The Importance of Water Retention of HPMC
April 24th 2024
Vinyl acetate-co-ethylene copolymers (VAE), available from SLEOCHEM in powder form, are white, free-flowing, dry powders that are readily redispersed into water to re-form a stable emulsion. Sometimes called “solid latex,” VAE redispersable powders (RDPs) are easy to ship, store (excellent storage stability), handle, and dry-mix versus VAEs in an emulsion form. VAEs account for the majority of the global market for redispersible polymer powders.
Vinyl acetate-co-ethylene copolymers (VAE), available from SLEOCHEM in powder form, are white, free-flowing, dry powders that are readily redispersed into water to re-form a stable emulsion. Sometimes called “solid latex,” VAE redispersable powders (RDPs) are easy to ship, store (excellent storage stability), handle, and dry-mix versus VAEs in an emulsion form. VAEs account for the majority of the global market for redispersible polymer powders.
Dry mixing with other powders such as cement, sand, or light aggregate at a field site or manufacturing location can facilitate consistency and reliable performance. VAE-RDPs are used as cement and plaster modifiers or as a binder resin for inorganic materials such as gypsum and hydrated lime. Formulators also use VAE-RDPs as the sole binder resin for construction adhesives.
The advantages of incorporating VAE-RDPs in dry-mix formulations include improvements in workability and water retention, plasticity, dispersion, and freeze stability. The VAE resins are soft and flexible because of their relatively high ethylene contents. As a modifier, VAE-RDPs improve flex strength, crack resistance, adhesion, abrasion and impact resistance, and water repellency.
Applications for VAE-RDPs include the formulation of construction materials such as tile adhesives, grouts, finishing plasters, troweling compounds, thin set mortars, and sealing slurries.. The amount of VAE-RDPs added to cements and plaster is about 2-10 percent, depending on the improvement of strength, impact resistance, adhesion, and water resistance required of the compound.
VAE-RDP: Manufacturing Process
Vinyl acetate and ethylene are copolymerized in an emulsion process to first produce VAE compositions containing between 10 and 40 percent ethylene in the copolymer. Ethylene is a soft, hydrophobic monomer unit in the copolymers, functioning as an internal “plasticizing” moiety. In copolymers, ethylene effectively reduces the glass transition temperature (Tg) of the hard, polar vinyl acetate monomer, which has a Tg of 30 °C. Thus, we can achieve copolymers with Tgs ranging from +15 °C to minus 15 °C while converting the base emulsion resins used in the production of the VAE into redispersible powders. By using ethylene monomer to adjust the Tg, the formulator does not require any external plasticizers.
VAE-RDP Grades, Properties and Applications
We can segregate the grades and general applications of the VAE-RDPs by glass transition temperature (Tg). The Tg of an amorphous polymer like VAE is the critical temperature at which the material changes its behavior from being a glassy solid to a rubber material. When the ambient temperature is above the Tg, the polymer becomes a rubber. When the ambient temperature is less than the Tg, the polymer becomes a glassy material.
Special Grade
The dominant market for VAE RDPs is in the building and construction industry, where they are used to formulate dry-mix products. The global market for these types of products is projected to grow at more than seven percent. Technological developments in the field of thin-bed tile adhesives is one driver of growth. For wall tile adhesive applications, VAE-RDPs improve slump property, water retention, and workability. This allows tiles to be laid from the top to the bottom without experiencing tile slippage or the need to use spacers. VAE-RDPs also improve the leveling properties of tile adhesives and other cementitious materials.
Demand for VAE-RDPs has also grown into the area of skim-coat compounds, where VAE contributes increased wall adhesion and crack-bridging properties.
Tags:
