▍I. Core Product Characteristics

Dual Water-Stopping Mechanism: In the dry state, the rubber's elasticity ensures a tight seal with the concrete joints, achieving initial sealing. Upon contact with water, the internal expansion components react rapidly, expanding uniformly to fill the gaps, forming a secondary water-stopping barrier. The expansion pressure counteracts the water pressure, eliminating seepage channels.

Excellent Mechanical Properties: After vulcanization and setting, it possesses high tensile strength and tear resistance, with a Shore A hardness of 40-60 degrees and an elongation at break ≥300%. It can adapt to slight settlement and shrinkage deformation of concrete, and is not easily damaged or detached.

Controllable Slow Expansion Performance: The expansion rate ≤50% of the design value within 72 hours before immersion, preventing excessive expansion from cracking the concrete. The final expansion ratio is stable, with no swelling or detachment, ensuring a long-lasting water-stopping effect.

Weather and Media Resistance: With the addition of special anti-aging agents and anti-corrosion components, it shows no cracks at -20℃ and maintains stable performance at 70℃. It is resistant to weak acids, weak alkalis, and groundwater corrosion, and will not age or fail with long-term outdoor use.

High dimensional accuracy: The vulcanizing mold is integrally formed, with a cross-sectional dimensional tolerance of ±0.5mm, a straightness deviation of ≤1mm/m, a smooth surface, and clear edges and corners, which can be used to precisely fit the regular gaps in engineering projects.

▍II. Product Specifications and Models

1. Standard Cross-Section Dimensions (mm, custom shapes available)

20×30, 30×40, 30×50, 40×40, 40×60, 50×50 (Width × Height, suitable for construction joints/expansion joints of different widths)

2. Standard Length

2m/piece, 5m/piece (length can be customized according to project requirements)

3. Model Classification (based on final expansion ratio at room temperature, core selection indicator)

▍III. Core Application Scenarios

It is suitable for sealing regular and flat construction joints, deformation joints, and settlement joints in various buildings, municipal projects, and water conservancy projects. It is not applicable to irregular and narrow gaps or patching scenarios (for such scenarios, putty-type sealing strips are preferred). Typical application fields:

Underground engineering: basement floor, exterior wall, and roof construction joints of subway tunnels and underground pipe galleries;

Water conservancy projects: structural joints of reservoirs, dams, water tanks, and sluices, construction joints of sewage treatment plants;

Municipal engineering: construction joints of comprehensive pipe galleries and urban bridges' piers, construction joints of rainwater and sewage pumping stations;

Industrial and civil buildings: construction joints of large shopping malls and office buildings' underground parts, sealed joints of civil defense projects.

▍IV. Core Product Advantages

Stable structure, high durability: Through high-temperature vulcanization and cross-linking, the rubber molecules form a stable three-dimensional structure. Without external force compression, it is unlikely to deform. The shelf life is up to 18 months (sealed storage), which is much longer than that of the putty-type waterstop strips.

Wide adaptability, resistance to deformation: Excellent elasticity and extensibility enable it to adapt to minor deformations of concrete caused by temperature and settlement, preventing the re-opening of cracks and water seepage.

Convenient construction, precise positioning: Moderate hardness allows for direct adhesion and fixation on the concrete cracks, without shifting. No additional complex processing is required, making it suitable for batch standardized construction.

Controllable performance, safe and reliable: The expansion ratio is clearly defined. The slow expansion performance complies with national standards, and it will not cause damage to the concrete structure due to rapid expansion. The waterstop effect can be quantified and detected.

Environmentally friendly, non-toxic, compatible with concrete: The raw materials are all environmentally friendly polymer materials. There is no odor or harmful substances. Good adhesion to concrete, no interface cracks.

▶ The complete production process of the water-expanding waterstop strip (PZ type)

(Standard for implementation: GB/T 18173.3 "Polymer Waterproofing Materials - Part 3: Water-Gluing Rubber", The core difference from the putty-type PN strips: requires high-temperature vulcanization for final shaping, higher hardness, strong dimensional stability, excellent mechanical properties, suitable for sealing of regular gaps)

The product type waterstop strip is made with natural rubber / nitrile rubber as the elastic base, combined with water-absorbing resin, bentonite, vulcanizing agent, accelerator and other additives. It is processed through the core manufacturing process of batching → mixing → cutting into sheets → vulcanization molding → cooling → trimming → quality inspection → packaging. Throughout the process, precise control of vulcanization temperature and time is required to ensure the final shaping of the product and the dual performance of water expansion and elastic sealing. The complete process and key points are as follows:

I. Raw Material Preparation and Pre-treatment (Strictly control raw material purity and adapt to the vulcanization process)

1. Core raw materials (distribute according to function ratios, different from putty type)

Elastic matrix: Natural rubber (NR), nitrile rubber (NBR, selected for oil-resistant scenarios), accounting for 40%-60%, ensuring elasticity and mechanical strength after vulcanization

Expansion system: Sodium-based high-hygroscopic resin (main expansion source, water-resistant and insoluble), sodium-based bentonite (auxiliary expansion + regulating retardation), accounting for 20%-30%

Vulcanization system: Sulfur (main vulcanizing agent), accelerator (CZ/DM, accelerating vulcanization), zinc oxide / stearic acid (activator), accounting for 3%-8% (precisely controlled to avoid over-vulcanization / under-vulcanization)

Reinforcement / additive system: High-maintenance carbon black (N330/N550), calcium carbonate (filler), antioxidant (4010NA, resistant to aging), plasticizer (phthalate, enhancing flexibility)

2. Raw material pre-treatment (avoiding impurities affecting the vulcanization effect)

Rubber blocks: Cut into 5-10cm small pieces using a cutting machine, soften at room temperature (40℃ for winter), without lumps or impurities

Powdered raw materials (carbon black, bentonite, calcium powder, etc.): Dry and dehydrate (water content ≤ 0.3%), pass through 100-120 mesh sieve, remove hard lumps

Hygroscopic resin: Store separately to avoid moisture absorption and lumps formation; vulcanizing agents / accelerators store separately to prevent premature reaction

3. Precise batching

Weigh according to the formula proportion using an electronic scale (accuracy ±0.05%), place in batches (powdered materials mixed evenly, liquid additives placed separately, add the vulcanization system last), eliminate batching errors to prevent vulcanization failure.

II. Mixing Process (Stage-by-stage mixing / compounding, avoiding degradation of water-absorbing resin at high temperatures)

Mixing is the core for ensuring the uniformity of the material. The temperature is strictly controlled at ≤ 90℃ throughout the process (as water-absorbing resins are prone to degradation at high temperatures and lose their expansion properties). The process is completed in 3 stages, starting with the use of a compounding machine (high efficiency), followed by the open-mixing machine to produce sheets:

Stage 1: Rubber plasticization: The compounding machine is preheated to 60-70℃, rubber blocks are added, and compounding lasts for 5-8 minutes until the rubber is fully plasticized and the surface is smooth, forming the base of the rubber compound.

Stage 2: Adding fillers / additives: Carbon black, calcium carbonate, antioxidants, and plasticizers are added successively, and compounding lasts for 6-10 minutes with the temperature controlled at 70-80℃. The powder is completely dispersed in the rubber compound without white spots.

Stage 3: Adding expansion system + vulcanization system: Water-absorbing resin and bentonite are first added to the compounding machine for 3-5 minutes; finally, vulcanization agent and accelerator are added and compounding is carried out quickly for 2-3 minutes at a temperature ≤ 90℃, and the material is immediately discharged (to prevent premature reaction of the vulcanization system).

Sheet cooling: The rubber compound after compounding is fed into the open-mixing machine, the roller temperature is 50-60℃, and the sheet is pressed into a uniformly thick rubber sheet (thickness is adjusted according to the vulcanization mold), naturally cooled to room temperature (around 25℃), and left to stand for 4-6 hours (for aging, allowing the rubber compound molecules to relax).

III. Vulcanization (Core Process, Determines Product Hardness / Strength / Dimensional Stability)

Vulcanization is the most crucial difference between the product type waterstop strip and the putty type. Through high temperature and high pressure, the rubber molecules undergo cross-linking reactions to achieve shaping, while ensuring that the expansion system is tightly combined with the rubber matrix. Commonly, flat vulcanization machines are used for batch production, while some special-shaped products use injection vulcanization machines:

Mold Preparation: Clean the special mold for the waterstop strip (common sizes: 20×30, 30×40, 50×50 mm rectangles, or custom shapes can be made). Coat the inner wall of the mold with a release agent (to avoid mold sticking), and preheat to 100-110℃.

Material Loading: Cut the cooled sheet according to the weight of the mold cavity, precisely load it into the mold, ensuring that the rubber material fills the cavity without any gaps.

High Temperature and High Pressure Vulcanization:

Vulcanization Parameters: Temperature 140-150℃, Pressure 15-20 MPa, Time 8-15 minutes (adjust according to the cross-sectional thickness of the product: for every 10 mm increase in thickness, the vulcanization time increases by 2-3 minutes)

Core Requirements: Maintain constant temperature and pressure, avoiding excessive high temperatures (over-vulcanization, resulting in brittle rubber) or excessively low temperatures (under-vulcanization, causing the rubber to become sticky, insufficient hardness, and prone to deformation)

Demolding and Removal: After the vulcanization time is completed, the flat vulcanization machine releases pressure and opens the mold, removes the formed waterstop strip, and removes the excess material from the mold (initial trimming).

IV. Cooling and Finishing

Cooling: Allow the water-stretched waterproof strip to cool naturally (or by air cooling, and avoid water cooling to prevent sudden cooling and internal stress) to room temperature. The cooling time should be ≥ 30 minutes to ensure the product dimensions are completely stable and to prevent deformation in the later stage.

Fine trimming: Use a trimming machine / utility knife to remove the water-stretched overhangs and burrs on the product surface, ensuring a smooth surface, clear edges, no missing corners, and no burrs (the cross-sectional dimensions after trimming should meet the standard requirements).

V. Quality Inspection (Comprehensive Testing, Strictly Controlled Performance in Accordance with National Standards, Higher than the Inspection Standards for Putty Type)

Testing is conducted in accordance with the GB/T 18173.3 standard for each batch. The inspection covers appearance + dimensions + physical and mechanical properties + expansion performance. Non-conforming products are directly eliminated. The inspection items and standards are as follows:

1. Appearance Inspection

The surface is uniformly black and smooth, without bubbles, cracks, missing corners, impurities, and the edge trimming is flat, with no obvious overflow marks.

2. Dimension Inspection

The cross-sectional size tolerance is ±0.5mm, the length tolerance is ±20mm (conventional length 2m/5m), and the straightness deviation is ≤1mm/m.

3. Core Physical Mechanical Properties (Key Indicators for Product Type, No Such Requirements for Putty Type)

Hardness (Shore A): 40-60 degrees (conventional), tolerance ±5 degrees

Tensile Strength: ≥3.0MPa

Tensile Elongation Rate: ≥300%

Low Temperature Flexibility: No cracks at -20℃

Aging Resistance: After 70℃×168h aging, the tensile strength retention rate is ≥80%, and the elongation rate retention rate is ≥70%