Surface treatment, plastics fillers

Cell morphology of foamed PVC depends on concentration of a plasticizer, surface treatment of filler and foaming time and temperature. High concentrations of plasticizers produced poly disperse cell structure. Polyester plasticizer blends are useful for production of heat-shrinkable film. Plasticizer migration from geomembranes causes membrane shrinkage. ... 

Althouse, L.M., Bigg, D.M. and Wong, W.M. (1983) Evaluating the effectiveness of filler surface treatments. Plastics Compounding, (March/ April). 

For some plastics, surface treatments were necessary—for example, chromic acid treatment for polypropylene. When fillers were present in the plastics the results with cyanoacrylates often were better (this was apparent in particular with polyethylene). 

Under the microscope, Biodac appears as small rocks attached to cellulose fibers and bundled into granules. Because of short cellulose fibers on the surface of Biodac , the filler provides a mechanical adhesion (interlocking) with the plastic matrix without any surface treatment. The thermal expansion-contraction coefficient of Biodac appears to be much closer to that of plastics, compared to the coefficients of common mineral fillers. Hence, the bond between Biodac and the plastic after weathering of the composite material becomes loose at lesser extent compared to inorganic fillers. 

Schofield J, Sunderland P. Surface treatments for calcium carbonate fillers in high performance systems. Rubber Fibres Plastics Int [trade journal—Rapra Technology] March 2008. 

Rothon, R.N., Schofield, J., Thetford, D., Sunderland, P Lees, G Liauw, C.M., and Wild, F. (2002) Functionalized adds as filler surface treatments. Proceedings of the Functional Fillers for Plastics 2002, Intertech Corp., Toronto, Canada, September 2002, Paper 5. 

Surface treatment is another value-added step that can improve the performance of kaolin. Since the filler is naturally very hydrophilic due to its hydroxyl groups, a treatment can be applied to render its surface hydrophobic or organophilic. These surface-modified kaolins are useful especially in plastics and rubber industries, where they improve adhesion and dispersion and hence act more effectively as functional fillers. Silanes, titanates, and fatty adds as discussed in Chapters 4-6, respectively, may be used to modify the surface charaderistics of either hydrous or calcined kaolins, promoting dea lomeration, often lower viscosities, and improved mechanical and eledrical properties. 

In selecting wollastonite as the functional filler for plastics, most of the properties to be considered are white color, high brightness, moderate specific gravity, moderate Mohs hardness, moderate range of loose and tapped bulk densities, needle-like particle shape, high processing melt temperature, wide compatibility with silane and titanate surface treatments, and low CLTE. 

Kaolin deposits are cored and analyzed before mining to determine quality. Mined clays are then either wet or dry processed by air floatation or water fractionation. Surface-modified clays can be made by treating standard, delaminated, and calcinated grades with surface modifiers. The treatment can be performed by either the supplier or the end user. These surface modifiers include silane, titanate, polyester, and metal hydroxide. The objective of these surface treatments is to increase filler loadings and/or improve physical properties such as melt viscosity, thermal stability, and modulus without loss of physical characteristics. Electrical applications represent the largest use of surface-modified kaolin in plastics. 

Katz, H. S. Milewski, J. V. Handbook of Fillers for Plastics, RAPRA, (1987). Mareri, R Bastrole, S. Broda, N. Crespy, A. Mechanical behaviour of polypro-pyl-ene composites containing fine mineral filler Effect of filler surface treatment. Comp. Sci. and Techn., 1998, 58(5), 747. 

Description Most widely used filler for plastics forms vary according to geographical source. Surface treatments greatly improve properties and controlled particle size makes functional fillers possible improved flow properties, low-profile anti-shrinkage, anti-blocking additives treatment with aluminium trihydroxide (ATH) gives some flame retardancy ... 

All natural fibers are hydrophihc and their moisture content ranges from 3 to 13%. This leads to a very poor interface between natural fiber and the hydrophobic matrix and very poor moisture resistance. Several fiber surface treatments are used to improve the interface viz-thermal treatment, chemical treatment, and use of coupling agents (Bledzki and Gassan, 1999). Fillers are added to composites for technical and chemical reasons (Milewski and Katz, 1980). Calcium carbonate has maximum usage as filler in plastics and FRP due to its low cost, non-toxicity and lack of odor. Present work gives effectiveness of jute fabric treatment and addition of filler on properties of jute reinforced polyester composites (JFRP). 

There is a separate entry in this book dealing with the surface treatment of particulate fillers in plastics, and so the main discussion here will be about the surface treatment of glass fibres. 

The reader is referred to the entry in this book, entitled Surface treatments for particulate fillers in plastics, for further information. 

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