Polypropylene filler compounds, effect

C. Paynter, Anisotropic Mineral Fillers Compounded with Polypropylene, A Study of the Differing Stiffening Effects of Talc and Kaolin, University of Surrey, UK, 1999. [MSc Thesis]... 

Substitute for Conventional Vulcanized Rubbers, For this application, the products are processed by techniques and equipment developed for conventional thermoplastics, ie, injection molding, extrusion, etc. The S—B—S and S—EB—S polymers are preferred (small amounts of S—EP—S are also used). To obtain a satisfactory balance of properties, they must be compounded with oils, fillers, or other polymers compounding reduces costs. Compounding ingredients and their effects on properties are given in Table 8. Oils with high aromatic content should be avoided because they plasticize the polystyrene domains. Polystyrene is often used as an ingredient in S—B—S-based compounds it makes the products harder and improves their processibility. In S—EB—S-based compounds, crystalline polyolefins such as polypropylene and polyethylene are preferred. Some work has been reported on blends of liquid polysiloxanes with S—EB—S block copolymers. The products are primarily intended for medical and pharmaceutical-type applications and hardnesses as low as 5 on the Shore A scale have been reported (53). 

Coating is increasingly used to enhance the properties of fillers. One of the most widely used materials is stearic acid. Metal stearates are particularly effective as coatings for reactive particulate fillers, such as magnesium hydroxide (MH), producing polypropylene compounds with better impact resistance than those containing uncoated, or stearic acid-coated fillers. 

C. M. Liauw, G. C. Lees, and S. J. Hurst, The effect of filler surface modification on the mechanical properties of aluminium hydroxide filled polypropylene. Plastics Additives and Compounding, 24 (1995), 249-60. 

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