Process for manufacturing composite articles

A process for manufacturing a composite article by injection molding a polymer composition comprising at least one semi-crystalline thermoplastic polymer and/or at least one amorphous thermoplastic polymer, comprising the following steps:

• (a) Introducing at least one reinforcement material into a preheated mold having a temperature T1 that is in the range of from 50° C. to a temperature T1max, wherein T1max is defined as follows:
• T1max=Tgmax+40° C., (i)
• if the polymer composition has no melting transition, or
• if the polymer composition has at least one melting transition and the highest melting temperature Tmmax of the polymer composition is lower than Tgmax+40° C., wherein Tgmax denotes the highest glass transition temperature of the polymer composition,
• or
• T1max=Tmmax, (ii)
• if the polymer composition has at least one melting transition and the highest melting temperature Tmmax of the polymer composition is equal or greater than Tgmax+40° C.;
• and
• (b) after the introducing, partially closing the mold including the at least one reinforcement material, such that the mold exhibits an open gap with a volume of from 70% to 200% of the polymer volume to be injected;
• and
• (c) after the partial closing, raising the temperature of the mold to a temperature T2 that is in the range of from T2min to T2max, wherein T2min and T2max are defined as follows:
• T2min=Tgmax+50° C., T2max=Tgmax+300° C., (i)
• if the polymer composition has no melting transition,
• or
• T2min=Tgmax+50° C., T2max=Tgmax+150° C., (ii)
• if the polymer composition has at least one melting transition and the highest melting temperature Tmmax of the polymer composition is lower than Tgmax+40° C.,
• or
• Tgmin=Tmmax+10° C., T2max=Tmmax+100° C., (iii)
• if the polymer composition has at least one melting transition and the highest melting temperature Tmmax of the polymer composition is equal or greater than Tgmax+40° C.;
• and
• (d) optionally maintaining the raised temperature of the mold for a period of time;
• and
• (e) after the raising the temperature and the optional maintaining, injecting a polymer composition having a melt viscosity of from 5 to 200 Pa·s, determined according to ISO 11403-2 at the temperature of step (c) and a shear rate of 100 s−1, into the mold, filling the free cavity obtained by partial closure of the mold;
• and
• (f) after the injecting, closing the mold to the final thickness of the part, maintaining the temperature of step (c), employing a compression rate of from 0.001 to 0.5 mm/s and permitting the mold pressure to rise to a range of from 0.2 to 17.5 MPa;
• and
• (g) after the mold pressure rises, cooling the mold to a temperature T3 that is in the range of from T3min to T3max, wherein T3min and T3max are defined as follows:
• T3min=Tgmin−100° C., T3max=Tgmin+50° C., (i)
• if the polymer composition has no crystallization transition, and wherein Tgmin denotes the lowest glass transition temperature of the polymer composition,
• or
• T3min=Tcmin−120° C., T3max=Tcmin+25° C., (ii)
• if the polymer composition has at least one crystallization transition, and wherein Tcmin denotes the lowest crystallization temperature of the polymer composition;
• and
• (h) after the cooling, opening the mold, ejecting and recovering the produced composite article.