In the production process of putty powder dry mortar, the viscosity selection of hydroxypropyl methylcellulose (HPMC) is crucial to the product performance. HPMC is an important cellulose ether, widely used in building materials, especially in putty powder and dry mortar, playing a variety of roles such as thickening, water retention, and improving construction performance.

Functions and effects of HPMC

In putty powder dry mortar, HPMC mainly plays the following functions:
Water retention: HPMC can absorb and retain water, reduce water loss during application, thereby extending the operability time of the material and ensuring the construction quality.
Thickening: HPMC provides appropriate viscosity and consistency, so that putty powder or dry mortar is evenly dispersed during mixing, increasing adhesion and smoothness of construction.
Anti-slip: The viscosity provided by HPMC can effectively reduce the slippage of materials during construction, especially during wall construction.
Improve anti-sagging: Increase the stability of materials during vertical construction to prevent slippage.

Selection of HPMC viscosity
The viscosity of HPMC directly affects the performance and application effect of putty powder dry mortar, so it is very important to choose the right viscosity. Here are some principles and considerations for viscosity selection:

1. Construction requirements
High viscosity HPMC (100,000cps and above):
Suitable for construction with high verticality requirements, such as putty powder on high walls.
It can improve anti-slip properties and reduce the flow of materials on vertical surfaces.
Increase water retention, suitable for high temperature or dry climate conditions to prevent excessive water loss.
Provide a strong thickening effect, which is conducive to the construction of thicker coatings.

Medium viscosity HPMC (20,000cps to 100,000cps):
Suitable for ordinary wall construction and floor leveling.
Balances the operation time and construction fluidity, suitable for a variety of climatic conditions.
Suitable for applications that require good anti-sagging but do not require extremely high viscosity.

Low viscosity HPMC (10,000cps and below):
Used for putty powder that requires higher fluidity, such as thin coatings.
It helps to improve the leveling and smoothness of the material and is suitable for fine surface treatment.
Suitable for areas with relatively humid construction environments.

2. Material composition and ratio
Formulas with high filler content usually require high viscosity HPMC to provide sufficient thickening effect and ensure the stability of the material.
Formulas containing fine aggregates or requiring high smoothness can use low viscosity HPMC to ensure good fluidity and flatness of the material during construction.
Formulas with added polymers may require medium or low viscosity HPMC to avoid excessive thickening affecting construction performance.

3. Environmental conditions
High temperature and dry climate: Choose high viscosity HPMC to extend the open time of the material and reduce construction problems caused by rapid evaporation of water.
Low temperature and humid environment: Choose low or medium viscosity HPMC to avoid coagulation or excessive viscosity of the material in a humid environment.

4. Construction process
Mechanical spraying usually requires good fluidity of the material, so low viscosity HPMC is selected.
For manual leveling, medium viscosity HPMC can be selected to ensure good construction operability.
Testing and Control of HPMC Viscosity
When selecting HPMC, in addition to the viscosity value, its solubility, solution transparency, water retention, etc. should also be considered. A rotational viscometer is usually used to measure the viscosity of the HPMC solution at different temperatures and shear rates to ensure its performance in actual applications.

Laboratory Testing
The viscosity and performance of HPMC can be tested in the laboratory by the following steps:
Dissolution preparation: Dissolve HPMC at room temperature and ensure complete dissolution and no particles.
Viscosity measurement: Use a rotational viscometer to measure the viscosity at different shear rates.
Water retention test: Evaluate the water retention capacity of HPMC to ensure that it can maintain sufficient moisture at high temperatures.
Application test: Simulate actual construction conditions to observe the effect of HPMC on the construction performance of putty powder dry mortar.

Quality control
During the production process, each batch of HPMC needs to be strictly controlled for quality, including viscosity testing, purity testing, etc., to ensure product consistency and stable performance.

Selecting HPMC with appropriate viscosity is crucial for the production of putty powder dry mortar. High viscosity HPMC is suitable for construction environments that require high anti-sag and water retention, medium viscosity HPMC is suitable for general construction conditions, and low viscosity HPMC is suitable for thin coating applications that require high fluidity. Manufacturers should optimize the viscosity of HPMC based on specific application scenarios, environmental conditions, and construction requirements, combined with laboratory test results, to improve product quality and construction effects.