Radiation curable compositions for additive fabrication with improved toughness and high temperature resistance

A process of forming a three-dimensional object comprising the steps of forming a liquid layer of the radiation curable composition for additive fabrication;

• selectively curing said liquid layer of the radiation curable composition with actinic radiation;
• and repeating the steps of forming and selectively curing the liquid layer of the radiation curable composition for additive fabrication a plurality of times to obtain a three-dimensional object;
• wherein the radiation curable composition comprises:
• a rubber toughenable base resin further comprising
• a cationically polymerizable component;
• a radically polymerizable component;
• a cationic photoinitiator;
• a free radical photoinitiator;
• and
• optionally, customary additives;
• and
• a liquid phase-separating toughening agent;
• wherein the liquid phase-separating toughening agent is present in an amount, relative to the weight of the rubber toughenable base resin, in a ratio from 1:50 to about 1:3;
• wherein the liquid phase-separating toughening agent comprises a polyether polyol of from about 2,000 g/mol to 10,000 g/mol;
• wherein the average molecular weight between crosslinks (Mc) of the rubber toughenable base resin is between 150 and 500 g/mol;
• and
• wherein the radiation curable composition being polymerized exhibits an increase in an elongation-at-break (EAB) value of at least 5%, maintains a change of a heat deflection temperature (HDT) value within 7 degrees Celsius (° C.) when compared to the rubber toughenable base resin, and possesses an HDT value of at least 75 degrees Celsius (° C.).