Self-Healing Polyurethane Elastomers

Patent Title: POLYURETHANE

 Number/Link: W02016185172

Applicant/Assignee: Croda

Publication date: 24-11-2016

Gist”: PU from polyols which contain both a fatty dimer residue and an H-bonding group, show self-healing properties

Why it is interesting: Polyurethane elastomers with ‘intrinsic’ self-healing properties (i.e. without the need for external chemicals like encapsulated monomers) can be prepared by reacting isocyanates with polyols that have at least one urethane, amide or carbonate group and at least one fatty dimer residue. It is theorized that the fatty dimer allows the soft-phase of the polymer to flow and H-bonds to form, thus restoring most of the properties after damage.  In the examples polyols with internal urethane groups were prepared by reacting C36 dimer diol with HDI, which were then reacted with MDI and BDO. Samples of the resulting elastomers were cut in half, and manually stuck together again under mild heating (60°C), thus recovering most of their tensile and elongation properties.

A dimer diol

A dimer diol

Thermoplastic Polyurea Elastomers

Title: MELT PROCESSIBLE POLYUREAS AND POLYUREA-URETHANES, METHOD FOR THE PRODUCTION THEREOF AND PRODUCTS MADE THEREFROM

 Number/Link: US2013/0331538

Applicant/Assignee: University of Akron

Publication date: 12-12-2013 (priority PCT)

Gist”: Polyurea is made melt-processable by incorporating hydrogen-bond accepting chain extenders (HACE)

Why it is interesting: It is well known that polyurea elastomers with a decent hardblock content (of e.g. 30-35%) are not melt-processable. Because of very strong (bi-dentate) H-bond formation in the hard domains the material will degrade sooner than flow when heated. In this invention it is proposed to incorporate a relatively small amount of HACE to disrupt the hard domain structure and reduce flow temperature.  In an example a few parts of OH-ended pentamethylenepolycarbonate with a MW of 500 to 800 was used next to the conventional 1,6-hexamethylene chain extender to drop the flow temperature by 50°C while not affecting the tensile strength. (I suppose a NH2-ended polycarbonate could have been used as well to make an all-polyurea material).

Bi-dentate H-bonds between polurea molecules (left) disrupted by a polycarbonate group (right)

Bi-dentate H-bonds between polurea molecules (left) dusrupted by a carbonate group (right)

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