Monomers

Functional monomers are mostly water soluble simultaneously and used to incorporate hydrophilic centers within hydrophobic polymers to stabilize the particles and to achieve adhesion and acceptance of pigments. They are usually used in very small amounts (1-3%) and have reactive sites for crosslinking, surface modification of the particles and post-polymerization process the latex particles.

Functional groups that may be involved in such monomers are:

1. carboxyl groups (example acrylic and methacrylic acids). Discussed below

2. epoxy groups (example monomers such as glycidyl methacrylate). They are usually used to enhance chemical resistance, film hardness, chemical resistance and heat resistance and l abrasion.

3. acrylamide derivatives (example N-methylol). Such monomers are usually used in proportions of 1 to 7% and incorporating generate crosslinking sites within the latex particles. It can undergo crosslinking via hydrogen bridge at room temperature, as well, they can be crosslinked at higher temperatures (120 -150 ° C) with formation of covalent bonds between different N-methylol groups present in the chain.

4. Chlorides (example vinylbenzyl chloride). with electrophilic monomers are sites that may be reacted post-polymerization with nucleophiles such as amines, mercaptans, etc.

5. isocyanate groups (example TMI). These groups can be crosslinked post-polymerization, by amino or hydroxyl groups, or crosslink during film formation.

6. amino groups (example functional monomers such as diethylaminoethyl)

7. sulfonate groups (example sodium styrene sulfonate)

8. hydroxyl groups (example 2-hydroxyethyl methacrylate)

 

Monomers containing carboxyl are often introduced to act as a site for crosslinking reactions post-polymerization rheological modification or dispersion polymer for the colloidal stability of the latex particles. These groups tend to improve mechanical stability, shear and freeze - thawing of latex, to improve tolerance for electrolytes, to enhance the film hardness and the adhesion of a latex film to a substrate.

The carboxyl groups are capable of forming hydrogen bonds and covalent bonds and can be crosslinked ionically.

Acrylic and methacrylic acid are most commonly used, both are very soluble in water and have a high tendency to self-crosslinking.

In some cases dicarboxylic acids can be introduced (eg., Itaconic acid, fumaric acid) that can not be homopolymerized, which allows us to greatly increase the colloidal stability and the number of active sites.

How these acids are charged to the reactor, the pH and the type of acid influence the location of the carboxyl groups in the resulting particles.

And this in turn, will influence the properties of the latex.

Acrylamide fulfills essentially the same requirements as carboxylic monomers without introducing a load in the basic medium. Acrylamide is a neurotoxin, and exposure should be avoided at the same.

The influence of the structure of the monomer in the glass transition temperature of the homopolymers.

The glass transition temperature is defined as the temperature at which a polymeric material loses its characteristics that make it similar to rubber and passes instead to a state like glass. At this temperature the rotational flexibility of the C-C bonds in the chain and segmental mobility independent concomitant lost, becoming rigid material.

The possibility of different molecular conformations no longer occurs easily, leaving the polymer molecules effectively frozen in position.

In the first section of the table below the influence of the chain length of the alcohol compound in an acrylic ester on the glass transition temperature it is represented.

The introduction of longer alkyl chain in the monomer prevents the polymer chains are added and microcristalicen and therefore acts as an internal softener in the homopolymer. The longer the alkyl chain, thus lower the glass transition temperature.

Products

Name Catalogue Bulletin/Spe. Sheet. Sec. Sheet GHS Sec. Sheet View
Name Catalogue Bulletin/Spe. Sheet. Sec. Sheet GHS Sec. Sheet View
Styrene Monomer

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