Lightweight particles and compositions containing them
Particles that have an exterior surface coated with a thin polymer coating, such as a coating that includes a sulfur-containing polymer can be used as lightweight fillers in compositions, such as fuel resistant sealant and coating compositions. The compositions can be used to seal apertures on aerospace vehicles.
1. A composition comprising:
a) a polymeric film-forming binder comprising reactive functional groups; and
b) particles dispersed in the binder, wherein,
the particles comprise expanded thermoplastic microcapsules comprising an exterior surface having a coating thereon wherein the coating comprises an aminoplast resin;
the aminoplast resin-coated expanded thermoplastic microcapsules are characterized by a specific gravity of no more than 0.1;
the composition comprises less than 5 wt % of the aminoplast resin-coated expanded thermoplastic microcapsules, wherein wt % is based on the total weight of the composition; and
the composition is formulated as an aerospace sealant having a specific gravity of less than 1.0.
2. The composition of claim 1 , wherein the polymeric film-forming binder comprises a sulfur-containing polymer.
3. The composition of claim 2 , wherein the sulfur-containing polymer comprises a thiol-functional polythioether.
4. The composition of claim 1 , wherein the aminoplast resin comprises melamine.
5. The composition of claim 1 , further comprising a curing agent.
6. The composition of claim 5 , wherein the curing agent comprises a polyepoxide.
7. A cured sealant, comprising the composition of claim 1 .
8. The cured sealant of claim 7 , having a tensile strength of 1900 mega-Pascals or greater measured according to AS 5127/1a7.7.
9. The cured sealant of claim 7 , wherein the cured sealant exhibits:
a percent volume swell of not greater than 40% after immersion for one week at 140° F. (60° C.) and ambient pressure in Jet Reference Fluid Type 1;
an elongation of at least 80% measured as described in AMS 3269a; and
a tensile strength of at least 2000 mega-Pascals when measured according to AS 5127/1a7.7.
10. An aerospace vehicle, having an aperture at least partially sealed with a sealant deposited from the composition of claim 1 .
11. An aerospace vehicle, having an aperture at least partially sealed with a sealant deposited from the composition of claim 6 .
12. A composition comprising:
c) a sulfur-containing polymer binder;
d) a curing agent comprising a polyepoxide; and
e) particles dispersed in the binder, wherein,
the particles comprise expanded thermoplastic microcapsules comprising an exterior surface having a coating thereon wherein the coating comprises an aminoplast resin;
the aminoplast resin-coated expanded thermoplastic microcapsules are characterized by a specific gravity of no more than 0.1, and a particle size from 5 μm to 300 μm;
the composition comprises less than 5 wt % of the aminoplast resin-coated expanded thermoplastic microcapsules, wherein wt % is based on the total weight of the composition; and
the composition is formulated as an aerospace sealant having a specific gravity of less than 1.0.
13. The composition of claim 12 , wherein the sulfur-containing polymer binder comprises a thiol-functional polythioether.
14. The composition of claim 13 , further comprising a reinforcing filler and/or an adhesion promoter.
15. The composition of claim 14 , wherein the reinforcing filler comprises calcium carbonate.
16. The composition of claim 14 , wherein the adhesion promoter comprises a silane.
17. A composition comprising:
a) a thiol-functional polythioether binder;
b) a curing agent comprising a polyepoxide;
c) a reinforcing filler;
d) an adhesion promoter; and particles dispersed in the composition, wherein the particles dispersed in the binder, wherein,
the particles comprise expanded thermoplastic microcapsules comprising an exterior surface having a coating thereon wherein the coating comprises an aminoplast resin;
the aminoplast resin-coated expanded thermoplastic microcapsules are characterized by a specific gravity of no more than 0.1, and a particle size from 5 μm to 300 μm;
the composition comprises less than 5 wt % of the aminoplast resin-coated expanded thermoplastic microcapsules, wherein wt % is based on the total weight of the composition; and
the composition is formulated as an aerospace sealant having a specific gravity of less than 1.0.
18. An aerospace vehicle having an aperture at least partially sealed with a sealant deposited from the composition of claim 17 .
19. The composition of claim 1 , wherein the composition comprises from 1 wt % to less than 5 wt % of the aminoplast resin-coated expanded thermoplastic microcapsules, wherein wt % is based on the total weight of the composition.
20. The cured sealant of claim 7 , which when cured exhibits:
a percent volume swell of not greater than 40% after immersion for one week at 140° F. (60° C.) and ambient pressure in Jet Reference Fluid Type 1;
an elongation of at least 80% measured as described in AMS 3269a; and
a tensile strength of at least 2000 mega-Pascals when measured according to AS 5127/1a7.7.
21. The composition of claim 1 , wherein the specific gravity of the composition is less than 0.9.
22. The composition of claim 1 , wherein the specific gravity of the composition is less than 0.8.
23. The composition of claim 1 , wherein the composition comprises a reinforcing filler.