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Types of UV Resins with Poor Adhesion to Substrates (Part II)

Release time:

2026-09-29 17:15

Types of UV Resins with Poor Adhesion to Substrates (Part II)

The reason why UV‑curable resins can achieve reliable adhesion to low‑surface‑energy plastics lies in a variety of adhesion mechanisms. These mechanisms correspond to different resin types: some rely on physical anchoring, others on chemical bonding, some employ reactive functional groups for dual‑mode anchoring, and still others leverage surface‑enrichment phenomena to optimize interfacial performance. Understanding resin types from the perspective of their adhesion mechanisms helps practitioners grasp the underlying principles during formulation design and select appropriate strategies tailored to specific substrates.

I. Physical Anchorage Type

Physical anchoring primarily relies on the coating penetrating the substrate’s surface microstructure to form mechanical interlocking. These resins typically contain components capable of infiltrating the substrate’s fine surface textures, and upon curing, they create an embedded structure between the substrate and the coating. When the coating is subjected to external forces, this mechanical anchoring effectively resists delamination from the substrate.

Chlorinated polyolefin resins are a quintessential example of physically anchored systems. The molecular chains of chlorinated polypropylene can penetrate the microstructure of the polyolefin substrate, and upon curing they establish robust mechanical anchorage. Chlorinated polyolefins share a similar molecular architecture with polypropylene substrates, enabling strong interfacial adhesion through the principle of “like dissolves like.” Grafted chlorinated polyolefins exhibit enhanced polarity, which, while preserving physical entanglement, also improves their compatibility with UV‑curable resins.

The performance of physically anchored resins is strongly influenced by the surface morphology of the substrate. For substrates with relatively smooth surfaces, physical anchoring is limited and must be supplemented by other mechanisms to enhance adhesion.

II. Chemically Bonded Type

Chemically bonded adhesion is achieved by introducing functional groups that can form chemical bonds with the substrate surface. Specific functional groups in these resins can undergo chemical reactions with active sites on the substrate surface, thereby forming chemical bond bridges at the interface.

Phosphate ester adhesion promoters are representative of chemically bonded types. Phosphate groups exhibit specific affinity for metal and glass substrates, forming strong interactions with surface hydroxyl groups. Acrylate‑functionalized phosphates can be incorporated into the cured network via copolymerization, thereby mitigating issues associated with additive migration and precipitation. The acid value of these raw materials must be carefully controlled; a high acid value may accelerate the decomposition of alkaline photoinitiators, shortening the formulation’s shelf life.

Silane coupling agents hydrolyze to generate silanol groups, which can both react with surface hydroxyls on the substrate and interact with functional groups in the resin matrix. The potential for chemical bonding and mechanical anchoring is enhanced by increased functionality and improved substrate wetting. However, the application of silane coupling agents requires careful consideration of hydrolytic stability and compatibility with the resin system. For polyolefin substrates that lack reactive functional groups on their surfaces, the purely chemical‑bonding mechanism is limited and must be combined with other mechanisms.

III. Reactive Anchoring Type

Reactive anchoring combines the dual mechanisms of physical anchoring and chemical bonding, achieving dual anchorage at the interface through reactive functional groups.

Reactive metal salts are a typical example. The metallic moiety can interact with the substrate, forming ionic bonds that anchor the cured formulation to the surface; meanwhile, the polymerizable segment participates in the curing reaction, becoming part of the polymer network. This dual‑action mechanism ensures stronger adhesion while preventing the migration and precipitation of additives. Reactive phosphates also belong to this category: acrylate‑functionalized phosphates are covalently incorporated into the cured network via copolymerization, and the phosphate groups exhibit specific affinity for the substrate.

The advantage of reactive anchoring resins lies in the durability of their adhesion. Because the adhesive functional groups are chemically bonded into the polymer network, they do not migrate or precipitate over time, ensuring long-term stability of adhesion. These resins are well suited for applications with stringent durability requirements.

IV. Surface-Enriched Type

Surface‑enriched types leverage the selective migration of specific functional groups to the interface during film formation to enhance adhesion. During curing, the functional groups in these resins spontaneously accumulate at the coating surface or interface, forming a functional layer in the interfacial region without compromising the bulk properties.

Fluorinated epoxy acrylate oligomers with a comb-like architecture achieve selective enrichment of fluorinated segments at the coating–air interface during film formation by covalently attaching fluorinated side chains to a UV‑curable backbone. This results in a thin, fluorinated surface layer that governs wetting behavior while preserving the bulk material’s intrinsic properties. This interfacial engineering strategy delivers superior surface performance with reduced fluorine content, thereby complying with relevant environmental regulations.

The photocuring modification of fluorinated resins also exemplifies this mechanism. The presence of fluorocarbon segments and fluorine‑containing side groups causes fluorine atoms to enrich at the coating surface during curing, thereby significantly reducing surface energy; meanwhile, residual polar functional groups help maintain adhesion to the substrate. The key advantage of surface‑enriched resins is that they can deliver substantial improvements in interfacial properties with a relatively low loading, while preserving the bulk mechanical and optical properties.

V. Conclusion

Based on their adhesion mechanisms, UV‑curable resins for difficult‑to‑adhere substrates can be classified into physical interlocking, chemical bonding, reactive anchoring, and surface‑enrichment types. The physical interlocking type relies on mechanical interlocking and is suitable for substrates with a certain degree of surface microstructure; the chemical bonding type achieves interfacial adhesion through functional group reactions and is well suited to substrates bearing active sites; the reactive anchoring type combines dual mechanisms, offering superior long‑term adhesion; and the surface‑enrichment type optimizes performance via interfacial migration, delivering significant results with minimal additive loading. These mechanisms do not operate in isolation; in practical formulations, they are often employed in synergy to address complex adhesion requirements.

Disclaimer: The above content has been compiled from publicly available sources and is provided for reference only. If any infringement occurs, please contact us, and we will address it promptly.

Bossin Related Product Recommendations – Membrane Materials
Difficult to adhere to the substrate
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-186	Modified epoxy acrylate	Boil-resistant, excellent adhesion, high-temperature resistant, chemically resistant
B-509B	Polyester acrylate	Good adhesion, good flexibility, and excellent pigment wetting.
B-531	Polyester acrylate	Good adhesion, impact resistance, excellent flexibility, and yellowing resistance.
B-546	Polyester acrylate	Good adhesion, fast curing, and excellent flexibility.
B-590	Polyester acrylate	Good adhesion, fast curing, and excellent pigment wetting.
BM2224 (EO-HDDA)	Ethoxylation of 1,6-hexanediol diacrylate	Excellent adhesion to plastics, good dilutability, and low volatility.

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Types of UV Resins with Poor Adhesion to Substrates (Part 3)

Types of UV Resins with Poor Adhesion to Substrates (I)