Spray processable polyurea formulations: Effect of chain extender length on material properties of polyurea coatings

Abstract

The increasing usage of polyurea coatings has attracted the attention of researchers worldwide. Commercial polyurea formulations contain chain extenders as an essential ingredient, which increases the possibility of intermolecular H-bonding by bringing the urea linkages closer. In this work, we establish the effect of increasing chain length of chain extender on the material properties of the polymer. Different types of chain extender were blended with a long chain diamine and subsequently reacted with an MDI-based isocyanate prepolymer through a reactive spray processing technique. Polyurea coatings containing aromatic chain extenders were found to exhibit higher tensile strength as compared to their aliphatic analogues. Increasing the chain length of the aliphatic chain extender led to a reduction in the mechanical strength. A suitable combination of aromatic and aliphatic chain extender of short length was found to force the macromolecule to orient in such a fashion so as to result in optimal H-bonding. This manifested in terms of improved processability, as confirmed by chemorheological investigations. Fourier transform infrared spectroscopy was used to understand the Hbonded internal structure of the polymer. Optimum H-bonding resulted in improved mechanical properties of the spray-coated polyurea.The structure-property relationship of polyurea can be adjusted primarily by three factors: choice of the monomer pairs, polymer composition, and its final macromolecular architecture. 11 In view of the above, it is possible to design formulations by varying the isocyanates and amines to result in coatings displaying a range of properties. Much like the diisocyanates, aliphatic or aromatic amines and chain Additional Supporting Information may be found in the online version of this article.

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“…Their studies further confirm that it is prudent to introduce a blend of aromatic and aliphatic chain extender. It appears that in the presence of a combination of these two, the growing macromolecule orients in a manner which results in optimal H-bonding [12,13]. It has also been found that the sub-zero glass transition temperature (T g ) shifts methodically towards higher temperature as the total hard segment content decreased.…”

Preparation, characterization, and influence of polyurea coatings on their layered composite materials based on flexible rebonded polyurethane

“…Polyurea (PU) coatings are gaining attention because of its rapid cure, even at low temperatures, water resistivity, outstanding mechanical properties, and chemical durability. [1][2][3] The fast reaction makes PU especially suitable for outdoor applications. [4][5][6] Due to its specific curing profile and exceptional film properties, PU materials are used in roof coatings, flat roof repair, pipe protection, tank coatings, etc.…”

New Hybrid Polyurea-Polyurethane Elastomers with Antistatic Properties and an Influence of Various Additives on Their Physicochemical Properties

“…In addition, this compound can act as a monomer, a polymer, or a mixture thereof. In almost all commercial formulations, the resin is a homogenous blend of polyetheramine characterized by repeating oxypropylene units in the backbone and chain extender [ 1 , 2 ]. In polyurethanes, hydroxyl-terminated compounds are present instead of amines, while the cross-linking reaction occurs through isocyanate and both amine and hydroxyl-terminated compounds in hybrids [ 3 ].…”