PTMEG are known as high-performance polyols capable of formulating polyurethane elastomers in several positive directions. PTMEG polyols afford polyurethane elastomers with enhanced performance with respect to flexibility, dynamic properties, low-temperature performance, resiliency/rebound, hydrolytic stability, low hysteresis, and abrasion resistance.
Polycaprolactone polyols represent a special class of aliphatic polyester polyols used in high-performance polyurethane elastomers. We can produce polycaprolactone polyols with very low acid values (increasing hydrolytic stability and controlled reactivity); perfect end-group functionality (controlled reactivity and improved network formation); narrow molecular weight distributions (low viscosity including in the prepolymer form), and low Tg's (flexibility at low temperatures). Polycaprolactone-based polyurethanes incorporate many of the benefits assigned to PTMEG polyols, such as good hydrolytic stability in wet environments, low-temperature flexibility, excellent toughness and abrasion resistance, excellent flex fatigue life, durability, and good elastic memory. In addition, polycaprolactone-based PURs are tougher materials than PTMEG-based PURs and exhibit higher temperature properties and better solvent resistance.
The polyurethane elastomers formulated with the PCL-PTMEG-PCL triblock polyols exhibited outstanding physical properties at low and elevated temperatures, good hydrophobicity, toughness, low compression set, and good mechanical properties. Notable is the higher tensile strengths of the triblock-based PURs vs. PTMEG-based PURs. Another important attribute of the triblock polyols in polyurethanes was their low tendency to "cold-harden" by crystallization in the "soft blocks."
Applications
The applications for the PTMEG-PCL blends in polyurethanes include cast polyurethanes (CPUR) elastomers and thermoplastic polyurethane (TPU) parts. coatings, adhesive and sealants, polyurethane dispersions, and microcellular foam. End-use markets include seals and gaskets, wheels and rollers, pipeline coatings, compostable packaging adhesives, and TPU protective films.
Conclusions
Miscible blends of PTMEG with polycaprolactone polyols have been identified that fill the gap in polyurethane performance between PTMEG and polycaprolactone polyol systems. Attributes of the blends in polyurethanes include a wider temperature performance range, enhanced flex-bending lifetimes, increased tensile properties, and a lower tendency to "cold harden" through soft segment crystallization. End uses include seals and gaskets, wheels and rollers, parts experiencing water immersion and solvent exposure, coatings, adhesives including compostable packaging adhesives, and protective film.