Acrylate is widely used in the manufacture of various polymer materials because of its low temperature flexibility, heat resistance, aging resistance, high transparency and color stability. These properties enable it to be used in a wide range of applications, including plastics, floor varnishes, coatings, textiles, paints and adhesives. The type and amount of acrylate monomers used have a significant impact on the performance of the final product, including glass transition temperature, viscosity, hardness and durability. More polymers suitable for different applications can be obtained by copolymerization with the monomers with the hydroxyl, methyl or carboxyl functional groups.
The materials obtained by polymerization of acrylate monomers are widely used in industry, but residual monomers are often found in polymeric materials. These residual monomers may not only cause skin irritation and other problems, but also cause unpleasant odor in the final product due to the unpleasant odor of these monomers.
The olfactory system of human body can sense acrylate monomer in very low concentration. For many acrylate polymer materials, the odor of products mostly comes from acrylate monomers. Different monomers have different odors, but what is the relationship between monomer structure and odor? Patrick Bauer from Friedrich Alexander Universit ä t erlangen-n ü rnberg (Fau) in Germany studied the odor types and odor thresholds of a series of commercialized and synthesized acrylate monomers.
A total of 20 monomers were tested in this study. These monomers include commercial and laboratory synthesized. The test shows that the odor of these monomers can be divided into sulfur, lighter gas, geranium and mushroom.
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 are also described as having lighter gas smell, while ethyl acrylate and 1,2-propylene glycol diacrylate have the impression of a little glue smell. Vinyl acrylate (No. 5) and propenyl acrylate (No. 6) are described as gas fuel odors, while 1-hydroxyisopropyl acrylate (No. 10) and 2-hydroxypropyl acrylate (No. 12) are described as geranium and lighter gas odors. N-butyl acrylate (No. 4), 3- (z) pentene acrylate (No. 7), SEC butyl acrylate (geranium, mushroom flavor; No. 8), 2-hydroxyethyl acrylate (No. 11), 4-methylamyl acrylate (mushroom, fruit flavor; No. 14) and ethylene glycol diacrylate (No. 15) are described as mushroom flavor. Isobutyl acrylate (No. 9), 2-ethylhexyl acrylate (No. 13), cyclopentanyl acrylate (No. 17) and cyclohexane acrylate (No. 18) are described as carrot and Geranium odors. 2-methoxyphenyl acrylate (No. 19) is the smell of geranium and smoked ham, while its isomer 4-methoxyphenyl acrylate (No. 20) is described as the smell of anise and fennel.
The odor thresholds of the tested monomers showed great differences. Here, the odor threshold refers to the concentration of the substance that produces the minimum stimulus to human odor perception, also known as the olfactory threshold. The higher the odor threshold, the lower the odor. It can be seen from the experimental results that the odor threshold is more affected by functional groups than by chain length. Among the 20 monomers tested, 2-methoxyphenyl acrylate (No. 19) and SEC butyl acrylate (No. 8) had the lowest odor threshold, which were 0.068ng/lair and 0.073ng/lair, respectively. 2-hydroxypropyl acrylate (No. 12) and 2-hydroxyethyl acrylate (No. 11) showed the highest odor threshold, which were 106 ng/lair and 178 ng/lair, respectively, more than 5 and 9 times that of 2-ethylhexyl acrylate (No. 13).
If there are chiral centers in the molecule, different chiral structures also have an impact on the odor of the molecule. However, there is no rival study for the time being. The side chain in the molecule also has some influence on the odor of the monomer, but there are exceptions.
Methyl acrylate (No. 1), ethyl acrylate (No. 2), propyl acrylate (No. 3) and other short chain monomers show the same odor as sulfur and garlic, but the odor will gradually decrease with the increase of chain length. When the chain length increases, the garlic odor will decrease, and some lighter gas odor will be produced. The introduction of hydroxyl groups in the side chain has an impact on the intermolecular interaction, and will have a greater impact on the odor receiving cells, resulting in different odor senses. For the monomers with vinyl or propenyl unsaturated double bonds, namely vinyl acrylate (No. 5) and propenyl acrylate (No. 6), they only show the smell of gaseous fuel. In other words, the introduction of the second capped unsaturated double bond leads to the disappearance of sulfur or garlic odor.
When the carbon chain is increased to 4 or 5 carbon atoms, the perceived odor will obviously change from sulfur and garlic to mushroom and Geranium. On the whole, cyclopentanyl acrylate (No. 17) and cyclohexane acrylate (No. 18), which are aliphatic monomers, show similar odor (geranium and carrot odor), and they are slightly different. The introduction of aliphatic side chains does not have a great impact on the sense of odor.
Post time: Jun-07-2022
