Polymer matrix composites, filled additives

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. 

The interaction between the surface of particulate and fibrous fillers and a polymer matrix plays a key role in deterrnining the processability and properties of filled composites. Unmodified filler surfaces often give poor interactions and this has led to the growth of an industry based on the use of additives to modify filler surfaces and improve their interactions with polymers. Several types of additives have been evolved for this purpose. Two of these, organofunctional silanes and titanates, have been described in Chapters 4 and 5. This chapter covers other approaches that have been studied, although only a few of these, notably fatty and unsaturated carboxylic acids and functionalized polymers, have achieved much commercial importance. 

Composites with 1-3 connectivity pattern could be also transversely poled (TP). PZT tubes with the electrodes on the inner and outer radius surfaces are dispersed in the polymer matrix (Zhang et al. (1993 Wang et al. 1995). Volume in the tube is either filled by the polymer or left empty and end-capped by the additional polymer cover plate. Under the assumption of the isotropic PZT ceramics the effective piezoelectric coefficients could be calculated for single tube... 

The case of fillers which adhere to the polymer matrix is important in most applications. This is general whether the adhesion is intrinsic to the materials or enhanced by surface treatment of the fillers or additives to the polymer. When the adhesion between the filler and the resin matrix is adequate, the resin and the filler coact under stress. From the standpoint of visualizing how these effects alter the performance of the composite to make the whole greater than the parts, we will examine the combination of a fibrous filled fiber glass and a suitable resin matrix such as an adhering polyester resin. The case of a simplified configuration of a bundle of parallel fibers before and after the addition of the resin matrix is illustrated. The analysis will be extended to random fiber orientation and then to other filler shapes. 

Filling modification of polymer is the addition of solid additives with different composition and structure to the polymer matrix material to reduce costs or obviously change the performance of polymer products, which will improve the desired performance at the expense of other kinds of performance at the same time. Such an additive is known as a filler. Because these fillers are mostly inorganic powder, filling modification relates to performance difference and complementation of organic polymer and inorganic matter. This provides diverse areas of research and broad fields of application for filling modification. 

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