The powdering of putty powder usually refers to the phenomenon that the surface of the putty coating becomes powdery and falls off after construction, which will affect the bonding strength of the putty and the durability of the coating. This powdering phenomenon is related to many factors, one of which is the use and quality of hydroxypropyl methylcellulose (HPMC) in putty powder.
1. The role of HPMC in putty powder
HPMC, as a commonly used additive, is widely used in building materials, including putty powder, mortar, glue, etc. Its main functions include:
Thickening effect: HPMC can increase the consistency of putty powder, making the construction smoother and avoiding the slipping or flow of putty powder during construction.
Water retention: HPMC has good water retention, which can extend the operability of putty powder and prevent the putty from losing water too quickly during the drying process, resulting in cracking or shrinkage.
Improved adhesion: HPMC can increase the adhesion of putty powder, so that it can better adhere to the wall or other substrate surface, reducing the occurrence of problems such as hollowing and falling off.
Improve construction performance: Adding HPMC to putty powder can improve the fluidity and plasticity of construction, make construction operations smoother, and reduce waste.
2. Reasons for putty powder pulverization
Putty powder pulverization is a common problem with complex reasons, which may be related to the following factors:
Substrate problem: The water absorption of the substrate is too strong, causing the putty to lose moisture too quickly and solidify incompletely, resulting in pulverization.
Putty formula problem: Improper formula of putty powder, such as unreasonable proportion of cementitious materials (such as cement, gypsum, etc.), will affect the strength and durability of putty.
Construction process problem: Irregular construction, high ambient temperature or low humidity may also cause putty powder to pulverize during the drying process.
Improper maintenance: Failure to maintain the putty in time after construction or prematurely proceeding to the next process may cause the putty powder to pulverize without being completely dried.
3. The relationship between HPMC and pulverization
As a thickener and water-retaining agent, the performance of HPMC in putty powder has a direct impact on the quality of putty. The influence of HPMC on powdering is mainly reflected in the following aspects:
(1) The influence of water retention
The powdering of putty powder is often related to the rapid evaporation of water in the putty. If the amount of HPMC added is insufficient, the putty powder loses water too quickly during the drying process and fails to fully solidify, resulting in surface powdering. The water retention property of HPMC helps the putty maintain appropriate moisture during the drying process, allowing the putty to gradually harden and prevent powdering caused by rapid water loss. Therefore, the water retention of HPMC is crucial to reducing powdering.
(2) The influence of thickening effect
HPMC can increase the consistency of putty powder, so that the putty can be more evenly attached to the substrate. If the quality of HPMC is poor or it is used improperly, it will affect the consistency of the putty powder, making its fluidity worse, resulting in unevenness and uneven thickness during construction, which may cause the putty powder to dry too quickly locally, thereby causing powdering. In addition, excessive use of HPMC will also cause the surface of the putty powder to be too smooth after construction, affecting the adhesion with the coating and causing surface powdering.
(3) Synergy with other materials
In putty powder, HPMC is usually used in combination with other cementitious materials (such as cement, gypsum) and fillers (such as heavy calcium powder, talcum powder). The amount of HPMC used and its synergy with other materials have a great impact on the overall performance of putty. An unreasonable formula may lead to insufficient strength of putty powder and eventually lead to powdering. Reasonable HPMC usage can help improve the bonding performance and strength of putty and reduce the powdering problem caused by insufficient or uneven cementitious materials.
4. HPMC quality problems lead to powdering
In addition to the amount of HPMC used, the quality of HPMC itself may also affect the performance of putty powder. If the quality of HPMC is not up to standard, such as low cellulose purity and poor water retention performance, it will directly affect the water retention, construction performance and strength of putty powder, and increase the risk of powdering. Inferior HPMC is not only difficult to provide stable water retention and thickening effects, but may also cause surface cracking, powdering and other problems during the drying process of putty. Therefore, choosing high-quality HPMC is crucial to avoid powdering problems.
5. Effect of other factors on powdering
Although HPMC plays an important role in putty powder, powdering is usually the result of the combined effect of multiple factors. The following factors may also cause powdering:
Environmental conditions: If the temperature and humidity of the construction environment are too high or too low, it will affect the drying speed and final curing effect of the putty powder.
Improper substrate treatment: If the substrate is not clean or the surface of the substrate absorbs too much water, it will affect the adhesion of the putty powder and cause powdering.
Irrational putty powder formula: Too much or too little HPMC is used, and the proportion of cementitious materials is improper, which will lead to insufficient adhesion and strength of the putty powder, thereby causing powdering.
The powdering phenomenon of putty powder is closely related to the use of HPMC. The main function of HPMC in putty powder is water retention and thickening. Reasonable use can effectively prevent the occurrence of powdering. However, the occurrence of powdering depends not only on HPMC, but also on factors such as the formula of putty powder, substrate treatment, and construction environment. In order to avoid the problem of powdering, it is also crucial to choose high-quality HPMC, reasonable formula design, scientific construction technology and a good construction environment.
Post time: Oct-15-2024