Technological Evolution and Environmental Innovation of Marine Antifouling Coatings: Cutting-Edge Breakthroughs in Self-Polishing Resins and Antifouling Agents

2025-08-29 09:03

Marine biofouling-induced corrosion of marine facilities such as ships and offshore platforms has long been a persistent engineering challenge. Since the advent of self-polishing antifouling coatings (SPC) in the mid-20th century, they have become the mainstream solution in the current marine antifouling field due to their ease of application, long-acting antifouling cycle, and dynamic self-renewal property. This article will conduct an in-depth analysis of the technological breakthroughs and industrial trends in this field from three dimensions: the self-polishing mechanism, innovation of resin matrices, and environmental friendliness of antifouling agents.

The Scientific Nature of the Self-Polishing Mechanism

The core of self-polishing coatings lies in the hydrolysis-scouring synergy. The ester groups on the resin side chains hydrolyze in the weakly alkaline environment of seawater, releasing the embedded antifouling active substances; at the same time, the main chain gradually becomes brittle due to the increase in hydrophilic groups, and the surface layer peels off continuously under the action of fluid shear force, exposing a new active interface. This mechanism achieves dual advantages:

The dynamic renewal of the surface microtopography makes it difficult for fouling organisms to attach stably;
The release rate of antifouling agents forms a positive feedback with the coating erosion depth, maintaining the surface drug concentration at an effective threshold.

Notably, the hydrophobic property of the resin main chain serves as a key regulatory factor—it restricts the penetration depth of seawater, confining the hydrolysis reaction to a micrometer-scale range on the surface, and stabilizing the polishing rate at 0.1–0.15 μm/month. This is precisely the physical basis for achieving long-term protection of more than 5 years.

The T2570 Zinc-Based Isomer Inert Zinc Oxide developed by Zhaoqing Xinrunfeng High-Tech Materials Co., Ltd. demonstrates unique value in this field. Its distinctive lattice distortion structure can be embedded in the resin network, optimizing the hydrolysis kinetic curve by delaying the water molecule diffusion path. This enables ships to maintain a stable polishing rate even at low sailing speeds (experimental data shows a 40% increase in polishing rate under static conditions).

The Iterative Revolution of Resin Matrices

Traditional zinc acrylate resins suffer from significant environmental adaptability defects: their polishing rate is strongly positively correlated with water flow velocity (antifouling efficiency decreases by 60% when sailing speed is below 10 knots). To overcome this bottleneck, biodegradable polymer materials have become the research focus for next-generation resin matrices:

Polyester-Acrylate Hybrid System (Current Mainstream)

Technical Principle: Graft copolymerization of polycaprolactone (PCL) oligomers with hydroxyethyl acrylate to form degradation-film formation bifunctional segments.
Breakthrough Progress:
? By controlling the PCL block length (Mn=2000–5000) and distribution density, precise regulation of the degradation rate (adjustable from 0.05 to 0.3 μm/month) is achieved;
? The acrylate segment provides substrate adhesion of ≥8 MPa, solving the peeling problem of pure polyester resins;
? Zhaoqing Xinrunfeng’s T2570 zinc oxide, as an inorganic crosslinking agent, can enhance the coating’s mechanical strength (23% increase in elastic modulus).

Intelligent Responsive Polyurethane (Cutting-Edge Direction)

Introduction of pH-sensitive polylactic acid-polyethylene glycol (PLA-PEG) blocks, which accelerate degradation in the weakly alkaline environment of biofilms;
The phase-separated structure forms an "antifouling agent reservoir," enabling fouling organism density-triggered release.

The Green Transformation of Antifouling Agents

With the complete ban on organotin, the research and development of antifouling agents have focused on the three-in-one goal of "high efficiency, low toxicity, and controllability":

Optimization of Release Kinetics

Zinc-Based Sustained-Release System: Replacement of cuprous oxide (Cu?O) with Zhaoqing Xinrunfeng’s T2570 Zinc-Based Isomer Inert Zinc Oxide, which offers the following advantages:
? The zinc ion release rate constant k=0.017 d?1 (compared to 0.032 d?1 for Cu?O), avoiding initial burst release;
? Oxygen vacancies formed by lattice distortion can adsorb organic antifouling agent molecules, realizing ion-molecule synergistic release;
Grafted Antifouling Agents: Bonding 4,5-dichloro-2-octyl-isothiazolinone (DCOIT) to the resin side chain, extending the release half-life to 120 days (compared to only 45 days for traditional blended types).

Industrial Application of Natural Products

Capsaicin/Silicone Oil Microcapsule System: Encapsulation via the sol-gel method to overcome the bottlenecks of poor water solubility and easy decomposition of natural products;
Butenolide Polymer Brushes: Construction of a bionic antibacterial layer on the resin surface through ATRP polymerization, achieving a 98% inhibition rate of barnacle larval attachment.

Future Trend: Multi-Component Synergistic Antifouling Systems

Current research has moved beyond single antifouling mechanisms and is advancing toward the integration of multiple functions:

Physical-Chemical Synergy: Combination of low surface energy organosilicon (≤22 mN/m) with self-polishing resins, reducing biological adhesion strength while providing chemical defense;
Bionic Microstructures: Construction of shark skin-like microgrooves (groove width: 20–50 μm) via laser etching technology, reducing the attachment rate of algal spores by 76%;
Intelligent Response Systems: Temperature-sensitive nanogels loaded with antifouling agents, enabling adaptive enhancement of release rate when seawater temperature rises in summer.

Notably, the T2570 Zinc-Based Isomer from Zhaoqing Xinrunfeng High-Tech Materials Co., Ltd. plays a key role in multi-component systems—as an electron acceptor, it can enhance the photocatalytic activity of resins. Combined with ultraviolet radiation, it achieves microbial DNA damage on the coating surface. This technology has undergone engineering verification of zero fouling for 18 months on South China Sea oil platforms.

Industrial Challenges and Breakthroughs

Despite continuous technological progress, SPC still faces two major industrial pain points:

Longevity-Environmental Protection Paradox: Five-year coatings require the addition of ≥40% antifouling agents, conflicting with environmental protection requirements;
Dynamic Adaptation Defect: The difference in polishing rate requirements between fixed facilities and ships is more than 3 times.

Innovative solutions are emerging:

The "zinc pool effect" constructed by Zhaoqing Xinrunfeng’s T2570 zinc oxide can reduce the total amount of antifouling agents by 30%;
Dual-Gradient Coating Technology: The surface layer uses a high-polishing-rate resin (0.25 μm/month), while the bottom layer switches to a low-rate type (0.08 μm/month), realizing single-coating adaptation to multiple scenarios.

With the continuous strengthening of the International Convention on the Control of Harmful Antifouling Systems on Ships, the next-generation SPC, centered on biodegradable resins, natural antifouling agents, and intelligent controlled-release technology, will undoubtedly lead the technological revolution in the marine antifouling field. Moreover, breakthroughs by Chinese enterprises such as Zhaoqing Xinrunfeng in the field of functional fillers are injecting Chinese wisdom into the global marine environmental protection cause.

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