Experimental and modeling studies of IPDI‐based polyurea elastomers – The role of hard segment fraction

Abstract

Segmented polyureas (PUa) are industrially important class of polymers widely used in coatings, sealant, and adhesive applications. Here, we report synthesis, characterization, and modeling of Isophorone Diisocyanate-Diethyl-Toluene-Diamine-Polyether amine (IPDI-DETDA-PO PUa) with varied hard segment contents of 20, 30, and 40 weight percent. For each of the three materials, we study its structure and phase behavior using FTIR, DSC, and TEM, and clearly show the presence of microphase separation between the hard and soft nanodomains. We then measure the linear viscoelastic response of the PUa-s using DMA (frequency sweeps at multiple temperatures). The DMA data are shown to obey the time-temperature superposition. Finally, we develop a new micromechanical model describing the DMA results; the model describes a phaseseparated PUa as two "Fractional-order Maxwell gels" branches, connected in parallel, with the first FMG branch representing the "percolated hard phase" and the second one modeling the "filled soft phase". In agreement with the earlier thermodynamic theories, the volume-fraction of the percolated hard phase is related to the hard segment weight-fraction (HSWF), defined as the combined mass of IPDI and DETDA normalized to the total mass of the polymer. The data and model are found to be in a good qualitative and quantitative agreement.adhesive, dynamic mechanical analysis, fractional calculus, hard domains, polyurea, time temperature superposition | INTRODUCTIONPolyurethanes (PU), polyureas (PUa), and poly (urethaneureas) (PUU) represent a fascinating family of polymers. [1][2][3][4] Their applications include coatings, 5 adhesives and sealants, 6,7 elastomers, 8 as well as rigid foams for thermal insulation 9 and flexible foams for furnishings

Polyurea–Graphene Nanocomposites—The Influence of Hard-Segment Content and Nanoparticle Loading on Mechanical Properties

“…Given the relatively low mass fraction of the added nanoparticles (only up to 1.5%), we assumed that they were ultimately dispersed within the two phases and not forming a new phase by themselves. Thus, no additional parallel branch was introduced, consistent with our prior work [19]. Consequently, each polymer was characterized by six model parameters, encompassing two characteristic moduli (often called plateau modulus) (𝐸 , and 𝐸 , ), two relaxation characteristic times (𝜏 , and 𝜏 , ), and two power-law exponents (𝛼 and 𝛼 ).…”

“…The synthesis of the PUa-Neat materials is described in detail in our earlier paper [19]. We used isophorone diisocyanate (IPDI)-Vestanat from Evonik Corporation, Pisca-taway, NJ, USA; Jeffamine T5000 and D2000 polyetheramines from the Huntsman Corporation, The Woodlands, TX, USA; and the diethyltoluene diamine (DETDA) (Lonzacure) chain extender from Lonza, Morristown, NJ, USA.…”

“…The equation for the shift factor as a function of temperature is discussed next. In our previous paper [19], we applied three different functional forms to describe the shift factor-the Arrhenius, the Williams-Landel-Ferry (WLF) [46], and the TS2 [22] functions. The TS2 model describes the glass transition as the transition between the hightemperature and low-temperature Arrhenius regions, To integrate the DMA data across various temperatures, the time-temperature superposition (TTS) principle was employed and the shift factor, denoted as a T , was assumed to hold the same for both the soft and hard phases.…”

“…require a good understanding of material performance in a wide range of temperatures and frequencies/strain rates. Thus, recently, Tzelepis et al [19] used both temperature-sweep and frequency-sweep DMA to study the properties of PUa elastomers with different hard-segment weight fractions (HSWF). It was shown that the studied PUa materials obeyed the time-temperature superposition (TTS) principle.…”

Recent Developments in Polyurea Research for Enhanced Impact Penetration Resistance and Blast Mitigation

“…In a study by D.A. Tzelepis et al [33], several polyureas were synthesized with the same molecular weight of the soft segments but varying weight fractions of the hard segments. The structure of the polyurethanes was characterized using differential scanning calorimetry (DSC) and a transmission electron microscope (TEM) which revealed that the three polymers had almost the same Tg.…”