Mechanical enhancement of ripples and dimples in CaCO3/low-density unsaturated polyester resin composites

Abstract

Incorporation of different fine grain calcium carbonate into CaCO3/low-density unsaturated polyester resin (LDUPR) composites was studied and evident mechanical enhancement of CaCO3 on composites was investigated. Preliminary experiment results indicated that proper content of CaCO3 was less than 30.00 phr (parts per hundreds of resin), suitable preparation temperature range was from 72.0 °C to 80.0 °C, and initiator content was 1.80 phr. Optimal preparation conditions of CaCO3/LDUPR samples were obtained with the presence of 25.00 phr CaCO3 and 2.50 phr NH4HCO3 at 76.0 °C based on preliminary experiments. The lowest apparent density of A-CaCO3/LDUPR composite was 0.53 ± 0.02 g · cm−3 with a compressive strength of 20.27 ± 0.51 MPa · g−1 · cm3, and the highest specific compressive strength of the sample was 38.25 ± 1.43 MPa · g−1 · cm3. It is attributed to the hindrance to cross-linking between unsaturated polyester and styrene, and to the decrease of exothermic heat of the polymerization, which was caused by the existence of CaCO3. Unusual matrix microstructure with regular ripples and dimples formed by CaCO3, and the particular mechanical enhancement of regular ripples and dimples in composites were explored. ‘CaCO3 reefs’ concept, reefs-induced ripples, dimples of streams flowing, and resolution of external force with major force further being consumed models comprised the regulated mechanical enhancement of CaCO3 in CaCO3/LDUPR composites. This particular polymerization retarding and mechanical strengthening were obvious for the finest grain CaCO3.