Abstract: ABA block copolymers having saturated polyester midblocks "B" and unsaturated polyester condensation end blocks A of molecular weight from about 100 to 500 or 600 are described which increase the flexural strain to failure of unsaturated polyester or vinyl ester resins. These ABA block copolymers are generally compatible with unsaturated polyester resins and increase flexural strain by a different mechanism than used by incompatible rubbery polymers. These ABA block copolymers are compatible with the unsaturated polyester compositions and do not phase separate.

Abstract: This invention relates to a thermosetting unsaturated polyester or vinyl ester resin compositions modified with AB or ABA block copolymers. The A blocks are unsaturated polyester while the B blocks are flexible poller having a Tg of 0.degree. C. or lower. The blocks are generally separately prepared having a variety of terminal groups such as hydroxyl, carboxyl, amine, or isocyanate groups, but low molecular weight A blocks can be prepared in situ on the B blocks, The functionality of the blocks can be controlled to get AB or ABA diblocks and polyblocks, These modified unsaturated polyester or vinyl ester resin compositions have higher flexural strain to failure and are generally tougher than standard resins without modification. Control of the reaction conditions and the functionality of the blocks prior to coupling minimizes the formation of A(BA).sub.n where n is an integer above 1.

Abstract: ABA block copolymers having saturated polyester midblocks "B" and unsaturated polyester condensation end blocks A of molecular weight from about 100 to 500 or 600 are described which increase the flexural strain to failure of unsaturated polyester or vinyl ester resins. These ABA block copolymers are generally compatible with unsaturated polyester resins and increase flexural strain by a different mechanism than used by incompatible rubbery polymers. These ABA block copolymers are compatible with the unsaturated polyester compositions and do not phase separate.

Abstract: A block copolymer of generally an AB, ABA, or A(BA).sub.n structure, or mixtures thereof where the A block is an unsaturated polyester, the B block is a flexible polymer having a Tg of 0.degree. C. or lower, and n is 2 to 5. The various block components are generally first separately prepared as polymers with the flexible polymer generally having 1 or 2 functional end groups such as an amine group, a carboxyl group, or a hydroxyl group with the later being preferred. Alternatively, for low molecular weight unsaturated polyester blocks, the block can be made in situ. The preferred reaction route is to react a mono or dihydroxy terminated flexible polymer with a diisocyanate which subsequently can be readily reacted with the polyester. The block copolymers can be utilized as toughening agents.

Abstract: Vinyl-terminated polyesters and vinyl-terminated aliphatic polycarbonates are described which improve the flexibility and elongation at failure of cured samples of unsaturated polyesters or vinyl ester resins both at room temperature and at high temperatures, and without significant loss of surface quality or other mechanical properties. Further, these polymers do not phase separate from uncured polyester resin/styrene solutions, do not significantly increase the initial viscosity of molding compositions in which they have been incorporated, and do not negate the effect of low shrinkage additives during cure.