Evolution of Reaction‐Induced Phase Segregations in Bi‐Soft Segment Urethane Oligomers

Abstract

Oligomeric bi‐soft segment isocyanate‐terminated polyurethanes (ITPUs) are semi‐finished goods crucial for the fabrication of various polyurethane (PU) products such as foams, thermoplastics, adhesives, dispersions, and elastomers. Incompatibilities and thus phase segregation phenomena play an essential role in tailoring the properties of the final products. In this work, the evolution of reaction‐induced phase segregation (RIPS) in ITPUs is explored in terms of composition and morphology of the phase segregated products as well as competing second order kinetics of the reaction. The results suggest that mechanism and extent of the phase segregation are thermodynamically controlled following the ternary phase diagram of the reactants. A comprehensive description of the phase behavior during the reaction is provided demonstrating excellent control over the morphology of ITPUs by means of appropriate adjustment of the initial reactant composition. These results are fundamental for tailored morphology design as it is employed for instance in membrane synthesis.

Sophorolipid-Based Oligomers as Polyol Components for Polyurethane Systems

“…The reaction between OH and NCO groups is generally accepted to follow second order kinetics [ 36 , 82 ] and can be studied by investigation of the corresponding second order plot and determination of k app according to Equation (2) [ 38 ]. with concentration of NCO groups at time t and concentration of NCO groups at the beginning of the reaction.…”

“…This means that a successive conversion with (di)isocyanates is generally possible because the secondary OH groups are readily available for the reaction with NCO groups, whereas the primary OH groups become available after, e.g., saponification [ 33 ]. The complete deacetylated ASL should also allow a certain selectivity since primary OH groups react with NCO groups about three times faster than secondary OH groups [ 34 , 35 , 36 , 37 , 38 ]. Utilizing appropriate reaction conditions, primary OH groups can purposely be consumed first in order to produce linear and thus thermoplastic PU [ 38 , 39 , 40 , 41 , 42 , 43 ].…”

“…The complete deacetylated ASL should also allow a certain selectivity since primary OH groups react with NCO groups about three times faster than secondary OH groups [ 34 , 35 , 36 , 37 , 38 ]. Utilizing appropriate reaction conditions, primary OH groups can purposely be consumed first in order to produce linear and thus thermoplastic PU [ 38 , 39 , 40 , 41 , 42 , 43 ]. In contrast, complete conversion of all OH groups leads to significant crosslinking and therefore to a thermosetting material.…”

Preparation, Structure and Properties of Urethane-Containing Elastomers Based on Epoxy Terminal Oligomers

“…Segmented polyurethanes (SPU) and polyurethane ureas (SPUM) are block copolymers with macromolecular chains consist of alternating flexible soft and hard segments, SS and HS respectively [ 6 , 7 ]. These polymers are usually synthesized via a two-step route.…”

A polyurethane binder with excellent mechanical properties based on copolymerization and dynamic bond crosslinking

“…Its mechanical properties are the key factors to determine the structural integrity of the solid motors, and to a large extent, it relies on the mechanical properties of the matrix binder [9,10]. Because of its high strength, good fluidity, and good adhesion, hydroxyl-terminated polybutadiene (HTPB) is often used in binders [11][12][13]. However, the binder will still have cracks and damage, which will lead to structural safety issues of composite solid propellants, resulting in serious security risks.…”