Particulate build materials for three-dimensional printing

A method of making a three-dimensional printed object, the method comprising:

• iteratively applying a particulate build material as individual build material layers, wherein the particulate build material includes from about 80 wt % to 100 wt % of polymer particles, the polymer particles including a polyolefin polymer backbone including polypropylene polymeric units, the polymer particles further including a crosslinkable component appended to or compounded with the polyolefin polymer backbone, wherein the crosslinkable component is an organic acid anhydride-containing crosslinkable component, a sulfur-containing crosslinkable component, an organosilicon-containing crosslinkable component, or a combination thereof;
• based on a three-dimensional object model, selectively jetting a fusing agent onto the individual build material layers, wherein the fusing agent comprises water and a radiation absorber that absorbs electromagnetic energy and converts the electromagnetic energy to heat;
• based on the three-dimensional object model, selectively jetting a multifunctional compound reactive with the crosslinkable component onto the individual build material layers to cause the polymer particles to become crosslinked, wherein the multifunctional compound is selected from the group consisting of a multifunctional amine and a multifunctional acrylate, and wherein the multifunctional compound is:
• i) present in the fusing agent, ii) separately jetted onto the individual build material layers as part of a separate crosslinking agent, or iii) both present in the fusing agent and separately jetted onto the individual build material layers as part of the separate crosslinking agent;
• and
• exposing the particulate build material to electromagnetic energy to selectively fuse the polymer particles in contact with the radiation absorber at the individual build material layers,
• wherein the three-dimensional printed object formed is both physically fused by exposing the particulate build material to the electromagnetic energy and chemically crosslinked at the crosslinkable component appended to or compounded with the polyolefin polymer backbone.