Role of Grafting on Particle and Film Morphology and Film Properties of Zero VOC Polyurethane/Poly(meth)acrylate Hybrid Dispersions

Abstract

Hybrid waterborne dispersions of polyurethane (PU)/poly(meth)acrylic are widely applied in coating and adhesive products, as well as in many other applications. The synergetic performance of the two component polymers is highly dependent on the ability to control the PU and (meth)acrylic network structure. In this work, the effect of grafting and the impact of macromolecular architecture on the particle and film morphology as well as on the properties of PU/(meth)acrylic hybrid films is investigated. It is shown that with grafting, the absolute molar mass distribution (MMD) is shifted toward higher values as the low molar mass PU chains become incorporated in the (meth)acrylic polymer network. Furthermore, by using different types of functional monomers, the nature of the MMD can be altered. Using transmission electron microscopy (TEM) analysis, it is demonstrated that more homogeneous particle and film morphologies are obtained in the case of grafted hybrids. Finally, the impact of network structure on tensile strength is outlined highlighting that grafted polymer films have higher Young's modulus and strain hardening than the non‐grafted ones.

The Influence of Macromolecular Structure and Composition on Mechanical Properties of Films Cast from Solvent‐Free Polyurethane/Acrylic Hybrid Dispersions

“…After that, the chain extender (DAD) dissolved in monomers (5 wt% of the MMA/BA) was added in the reactor and left to react 1 h at 70 °C. It should be noted that previous work has demonstrated that under similar reaction conditions Michael addition of the amine to the (meth)acrylic monomers does not take place to a significant extent and the amine primarily reacts with the isocyanate groups to chain extend the PU . The theoretical molar ratio of NCO/OH (defined as a molar ratio of IPDI and sum of polyol, DMPA, BDO, GMMA and DAD) was 1.8 before chain extension, 1.6 for the functionalized prepolymer, and 1.0 after chain extension.…”

“…Despite their relatively high price tag, polyurethane dispersions (PUDs) are used commercially in many coating applications due to their unique mix of strength and flexibility . By combination with acrylic dispersions it is often possible to maintain the mechanical strength of a conventional PUD while including additional beneficial properties of the acrylic phase . However, such synergetic use of the two distinct polymer phases requires proper selection of the each component and it remains unclear what the optimum structure of such hybrids should be in order to maximize the mechanical properties of the material.…”

“…However, such synergetic use of the two distinct polymer phases requires proper selection of the each component and it remains unclear what the optimum structure of such hybrids should be in order to maximize the mechanical properties of the material. Furthermore, in addition to the polymer structure, the morphology of the PU/acrylic particles themselves are often not straightforward and are heavily influenced by interactions between the chains by both physical interactions (most notably hydrogen bonding) and chemical bonds in the case of grafting …”

“…In this work, we seek to explore the extent to which mechanical strength can be manipulated by changing the structure of the two polymer phases and their interaction. PU/acrylic dispersions are synthesized by a zero‐volatile organic content (VOC) process utilizing a PU prepolymer dissolved in the acrylic monomer mixture as a dispersant, followed by chain extension of the PU and radical polymerization of the acrylic phase as recently reported . The microstructure of PU/(meth)acrylic is modified by altering i) the PU chains via varying the polyol type (polypropylene glycol (PPG), polytetrahydrofuran (PTHF), polyester and polycarbonate (PCD)), ii) the (meth)acrylic chains via varying the MMA/BA proportion ((0/100), (25/75), (50/50), (75/25), and (100/0) w/w) in the formulation and iii) the grafting between the PU and acrylic phases.…”

Self‐assembled polyurea macromer nanodispersion and resulting hybrid polyurea‐acrylic emulsions and films

“…Many methods have been developed to hybridize these systems. These approaches include (a) polyurethane dispersion (PUD) seeded acrylic emulsion polymerization; (b) concurrent polymerization of polyol, isocyanate, and acrylic monomer in a single dispersed phase stabilized by an internal dispersing agent (IDA); (c) concurrent miniemulsion polymerization of polyol, isocyanate, and acrylic monomer; and (d) variations of these methods using copolymerization between PU and acrylic chains to avoid macro‐phase separation of PU and acrylic domains . However, all these methods have remained dependent on leveraging the underlying attributes of PU chemistry specified and optimized for film‐based applications.…”