Thermoplastic elastomer compounds exhibiting shape memory via thermo-mechanical action
View Patent ↗A thermoplastic elastomer compound has a high strain recovery rate and a high strain fixity rate to provide shape memory, preferably manageable shape memory. The thermoplastic elastomer compound includes a maleated styrenic block copolymer and polycaprolactone to achieve the shape memory. 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 20 to about 40 weight percent, by weight of the thermoplastic elastomer compound, of maleated polystyrene-poly(ethylene-butylene)-polystyrene block copolymer;
(b) from about 5 to about 35 weight percent, by weight of the thermoplastic elastomer compound, of polycaprolactone;
(c) from about 35 to about 55 weight percent, by weight of the thermoplastic elastomer compound, of plasticizer; and
(d) from about 2 to about 5 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 compound further comprises 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; waxes; and combinations of these additives.
3. The thermoplastic elastomer compound of claim 1 , wherein the thermoplastic elastomer compound has a strain recovery rate of at least 65%.
4. The thermoplastic elastomer compound of claim 1 , wherein the thermoplastic elastomer compound has a strain fixity rate of at least 65%.
5. The thermoplastic elastomer compound of claim 1 , wherein the thermoplastic elastomer compound comprises:
(a) from about 20 to about 30 weight percent, by weight of the thermoplastic elastomer compound, of the maleated polystyrene-poly(ethylene-butylene)-polystyrene block copolymer;
(b) from about 25 to about 30 weight percent, by weight of the thermoplastic elastomer compound, of the polycaprolactone;
(c) from about 40 to about 45 weight percent, by weight of the thermoplastic elastomer compound, of the plasticizer; and
(d) from about 3 to about 4 weight percent, by weight of the thermoplastic elastomer compound, of the polyolefin;
wherein the thermoplastic elastomer compound has a strain recovery rate of at least 90%; and
wherein the thermoplastic elastomer compound has a strain fixity rate of at least 90%.
6. The thermoplastic elastomer compound of claim 5 , wherein the maleated polystyrene-poly(ethylene-butylene)-polystyrene block copolymer has a weight average molecular weight of about 250,000 and a styrene content of about 32 weight percent.
7. The thermoplastic elastomer compound of claim 5 , wherein the polycaprolactone has a weight average molecular weight ranging from about 10,000 to about 80,000.
8. The thermoplastic elastomer compound of claim 5 , wherein the plasticizer is mineral oil.
9. The thermoplastic elastomer compound of claim 5 , wherein the polyolefin is polypropylene.
10. The thermoplastic elastomer compound of claim 5 , further comprising one or more additives selected from the group consisting of phenolic antioxidants, phosphite stabilizers, and waxes.
11. The thermoplastic elastomer compound of claim 1 , wherein the thermoplastic elastomer compound is in the form of extruded pellets.
12. An article molded from the thermoplastic elastomer compound of claim 1 .
13. The article of claim 12 , wherein the article is an injection molded article.
14. The article of claim 12 , wherein the article has a Shore A hardness of less than about 60.
15. A method of using the article of claim 12 , the method comprising the steps of:
(a) performing a thermo-mechanical event on the article; and
(b) optionally, performing a second thermo-mechanical event on the article;
wherein the article expands or contracts in at least one dimension of the article with each of step (a) and optional step (b) either sequentially or concurrently.