Antifouling coating is a kind of functional coating that is frequently applied to the surfaces of marine installations, such as ships, to block or delay the attachment of marine fouling organisms [
1]. In this way, the wastage of power energy and human resources [
2,
3,
4] can be significantly reduced. Antifouling coating is composed of film-forming resin and additives, such as an antifouling agent and coupling agent, each with its function [
5]. At present, most of the research on antifouling coatings covers two perspectives: improving the application environment matching of film-forming resin and investigations on the performance of antifouling agents and other additives. The latter can cause fatal damage to marine fouling organisms. However, the contradiction between toxic pollution and marine ecological maintenance cannot be handled well in a short time since the development of a nontoxic or low toxic antifouling agent that completely replaces toxic antifouling agents and complies with the law will undergo the process of screening, elimination and re-screening [
5,
6]. Morever, film-forming resin is the carrier of antifouling agents and other added materials. Therefore, the functional film-forming resin must be researched in the future to improve the matching of its application environment as much as possible and thus improve the effect of antifouling coatings, though this method is slightly conservative compared with the development of a new antifouling agent [
6]. The performance of film-forming resin, which functions as the dispersing carrier of functional additives, directly determines the functionality and timeliness of antifouling coatings. Hence, it is necessary to develop high-performance film-forming resin that is suitable for specific applications [
7].
Considering that it is easy for ship coatings to peel off under the shear stress of water flow at high speeds, excellent film-forming resin mechanical properties [
8] are required, because the mechanical properties of the coatings are mainly associated with film-forming resin. At present, film-forming resins are primarily composed of EP and PU. However, there are still many limitations to their performance. For example, EP has poor toughness and impact resistance [
9]. PU has the advantages of high elasticity, good impact resistance, and molecular design, while its mechanical strength is insufficient compared with that of EP. Therefore, epoxies and polyurethanes provide the best overall combination of film properties compared with other organic coatings [
10]. The two materials are physically blended to prepare film-forming resin for coatings, contributing to maximization of the performance advantages of the two materials [
11]. However, a poor hydrophilicity problem began to appear with the promotion of the above resin in the field of antifouling. This makes it difficult for antifouling agents to be released from the coating, leading to a remarkable decrease in the functional effect of the antifouling coating [
12]. Besides, the hydrophilicity of coatings can positively affect the adhesion of protein fouling organisms, and its antiadhesion mechanism is a research hotspot [
13,
14,
15]. Studies aimed at determining how to properly improve the hydrophilicity of materials without reducing the comprehensive performance of film-forming resin are becoming increasingly essential in the field of marine antifouling. There have been many cases of chemical modification of PU and EP. The effects of hydrogen bonding on the free volume and miscibility were first investigated for PU/EP interpenetrating polymer network (IPN) nanocomposites. The results demonstrated that stronger the hydrogen-bonding interactions are associated with a higher average chain packing efficiency, and smaller free volume hole sizes lead to better miscibility [
16]. Studies have revealed that the PU/EP interpenetrating network structure prepared by the microwave curing method not only has the same structure as thermal curing but it also has a shortened curing time. The tensile properties of microwave cured IPN are better than those of thermal cured IPN, while the impact strength of thermal cured IPN is slightly higher [
17]. Some studies have also suggested that after blending PU with EP, the damping performance of EP composites significantly increases with the increase in frequency, and the damping temperature range moves toward higher temperatures [
18]. In recent years, the tribological properties of polyurethane/epoxy interpenetrating network (PU/EP-IPN) composites have been explored to guide the research and development of polymer friction materials under water lubrication. The results indicate that the friction and wear properties in the water-lubricated medium are dramatically improved by adding different kinds of fillers (SiC submicron particles and short carbon fibers (SCF)) [
19].
As revealed from the above research, PU/EP materials have been widely studied, the technology is relatively mature, and the comprehensive properties have been optimized and improved [
20]. These studies have inspired the preparation of PU/EP hydrophilic graft blends. In this paper, a hydrophilic PU molecular chain was designed and then grafted onto the EP to effectively improve the hydrophilicity of PU/EP grafted blends without affecting the comprehensive properties of the material. It is a potential method that could be used to improve the antifouling effect of new antifouling coatings.