Modification of Unsaturated Polyesters by Poly(ethylene glycol) End Groups UWE SCHULZE, 1 MIK AEL SKRIFVARS, 2 NORBERT REICHELT, 1, * HANS-WERNER SCHMIDT 1 1 Makromolekulare Chemie I and Bayreuther Institut fu ¨ r Makromoleku ¨ lforschung ( BIMF ) , Universita ¨t Bayreuth, D-95440 Bayreuth, Germany 2 Neste Chemicals Research and Technology, P.O. Box 310, FIN-06101 Porvoo, Finland Received 27 August 1996; accepted 7 September 1996 ABSTRACT: This article reports on the modification of unsaturated polyesters by poly (ethylene glycol) end groups in order to influence the solution behavior in styrene and to modify mechanical properties of the cured resin. The synthesis was done by the reaction of a carboxyl-terminated unsaturated polyester with various poly ( ethylene glycol ) mono-methyl ethers of molecular weights from 350 to 2000 g /mol. The character- ization and curing properties of the synthesized block copolymers are presented. The glass transition temperatures decrease with increasing length of the poly ( ethylene glycol) end groups. The introduction of long poly(ethylene glycol) end groups (2000 g/ mol ) leads to a phase separated and partly crystalline block copolymer with a melting point of 48°C. The block copolymers can be easily diluted in styrene to create the curable resins. The mixtures containing the block copolymers with the short poly ( ethylene glycol) end groups (350 and 550 g/mol) could be cured in a reasonably short time. Compared to commercial unsaturated polyesters the mechanical testing revealed that the tensile strength is decreasing while the elongation is increasing.  1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 527–537, 1997 Key words: unsaturated polyester ; poly ( ethylene glycol ) ; block copolymer ; tough- ness; crosslinking INTRODUCTION In the development of high-performance poly- mer composites much attention has been paid to the improvement of fracture toughness and im- Unsaturated polyesters are one of the most im- pact resistance. This can be done by chemical or portant matrix resins for composite applications. physical methods. One possibility is the addition They possess a wide range of properties and are of dispersed elastomer particles such as butadi- used in marine, automobile, construction, sport, ene-acrylonitrile rubbers into the unsaturated and furniture applications. In these applications polyester matrix. 2 These low profile additives reinforcing glass fibers are embedded in the un- form a heterogeneous blend with the unsaturated saturated polyester matrix. Also, other compo- polyester. Chemical modification can be done ei- nents such as fillers, additives, and pigments may ther by incorporation of long-chain diols ( e.g., di- be present. 1 ethylene glycol, dipropylene glycol, triethylene glycol ) or by incorporation of long-chain saturated Correspondence to : Hans-Werner Schmidt. acids (e.g., adipic acid) into the polyester chain * Present address: OMV Werkstoff, PCD Polymere GmbH, during the polycondensation reaction. 3 A disad- St. Peter Str. 25, A-4021 Linz, Austria. vantage of this method is the fact that a large Contract grant sponsor: Neste Group, Finland.  1997 John Wiley & Sons, Inc. CCC 0021-8995/97 / 030527-11 amount of these compounds must be used in order 527 3953 / 8E84$$3953 02-18-97 18:14:52 polaa W: Poly Applied