High-strength molded body and method for manufacturing same

A method for producing a composite molded article (C) comprising a cellulosic nanomaterial (A) and a thermoplastic resin (B), the method comprising:

• (1) melting a composition comprising the cellulosic nanomaterial (A) and the thermoplastic resin (B) to prepare a molten composite composition comprising the cellulosic nanomaterial (A) and the thermoplastic resin (B) (step 1);
• (2) molding the molten composite composition obtained in step 1 in a molten state, followed by cooling, thereby preparing a melt-molded article (D) (step 2);
• and
• (3) warm-forming the melt-molded article (D) obtained in step 2 by at least one method selected from the group consisting of shearing, compression, stretching, and rolling (step 3),
• an area under a stress-strain curve of the composite molded article (C) (AUC1) being at least two times an area under a stress-strain curve of the melt-molded article (D) (AUC2),
• wherein the stress-strain curve is a curve drawn with strain (unit:
• %) on the horizontal axis and stress (unit:
• MPa) on the vertical axis and obtained by subjecting the composite molded article (C) or the melt-molded article (D) to a tensile test, and the area is an area up to the horizontal axis from under a curved portion of the curve that is from the origin (stress:
• 0) of the stress-strain curve to a fracture of the composite molded article (C) or the melt-molded article (D).

A method for producing a composite molded article (C) comprising a cellulosic nanomaterial (A) and a thermoplastic resin (B), the method comprising:

• (1) melting a composition comprising the cellulosic nanomaterial (A) and the thermoplastic resin (B) to prepare a molten composite composition comprising the cellulosic nanomaterial (A) and the thermoplastic resin (B) (step 1);
• (2) injection-molding the molten composite composition obtained in step 1 to prepare an injection-molded article (E) (step 2);
• and
• (3) warm-forming the injection-molded article (E) obtained in step 2 by at least one method selected from the group consisting of shearing, compression, stretching, and rolling (step 3),
• an area under a stress-strain curve of the composite molded article (C) (AUC1) being at least two times an area under a stress-strain curve of the melt-molded article (D) (AUC2),
• wherein the stress-strain curve is a curve drawn with strain (unit:
• %) on the horizontal axis and stress (unit:
• MPa) on the vertical axis and obtained by subjecting the composite molded article (C) or the melt-molded article (D) to a tensile test, and the area is an area up to the horizontal axis from under a curved portion of the curve that is from the origin (stress:
• 0) of the stress-strain curve to a fracture of the composite molded article (C) or the melt-molded article (D).