Filler-loaded polymers

Spherical indentor deformability tests of composites with PE synthesized on different fillers have shown [164] that the deformation of PFCM containing high percentages of filler (and polymer concentrations of less than 10% by mass) is substantially elastic and the specimen recovers completely after release of the load. As the polymer content increased to 60% by mass considerable residual deforma-... 

The important yet unexpected result is that in NR-s-SBR (solution) blends, carbon black preferably locates in the interphase, especially when the rubber-filler interaction is similar for both polymers. In this case, the carbon black volume fraction is 0.6 for the interphase, 0.24 for s-SBR phase, and only 0.09 in the NR phase. The higher amount in SBR phase could be due to the presence of aromatic structure both in the black and the rubber. Further, carbon black is less compatible with NR-cE-1,4 BR blend than NR-s-SBR blend because of the crystallization tendency of the former blend. There is a preferential partition of carbon black in favor of cis-1,4 BR, a significant lower partition coefficient compared to NR-s-SBR. Further, it was observed that the partition coefficient decreases with increased filler loading. In the EPDM-BR blend, the partition coefficient is as large as 3 in favor of BR. 

It has been well established that wear resistance of filled rubber is essentially determined by filler loading, filler morphology, and polymer-filler interaction. For fillers having similar morphologies, an increase in polymer-filler interaction, either through enhancement of physical adsorption of polymer chains on the filler surface, or via creation of chemical linkages between filler and polymer, is crucial to the enhancement of wear resistance. In addition, filler dispersion is also essential as it is directly related to the contact area of polymer with filler, hence polymer-filler interaction. 

They may also act as reactive super plasticisers to increase rubber flow while increasing the mechanical properties of the rubber. Viscosity reduction or polymer solvation and higher filler loading can be accomplished with less plasticiser. Flow is achieved through molecular rearrangement and not average molecular weight reduction of the rubber. 

In general, tin compounds do not exhibit flame-retardant properties in halogen-free polymer systems, unless the composition contains a high inorganic filler loading. However, tin additives often act as smoke suppressants in non-halogenated polymers. 

Filled resins, 18 292 Filled silicone networks, 22 570-572 Filler hybrid preparation method, 13 539 Filler loading, 10 430, 457 Fillers, 10 430-434 11 301-321. See also Filled polymers applications of, 11 301-302 butyl rubber applications, 4 448-449... 

Thermal expansion differences exist between the tooth and the polymer as well as between the polymer and the filler. The tooth has a thermal expansion coefficient of 11 x 10-6/°C while conventional filled composites are 2-4 times greater [63, 252], Stresses arise as a result of these differences, and a breakdown between the junction of the restoration and the cavity margin may result. The breakdown leads to subsequent leakage of oral fluids down the resulting marginal gap and the potential for further decay. Ideal materials would have nearly identical thermal expansion of resin, filler, and tooth structure. Presently, the coefficients of thermal expansion in dental restorative resins are controlled and reduced by the amount and size of the ceramic filler particles in the resin. The microfilled composites with the lower filler loading have greater coefficient of thermal expansions that can be 5-7 times that of tooth structure. Acrylic resin systems without ceramic filler have coefficients of thermal expansion that are 9 times that of tooth structure [202-204, 253],... 

Filler surface treatments, such as fatty acids, are very useful for reducing melt viscosities and some fillers would be impossible to use at the loadings needed for certain applications such as fire retardancy without some form of surface treatment. In some cases melt viscosities can be maintained at similar levels to the unfilled polymer, even in highly filled systems, despite the use of high filler loading [9]. 

Several studies have considered the influence of filler type, size, concentration and geometry on shear yielding in highly loaded polymer melts. For example, the dynamic viscosity of polyethylene containing glass spheres, barium sulfate and calcium carbonate of various particle sizes was reported by Kambe and Takano [46]. Viscosity at very low frequencies was found to be sensitive to the network structure formed by the particles, and increased with filler concentration and decreasing particle size. However, the effects observed were dependent on the nature of the filler and its interaction with the polymer melt. 

Interfacial structure is known to be different from bulk structure, and in polymers filled with nanofillers possessing extremely high specific surface areas, most of the polymers is present near the interface, in spite of the small weight fraction of filler. This is one of the reasons why the nature of the reinforcement is different in nanocomposites and is manifested even at very low filler loadings (<10 wt%). Crucial parameters in determining the effect of fillers on the properties of composites are filler size, shape, aspect ratio, and filler-matrix interactions [2-5]. In the case of nanocomposites, the properties of the material are more tied to the interface. Thus, the control and manipulation of microstructural evolution is essential for the growth of a strong polymer-filler interface in such nanocomposites. 

This depends on the polymer type and increases with higher dry filler loading and reduces with peptizing agents, plasticizers, softeners, reclaimed rubber or resins. 

It is usually not possible to match the adhesive s coefficient of thermal expansion to the substrate, because of the high filler loadings that would be required. High loading volumes increase viscosity to the point where the adhesive could not be easily applied or wet a substrate. For some base polymers, filler loading values up to 200 parts per hundred (pph) may be employed, but optimum cohesive strength values are usually obtained with lesser amounts. 

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