Thermoplastic apparent interpenetrating polymer networks of polyurethane and styrene/acrylic acid copolymer obtained by melt mixing. Structure‐property relationships

Abstract

Thermoplastic apparent interpenetrating polymer networks (thermoplastic‐AIPNs) were prepared at several compositions by melting and pressing of crystallizable polyurethane (CPU), based on butylene adipate glycol (BAG), and styrene/acrylic acid random copolymer (S/AA). Structure‐property relationships in the thermoplastic‐AIPNs were investigated by means of wide‐angle and small‐angle X‐ray scattering (WAXS, SAXS), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), thermally stimulated depolarization currents (TSDC) techniques, dielectric relaxation spectroscopy (DRS) and several physico‐mechanical characterization techniques. The results obtained by the various techniques were critically compared to each other. They suggest that the two components show weak affinity to each other and that the thermoplastic‐AIPNs can be classified into two groups with high and low contents of CPU, showing essentially the behavior of CPU and S/AA, respectively. However, deviations from additivity and significant changes for several properties on addition of small amounts of either of the components suggest partial miscibility. Most of the results are explained by physical interactions of COOH‐groups of AA in S/AA with the ester groups of the flexible CPU blocks, which promote microphase separation in both the CPU and the S/AA components.

Thermoplastic apparent interpenetrating polymer networks of polyurethane and styrene/acrylic acid block copolymer: Structure–property relationships

“…In previous work, we investigated the structure–property relationships in t‐IPNs prepared from a crystallizable polyurethane (CPU) and a random copolymer of styrene/acrylic acid (S/AA) 10–14. These mixtures were called thermoplastic apparent IPNs, t‐AIPNs, because S/AA was used in the acid form and not in the salt form.…”

“…A better understanding of these relationships is essential for optimizing composition and processing of materials to meet specific end‐use requirements. Both t‐AIPNs prepared by melt mixing of the components13, 14 and by casting from a common solvent10, 12 were investigated. The results by a variety of experimental techniques showed that the t‐AIPNs were microheterogeneous systems with contributions to microheterogeneity from both the heterogeneity of the individual polymers and the thermodynamic incompatibility of the components.…”

Phase-Separated Interpenetrating Polymer Networks

“…Some interactions between the components and their effect on the microphase structure of each other in thermoplastic AIPNs are realized, and wide-angle X-ray scattering (WAXS) and SAXS have been reported [212]. The mechanical properties of the thermoplastic AIPNs, density ρ, flow limit σ f , elasticity modulus E, and tensile strength σ , change nonadditively with composition, with extreme values at small contents (until 5-10%) of CPU or S-co-AA in compositions.…”

“…Thermoplastic AIPNs of several compositions prepared by mechanical blending in a roll mill of crystallizable polyurethane (CPU) and styreneacrylic acid random copolymer (S-co-AA) have been investigated using different techniques by Vatalis et al [212,213]. The CPU was based on TDI (mixture of 2,4-and 2,6-isomers, molar ratio 65 : 35) and oligomeric buty-lene adipate glycol (BAG, MM 2000); the molar proportion of reagents was 1.01 : 1.00.…”

“…Some secondary relaxation of components of thermoplastic AIPNs have been investigated by using thermally stimulated depolarization current (TSDC) techniques and thermally stimulated conductivity (TSC) measurements [212,213]. It was found that on addition of S-co-AA to CPU, the secondary γ and β CPU peaks (at ∼ -140 and ∼ -100 • C, respectively) shift slightly to lower temperatures, i.e., the corresponding relaxations become faster, the shifts being more pronounced at low S-co-AA contents.…”