Prepregs and production of composite material using prepregs

A prepreg comprising at least one layer of fibres and a curable thermosetting resin system, the curable thermosetting resin system at least partly impregnating the at least one layer of fibres, wherein the curable thermosetting resin system comprises:

• a. a curable thermosetting resin including at least two epoxide groups;
• b. a curing agent for curing the curable thermosetting resin, wherein the curing agent includes at least one amine group, wherein the curing agent comprises dicyandiamide, wherein the curing agent is present in an amount of from 2 to 18 wt % based on the weight of the curable thermosetting resin system;
• and
• c. an accelerator for accelerating the curing of the thermosetting resin by the curing agent, wherein the accelerator comprises a first accelerator which includes an azole group, wherein the first accelerator comprises at least one imidazole and the first accelerator is present in an amount of from 0.2 to 3 wt % based on the weight of the curable thermosetting resin system;
• and the accelerator further comprises second accelerator which comprises a substituted or unsubstituted urea of formula R1R2-N-CO-NR3R4, where R1 is hydrogen or any substituted or unsubstituted aliphatic group, R2 is hydrogen or any substituted or unsubstituted aliphatic, R3 is hydrogen or any substituted or unsubstituted aliphatic or aromatic group, and R4 is hydrogen or any substituted or unsubstituted aliphatic or aromatic group, and wherein the second accelerator is present in an amount of from 0.5 to 5 wt % based on the weight of the curable thermosetting resin;
• wherein the curable thermosetting resin, the curing agent and the accelerator are provided in respective concentrations in the prepreg to provide that, after heating the thermosetting resin at a cure temperature of at least 140° C. for a period of from 1 to 6 minutes, (i) the cured thermosetting resin has a glass transition temperature Tg which is greater than the cure temperature and is within the range of from 150° C. to 180° C. and (ii) the cured thermosetting resin is at least 90% cured;
• and
• wherein the curable thermosetting resin is present in an amount of from 60 to 95 wt % based on the weight of the curable thermosetting resin system.