Thermoplastic elastomer compounds exhibiting shape memory via thermo-mechanical action
View Patent ↗A thermoplastic elastomer compound is disclosed having a high strain recovery rate and a high strain fixity rate to provide shape memory, preferably manageable shape memory. One type of thermoplastic elastomer compound is comprises a maleated styrenic block copolymer and polycaprolactone to achieve the shape memory. A second type of thermoplastic elastomer compound comprises styrene-ethylene/butylene-styrene and a paraffin wax having less than about 0.5% oil content. Shape modes of articles made from the thermoplastic elastomer compound can be altered by at least one thermo-mechanical event to cause deformation of the compound from a first shape to a second shape with retention of the compound in the second shape for any reasonable time interval.
1. A thermoplastic elastomer compound comprising:
(a) from about 43 to about 48 weight percent, by weight of the thermoplastic elastomer compound, of at least one thermoplastic elastomer selected from styrene-ethylene/butylene-styrene block copolymer;
(b) from about 5 to about 40 weight percent, by weight of the thermoplastic elastomer compound, of at least one other material selected from paraffin wax having less than about 0.5 percent oil content according to ASTM D721 and a melting temperature ranging from 147 to 151° F. (63.9 to 66.1° C.) according to ASTM D87;
(c) from about 10 to about 40 weight percent, by weight of the thermoplastic elastomer compound, of mineral oil; and
(d) from about 4 to about 10 weight percent, by weight of the thermoplastic elastomer compound, of polyolefin;
wherein the thermoplastic elastomer compound has shape memory.
2. The thermoplastic elastomer compound of claim 1 , wherein the thermoplastic elastomer has a strain fixity rate of about 100%.
3. The thermoplastic elastomer compound of claim 1 , wherein the paraffin wax has:
a Saybolt color of at least about +25 according to ASTM D156;
a Needle Penetration at 77° F. of about 13 according to ASTM D1321;
a viscosity at 212° F. of about 5.5 centiStokes according to ASTM D445; and
a Flash Point, COC of greater than 465° F. according to ASTM D92.
4. The thermoplastic elastomer compound claim 1 further comprising one or more additives selected from the group consisting of adhesion promoters; biocides; anti-fogging agents; anti-oxidants; anti-static agents; blowing agents; dispersants; extenders; fillers; flame retardants; foaming agents; smoke suppressants; impact modifiers; initiators; lubricants; micas; pigments; colorants; dyes; oils; processing aids; release agents; silanes; titanates; zirconates; slip agents; anti-blocking agents; stabilizers; stearates; ultraviolet light absorbers; viscosity regulators; and combinations of these additives.
5. The thermoplastic elastomer compound of claim 1 , wherein the thermoplastic elastomer compound is in the form of extruded pellets.
6. An article molded from the thermoplastic elastomer compound of claim 1 .
7. The article of claim 6 , wherein the article is an injection molded article.
8. The article of claim 6 , wherein the article has a Shore A hardness of less than about 60.
9. The article of claim 6 , wherein the article has a strain fixity rate of about 100%.