Development and study on fast setting CTA

ZHANG Zhiliang,DUAN Yufang
[Wacker Chemicals(China) Co. Ltd.,Shanghai 200233,China]

Abstract:This paper first studies the 6 h TAS (Tensile Adhesion Strength) and pot life of binary system and ternary system, and screens a fast setting CTA(Ceramic Tile Adhesive) reference formula with 6 h TAS reach 0.5 MPa and pot life above 40 min. Then the influences of kind of raw materials and VINNAPAS Dispersible Polymer Powder (DPP) to the performance of fast setting CTA are also studied,the results show that VINNAPAS 8620E can improve the TAS after 20 min open time and TAS under water condition of fast setting CTA.

0 Introduction

In the past 20 years, with the development and expansion of a group of professional ceramic tile manufacturers, the types, sizes and quality of ceramic tiles have been greatly improved. However, the development of tile tiling technology and supporting tile adhesives (referred to as tile adhesives) has not been synchronized with it, which has led to many quality problems in domestic tile tiling. The current trend of lower water absorption and larger size of tiles has forced us to urgently need to improve the quality and variety of tile adhesives to meet the needs of tile paving.
With the continuous increase of labor costs and the requirements of the construction unit for rapid construction, various types of fast-drying and quick-setting products such as stucco plaster, quick-repair mortar, quick-drying cushion self-leveling and quick-drying joint fillers have been developed. The demand for rapid layup and the rapid repair of partially peeled tiles have also increased the demand for fast-hard tile adhesives. 

However, the development of domestic fast hard tile adhesives is still in the initial stage, and there are few such products on the market.
In addition, although the industry standard JC / T547—2005 “Ceramic Wall and Floor Tile Adhesives” referenced by China ’s ceramic tile product performance testing has classifications about fast-curing ceramic tile adhesives, the requirements for this grade of ceramic tile adhesives are tensile adhesion after 24 h. The junction strength reaches 0.5 MPa. When JC / T 547-2005 referred to the European standard EN12004 in 2007, the requirements of the fast-curing ceramic tile adhesive had been modified to a tensile bond strength of 0.5 MPa after 6 hours. At present, China’s industry standard JC / T 547-2005 is in the process of being revised. This revision has been changed to refer to the international standard ISO 13007. The requirements of ISO 13007 and EN 12004 for fast-setting ceramic tile adhesives are the same. 6 h tensile bond strength reaches 0.5 MPa. Therefore, in order to maintain consistency with the ISO standard, the JC / T547 report being revised has also revised the performance requirements of the fast-hard ceramic tile adhesive to a 6-hour tensile bond strength of 0.5 MPa.

Compared with ordinary tile adhesives, fast-hard tile adhesives not only increase the tensile bonding strength for 6 hours, but also adjust the drying time to 10 minutes, and the operable time of such products is greatly shortened compared with ordinary tile adhesives. This can easily cause the construction workers to get used to it. The operating time of fast-hard ceramic tile adhesives in the European market is generally 30 to 60 minutes, and individual products can reach 75 minutes. Considering that the domestic use of the thin-layer method for the construction of tile adhesives is still in its infancy, workers need to use the thin-layer method. The experience and efficiency of tile application are not high. The author believes that the fast-hard tile adhesive that can be operated for at least 40 minutes and allowed to air for at least 20 minutes can meet the needs of the construction.

The purpose of this paper is to study the 6-hour tensile bond strength of binary systems (ordinary portland cement OPC and aluminate cement AC) and ternary systems (ordinary portland cement OPC, aluminate cement AC and gypsum). And operable time, and the influence of raw materials on the performance of tile adhesives, it was developed that can meet the tensile bond strength of 6 h and the tensile bond strength of 0.5 MPa after 20 minutes of drying time, and the operable time is 40 min. The above fast-hardening tile adhesives meet the needs of the rapidly developing tile adhesive market and applications.

1 Experiment
1.1 Raw materials
Ordinary Portland Cement (OPC): P · O42.5, Conch Cement; Aluminate Cement (AC): CIMENT FONDU, Ternal CC (CA-50) [凯诺斯 ( (China) Aluminate Technology Co., Ltd.]. Anhydrite: produced by an Anhui company; β-hemihydrate gypsum: produced by a company in Hubei; quartz sand: 40-70 mesh, 70-140 mesh, Shanghai Jianda Technology Company; redispersible powder: WACKER VINNAPAS5010N, VINNAPAS 8620E; Cellulose ether: TYLOSE 60001P6, TYLOSE 10007 P4, Shin-Etsu Taylor Co., Ltd .; Comparative test cellulose ether for tile adhesive (1 imported brand and 4 domestic brands), commercially available; Accelerator: lithium carbonate, Shanghai Provided by Oujin Industrial Co., Ltd .; retarder: tartaric acid, Changmao Biochemical Engineering Co., Ltd.

1.2 Test method
Refer to JC / T 547—2005 for early tensile adhesive strength, original tensile adhesive strength (hereinafter referred to as standard culture), tensile adhesive strength after immersion in water (hereinafter referred to as hydrotrophic), and thermally aged tensile adhesive. Tack strength (hereinafter referred to as heat curing), and the test of tensile bond strength after 10 minutes and 20 minutes of drying time. The early tensile strength was changed to the 6-hour standard curing, and the drawing head should be adhered to the tile with epoxy adhesive in advance.
The test of the operable time is from the time when the water is added and stirred until the time when the tile adhesive starts to harden and thicken and it is difficult to sparse with a tooth scraper.

1.3 Test Formulation System
1.3.1 Binary System

Binary systems of Portland cement and aluminate cement have been studied at home and abroad. Binary systems can greatly reduce the time of setting and hardening and improve the strength.
In this test, the imported aluminate cement CIMENTFONDU and the domestic aluminate cement TERNAL CC were selected by Kenos to perform a binary system test with Conch P · O42.5 cement. When different OPC and AC ratios were studied, tile adhesive 6 h tensile bond strength and operable time.
The mass percentage of the gelled material in this test formulation system is 35% to 40%, the quartz sand is 55% to 65%, the vinyl acetate-ethylene (VAE) redispersible latex powder is 1.5%, and other additives are appropriate. The reference formula is shown in Table 1.

Reference formula for tile adhesives with different OPC / AC ratios

1.3.2 Ternary system
Ternary system is the addition of gypsum (represented by the code G) on the basis of the binary system, which uses the characteristics of the reaction of the three to generate canadite, so that the system has functions such as rapid hardening and compensation for shrinkage.
In this test, anhydrite from Anhui and β-hemihydrate gypsum from Hubei were selected to study the 6-h tensile bond strength and operable time of tile adhesives at different OPC / AC / G ratios.
In the tested ternary formula system, the mass percentage of the gelling material is 35% to 40%, the quartz sand is 55% to 65%, the vinyl acetate-ethylene (VAE) redispersible powder is 1.5%, and other additives are appropriate. The reference formula is shown in Table 2.

Reference formula of tile adhesive with different OPC / AC / G ratio

2 Results and discussion
2.1 Screening of the basic formula
Because the test period of the drying time is long, in the screening phase of the basic formula, the author first tests the operable time to determine whether the workability of the fast-hard tile adhesive reaches the target requirements.

2.1.1 Binary system

The test results of the 6-hour tensile bond strength and operable time of the binary system test formula are shown in Figure 1.

6-hour tensile bond strength and operable time of the binary system formula

It can be seen from Figure 1 that the operable time of the formula tested by the binary system can meet the requirement of 40 minutes, but only the 6h tensile bond strength of formula 2 # can reach the requirement of 0.5 MPa, which is imported Aluminate cement based CIMENTFONDU is an aluminate-rich system.

2.1.2 Ternary system

The ternary system test formula for the 6-hour tensile bond strength and operable time of the tile adhesive is shown in Figure 2.

6 h tensile bond strength and operable time of ternary system tile adhesive

It can be seen from Figure 2 that only 10 # and 11 # formulas can be operated in less than 40 minutes, and other formulas can meet the requirements of not less than 40 minutes; while only 9 # and 11 # formulas have a 6-hour tensile bond strength. It can meet the requirements of 0.5 MPa, and 9 # and 11 # are based on ordinary portland cement. Considering the convenience of raw materials and the economics of the cost of the formula, the follow-up test uses 9 # formula as the basic formula to study the impact of raw materials on product performance.

2.2 Effect of inorganic cementitious materials

In order to study the effect of inorganic cementitious materials on the performance of tile adhesives, the fixed amount of other raw materials is kept constant, and the aluminate cement content is selected to vary from 4.0% to 10.0% (the total cement mass remains unchanged). (Group A), the amount of anhydrite varies between 2.0% and 6.0% (group B), and the amount of β-hemihydrate gypsum varies between 0 and 2.0% (group C). The test reference formula is shown in Table 3.

Test reference formula of tile adhesive with different inorganic cementitious materials

The operation time of the formulated tile adhesive, the tensile bond strength at 6 hours, and the tensile bond strength after 10 minutes and 20 minutes of standing time were tested. The results are shown in Figure 3. The tensile bond strength of the formulation under several different curing conditions was tested, and the results are shown in Figure 4.

The effect of inorganic cementitious materials on the tensile adhesive strength and operable time of ceramic tile adhesives, and the effect of inorganic cementitious materials on the tensile adhesive strength of ceramic tile adhesives under different curing conditions

It can be seen from Figures 3 and 4:
(1) When the content of aluminate cement TERNAL CC is increased from 4.0% to 10.0%, the 6-hour tensile bond strength of the tile adhesive is significantly improved, and the content is basically about 7.0%. It can meet the requirements of 0.5 MPa; however, the operating time has decreased significantly, from 60 minutes to less than 40 minutes; the tensile bond strength after 20 minutes of drying time has also decreased significantly; with the aluminate cement TERNAL CC content With the increase, the tensile adhesive strength of the tile adhesive after standard curing and thermal curing is increased, and the tensile adhesive strength after water curing is decreased.
(2) When the amount of anhydrite is increased from 2.0% to 6.0%, the operable time of the tile adhesive is shortened; the change trend of other performance indicators is not obvious.
(3) When the content of β-hemihydrate gypsum is increased from 0 to 2.0%, the operable time of the tile adhesive is slightly increased, but the tensile bond strength after 20 minutes of air-drying is reduced; The tensile bond strength after heat curing also decreased.
Within the scope of the study on the changes in the content of several inorganic cementitious materials, the change in the amount of aluminate cement has a significant effect on the 6-hour tensile bond strength and operability time.

2.3 Effects of coagulation modifiers

To study the effects of coagulants and retarders on the performance of tile adhesives, the content of other raw materials was fixed, and the changes of coagulant lithium carbonate from 0.08% to 0.12% (group D) were studied. Performance of tile adhesive when tartaric acid changes from 0.08% to 0.12% (group E). The test reference formula is shown in Table 4. The test results of the operating time, the tensile bond strength at 6 hours, and the tensile bond strength after 10 minutes and 20 minutes of drying time are shown in Figure 5. The tile adhesive is stretched under several different curing conditions. The results of the bond strength test are shown in Figure 6.

Test reference formulations with different amounts of accelerators and retarders, effects of accelerators and retarders on the tensile bond strength and operable time of tile adhesives
Effect of accelerator and retarder on tensile bond strength of tile adhesive under different curing conditions

It can be seen from Figure 5 and Figure 6:
(1) When the content of the coagulant lithium carbonate is increased from 0.08% to 0.12%, the operation time of the tile adhesive is slightly increased, and the stretch viscosity of the 20 minute drying time is increased. The knot strength was significantly improved; the tensile bond strength of the tile adhesive after standard curing and thermal curing did not change significantly, and the tensile bond strength after water curing increased.
(2) When the amount of the retarder tartaric acid is increased from 0.08% to 0.12%, the 6-hour tensile bond strength of the tile adhesive is significantly reduced, and the tensile bond strength after operable time and 20 minutes of standing time is obvious. The tensile adhesive strength of the tile adhesive after thermal curing is obviously improved, and the tensile adhesive strength of the ceramic adhesive after water curing is not significantly changed. Within the range of the researched dosage, the effect of the retarder on the 6-hour tensile bond strength and operable time was more obvious.

2.4 Effect of cellulose ether

In order to study the effect of different cellulose ethers on the performance of tile adhesives, several imported and domestic cellulose ethers were selected for comparison tests, a total of 10 brands.
The performance parameters of different cellulose ethers used in the test are shown in Table 5.

Performance parameters of different cellulose ethers used in comparative tests

The reference formulas for the test of the influence of different cellulose ethers on the performance of tile adhesives are shown in Table 6. The water consumption of this group of test formulas is 22% of the powder quality. However, due to the different water-retaining properties of cellulose ethers and their influence on the water consumption of mortars, individual cellulose ethers, such as tile adhesives formulated by domestic brands D2, have poor workability.

Reference formula for testing tile adhesives with different cellulose ethers

The test results of different cellulose ether tile adhesive test formulas in terms of operation time, 6 h tensile bond strength, and 10 min and 20 min drying time are shown in Figure 7. The test results of the tensile bond strength under different curing conditions are shown in Figure 8.

Effects of different cellulose ethers on the tensile bond strength and operational time of tile adhesives, and different cellulose ethers on the tensile bond strength of tile adhesives under different curing conditions

In Figures 7 and 8, the first 5 samples use HEMC (hydroxyethyl methyl cellulose ether) and the last 5 samples use HPMC (hydroxypropyl methyl cellulose ether). Compare the test results of HEMC and HPMC No significant difference was shown between the two cellulose ethers.
In this test, two products of the same chemical type were selected for brands A, B, and D. Comparing two cellulose ethers of different viscosities under the same brand, it can be seen that the tile adhesive prepared by high viscosity cellulose ether 6 h The tensile bond strength is higher than that with low viscosity, but the operable time and the tensile bond strength after 20 minutes of drying time are lower than those with low viscosity; the reason why the domestic brand D2 has a longer operation time than D1 may be Because D2 is a modified product.
It can be seen from Figures 7 and 8 that different cellulose ethers have different effects on the performance indicators of tile adhesives. Since the author has limited understanding of the specific group content, modification methods and degree of modification of each brand of cellulose ether, it is impossible to Further analysis and comparison.

2.5 The impact of different grades of rubber powder.
From the test results of the previous groups, the tensile bond strength of all tile adhesive test formulations after 20 minutes of air-drying can not reach 0.5 MPa, and many formulations have been cured after immersion in water. Junction strength also does not reach 0.5 MPa. Combining the effects of several different raw materials on the performance of tile adhesives, especially the tensile bond strength after 20 minutes of drying time, the author increased the test of VINNAPAS 8620E based on the optimized formula. The test reference formula is shown in Table 7.

Tile adhesive test formula of different grades of powder

The test results of the tile adhesive test formula, the 6-hour tensile bond strength, and the 10- and 20-minute open-time tensile bond strength test results are shown in Figure 9. The tile adhesive was tested under several different curing conditions. The results of the tensile bond strength test are shown in Figure 10.
As can be seen from Figures 9 and 10, the tensile adhesive strength of the tile adhesive formula doped with VINNAPAS 8620E after operation time, 20 minutes of air-drying time, and tensile adhesive strength after immersion curing have been significantly improved. Among them, the F2 formula containing VINNAPAS 8620E has reached 0.5 MPa, which can meet the requirements of C1F (6 h) grade fast-hardening tile adhesive in the new standard.

Tensile bond strength and operable time of different grades of rubber powder formula tile adhesive
Tensile bond strength of different grades of rubber powder formula tile adhesive under different curing conditions

VINNAPAS 8620E is a ternary copolymerizable redispersible powder recommended by WACKER for C2 grade tile adhesives. It introduces VC (vinyl chloride) groups on the basis of traditional VAE. It is characterized by better hydroponics and air drying. Tensile bond strength after standing time. The test results in this article show that VINNAPAS 8620E also has a better effect on improving the tensile bond strength after water curing and drying time in the fast-setting tile adhesive.

3 Conclusions
(1) The 6-hour tensile bond strength and operable time of tile adhesive are two contradictory performance indicators. Most formulations with a longer operable time always have a lower 6-hour pull. Extension bonding strength.
(2) Compared with anhydrite and β-hemihydrate gypsum, the aluminate cement content in the ternary system has a more significant effect on the 6-hour tensile bond strength and operable time.
(3) In the same range of dosage changes, the retarder has a more significant effect on the operable time and 6 h tensile bond strength than the accelerator, and within the range of the dosage changes studied in this experiment, The amount of the additive can appropriately increase the tensile bond strength and operable time after 20 minutes of air-drying time.
(4) For the products of the same brand, the low viscosity cellulose ether has a longer operating time and a tensile bond strength after 20 minutes of standing time.
(5) VINNAPAS 8620E is a ternary copolymerizable redispersible powder, which can improve the tensile bond strength of ceramic tile after curing and drying time. In this test, VINNAPAS 8620E was used to obtain a 6-hour stretch adhesive Fast-strength tile adhesive with a bond strength and a tensile bond strength of 0.5 MPa after 20 minutes of standing time, and an operating time of more than 40 minutes.


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