Composites Reinforced with Fillers

Sand/clay UPR composites containing various amounts of styrene and sand/clay, with different particle sizes of clay were prepared [234]. The effect of a radiation-initiated (/-irradiation at 50 kGy) polyester curing on the physicomechanical properties of the prepared composites was investigated. It was found that the compressive strength decreased with an increase in the sand/clay and styrene contents, as well as the size of clay particles, whereas the apparent porosity and water absorption of the composites increased. New 

It has been shown that recycled FR-4 epoxy laminates are advantageous fillers for UPRs [58]. Moreover, caldiun carbonate and copper were used as additional fillers. The fillers affected the curing rate, decreased the flexural strength and increased the flexural modulus. The shredded laminates were used in the amount of 100 phr. 

The creep of UPRs and the UPR composites filled with marble powder and powdery PVC was studied [235]. The authors proposed a jump-like character for the creep rate of materials. It was also assumed that the creep on the micron level reflected the structural inhomogeneity of UPRs and their composites. An optimized cure cycle with reduced process-induced residual stresses and the optimum temperature profile for the manufacturing of UPR composites were searched using the numerical simulation [236]. 

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A series of six stress-strain cycles with a crosshead rate of 600 mm/min was applied to specimens having a parallel length of 25 mm and a cross-section of 1 x 4 mm2 on a tensile testing machine. The samples were continuously stretched in six hysteresis cycles up to 60% of their elongation at break values, as shown in Fig. 47. This procedure is an established one and widely practiced for elastomeric composites reinforced with fillers such as carbon black and silica, which tend to build a strong filler-filler network [83]. 

Similar to composite propellants, flexibilized epoxy or novolac epoxy resins reinforced with fillers or fibers are used for inhibition of fuel-rich propellants. 

Canadian Pat. No. 2,278,688 (June 17, 1999). Y. Kasahara and E. Goto. Thermoplastic composite composition reinforced with mica and wooden fiber filler. 

In addition, by scaling the filler size to the nanometer scale, it has been shown that novel material properties can be obtained. Nanoscaled fillers are those having at least one dimension in the range of nanometers (< 100 nm) [3]. When the dimensions of the reinforcement approach the nanometer scale, a number of effects make the properties of the corresponding composites different from those of composites reinforced with micro-scaled fillers. The major influencing factors of the properties of nanocomposites are nanofiller dispersion, dimensions, volume fractions, nature of the matrix material, interfacial properties between filler and matrix, and manufacturing process [4]. 

A thermoplastic polymer composition reinforced with fibers such as cellulose or other fillers, particularly from natural sources, and a process for manufacturing the composition has been described (26). The polymer is extruded with a salt which reduces the melting point and pelletized. The pellets are then extruded again with the filler. The composition with the filler can then be melted at the reduced melting temperature to manufacture an article. 

Reinforced polymers and thermally conductive polymer composites. Polymers are often reinforced with fillers to... 

A comparison of the mechanical properties of NR/CNT and NR/CB composites with 25 phr of filler is shown in Table 1.12. NR/CNT nanocomposites exhibit marked enhancement of Shore A hardness, tensile modulus and tensile strength by 16, 32 and 10%, respectively, as compared to NR composites reinforced with the same filler loading of CB. This may be due to the strong... 

CB is often used together with other fillers to get hybrid fillers, and the NR composites reinforced with hybrid fillers will be discussed in the next section. 

Jong et prepared NR composites reinforced with hybrid filler consisting of defatted soy flour (DSF) and CB. Aqueous dispersions of DSF and CB were first mixed, and then blended with NR latex and sulfur dispersion, respectively. The homogenous composite mixtures were quickly freeze-dried and compression moulded to offer the NR composites. They found that the NR composites reinforced with 40% of hybrid filler (the ratio of DSF to CB was 1 1) exhibited a 90-fold improvement in the rubber plateau modulus compared with unfilled NR, showing a significant reinforcement effect by the hybrid filler. 

Studies on a similar group of materials - polymeric composites reinforced with sisal fibers - were conducted by Manchado et al. [35]. They analyzed the presence of different fibers, such as sisal, on crystallization of polypropylene. The composites were prepared in special chamber for mixing where the matrix was plastified at 190°C. Obtained materials were subjected to thermal analysis by DSC. The analysis of thermograms allowed for a similar finding like in Joseph s studies [34], The presence of sisal fibers, as well as other fibers used in the study, accelerated crystallization of polypropylene. This was explained by the nucleating effect of sisal filler. Also, the half-time crystallization (ti/2) decrease was observed for polypropylene with the addition of sisal fibers in comparison with unfilled polypropylene. The analysis of nonisothermal crystallization showed that the degree of polypropylene crystallinity is higher for the composites filled with sisal fibers than for unfilled polymer. 

Water absorption results of neat UPE and its composites reinforced with raw, mercerized and benzoylated fibers have been shown in Table 13.1. It can be seen from the table that water absorption characteristics of polymer composites depend upon the content of fiber loadings, water immersion time and surface modification techniques. The water absorption of raw and surface-modified fiber-reinforced UPE composites has been found to increase with the increase in percent loading. Similar results were also reported by Rashdi et ah during their studies on the water absorption behavior of kenaf fibers-reinforced polyester composites [27]. This may be due to greater affinity of water for OH groups present on the fiber backbone, whose number increases with the increase in fiber contents. In comparison to raw filler, composites reinforced with surface-modified filler exhibited low water absorption, which may be due to the reduction in the hydrophilic character of cellulosic biofibers after surface modification. 

Guiraud, O., Dumont, R, Orgeas, L., Vassal, J. R, Le, T. H. and Favier, D. (2010), Towards the simulation of mould filling with polymer composites reinforced with mineral fillers and short fibres , International Journal of Material Forming, 3(S2), S1313-S1326. 

Finally, starting from the opinion [5] that today we cannot be happy with the mechanical performance of polymer composites reinforced with nano-sized fillers of various origins, new routes to create polymeric materials with improved properties have to be researched in addition to attempts to overcome the disadvantages. An attractive alternative in this respect seems to be the preparation of polymers themselves as nano-sized materials, as, for example, electrospinning does. 

Because of waste accumulation at the end of the life cycle of traditional polymer products, the development of environmentally-ffiendly, degradable, polymeric materials has attracted extensive interest. Nevertheless, the properties of such kinds of polymers are lower than that of traditional ones. Thermoplastic polymers have been widely used as matrix of composites reinforced with natural fibers in order to achieve a final material with improved mechanical properties with respect to the pure polymer. In order to obtain competitive products, the performance of biodegradable polymers can be greatly enhanced by the incorporation of nanometer-size fillers. 

In a filled rubber, agglomeration of the particles produces a filler network, in addition to the network of covalently-bonded polymer chains. In fact, Reichert et al. [30] modeled the deformation of single network of filled rubber as a double network, adopting an approach similar to that used to analyze unfilled double networks [35-37]. This implies that double-network mbber reinforced with filler can be viewed as a composite of three distinct networks. 

Conradi, M., Zorko, M., Kocijan, A., Verpoest, I., 2013. Mechanical properties of epoxy composites reinforced with a low volume fraction of nanosihca fillers. Materials Chemistry and Physics 137, 910—915. 

The resin matrix of commercial dental composites has bis-GMA (bisphenol-A-glycidyldimethacrylate) as its predominant base monomer. Due to its high viscosity, bis-GMA is mixed with other dimethacrylates, such as TEGDMA, UDMA or other monomers of lower molecular weight [26, 50] to reduce viscosity. The monomers are heavily reinforced with filler particles, which add dimensional stability, improve wear and strength of the material, also reducing polymerization shrinkage [51]. 

Polymer composites reinforced with inorganic fillers of dimensions in the nanometer range, known as nanocomposites, have attracted great attention of researchers due to unexpected synergistic properties derived from two components. The most studied polymer nanocomposites (PNs) are composed of thermoplastic or thermosetting matrix and organically modified montmorillonite (OMMT) l-4] or carbon nanotubes (CNTs) [5-7]. 

PNs, that is, polymer composites reinforced with inorganic fillers of dimensions in the nanometer range, have attracted great attention of researchers, due to unexpected synergistic properties derived from the two components. 

R. Huang, X. Xu, S. Lee, Y. Zhang, B. -J. Kim, and Q. Wu, High Density Polyethylene Composites Reinforced with Hybrid InorgcUiic Fillers. Morphology, Mechanical and Thermal Expansion Performance Materials 6, 4122-38 (2013). 

Choi, S.-S., C. Nab, and B.-W. Jo, Properties of natural rubber composites reinforced with silica or carbon black Influence of cure accelerator content and filler dispersion. Polymer International, 2003. 52(8) 1382-1389. 

Resin with an accelerator added but not catalyst. According to ASTM, those plastics having superior properties over those consisting of the base resin, due to the presence of high-strength fillers embedding in the composition. Reinforcing fillers are fibers, fabrics or mats made of fibers. 

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