The versatility of acrylic resin

Glass transition temperature

By selecting suitable monomers, polymers with different glass transition temperatures can be prepared, which are suitable for different application fields. The glass transition temperature of a polymer is a simple average of temperature in degrees Celsius. Changing the glass transition temperature polymer can turn a hard, often brittle, material into a soft, rubbery material. Although these average glass transition temperature (Tg) values ​​tend to vary with the test method used, they are reproducible within a certain range and represent the characteristics of a particular polymer. It is significant that the glass transition temperature is indicative of a characteristic of the hand, low temperature flexibility, and room temperature hardness and softening point. The glass transition temperature can be used to compare the latex hardness and flexibility of a single-structured polymer series.

Table 1 lists the Tg ranges of homopolymers derived from different monomers.

Table I, glass transition temperature

Homopolymer Tg/°C Homopolymer Tg/°C
Acrylic acid 112 Ethyl Acrylate -24
Methyl methacrylate 106 n-butyl acrylate -56
Methyl acrylate 8 Acrylic acid 2-ethylhexyl -65
Isopropyl acrylate-8

Acrylic emulsion

Emulsions play an important role in acrylic polymers, so we focused most of our discussion on this area. Table 2 relates the glass transition temperature range of acrylic acid to China policy to specific application areas. There is a clear overlap in these areas. By varying the composition of the monomers, the versatility of the acrylic polymer can be clearly characterized.

Various types of adhesives include pressure-sensitive polymers and heat-activated polymers, which can be dried to a non-sticky state.

Table 2 Glass transition temperature and applications

Tg/°C Applications Tg/°C Applications
80-100 high temperature resistant coating 10-40 decorative paint
50-65 Floor Maintenance Coating 25-35 Ink Adhesive
35-50 General Industrial Coating -65-25 Adhesive

Physical properties

General emulsions can be characterized by the following basic indicators: solids content, viscosity, pH, particle size, minimum film formation temperature (MFT), and particle charge.

The solids content was determined from the drying of the emulsion to constant weight. The viscosity was determined using a Brookfield viscometer and the pH was determined by a pH meter. The particle size is usually about 0.05-0.5 μm, and the particle size depends on the type and amount of emulsifier used; particle size is usually measured using laser light scattering techniques, electron microscopy, and ultracentrifugation.

The particle charge is discussed in the following paragraphs.

As previously mentioned, the emulsifier stabilizes the monomer droplets under stirring conditions. Polymerization occurs in monomeric micelles to form suspended polymer solids in water. Surfactants are divided into three categories: anionic, non-ionic and cationic.

The most common type is an anionic surfactant that ionizes in water leaving a negative charge on the surface of latex particles. Non-ionizing does not ionize, but the combination of hydrophobic phasic and hydrophilic phasic on the molecule stabilizes the particles. Cationic surfactants are generally not used to provide positively charged particles.

Surfactants help to improve the mechanical and chemical stability of the emulsion. However, it also tends to increase the sensitivity of the dry film to water.

Minimum film formation temperature

Unlike homogeneous solution polymers, emulsions are polymer particles dispersed in a continuous aqueous phase. When dry, the particles must combine to form a continuous film. If this process is dried with a polymer of 25 or more Tg below room temperature, no film will be formed. In this case, the polymer must be heated above Tg or a filming aid is added to the emulsion to soften it, plasticizing the particles so as to combine to form a continuous film. The commonly used coalescents are high-boiling liquids that solvate the polymer, but then evaporate to obtain the inherent physical properties of the single polymer. Usually these coalescents are glycol ethers. Its related toxicity has recently been studied.

Source: China Tobacco Packaging Ink Information Network