Polypropylene functional filler

Klingert B. Influence of stabilizers on light and thermal stability of filled polypropylene. Functional fillers and additives for thermoplastics and rubber conference. Berlin September 1994. p. 26-28. 

Stark N, Berger MJ. Effect of species and particle size on properties of wood-tlour-filled polypropylene composites. Proceedings of the Functional fillers for thermoplastics thermosets 1997 Madison, WI. Wisconsin USDA Forest Service. Forest Products Laboratory 1997. p 1. 

Magnetite functional filler a compounding study in polypropylene and polyamide, technical article (www.spedalchem4polymers.com). Elsevier Advanced Technology 2002 (downloaded 12 December 2007). 

The interaction of the polymer with the filler is promoted by the presence of reactive functionality in the polymer, capable of chemical reaction or hydrogen bonding with the functionality, generally hydroxyl, on the surface of the filler. Thus, carboxyl-containing polymers, e.g. ethylene-acrylic acid copolymers and maleic anhydride- and acrylic acid-grafted polyethylene and polypropylene interact readily with fillers. 

Figure 10.1 shows the effect of the addition of fillers to polypropylene on its crystallinity. This study was conducted under the same conditions for all specimens tested. There is a difference in the effect of CaCO-, and talc. Calcium carbonate lacks surface functional groups so it tends to have a very small influence on crystallinity and the crystallization behavior. Talc has interacting functional groups on its surface which cause the increase in crystallinity along with the concentration increase. 

It can be postulated that three factors may play a role in stabilization in the presence of fillers. One factor is the discussed absorption which immobilizes stabilizer to the extent that it cannot perform its function. The second is its desorption capability, which, if it exists, may enhance the performance of stabilizer due to its better retention. However, it should be mentioned that photochemical changes occur at very short time scales therefore, there must always be a sufficient concentration of free (not absorbed) stabilizer to react with radicals. The third factor is the effect of filler on structure and related stability of stabilizer. The reduced stability of polypropylene in the presence of some stabilizers in Table 13.4 can be explained only by the formation of degradation products. It... 

Relative (a) tensile modulus and (b) yield stress of polypropylene nanocomposites plotted as a function of inorganic volume fraction of filler. The dotted lines serve as guides. (Reproduced from Mittal, V., Eur. Polym. 43, 3727, 2007. With permission from Elsevier.)... 

The multiple functions of mica have been outlined in Chapter 1 of this book, along with an example of its role in the search of multifunctional fillers for polypropylene compounds for automotive applications. Mica-reinforced thermoplastics such as polypropylene, polyethylene, nylon, and polyesters are now established in a variety of automotive applications and consumer products where mica supplements or replaces glass fibers and other mineral fillers. The wider use of mica in many applications has been limited by low impact strength and low weld-line strength in certain plastics. These issues are the focus of continuing R D efforts by materials suppliers and compounders/molders. 

Mohamed et al. [149] evaluated the use of several types of sulfosuccinate anionic surfactants in the dispersion of MWCNTs in NR latex matrices. Sodium l,5-dioxo-l,5-bis(3-phenylpropoxy)-3-((3-phenylpropoxy)carbonyl) pentane-2-sul-fonate showed the best dispersion capabihty and improved the electrical conductivity of the resulted composites. These results have significant implications in the development of new materials for aerospace applications because the filler s dispersiou directly influences the properties of the final material. Jo et al. [150] obtained pristine MWCNt-Ti02 nanoparticles filled with NR-CllR and epoxidized NR-CUR, concluding that the second blend proved higher thermal conductivity because the epoxy branches in ENR and the functionalized MWCNT form a stronger network. Conductivity in CNTs reinforced with rubber-based blends can be improved when reaching a critical concentration of the filler known as the percolation threshold, when a continuous network structure is formed. Thankappan Nair et al. [151] discussed the percolation mechanism in MWCNT-polypropylene-NR blends. 

Fillers can be made to bond to polymers by functionalising the polymer (incorporating appropriate chemical groups into it) to enable it to react chemically with the filler siuface. Maleic anhydride is a widely used functional unit often incorporated into polypropylene, and to a lesser extent polyethylene. Alkoxysilyl groups can be incorporated into hydrocarbon polymers to increase their reactivity. 

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