In a nutshell, the formulation of putty products should be determined according to the use and performance requirements of the product (or the performance indicators specified in the standard), in accordance with the principle of optimizing performance and cost, using repeated trials and matching, and gradually approaching the target. Design, trial fit and confirm. That is, in accordance with the performance indicators specified in the product standard and based on the existing production or research experience, a series of formulas are designed for trial mixing, and a good formula is determined through the performance test results and cost calculation of the test samples.
1. Determine the raw materials for the putty configuration
Taking the formula determination of ordinary exterior wall putty (P type) as an example, it is necessary to first understand the performance requirements of the exterior wall putty in the use environment, the current product standards, the current market supply of raw materials, the packaging method of the putty products, etc.; To control the putty formula, first design a basic formula. According to the relationship between the main raw materials in the basic formula and the main performance indicators of the putty, one or two materials are used as the amount of change, and then a set of formulas is designed. After trial mixing, a satisfactory or relatively good formula is selected according to the results, and the formula design is carried out again after adjustment. , and the configuration test are repeated until a satisfactory result is obtained.
The formula design is first to determine the film-forming substance of the putty. According to the performance requirements of the putty for the exterior wall, latex powder or polymer emulsion can be selected according to the form of the putty (paste or powder). The amount and type of film-forming substances directly determine the water absorption, flexibility of putty film, dynamic crack resistance and bonding strength of the P-type exterior wall putty quality indicators in JG/T157-2009.
2. Determine the basic amount of main raw materials
There are two types of latex powder or polymer emulsion, VAE (ethylene-vinyl acetate copolymer) and polyacrylate. When using latex powder in powder putty, products with low glass transition temperature should be selected as much as possible, and there should be a basic Only when the amount is limited can there be a standard to meet the performance indicators and actual use requirements. For example, to meet the flexibility index of 100mm bending without cracks, when using latex powder, its dosage should not be less than 7%, and when using polymer emulsion, its dosage should not be lower than 11%.
Filler fineness (particle size) affects the amount of film-forming substances. Putty is different from paint. When selecting fillers, the particle size should be selected as much as possible. Fillers with a fineness of 200 mesh are the components of most putties (except for coarse leveling putty). main ingredient in. The reasons are as follows: first, it can reduce the amount of base material required for bonding fillers; second, it can reduce the cost of fillers in the putty; third, it can reduce the drying shrinkage of the putty film after batch coating, and prevent the initial drying and cracking of the putty film.
In addition to the physical and mechanical properties of the putty film, the construction of the putty is very important. The improvement of construction performance is solved by adding methyl or hydroxyethyl cellulose ether. The amount of cellulose ether should also be a reasonable amount to meet the requirements of easy scraping and proper drying time. The off-line amount should be 0.4%.
3. Try to configure the sample
When configuring experiments, attention should be paid to the weighing accuracy of various materials, and the weighing should be accurate. For additives with a small amount, there should be higher weighing accuracy. The prepared putty samples should reach a uniformly dispersed state, and the consistency should be easy The batch scraping shall prevail. If there are many bubbles (foam), it means that the formula needs to use a defoamer.
4. Sample performance inspection and formula adjustment
The main performance of the sample should be inspected first. The flexibility of the putty film is the main performance index that is difficult to meet the requirements, and the inspection is convenient, because this index can be inspected first, and then the water absorption, dynamic crack resistance and Bond strength etc.
After analyzing and comparing the test results, a relatively satisfactory formula is obtained, and on the basis of the satisfactory formula, adjustments and trial blending are made again.
According to the experience of putty research and production and various knowledges, the workload required for this process is also different. Generally, experienced people can get satisfactory results in a short period of time through the debugging of several formulas. Conversely, it is also possible to carry out a large number of long-term experiments and configuration work.
