Wollastonite filled

Lee [242] studied the dependence of the physico-mechanical properties of Wollastonite-filled polychloroprene rubber on the type of agent used to pre-treat the filler. The composition contained 26.9 part (weight) of the filler per 100 parts (weight) of the rubber (compositions CR-1100, CR-174, CR-151). The finishing agents were y-aminopropyl triethoxysilane (CR-1100 and CR-174) and vinyl triethoxysilane (CR-151). The mechanical properties of the compositions are listed in Table 7 below. The author proposed an empirical equation to relate the modulus with the equilibrium work of adhesion in the following form ... 

Physical and Mechanical Properties of Wollastonite-Filled Ceramicrete. 

Mechanical properties of wollastonite filled NBR vulcanizates decrease due to plasma modification of the filler (Fig. 12.6c), whereas in case of vulcanizates based on SBR an increase of TS and Eb is observed (Fig. 12.6d) - especially for the most effective 48 min treatment. SEM pictures of the vulcanizates confirm on adequate changes to their morphology. 

The use of conventional organofiinctional silanes, as described in the section on filled thermosetting resins, has been tried in filled thermoplastic resins with mixed results. Oren-ski and co-workers reported good results with the use of Union Carbide A-187 and A-1100 in wollastonite filled engineering resins at high filler loading. Attempts to extend this approach to less reactive thermoplastic resins, such as polyolefins, were less successful. 

Figs. 8-13 show the rim thickness variation of Wollastonite filled PBT by microcellular molding. From the curves observed, the thickness variation of Wollastonite filled PBT is smaller than that of glass fiber filled PBT, and the curves of the Wollastonite filled PBT are smoother than those of glass fiber filled PBT. For the process conditions used, only the MPP has the trend where as the MPP is increased, the rim thickness variation is decreased. MPP is the driving force to make cells smaller. 

The effect of the process parameters on the rim thickness of glass fiber and Wollastonite filled PBT has been conducted. It has been found that ... 

The Textile roller has more uniform thickness with Wollastonite filled PBT than glass filled PBT. 

Wollastonite filled PBT has more uniform cell strueture but lower shrinkage rate than glass filled PBT. 

Table 7. Effect of Wollastonite treatment method on the mechanical properties of filled chloroprene [242]...

Epoxynovolak resin and BPA/DC-BMI prepolymer, tert.butyl peroxide and Zn acetate [106, 107] or 2-phenylimidazole and other catalysts [108] were filled with wollastonite. Carbon-fiber reinforced composites were obtained using a binder, which consisted of BPA/DC, BMI, an epoxynovolak, 2-ethyl-4-methylimidazole and an organic solvent [109]. A BPA/DC-BMI prepolymer in methylethylketone was mixed with middle-molecular-weight epoxide resin (Epikote 1001), 2-ethyl-4-methyl-imidazole, Zn acetate and triethylenediamine thermal shock resistant GRP was thus obtained [110]. 

The moisture resistance properties of filled molding compounds are enhanced by the treatment of the fillers with silane adhesion promoters prior to compounding. Silane promoters on wollastonite fillers in thermoplastic polyester molding compounds (50 percent filled) will improve the flexural strength after 16 h in 50°C water by as much as 40 percent. Silane-treated silica fillers have been found to significantly increase the moisture resistance of epoxy adhesives used in the electronics industry for chip, surface-mounted, and printed-circuit processes.8... 

Figure 9.13 shows the effect of filler concentration on torque. The smallest increase was due to magnesium carbonate and the largest due to the presence of glass fibers. The mechanical properties of filled composites are substantially improved by additions of magnesium carbonate, wollastonite and glass fiber. The most important improvement is in creep resistance (Figures 6.68 and 8.69). 

The effect of fillers on creep phenomena (essentially the inverse of stress relaxation) is also of interest a detailed study by Nielsen (1969b) of creep in filled polyethylene is illuminating. Kaolin and wollastonite were used as fillers, both treated with a silane coupling agent and untreated. A major aim was to discover whether the major effect of a filler is due to its effect on elastic modulus, or whether a filler also changes the viscoelastic nature of the system. As reported in previous work by others, the presence of a filler did in fact reduce the creep, the relative effect being nearly independent of the applied stress. The nature of the filler and the surface treatment were also found to be important. In experiments at a constant volume fraction (0.2), kaolin was more effective than wollastonite. Silane treatment of the filler surface tended to decrease creep, especially if the specimens had been soaked in water. 

Mineral fillers used are calcium carbonate (CaCOj), China Clay (Al/0H [Si.,0 J), miea especially muscovite (KAyOHjFlJAlSijOj J), silica flour (SiO ), talc (Mg, (OH)j[Si Oj J), and wollastonite (CaSiOj). Parameters that need to be considered during inorganic filler selection are basicity, filler impurities that may influence the resin euring proeess, and filler hardness that eauses abrasion of the mold [1]. Mica filled phenolics are used in electrical parts because mica adds outstanding dielectric properties, high thermal and chemical resistance and low water absorption [1]. 

The second, obvious application is studying polvmer-filler interactions in filled and reinforced composites. Some data are presented for wollastonite and quartz filled Bisphenol-A based and cycloaliphatic epoxies [6]. These data show, that Tg shifts observed by different relaxation methods (dielectric spectroscopy, DSC, thermomechanical measurements) are not necessarily the same (Table 1.), they depend on the effective frequency, changes in activation energy have also to be taken into account. Correlations between Tg shift and polymer adsorption can be understood using Lipatov s theory [7]. Positive Tg shift usually indicates strong adhesion, while negative Tg shift can be explained by the fact that the adsorbed polymer layer forms a looser structure than that of the bulk material. If both the neat resins and their composites are studied dielectrically, the origin of the low-... 

Fig. 3. Dielectric permittivities of a non-filled Bisphenol-A based epoxy resin (C) and its composite filled with 60 wt% wollastonite (C/W, left) and of a non-filled cycloaliphatic epoxy resin (B) and its composites filled with 60 wt% wollastonite (B/W) and quartz (B/Q, right). The high-temperature, low frequency polarization process is most probably due to the matrix/electrode interface in the case of resin C, while it is related to the matrix/filler interface in the case of resin B. (After Ref. [6]).

The effectiveness of silanes in improving the properties of the filled polymer depends considerably on the filler. Silica, alumina and glass give very good results. Talc, wollastonite... 

Kaolin is used only in small quantities in PR The anisotropic particle geometry of wollastonite and mica reinforces the pol)uner. The latter is applied more extensively in USA and Canada due to the closer location of mining facilities. Barite-filled PP has excellent vibration damping properties due to the high density of this filler. Wood flour filled PP is occasionally applied in the automotive industry for the preparation of door panels. Water absorption of this filler creates problems in processing and application. The most important characteristics of mineral fillers are collected in Table 2. 

Because of their high crosslink density and very brittle behaviour, phenolic moulding compounds are invariably filled with reinforcing fillers such as wood floui wollastonite, mica, mineral wool flour and glass fibres. Solid moulding compounds are normally novolac based resins for transfer moulding (RTM) and other liquid laminating processes are resols. 

---