Putty is a coating that is often used as a substrate treatment when painting interior and exterior walls. The main function is to fill in defects in the base wall and to microfine the base surface. For better working results, we recommend the use of HPMC in putty powders.

What is Hydroxypropyl Methylcellulose (HPMC)?

Hydroxypropyl methylcellulose (HPMC) is a non-ionic cellulose ether. It is an odourless and tasteless white powder. It is produced from purified cotton or wood pulp by a series of etherification reactions.

Properties of HPMC

Hydroxypropylmethylcellulose (HPMC) has thermal gelation properties. Its aqueous solution precipitates and gels, then dissolves when cooled. The gelation temperature varies depending on the specification. Its solubility also varies with viscosity, the lower the viscosity, the higher the solubility. HPMC is essentially methane-epoxide-modified methyl cellulose and therefore has similar properties to methyl cellulose, being readily soluble in cold water and insoluble in hot water. The solution does not contain an ionic charge and therefore will not react with metal salts or ionic compounds.

HPMC has good dispersibility, emulsification, thickening, adhesion, water retention, and glue retention properties and is therefore widely used in pharmaceuticals, petrochemicals, construction, ceramics, textiles, food, daily chemicals, synthetic resins, coatings and other fields, as well as electronic products.

HPMC for Wall Putty

Application of HPMC in putty powder

Depending on the application, hydroxypropyl methyl cellulose (HPMC) can be classified as construction grade, food grade and medical grade. In construction, HPMC is mainly used in putty powder, accounting for 90% of the total.

HPMC in putty powder is mainly used as a thickener, water retention agent and lubricant.

• Thickeners: HPMC is added to putty powder to thicken it, enhance its suspension, resist sagging and keep it in a homogeneous solution.

• Water Retainer: HPMC is added to putty powder to keep it moist and to allow the auxiliary grey calcium to act as an underwater agent.

• Lubricant: Hydroxypropyl methylcellulose has a lubricating effect. The use of HPMC in putty powder gives the putty powder a good compatibility, keeps it flat during construction and saves labour.

Hydroxypropylmethylcellulose (HPMC) does not participate in any chemical reactions, except as an auxiliary molecule. The process of adding water to putty powder to the wall is a chemical reaction. During this process a new substance (calcium carbonate) is formed.

When wall putty powder and water, on the wall, is a chemical reaction, because of the generation of new substances, the wall putty powder down from the wall, ground into powder, and then use, not workable, because it has formed a new substance (calcium carbonate) during this period.The main components of grey calcium powder are:Ca(OH)2, CaO and a small amount of CaCO3 mixture.CaO+H2O=Ca(OH)2 — Ca(OH)2+CO2=CaCO3↓+H2O gray calcium in water and air under the action of CO2, the formation of calcium carbonate, and HPMC only water, auxiliary gray calcium better reaction, its own did not participate in any reaction.

The formulation of the putty can vary from one size to another. As a result, the viscosity and dosage of hydroxypropyl methylcellulose (HPMC) vary. In practice, it is recommended to use a lower viscosity HPMC product in winter, which is more conducive to construction. Otherwise, when the temperature is low, the viscosity will increase and this may cause problems for further applications.

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