Effect of the aramid pulp on the physicochemical, viscoelastic properties and rheokinetics of polyurethanes

Abstract

This publication highlights the effect of aramid pulp (1 wt.%) on equilibrium swelling, enthalpy reaction, solid viscoelastic properties, and rheokinetics of castor oil (CO) and polyether (PE) polyol blend (50/50 CO/PE) with polymeric isocyanate (pMDI). The CO-pMDI system showed a lower solubility parameter difference (Δδ i ) than the PE-pMDI and CO/PE-pMDI. Crosslink density values ν e are higher for CO-pMDI, and when added to aramid pulp, there is a slight increase due to the possible restriction of swollen volume. Regarding the pseudo-solid behavior, AP restricts the macromolecular movement and confers reinforcing characteristics to PU systems. The Prout-Tompkins autocatalytic model satisfactorily described the reactions, resulting in activation energy values E a within 45−54 kJ/mol. However, for the CO/PE blend, the difference between the reactivity of the polyols and the solubility parameter with pMDI results in a two-step reaction kinetics. Aramid pulp practically does not change the reaction mechanism, only the viscosity of the medium. Furthermore, the thermodynamic parameters (ΔS* and ΔH*) indicated that the PU with AP resulted in more ordered complexes. The adequate description of the polymerization reaction and the effect of the aramid pulp allowed obtaining PU formulations with tunable characteristics for strict composite processing composites.

Wood-Poly(furfuryl Alcohol) Prepreg: A Novel, Ecofriendly Laminate Composite

“…This decrease is related to the gelation process, in which the growing chains of oligomers, obtained via Diels–Alder cycloadditions, achieve infinite molar mass behavior through connections between furan rings. When polymers gel, a sudden and dramatic increase in viscosity is observed until the molecular weight becomes infinite (degree of polymerization, DP→∞) [ 24 ]. This promotes low molecular mobility, which induces a decrease in the overall reaction rate that becomes controlled by the diffusion of small unbranched oligomer chains.…”

“…The best kinetic model was chosen with the least squares and F-test methods. The kinetics model equations employed by the software were based on Cruz et al [ 24 ]. The tests and calculations were carried out following the indications of the ICTAC Kinetics Committee based on Vyazovkin et al [ 23 ].…”

Rheology, curing and time‐dependent behavior of epoxy/carbon nanoparticles systems

“…In particular, when rheological percolation is reached, viscosity of the resin changes to a certain point that the curing is affected. Thus, in highly demanding applications or in composite manufacturing processes where resin viscosity is crucial, e.g., RTM and vacuum infusion, it is necessary to understand the influence that these particles have on the curing process since the final properties of the composite significantly depends on the initial conditions of the resin 5–7 …”

“…Thus, in highly demanding applications or in composite manufacturing processes where resin viscosity is crucial, e.g., RTM and vacuum infusion, it is necessary to understand the influence that these particles have on the curing process since the final properties of the composite significantly depends on the initial conditions of the resin. [5][6][7] A poor chemical interaction is a significant obstacle to the effective dispersion of carbonaceous nanoparticles such as GN and CNT in liquids and resins. This is related to the van der Waals forces, that promote their agglomeration, and the polar groups in their structure, that enable hydrogen bonds and yield stable suspensions.…”

Polyurethane Adhesives for Wood Based on a Simple Mixture of Castor Oil and Crude Glycerin

“…Generally, polyether polyols derived from petroleum are employed. In order to reduce the reliance on fossil-fuel-based products, the use of polyethylene polyols derived from vegetable oils has been investigated in recent years [3,4]. These studies are motivated by the economic, environmental, and social advantages associated with the use of commercially disregarded oils to produce high-value products [5].…”