Mechanical and flame‐retarding properties of styrene–butadiene rubber filled with nano‐CaCO 3 as a filler and linseed oil as an extender

A nanosize CaCO 3 filler was synthesized by an in situ deposition technique, and its size was confirmed by X‐ray diffraction. CaCO 3 was prepared in three different sizes (21, 15, and 9 nm). Styrene–butadiene rubber (SBR) was filled with 2–10 wt % nano‐CaCO 3 with 2% linseed oil as an extender. Nano‐CaCO 3 –SBR rubber composites were compounded on a two‐roll mill and molded on a compression‐molding machine. Properties such as the specific gravity, swelling index, hardness, tensile strength, abrasion resistance, modulus at 300% elongation, flame retardancy, and elongation at break were measured. Because of the reduction in the nanosize of CaCO 3 , drastic improvements in the mechanical properties were found. The size of 9 nm showed the highest increase in the tensile strength (3.89 MPa) in comparison with commercial CaCO 3 and the two other sizes of nano‐CaCO 3 up to an 8 wt % loading in SBR. The elongation at break also increased up to 824% for the 9‐nm size in comparison with commercial CaCO 3 and the two other sizes of nano‐CaCO 3 . Also, these results were compared with nano‐CaCO 3 ‐filled SBR without linseed oil as an extender. The modulus at 300% elongation, hardness, specific gravity, and flame‐retarding properties increased with a reduction in the nanosize with linseed oil as an extender, which helped with the uniform dispersion of nano‐CaCO 3 in the rubber matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2563–2571, 2005