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Composition of UV resin for difficult-to-bond substrates
Release time:
2026-09-28 06:58
The reason why UV‑curable resins for difficult-to-bond substrates can achieve reliable adhesion on low‑surface‑energy plastics such as polypropylene, polyethylene, and polyester lies in the synergistic effects of their key formulation ingredients. Unlike conventional UV‑curable resins, these formulations require careful consideration of factors such as interfacial wetting, chemical anchoring, and shrinkage‑stress control during raw‑material selection. Their core ingredient system typically comprises several major categories: adhesion promoters, low‑surface‑energy modifying resins, reactive diluents, and photoinitiators.
I. Adhesion Promoters Based on Chlorinated Polyolefins
Chlorinated polyolefins are a well-established class of materials for addressing adhesion issues in polyolefin substrates. Chlorinated polypropylene, with a molecular structure similar to that of polypropylene, can form strong interfacial bonding with the substrate in accordance with the principle of “like dissolves like.” By grafting polar functional groups such as maleic anhydride onto chlorinated polypropylene, its compatibility with UV‑curable resins and its reactivity can be further enhanced.
These types of raw materials are typically used in the form of primers or adhesion promoters. Chlorinated polyolefins can penetrate the substrate surface, forming physical entanglements and developing surface crystallinity, thereby enhancing peel strength. Grafted chlorinated polypropylene exhibits higher molecular polarity and superior adhesion performance. In formulation design, chlorinated polypropylene resins are often blended with methyl methacrylate resins to serve as a bridge between nonpolar substrates and the coating film.
II. Phosphate Ester Adhesion Promoters
Phosphate ester–based adhesion promoters constitute another class of key raw materials for enhancing the adhesion to difficult-to-bond substrates. The phosphate ester group exhibits a unique affinity for metal and glass substrates, enabling strong interactions with surface hydroxyl groups.
Acrylate‑functionalized phosphate esters can be incorporated into the cured network via copolymerization, thereby mitigating additive migration and leaching. The acid value of such raw materials must be carefully controlled; a high acid value may accelerate the decomposition of alkaline photoinitiators, shortening the formulation’s shelf life. These materials are characterized by light color, low acid value, and excellent adhesion, and their multiple functional groups enhance the resin’s adhesion to a wide range of substrates, including metals, glass, and plastics.
Silane‑modified acrylate phosphate is a composite adhesion promoter that has emerged in recent years. By combining a silane coupling agent, an acrylate, and a phosphoric compound, it can simultaneously provide both chemical bonding and mechanical interlocking.
III. Low-Surface-Energy-Modified Resin
Low-surface-energy-modified resins are a key class of raw materials used in UV-curable resins for challenging substrates to enhance wetting and adhesion, primarily including fluorinated resins and organosilicon-modified resins.
Fluorinated polyurethane acrylate oligomers are widely used fluorine‑modified resins that reduce the surface tension of coatings, enabling them to spread effectively on low‑surface‑energy substrates. Fluorinated acrylate monomers are also frequently employed to tune the surface energy of the system. During film formation, these materials facilitate the selective enrichment of fluorinated segments at the coating surface, lowering surface energy while preserving bulk properties.
Silicone‑modified systems leverage the low surface tension of polysiloxanes, while acrylic‑modified polydimethylsiloxane combines silicone’s low surface tension with the photocurable reactivity of acrylate esters, enabling wetting and adhesion on extremely low‑surface‑energy substrates such as polyethylene and polypropylene. These raw materials typically contain polymerizable acrylate functional groups that participate in curing reactions, becoming integrated into the polymer network.
IV. Reactive Diluent Monomers
In UV-curable resins formulated for substrates with poor adhesion, reactive diluents not only help regulate viscosity but also directly influence the degree of cure‑induced shrinkage and interfacial stresses.
Isobornyl acrylate is a commonly used reactive diluent monomer, characterized by a bulky rigid side‑group structure. The steric hindrance of the isobornyl moiety during polymerization suppresses back‑addition of the monomer to the chain‑terminal radical, thereby significantly reducing both short‑chain and long‑chain branching. The regularity of its molecular architecture contributes to the stability of interfacial adhesion. Moreover, isobornyl acrylate exhibits a low shrinkage rate, which helps mitigate interfacial stresses during the curing process.
Other commonly used reactive diluents include hydroxyethyl acrylate, hydroxyethyl methacrylate, 1,6-hexanediol diacrylate, and trimethylolpropane triacrylate. Low‑functionality monomers help reduce curing shrinkage, while high‑functionality monomers are used to tune crosslink density and hardness. When selecting monomers, it is essential to strike a balance between adhesion and other performance characteristics.
V. Polyurethane Acrylate Oligomers
Polyurethane acrylate oligomers serve as the film-forming backbone in UV‑curable resins for substrates with poor adhesion, determining the coating’s fundamental mechanical properties and flexibility. Aliphatic polyurethane acrylates exhibit superior flexibility and weatherability, enabling them to accommodate substrate deformation without cracking.
In formulation design, selecting specific isocyanates, polyols, and acrylate monomers allows for fine-tuning of the resin’s cure rate and flexibility. Polyether polyols, with their lower cohesive energy due to ether linkages and facile bond rotation, can maintain high functionality while preserving the film‑forming flexibility of the resin. By adjusting the weight ratio of different polyurethane acrylate oligomers, the resin can simultaneously exhibit rapid surface drying, hardness, and toughness, reduce shrinkage stresses during film formation, and thereby enhance adhesion to the substrate.
VI. Photoinitiators and Additives
Photoinitiators are key components of UV-curing systems, and their selection must be compatible with both the reactivity of the resin system and the wavelength of the curing light source. Commonly used photoinitiators include 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and 2-hydroxy-2-methyl-1-phenylpropan-1-one, among others.
In terms of additives, silane coupling agents are commonly used to enhance interfacial adhesion. Titanate and zirconate-based adhesion promoters are also employed in transparent coatings for low‑surface‑energy substrates; zirconates, in particular, retain excellent adhesion even after aging. The dosage of these additives must be carefully controlled to strike a balance among adhesion, storage stability, and other performance characteristics.
VII. Conclusion
The core raw materials for UV resins designed to adhere to difficult-to-bond substrates encompass several categories, including chlorinated polyolefin‑based adhesion promoters, phosphate‑ester adhesion promoters, low‑surface‑energy modified resins, reactive diluents, polyurethane acrylate oligomers, as well as photoinitiators and various additives. Chlorinated polyolefins address the adhesion challenges of polyolefins through “like‑dissolves‑like” interactions and physical entanglement; phosphate‑ester compounds enhance adhesion to metals and glass via chemical bonding; fluorine‑ and organosilicon‑modified resins reduce surface tension to improve wetting; monomers such as isobornyl esters mitigate shrinkage and promote branching through steric effects; and polyurethane acrylate oligomers enable formulation‑driven tuning of the balance between flexibility and hardness. The synergistic combination of these ingredients collectively ensures reliable adhesion of UV resins for challenging substrates on low‑surface‑energy plastics.
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 | ||
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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 | Excellent adhesion, impact resistance, good 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 | It exhibits excellent adhesion to plastics, good dilutability, and low volatility. |
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