▶ Main Materials and Classifications

1. Material Types (Commonly Used)

2. Structural and Installation Classification

**Embedded Type (Type 651/652):** The central rib is embedded in the joint, and both sides are embedded in concrete. Suitable for waterproofing the main structure of expansion joints, such as tunnels, dams, and basements.

**External Adhesive Type (Back-Adhesive Type):** Attached to the water-facing side of the concrete and welded to the waterproofing membrane. Used for auxiliary waterproofing, such as the water-facing side of subways and underground utility tunnels.

**Grouting Type:** Contains built-in grouting channels, allowing for later injection of polyurethane/epoxy resin. Suitable for important projects (such as nuclear power plants and large reservoirs) providing secondary waterproofing protection.

**Steel-Edged Composite Type:** Plastic body + steel edge, enhancing anchoring and tensile strength. Used for structures with high water pressure and large deformation.

▶ Core Performance Characteristics

Advantages

**Strong Corrosion Resistance:** Resistant to acids, alkalis, salts, and chemical media; long service life (up to 50+ years for underground projects).

Easy Construction: Lightweight, easy to cut, and uses heat-fusion butt joints for high efficiency.

Economical: Lower cost than rubber waterstops, offering excellent value.

Reliable Waterproofing: Dense material; with proper installation, stable waterproofing performance.

Environmentally Friendly and Safe: Non-toxic and odorless; suitable for drinking water projects (compliant with NSF 61 standards).

Installation Key Points and Precautions

▶ Installation Process

1. Preparation: The base layer should be flat, dry, and free of oil stains. Mark the lines according to the design.

2. Positioning: For embedded waterstops, ensure the center is aligned and the fixed spacing is **≤50cm**. Avoid twisting or flipping. Round off corners (radius ≥100mm).

3. Joints: Use heat fusion butt welding. The overlap length should be ≥10cm to ensure a firm and waterproof seal.

4. Pouring: Vibrate the concrete until it is dense. Avoid direct contact between the vibrator and the waterstop.

5. Curing: Prevent exposure to sunlight and sharp objects. Protect the finished product.

Key Prohibitions

**Do not use waterstops made from recycled materials, as this will affect durability.**

**Leaks are likely if joints are not properly heat-fused or if adhesive tape is used.**

**Off-center waterstops will cause uneven stress and waterproofing failure.**

Introduction to the Manufacturing Process of Plastic Waterstops

Plastic waterstops are typically made from polymers such as polyvinyl chloride (PVC), high-density polyethylene (HDPE), and ethylene-vinyl acetate copolymer (EVA). The manufacturing process mainly includes the following steps:

▶ I. Raw Material Preparation and Formulation Design

1. Raw Material Selection: Based on the performance requirements of the waterstop (such as corrosion resistance, elasticity, strength, etc.), select a suitable polymer resin. Simultaneously prepare stabilizers (such as calcium-zinc stabilizers to prevent aging and decomposition of the plastic during processing and use), plasticizers (such as dioctyl phthalate to increase the flexibility of the plastic), fillers (such as calcium carbonate to reduce costs and improve performance), lubricants (such as stearic acid to facilitate material flow during processing), and other additives.

2. Formulation Design: Determine the optimal proportions of each component through experimentation. For example, when producing PVC waterstops, PVC resin typically accounts for 60%-70%, plasticizer for 20%-30%, and stabilizers and other additives for approximately 5%-10% to balance the elasticity, strength, and aging resistance of the waterstop.

▶ II. Raw Material Mixing: 

Add the resin and various additives to a high-speed mixer according to the formulation proportions and mix at a specific temperature (usually 80-120℃). The purpose of high-speed mixing is to uniformly disperse the components and form a homogeneous premix. Mixing time is generally 10-20 minutes. After mixing, the material needs to be cooled to approximately room temperature to prevent premature chemical reactions during subsequent processing.

▶ III. Granulation 

If extrusion molding is used to produce waterstops, the mixed material usually needs to be granulated first. The premix is added to a granulator, where, under heating (temperature varies depending on the raw material; for PVC, it is generally 160-180℃) and shearing action, the material melts and is extruded, then cut into granules by a pelletizer. Granulated material is easier to transport and process in the extruder and improves the stability of subsequent extrusion molding.

▶ IV. Extrusion Molding

1. Equipment Preparation: A dedicated plastic extruder is used. The screw and barrel of the extruder need to be selected and adjusted according to the characteristics of the raw material to adapt to the processing requirements of different plastics.

2. Melt Extrusion: The prepared granules or directly mixed powder are added to the extruder hopper. The material undergoes heating (barrel temperature is controlled in stages; for example, in PVC waterstop extrusion, the front section of the barrel is approximately 140-160℃, the middle section 160-180℃, and the rear section 170-190℃), compression, and shearing within the extruder, gradually melting into a viscous flow state.

3. Molding Die: The molten material enters the molding die through the extruder die head. The die shape matches the cross-sectional shape of the waterstop (e.g., embedded type, back-attached type, etc.). Within the die, the material is shaped into the desired waterstop shape.

4. Cooling and Shaping: The high-temperature waterstop blank extruded from the die enters a cooling water tank or cooling and shaping sleeve. Water cooling rapidly solidifies the plastic, forming a waterstop with specific dimensional accuracy and shape. The cooling water temperature is generally controlled between 20 and 40°C, and the cooling time depends on the thickness and size of the waterstop, usually 1 to 3 minutes.

Testing standards and test reports

5.3 Physical and Mechanical Properties

The physical and mechanical properties of plastic waterstops should meet the requirements of Table 3.

Table 3 Physical and mechanical properties of plastic waterstops