Synthesis and characteristics of poly(ethylene terephthalate) with EO-PO-EO triblock copolymers: A thermal and mechanical property study

A series of multiblock copolymers poly(ethylene terephthalate)-co-poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PET-X%-E-P-E) were synthesized from dimethyl terephthalate (DMT), ethylene glycol (EG) and poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (E-P-E) with a two-step procedure via melt polymerization. The structure, composition, crystallization behavior, and thermal stability of the synthesized copolymers were determined by H-1-NMR, FT-IR, XRD, DSC, and TGA measurements. All samples exhibited good thermal stability at a Td-5% above 300 degrees C. DSC results revealed an increment trend of crystallization ability of copolymers in lower E-P-E content and then decreased when E-P-E concentration gradually raised to 40 wt%. Furthermore, the mechanical properties of copolymers were investigated systematically; the incorporation with E-P-E segments significantly enhanced the toughness and water absorption ability. Impact strength increased from 670.46 to 4448.75 J/m(2), and water absorption values raised from 0.7% to 3.4% of the content of E-P-E increased. The stress-strain curve exhibited that tensile strength reduced from 40.38 to 17.88 MPa, the elongation at break increased from 4.6 to 27.9%. These new tough PET materials have an important application in toughness polyester fiber by the melt-spinning techniques.