This invention relates to blends containing two or more polyhydroxyalkanoates (PHAs), and related methods and articles.
1. A blend comprising a first PHA and a second PHA,
wherein:
the first PHA is a copolymer consisting of a comonomer I-A and a comonomer I-B;
the second PHA is a copolymer consisting of a comonomer 2-A and a comonomer 2-B;
the first PHA copolymer and the second PHA copolymer are the same copolymer, in which the ratio of comonomer 1-A:comonomer I-B in the first PHA is different from the ratio of comonomer 2-A:comonomer 2-B in the second PHA;
comonomer I-A and comonomer 2-A are both 3-hydroxybutyrate;
the first PHA and the second PHA are miscible; and
the first PHA has a first glass transition temperature and the second PHA has a second glass transition temperature, wherein the difference between the first and second glass transition temperature is at least about 5° C.
2. The blend of claim 1 , wherein comonomer I-B and comonomer 2-B both are 3-hydroxypropionate, 4-hydroxybutyrate, 3-hydroxyhexanoate, 3-hydroxyoctanoate, 6-hydroxyhexanoate, 3-hydroxydecanoate, 3-hydroxydodecanoate, or 3-hydroxydodecenoate.
3. The blend of claim 1 , wherein comonomer I-B and comonomer 2-B both are 4-hydroxybutyrate.
4. The blend of claim 1 additionally comprising a third PHA.
5. The blend of claim 1 , wherein when the first PHA and the second PHA are blended and the blend is molded, the blend has a deformation angle tolerance of at least 5°.
6. The blend of claim 1 , wherein when the first PHA and the second PHA are blended and the blend is molded, the blend has a thermal deformation resistance temperature of at least 80° C.
7. The blend of claim 1 , wherein the difference between the first and second glass transition temperature is at least 10° C.
8. The blend of claim 1 , wherein the difference between the first and second glass transition temperature is at least 20° C.
9. An article comprising at least 1 percent by weight of a PHA blend comprising a first PHA and a second PHA,
wherein:
the first PHA is a copolymer consisting of a comonomer I-A and a comonomer I-B;
the second PHA is a copolymer consisting of a comonomer 2-A and a comonomer 2-B;
the first PHA copolymer and the second PHA copolymer are the same copolymer, in which the ratio of comonomer 1-A:comonomer I-B in the first PHA is different from the ratio of comonomer 2-A:comonomer 2-B in the second PHA;
comonomer I-A and comonomer 2-A are both 3-hydroxybutyrate;
the first PHA and the second PHA are miscible; and
the first PHA has a first glass transition temperature and the second PHA has a second glass transition temperature, wherein the difference between the first and second glass transition temperature is at least about 5° C.
10. A method of preparing a PHA blend comprising blending a first PHA with a second PHA;
wherein:
the first PHA is a copolymer consisting of a comonomer I-A and a comonomer I-B;
the second PHA is a copolymer consisting of a comonomer 2-A and a comonomer 2-B;
the first PHA copolymer and the second PHA copolymer are the same copolymer, in which the ratio of comonomer 1-A:comonomer I-B in the first PHA is different from the ratio of comonomer 2-A:comonomer 2-B in the second PHA;
comonomer I-A and comonomer 2-A are both 3-hydroxybutyrate;
the first PHA and the second PHA are miscible; and
the first PHA has a first glass transition temperature and the second PHA has a second glass transition temperature, wherein the difference between the first and second glass transition temperature is at least about 5° C.
11. The method of claim 10 , wherein the blending is by solvent blending, emulsion blending or melt blending.
12. The method of claim 10 , wherein the PHA blend is prepared using solvent blending.
13. The method of claim 10 , wherein the solvent blending comprising:
(i) dissolving the first PHA and the second PHA in a solvent or solvent mixture; or dissolving the first PHA and the second PHA separately in a solvent or solvent mixture and combining; to form a blended PHA solution containing at most 50 weight percent of the first PHA and the second PHA;
(ii) applying the PHA solution to a surface to form a PHA blend solution layer on the surface; and
(iii) removing some or all of the solvent to form a PHA blend layer on the surface.