Effect of ionic content, solid content, degree of neutralization, and chain extension on aqueous polyurethane dispersions prepared by prepolymer method

Abstract

There are many variables in the preparation of aqueous polyurethane (PU) dispersions. Carboxylic acid content, solid content, degree of pre/postneutralization of the carboxylic acids, and chain extension all impact dispersion particle size, viscosity, pH, molecular weights, and glass transition temperature. This study evaluated the impact of these variables on a given PU dispersion formulation prepared from isophorone diisocyanate, an aliphatic polyester polyol, dimethylol propionic acid, and hexamethylene diamine with triethyl amine as the neutralizing base and N-methyl pyrrolidone as the cosolvent. Changes in carboxylic acid content, degree of preneutralization, and chain extension were found to have the expected impacts on dispersions properties. Increased ionic content in the dispersion step led to lower particle size and higher viscosity, increased chain extension with its concurrent increase in molecular improved subsequent film properties. Surprising results were obtained by varying the amount of postneutralization and from increased solids content at the time of dispersion. Unexpectedly, both of these variations led to much higher dispersion viscosities and particle size in solution. To have these changes take place, it is theorized that there is a major change in solution morphology caused by these modifications.

Self-Organization of Polyurethane Pre-Polymers as Studied by Self-Consistent Field Theory

“…As a consequence of the relatively high Figure 2. SF-SCF results for self-assembly of the pre-polymer sequence depicted in Figure 1 into a spherical micelle in an aqueous salt solution with an ionic strength of 10 mM (monovalent salt) at pH 8: (a) grand potential V of micelle formation as a function of the aggregation number g, (b) radial volume fraction profiles w of the pre-polymer building block sequence IPDI-polyol-IPDI-(DMPA-IPDI) 2 and water as a function of r for an equilibrium micelle (V ¼ 0).…”

“…Within the cell model, the system size is specified by the number of lattice layers M in the system. As reflecting boundaries are implemented, we effectively model a system wherein the inter-micelle distance r m is twice the value of M. We computed the chemical potential lnðw b Þ of the IPDIpolyol-IPDI-(DMPA-IPDI) 2 building block sequence in the micelle as a function of the system size M for various values of pH at a fixed ionic strength of 10 mM. As shown in Figure 4, the chemical potential of the polymer remains stable for M > 35 at pH 6, pH 7, and pH 8 indicating that at these distances the micelles do not feel each other.…”

“…In aqueous systems, polyurethanes are not molecularly dissolved but they self-and co-assemble into colloidal particles with a typical size between 10 and 200 nm. [2] The nature, size, and stability of the resulting polyurethane particle dispersions will affect film formation and final coating properties. Understanding the behavior of the polymer dispersions will open up routes to modify and further improve the quality of WPU products.…”

Effects of TDI and FA‐703 on physico‐mechanical properties of polyurethane dispersion

“…Since ions are introduced into either hard or soft segments, and imparting many properties to the PU matrix, attention is being drawn to these PUDs ionomers. [15][16][17] The existence of the hard segment domains also gives PUDs ionomers excellent mechanical strength. The dispersion of polymers in water and properties of cast films are affected by the type and content of ionic centers and polyols as soft segment.…”

Preparation and characterization of aqueous polyurethane dispersions with well‐defined soft segments

“…1 These properties could be improved with different mixing compositions of soft segments. 3 Polydimethylsiloxane (PDMS) has unique properties, such as a low surface energy, good thermal stability, and excellent flexibility mainly because of their structure, which is composed of inorganic SiAO bonds and organic grafted CH 3 groups.…”