Abstract : Modification of heat cured acrylic resin to gain improved properties. The lines comprise modification of structure to prepare copolymers and testing the degree of bond conversion. The specimens were made of acrylic resin (heat cured) and three liquid additives: Acryester B, Ethoxycarbonylethylene, and Propenoic acid using two percentages for each additive (5% and 10%). The degree of conversion was inspected and related. The one way analysis of variance test display statistically significant difference among the tested groups and the P- value was (0.000). The highest value of degree of conversion found in the group of 10% Propenoic acid which is (96.625), while the lowest value found in the group of 5% Ethoxycarbonylethylene which is (86.34). Acryester B and Propenoic acid enhance the degree of conversion. Ethoxycarbonylethylene does not affect the degree of conversion. Increasing Acryester B concentration improve the degree of conversion. The effect of Propenoic acid is more than that of Acryester B.