Engineered crosslinked thermoplastic particles for interlaminar toughening

1. An engineered crosslinked thermoplastic particle comprising a crosslinked network formed by reacting (a) a thermoplastic polymer having backbone or end functional groups with (b) a polyfunctional crosslinking agent that is reactive with the functional groups of the thermoplastic polymer and has a reactivity of two or greater,

wherein

said thermoplastic polymer is selected from: poly ether sulfone (PES), poly ether ether sulfone (PEES), and a copolymer thereof,

said crosslinking agent is selected from methylated melamine resins, alkylated glycoluril resins, and multi-functional epoxies, and

the engineered crosslinked thermoplastic particle is capable of swelling in an uncured thermosetting resin.

2. The engineered crosslinked thermoplastic particle according to claim 1 ,

wherein the thermoplastic polymer is a copolymer of poly ether sulfone (PES) and poly ether ether sulfone (PEES).

3. The engineered crosslinked thermoplastic particle according to claim 1 , wherein the thermoplastic polymer is amine-ended PES/PEES copolymer.

4. The engineered crosslinked thermoplastic particle according to claim 1 ,

wherein the crosslinked thermoplastic particle contains two or more layers.

5. The engineered crosslinked thermoplastic particle according to claim 1 ,

wherein the molecular weight of the thermoplastic polymer is about 3,000-50,000 g/mol.

6. A treated preform comprising

a plurality of engineered crosslinked thermoplastic particles of claim 1 ; and

a fiber preform comprising fibers without matrix resin;

wherein the engineered crosslinked thermoplastic particles are dispersed in the fiber preform.

7. A resin system comprising

a plurality of engineered crosslinked thermoplastic particles; and

an uncured thermosetting resin;

wherein

said engineered crosslinked thermoplastic particles are formed by reacting (a) a thermoplastic polymer having backbone or end functional groups with (b) a polyfunctional crosslinking agent that is reactive with the functional groups of the thermoplastic polymer and has a reactivity of two or greater,

said thermoplastic polymer is selected from: poly ether sulfone (PES), poly ether ether sulfone (PEES), and a copolymer thereof,

said crosslinking agent is selected from methylated melamine resins, alkylated glycoluril resins, and multi-functional epoxies, and

the engineered crosslinked thermoplastic particles are capable of swelling in the thermosetting resin by forming a gradient interface with the thermosetting resin when the resin system exceeds a specific onset temperature.

8. The resin system as in claim 7

wherein the thermosetting resin is capable of diffusing into the engineered crosslinked thermoplastic particle.

9. The resin system as in claim 7

wherein the engineered crosslinked thermoplastic particles comprise crosslinked co-polymer of poly ether sulfone (PES) and poly ether ether sulfone (PEES).

10. A prepreg comprising the resin system of claim 7 .

11. A composite comprising the resin system of claim 7 .

12. The resin system as in claim 7 , wherein the functional groups on the thermoplastic polymer are amine or hydroxyl groups.