What is the relationship between the odor and structure of UV monomers?

January 17, 2022 Longchang Chemical

What is the relationship between the odor and structure of UV monomers?

Acrylate is widely used in the manufacture of various polymer materials, mainly because of its low temperature flexibility, heat resistance, aging resistance, high transparency and color stability. These properties allow it to be used in a very wide range of applications including plastics, floor varnishes, coatings, textiles, paints and adhesives. The type and amount of acrylate monomer used has a significant impact on the properties of the final product, including glass transition temperature, viscosity, hardness and durability. Copolymerization with monomers with hydroxyl, methyl or carboxyl functional groups can result in more polymers suitable for different applications.

The materials obtained by the polymerization of acrylate monomers are widely used in industry, but residual monomers are often found in polymerized materials. These residual monomers may not only cause problems such as skin irritation, but also cause an unpleasant odor in the final product due to the unpleasant odor of these monomers themselves.

The human olfactory system can perceive very low concentrations of acrylate monomers. For many acrylate polymer materials, most of the product odor comes from acrylate monomers. Different monomers have different odors, but what is the relationship between monomer structure and odor?

Figure 1 Chemical structures of the studied acrylate monomers (both commercial and synthetic)

A total of 20 individual odors were tested for the study. These monomers include commercial and laboratory-synthesized ones. Tests have shown that the odors of these monomers can be classified as having sulfur, lighter gas, geranium and mushroom odors.

1,2-Propanediol diacrylate (no. 16), methyl acrylate (no. 1), ethyl acrylate (no. 2) and propyl acrylate (no. 3) are mainly described as sulfur and garlic odors. In addition, the latter two substances were also described as having a lighter gas odor, and ethyl acrylate and 1,2-propylene glycol diacrylate had the impression of a little glue odor. Vinyl acrylate (no. 5) and propylene acrylate (no. 6) were described as gaseous fuel odors, 1-hydroxyisopropyl acrylate (no. 10) and 2-hydroxyn-propyl acrylate (no. 12) Described as the smell of geranium and lighter gas. n-butyl acrylate (no. 4), 3-(Z)pentenyl acrylate (no. 7), sec-butyl acrylate (geranium, mushroom flavor; no. 8), 2-hydroxyethyl acrylate (no. 11), 4-methylpentyl acrylate (mushroom, fruity; no. 14) and ethylene glycol diacrylate (no. 15) were described as mushroom odors. Isobutyl acrylate (no. 9), 2-ethylhexyl acrylate (no. 13), cyclopentyl acrylate (no. 17) and cyclohexane acrylate (no. 18) are described as carrots Smell and geranium scent. 2-Methoxyphenyl acrylate (no. 19) smells like geranium and prosciutto, while its isomer 4-methoxyphenyl acrylate (no. 20) is described as anise and anise odor.

The odor thresholds of the tested monomers showed large differences. The odor threshold here refers to the concentration of the substance that produces the smallest stimulus to human odor perception, also known as the olfactory threshold. The higher the odor threshold, the lower the odor. From the experimental results, it can be seen that the odor threshold is more affected by functional groups than by chain length. Among the 20 tested monomers, the lowest odor thresholds were 2-methoxyphenyl acrylate (no. 19) and sec-butyl acrylate (no. 8), with odor thresholds of 0.068ng/Lair and 0.068ng/Lair, respectively. 0.073ng/Lair. 2-Hydroxy-n-propyl acrylate (no. 12) and 2-hydroxyethyl acrylate (no. 11) exhibited the highest odor thresholds at 106 ng/Lair and 178 ng/Lair, respectively, for acrylic- 5 and 9 times more than 2-ethylhexyl ester (no. 13).

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