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Abstract: Traditional rubber asphalt waterproof coatings have the advantages of good waterproof and anti-seepage properties, strong adhesion, low cost, and good self-healing properties. They are commonly used materials for building roofs, basements, and kitchen and bathroom waterproofing projects. However, they have inherent defects such as high temperature flow, low temperature brittleness, insufficient elasticity, and long-term aging, which make it difficult to adapt to modern building large deformation, high and low temperature alternation, and long-term durability waterproof working conditions. In order to improve the shortcomings of poor temperature stability and limited elasticity of traditional rubber asphalt coatings, this paper uses pre emulsification semi continuous polymerization process to prepare high elasticity styrene acrylic latex, which is used as a polymer modification component to composite modify rubber asphalt waterproof coatings. The influence of styrene acrylic latex dosage on the mechanical properties, elastic deformation, bonding strength, high and low temperature stability, and water penetration resistance of the coating is systematically explored, and the optimal blending ratio is clarified to reveal the synergistic modification mechanism of styrene acrylic latex and rubber asphalt. The experimental results show that styrene acrylic latex can form an interpenetrating network composite structure with rubber asphalt, significantly improving the flexibility, elastic recovery rate, and temperature adaptability of the coating; When the content of styrene acrylic latex is 32%, the comprehensive performance of the coating reaches its optimum, with a fracture elongation of up to 1150%, balanced and stable tensile strength, continuous impermeability under 0.3 MPa water pressure, and significantly improved adaptability to high and low temperature deformation. Research has confirmed that high elasticity styrene acrylic modification can effectively solve the industry pain points of low-temperature brittleness, high-temperature flow, and elastic attenuation of ordinary rubber asphalt coatings, providing technical basis for the engineering application of high adaptability, long service life, and wide temperature range asphalt based waterproofing systems.

1 Introduction

Rubber asphalt waterproof coating is a water-based waterproof system prepared by emulsification, grinding, and composite modification using matrix asphalt, rubber powder, and emulsifier as the main raw materials. With excellent base adhesion performance, micro crack self-healing ability, anti-seepage barrier performance, and economy, it is widely used in civil building roofs, basement baseboards, exterior wall basements, kitchen and bathroom waterproofing, and road and bridge waterproofing and sealing projects. Compared with pure acrylic and polyurethane waterproof coatings, traditional rubber asphalt coatings have high solid content, strong anti-seepage ability, good adaptability to wet substrates, high construction fault tolerance, and are suitable for large-scale foundation waterproofing projects.

However, the pure rubber asphalt waterproofing system has obvious performance shortcomings, which restrict its application in high durability, high deformation, and wide temperature range scenarios. Rubber asphalt coating is prone to softening, flowing, and significant thermal deformation in high-temperature environments. Long term exposure to sunlight can lead to coating slippage, thinning, and surface sticking with dust; Under low temperature conditions, the movement of polymer chains is hindered, resulting in a sharp decrease in the flexibility of the coating and an increase in brittleness. It is highly susceptible to cracking, hollowing, and peeling diseases due to shrinkage and deformation of the base layer. At the same time, the elasticity of ordinary rubber asphalt coating is limited, and it has insufficient adaptability to temperature changes, expansion, and slight settlement deformation of building roofs and exterior wall bases. After long-term service, the integrity of the waterproof system gradually deteriorates, and the risk of leakage significantly increases.

Polymer lotion modification is the mainstream technology to improve the temperature change performance, elastic performance and weather resistance of asphalt coatings. Styrene acrylic lotion has the advantages of both the rigid abrasion resistance and temperature resistance of styrene and the high elasticity, flexibility and adhesion of acrylate. It has excellent film-forming property, outstanding weather resistance and good compatibility with asphalt system. By composite modification of rubber asphalt with high elasticity styrene acrylic latex, an organic polymer elastic network can be constructed within the system to compensate for the shortcomings of insufficient elasticity and poor temperature variability in pure asphalt systems, achieving a synergistic effect of “asphalt anti-seepage+latex toughening”. Based on this, this article prepares high elasticity styrene acrylic latex modified rubber asphalt waterproof coatings with different dosages, systematically studies their mechanical elasticity, bonding performance, impermeability performance, and temperature stability, determines the optimal formula parameters, clarifies the composite modification mechanism, and provides theoretical support for the engineering promotion of high-performance modified asphalt waterproof systems.

2 Experimental section

2.1 Experimental raw materials

The main raw materials for the experiment include matrix emulsified asphalt, rubber powder, self-made high elasticity styrene acrylic latex, anionic emulsifier, stabilizer, defoamer, thickening agent, and deionized water. Among them, high elasticity styrene acrylic latex is prepared by pre emulsification semi continuous polymerization process, optimizing the ratio of soft and hard monomers, improving the elongation at break and elastic recovery performance of the coating film, ensuring low-temperature flexibility and high-temperature stability; The rubber powder adopts fine activated rubber powder to improve the interface compatibility with asphalt and styrene acrylic latex; All types of additives are suitable for water-based asphalt systems, ensuring storage stability and ease of construction.

2.2 Sample Preparation Process

Firstly, pour emulsified asphalt, activated rubber powder, and stabilizer into the mixing kettle in proportion, stir evenly at low speed, and prepare a stable rubber asphalt base material; Subsequently, high elasticity styrene acrylic latex with different dosages (20%, 26%, 32%, 38%) was added in groups and stirred at a constant speed and low speed to avoid high-speed shear emulsification; Add defoaming and thickening agents in sequence to adjust the viscosity and workability of the system, ensuring that the coating is uniform, fine, particle free, oil free, and non layered. Evenly apply the prepared modified coating onto the standard template, forming it in two stages to ensure uniform coating thickness. Cure at room temperature for 7 days, and conduct various performance tests after the coating is completely formed and stable.

2.3 Performance Testing Methods

Mechanical elasticity test: According to the general testing standards for waterproof coatings, test the tensile strength, elongation at break, and elastic recovery rate of the coating film under different latex content, and evaluate the deformation adaptability of the coating film;

Interface bonding performance testing: testing the bonding strength between the coating and the cement mortar base, evaluating the base adaptation and anti detachment ability;

Anti permeability performance test: using water pressure anti permeability test, maintaining constant pressure under 0.3 MPa water pressure conditions, observing the permeability and leakage of the coating film;

High and low temperature stability testing: Conduct high temperature heat resistance and low temperature bending tests separately to evaluate the coating’s ability to resist flowing and brittle cracking;

Storage stability test: Observe the static stratification, sedimentation, and emulsion breaking of different formula systems to evaluate the stability of the formula.

3 Experimental results and analysis

3.1 Effect of styrene acrylic latex dosage on the elastic properties of coating film

The experimental results indicate that the dosage of styrene acrylic latex has a significant impact on the elastic properties of the coating. The unmodified pure rubber asphalt coating has a low elongation at break and limited deformation capacity, and is prone to cracking under slight deformation of the base layer. As the dosage of styrene acrylic latex gradually increases, the internal elastic polymer network of the system continues to improve, and the flexibility and tensile deformation ability of the coating film continue to improve. When the latex content reaches 32%, the comprehensive elastic performance of the system is optimal, with a coating fracture elongation rate of up to 1150%, possessing a super large deformation and stretching ability, which can perfectly adapt to the expansion, settlement, and micro crack deformation of roofs and exterior wall substrates, fundamentally avoiding rigid cracking of the coating.

When the latex content is less than 32%, the elastic polymer network is sparse and lacks continuity, and the improvement effect of modification is limited. The coating still has problems of low-temperature brittleness and insufficient elasticity; When the dosage exceeds 32%, the proportion of high polymer in the system becomes too high, the proportion of asphalt matrix decreases, the impermeability and bonding strength of the coating slightly decrease, and the viscosity of the system increases, the leveling performance of construction decreases, the cost-effectiveness decreases, and the comprehensive performance shows negative growth. Therefore, 32% is the optimal blending ratio for high elasticity styrene acrylic latex.

3.2 Effects on tensile strength and bonding performance

The introduction of high elasticity styrene acrylic latex can significantly optimize the flexibility and balance of the coating without compromising the structural strength of the system. Pure rubber asphalt coating has high bonding strength but poor toughness, and is prone to brittle fracture under stress; The single styrene acrylic lotion coating has good elasticity but weak anti-seepage and base anchoring capacity. After composite modification, the styrene acrylic elastic network forms a complementary and synergistic system with the rubber asphalt matrix, and the tensile strength of the coating is stable and controllable. At the same time, the interface bonding performance is excellent, which can firmly adhere to cement mortar, concrete, and old asphalt substrates, and is not prone to hollowing, delamination, and edge curling defects. It is suitable for complex working conditions such as renovation of new and old roofs and construction of wet base layers.

3.3 Impact on water resistance and impermeability performance

Rubber asphalt itself has the advantage of dense waterproofing and anti-seepage, but pure asphalt coating is prone to micro cracks after elastic deformation, forming permeation channels. After modification with styrene acrylic latex, the polymer segments fill the micro pores of asphalt, repair the micro defects of the system, and form a more continuous and dense film. The optimal ratio sample is impermeable for a long time under high water pressure conditions of 0.3 MPa, with excellent impermeability grade. The core mechanism is that the asphalt matrix bears the main waterproof and anti-seepage function, and the styrene acrylic elastic network bears the deformation buffering and crack closure function. During the deformation process, the coating film will not produce a continuous water seepage channel, achieving a high stability waterproof effect of “deformation without water seepage and tensile without cracking”.

3.4 Optimization effect of high and low temperature stability performance

Poor thermal stability is the most prominent engineering defect of traditional rubber asphalt coatings. Under high temperature conditions, pure asphalt coatings are prone to softening and flowing, surface stickiness, and uneven thickness; Asphalt molecular chains freeze and the coating becomes stiff and brittle in low-temperature environments. After introducing high elasticity styrene acrylic latex, the heat-resistant polymer segments can effectively bind the high-temperature flow of asphalt molecules, suppress the high-temperature flow and thermal deformation of the coating film; Under low temperature conditions, the flexible acrylic chain segment maintains high elasticity, avoiding brittle cracking and bending cracking of the coating. The modified coating achieves high temperature non flowing and low temperature non brittle cracking, greatly expanding the temperature range and adapting to the seasonal temperature variation conditions in the north and south regions.

4. Analysis of Composite Modification Mechanism

The high elasticity styrene acrylic latex and rubber asphalt system can form a polymer asphalt interpenetrating composite network structure, achieving complementary and synergistic performance enhancement. Rubber asphalt, as a continuous phase, provides excellent waterproof and anti-seepage properties, substrate bonding, and micro self-healing, ensuring basic waterproofing function; Highly elastic styrene acrylic latex serves as a dispersed reinforcement phase, uniformly intercalating within the asphalt matrix to form a flexible elastic network skeleton.

Under the effects of grassroots deformation, external tension, and temperature induced stress, the styrene acrylic elastic network preferentially bears the deformation stress, absorbs deformation energy through molecular chain stretching, tension, and rebound, buffers stress concentration in the matrix, and avoids brittle cracks in the asphalt matrix; In a static state, the elastic network quickly rebounds and resets, maintaining the complete and dense structure of the coating. At the same time, styrene acrylic polymer can fill the micro pores of asphalt systems, optimize interface compatibility, reduce system defects, improve the overall density, weather resistance, and durability of coatings, and solve the technical bottlenecks of traditional asphalt coatings such as insufficient elasticity, poor temperature variability, and easy cracking at the micro level.

5 Advantages and Applicable Scenarios of Engineering Applications

Compared with ordinary rubber asphalt coatings and pure acrylic waterproof systems, high elasticity styrene acrylic modified rubber asphalt waterproof coatings have multiple engineering advantages: firstly, they have ultra-high elastic deformation ability, with a 1150% elongation at break that can adapt to large deformation base layers and excellent crack resistance; The second is the wide temperature range stability performance, which completely improves the common problems of high-temperature flow and low-temperature brittle cracking of asphalt coatings; The third is to balance the anti-seepage and bonding performance, taking into account the advantages of high impermeability of asphalt and high adhesion of polymers; The fourth is strong adaptability in construction, with water-based environmental protection, wet construction, compatibility between new and old base layers, and good adaptability for renovation.

This material can be widely used in the renovation of asphalt base surfaces on old roofs, overall waterproofing of new building roofs, flexible waterproofing of basement ceilings, waterproofing of heavy water areas in kitchens and bathrooms, waterproofing and sealing of bridge decks, flexible protection of exterior wall mortar, etc. It is particularly suitable for exposed waterproofing systems with large temperature differences, easy deformation of base layers, and high durability requirements.

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