one-seventh. If this analysis is valid, the composition of the octahedral sheet would be similar to that of Mg-biotites (Fig.24), considerably extending the range of isomorphous substitution. If chamosite behaves as the trioctahedral micas (Foster, 1960), then as octahedral Mg increases at the expense of Fe2+, octahedral Al and tetrahedral Al both tend to decrease and the composition... 

The persistence of the above pattern in Figures 2 and 3 is self-evident. E-modlfied micas produce a decrease in e of PS composites, while S-treatment and sequentially-treated micas enhance the elastic modulus. The overall reinforcement of 40% relative to virgin PS is not as pronounced as in the case of PE, though at 20% mica, the relative increase in e is still a substantial one (e.g. 250% for E/S vs. unmodified, filled stocks). The results for PE/PS blends are analogous to those for PS. 

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