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Hydroxyacrylate monomer

Release time:

2025-01-10 17:02

In the synthesis of polyurethane acrylates, hydroxy esters of acrylic acid react with NCO groups to introduce acryloyloxy groups. These acryloyloxy groups typically reside at the chain ends of the polyurethane prepolymers.

Suitable acrylic hydroxy esters can be classified into the following types based on the number of functional groups:

1. Monofunctional: Hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate (HEMA), hydroxypropyl acrylate (HPA), hydroxypropyl methacrylate (HPMA), hydroxybutyl acrylate (HBA);

In general, monofunctional UV monomers tend to have stronger odors, higher volatility, and greater irritancy—for example, HEA and HPA. Hydroxy esters of methacrylic acid, on the other hand, have an additional methyl group attached to the carbon atom of the double bond, which reduces their odor and skin irritancy but also lowers their reactivity. Polyurethane acrylates prepared using hydroxy esters of methacrylic acid as end-capping agents tend to exhibit slightly higher hardness compared to those capped with hydroxy esters of acrylic acid; however, their curing rate is somewhat slower. Compared to HEA and HPA, HBA exhibits significantly lower irritancy. HBA comes in two structural forms: 2-HBA and 4-HBA; among these, 4-HBA generally demonstrates superior performance.

Since the photopolymerization rate of acrylates is much faster than that of methacrylates, the vast majority of applications use acrylate hydroxy esters. The reactivity of isocyanates toward alcohol hydroxyl groups follows the order: primary alcohols > secondary alcohols > tertiary alcohols. Therefore, most applications involve the reaction of HEA (a primary alcohol) with isocyanates, while HPA and HBA are used less frequently.

2. Bisfunctional: Trimethylolpropane diacrylate (TMPDA);

TMPDA is a bifunctional monomer derived from TMPTA. In TMPDA, one of the acrylate double bonds in TMPTA is converted into a hydroxyl group. This monomer is virtually unavailable from manufacturers on the market; typically, only those companies with monomer-production licenses will produce it for their own use. Moreover, due to the difficulty in precisely controlling the reaction of the hydroxyl group, the final product—TMPDA—is not purely pure but rather a mixture containing TMPTA as well. TMPDA can be used to synthesize polyurethane acrylates with four, six, or even higher functionalities.

3. Trifunctional: Pentaerythritol triacrylate (PET3A);

PET3A is commonly used to produce high-functional polyurethane acrylates. The resulting high-functional resins exhibit characteristics such as rapid curing speed, high hardness, and excellent abrasion resistance.

4. Dipentaerythritol pentaacrylate (DPHA);

During the esterification process of DPHA, by controlling the degree of esterification, a portion of the hydroxyl groups can be retained. Due to differences in manufacturing processes among various producers, the final DPHA product typically exists as a mixture. DPHA can be used to synthesize polyurethane acrylates with ten or more functional groups; products made from DPHA exhibit higher crosslinking density and improved abrasion resistance. However, because of their relatively high double-bond content, these materials tend to crack during photopolymerization.

The above are commonly used hydroxy acrylates in the synthesis of polyurethane acrylates. As a manufacturer of UV-curable resins, Boxing New Materials specializes in the R&D, production, sales, and technical services of new UV-curable materials. We welcome inquiries from both new and existing customers.

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