Abstract: Conventional water-borne acrylic lotion building sealant is widely used in the field of building joint sealing due to its advantages of green environment protection, convenient construction, wide range of bonding substrates, and outstanding cost performance. However, pure acrylic acid and styrene acrylic acid systems generally have inherent defects of poor low-temperature adaptability. In low-temperature environments, the movement ability of latex segments decreases significantly, the modulus of the adhesive film increases significantly, and problems such as hardening, brittle cracking, and elastic failure are prone to occur, which cannot meet the long-term sealing requirements of low-temperature areas in the north and outdoor high and low temperature alternating working conditions. At the same time, ordinary acrylic sealant has insufficient surface hydrophobicity and limited weather resistance. Long term outdoor service is prone to failure phenomena such as water absorption swelling, powdering cracking, and adhesive detachment. In view of the industry pain points of traditional acrylic sealant, such as high brittleness at low temperature, weak weather resistance, and insufficient hydrophobic and moisture-proof ability, this master’s thesis adopts the synergistic copolymerization modification technology of organic silicon and organic fluorine functional monomer to prepare silicone fluorine composite modified acrylic lotion, which is used as a film forming substrate to develop low-temperature water-based building sealant. Systematically explore the influence of the ratio of soft and hard monomers, the amount of silicon fluoride functional monomers, and the polymerization process parameters on the particle size distribution, system stability, minimum film forming temperature, and rheological properties of the lotion, comprehensively characterize the low temperature mechanical properties, hydrophobic properties, cold and heat cycle resistance, artificial aging resistance, and immersion bonding stability of the modified lotion film, clarify the multiple action mechanism of the toughening modification of silicon fluoride group, low surface energy hydrophobic, weather stability, analyze the technical problems such as polymerization instability, lotion gel, cost increase caused by the excess of silicon fluoride monomers, complete the system optimization through the formula orthogonal test, and finally obtain a water-based sealant with excellent low-temperature elasticity, high weather resistance, and good storage stability system, This provides important experimental basis and theoretical support for the development and engineering application of high-performance water-based acrylic sealant for low-temperature environments.
1. Research background and significance of topic selection
Water based acrylic building sealant has become the mainstream material for indoor and outdoor joint sealing, waterproof filling, and detail treatment in civil buildings due to its comprehensive advantages of no VOC pollution, strong construction operability, secondary coating, and good adhesion to substrates such as cement, metal, and glass. However, the molecular chain of the traditional unmodified acrylic acid lotion is too rigid, the low temperature flexibility is poor, and the glass transition temperature is generally high. Under the low temperature environment, the polymer chain segments are frozen, and the adhesive film changes from a high elastic state to a glass state, with a sharp decline in elasticity and a significant increase in hardness. When the construction joints undergo slight displacement deformation due to low-temperature shrinkage, ordinary acrylic sealant cannot adapt to the deformation, and is prone to engineering failure problems such as brittle cracking, interface peeling, water seepage and air leakage. This seriously limits the application range of water-based acrylic sealant in high-altitude areas, outdoor exposed joints, and winter construction scenarios.
In addition, conventional acrylic adhesive films have high surface energy, limited hydrophobic and moisture-proof properties, and are prone to water absorption and penetration under long-term exposure to rain and condensation conditions, resulting in softening of the adhesive layer, decreased cohesive strength, and interface bonding failure. At the same time, their UV aging resistance is insufficient, and long-term outdoor use is prone to yellowing, powdering, and cracking. Organic fluorine and silicone monomers have extremely low surface energy, excellent low softness, weather stability, hydrophobic and moisture-proof properties, and are ideal functional monomers for low temperature performance and weather resistance of modified acrylic lotion. Based on this, this paper uses silicon fluoride synergistic copolymerization modification technology to optimize the molecular structure of ordinary acrylic lotion, build a modified lotion system with low temperature flexibility, high hydrophobicity and aging resistance, specifically solve the technical bottleneck of low temperature brittleness and insufficient weather resistance of water-based sealant, which has important engineering value in broadening the temperature range of water-based acrylic sealant and improving the outdoor durability service performance.
Analysis of Core Research Results and Modification Mechanisms
2.1 Optimization mechanism of silicon fluoride modification on low temperature film forming performance of lotion
The results show that the molecular chain of silicone monomer is extremely flexible, with large bond energy and low rotational barrier. The introduction of acrylic acid molecular chain into copolymerization can significantly increase the mobility of polymer chain segments, effectively reduce the glass transition temperature and minimum film forming temperature of lotion, and significantly improve the low-temperature film forming property and flexibility of adhesive film; Organic fluorine monomers have extremely low surface energy and excellent molecular stability, which can be enriched and arranged on the surface of latex films, further optimizing the low-temperature mechanical stability of the film and suppressing the phenomenon of low-temperature hardening and brittleness. The silicon fluoride binary synergistic modification can effectively break the freezing defect of ordinary acrylic lotion at low temperature chain segment, keep the adhesive film in a good high elastic state under low temperature environment, have excellent deformation following ability, and solve the core problem of low-temperature cracking of acrylic sealant from the molecular structure level.
2.2 Improvement of hydrophobic and water-resistant adhesion performance of silicone fluorine groups in sealants
The silicofluoride modified groups have extremely strong hydrophobic and oil repellent properties. During the film forming process of the lotion, the silicofluoride groups with low surface energy will spontaneously migrate and enrich to the surface of the film, forming a dense hydrophobic protective layer, greatly reducing the surface energy of the film, and effectively blocking the penetration and diffusion of water. The immersion performance test results show that the water absorption rate of silicone fluorine modified sealant is significantly lower than that of ordinary acrylic sealant. After long-term immersion, the adhesive film does not turn white, soften, or swell, and the retention rate of interface bonding strength is greatly improved. This effectively solves the engineering shortcomings of poor water resistance and easy debonding of traditional water-based sealant, and significantly improves the durability and stability of sealing under humid conditions.
2.3 Enhancement effect of modified system on the aging resistance and high and low temperature cycling performance of sealant
The bond energy of organic silicon and organic fluorine chemical bonds is much higher than that of ordinary carbon carbon bonds, and they have excellent resistance to UV and thermal oxidative aging, which can greatly improve the weather stability of acrylic adhesive films. The artificial accelerated aging test shows that the silicone fluorine modified sealant has no obvious yellowing, powdering, or cracking after long-term UV irradiation and high-temperature aging, and the mechanical performance degradation rate is extremely low; The high and low temperature alternating cycle test confirms that the modified sealant can repeatedly adapt to thermal expansion and contraction deformation, with excellent elastic recovery rate. After cyclic service, there are no problems of brittle cracking, delamination, or failure, greatly expanding the service temperature range of water-based acrylic sealant and adapting to complex outdoor climate conditions.
2.4 Performance balance law and polymerization stability issues of silicon fluorine monomer dosage
The research clarified the remarkable performance balance of the silicon fluoride modification system: an appropriate amount of silicon fluoride monomer can achieve excellent low-temperature toughening, hydrophobic and weather resistant modification effects, lotion polymerization is stable, particle size is uniform, and there is no gel defect; However, due to the special surface activity and strong hydrophobicity of silicofluoromer monomer, excessive addition will significantly improve the phase interface difference of the polymerization system, leading to the decline of monomer copolymerization compatibility, uneven nucleation of lotion, and easy to cause polymerization gel, particle size increase, system instability, storage stratification and other problems. At the same time, the high cost of raw materials for high content silicone fluorine monomers will significantly increase the industrial production cost of sealants. In this paper, the gradient test is used to precisely lock the optimal dosage range of silicon fluoride monomer, maximize the low-temperature performance and weather resistance, ensure the stability of lotion polymerization and product economy, and achieve the balance between performance and cost.
3 Shortcomings and Optimization Directions of Existing Technologies
This study points out that although silicone fluorine modification can significantly improve the low-temperature and weather resistance of acrylic sealant, the system still has certain limitations. On the one hand, excessive silicon fluoride components tend to cause the surface energy of lotion to be too low, resulting in a slight decline in the wetting and bonding properties of sealant to some polar substrates; On the other hand, the silicone fluorine modified acrylic system is still a water dispersed film-forming system. Compared with chemically crosslinked polyurethane and silicone sealants, there is still a gap in the ultimate displacement ability, which is not suitable for joints in ultra large deformation structures. In addition, the storage stability and construction adaptability of high silicon fluorine content systems still need to be further optimized. In response to the above issues, the paper proposes to further balance the adhesive performance, low-temperature elasticity, and storage stability through fine-tuning of monomer ratios, compounding of functional polar monomers, and optimization of additive systems.
4 Research conclusions and application value
Research has confirmed that silicon fluorine composite modification can effectively reduce the low-temperature modulus of acrylic adhesive film, solve the pain points of traditional water-based sealants such as low-temperature hardening, brittle cracking, and poor deformation adaptability, and significantly improve the hydrophobic, moisture-proof, water-resistant, adhesive, and high and low temperature cyclic aging properties of the sealant. The research improved the design theory and formula system of low-temperature acrylic modified lotion, provided detailed test data and technical reference for the research, development, optimization and industrial application of water-based building sealant in cold regions and outdoor complex working conditions, and effectively expanded the engineering application scenarios of green water-based acrylic sealing materials.
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Post time: Sep-21-2026