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

Incorporation of different fine grain calcium carbonate into CaCO 3 /low-density unsaturated polyester resin (LDUPR) composites was studied and evident mechanical enhancement of CaCO 3 on composites was investigated. Preliminary experiment results indicated that proper content of CaCO 3 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 CaCO 3 /LDUPR samples were obtained with the presence of 25.00 phr CaCO 3 and 2.50 phr NH 4 HCO 3 at 76.0 °C based on preliminary experiments. The lowest apparent density of A-CaCO 3 /LDUPR composite was 0.53 ± 0.02 g · cm −3 with a compressive strength of 20.27 ± 0.51 MPa · g −1  · cm 3 , and the highest specific compressive strength of the sample was 38.25 ± 1.43 MPa · g −1  · cm 3 . 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 CaCO 3 . Unusual matrix microstructure with regular ripples and dimples formed by CaCO 3 , and the particular mechanical enhancement of regular ripples and dimples in composites were explored. ‘CaCO 3 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 CaCO 3 in CaCO 3 /LDUPR composites. This particular polymerization retarding and mechanical strengthening were obvious for the finest grain CaCO 3 .