Since its industrial production in the 1950s, HDPE welding rods have been widely used in chemical storage tanks, municipal pipelines, marine engineering and other fields due to their high matching with the base material performance and welding strength ≥90% of the base material. In recent years, with the upgrading of blending modification (such as adding carbon fiber and nano-montmorillonite) and welding technology (such as hot air welding and extrusion welding), HDPE welding rods have continued to make breakthroughs in environmental stress cracking resistance (ESCR) and low-temperature toughness, further expanding their application scenarios in extreme environments.
Properties
Molecular structure and basic properties
The molecular chain of HDPE is composed of repeated linear arrangement of -CH₂- units. Its unique structure gives it the following characteristics:
High crystallinity (60% - 80%): The molecular chains are regularly stacked to form a compact crystal structure with a density of 0.941 - 0.965 g/cm³ and a tensile strength of up to 25 - 40 MPa;
Low permeability: The gap between the molecular chains is small, and the permeability coefficient to water vapor and gas is only 1/10 of that of LDPE;
Excellent mechanical properties
High strength and high modulus: Tensile strength of 25 - 40 MPa, elastic modulus of 800 - 1200 MPa, suitable for load-bearing structural parts;
High toughness: Simple beam notched impact strength ≥20 kJ/m², better than PVC;
Creep resistance: Creep strain ≤5% at 80℃ and 1MPa stress, no deformation after long-term use.
Excellent physical and chemical properties
Chemical corrosion resistance: Stable to most acids (such as sulfuric acid, hydrochloric acid), alkalis (such as sodium hydroxide solution, concentration ≤30%), and salt solutions (no swelling after immersion for 1 year), but sensitive to strong oxidizing acids (such as concentrated nitric acid, concentrated sulfuric acid);
Temperature resistance: Continuous use temperature -60℃ to +80℃, brittle temperature -80℃, suitable for low temperature environment;
Electrical insulation: Volume resistivity ≥10¹⁵ Ω·cm, dielectric constant 2.3, suitable for electrical insulation parts.
Accurate welding adaptability
Melting temperature range: 125℃ - 135℃, consistent with the melting characteristics of HDPE substrate (no stratification at welding interface);
Thermal expansion coefficient: 12×10⁻⁵/℃;
Welding strength: Using hot air welding or extrusion welding process, the strength of the welding joint is ≥90% of the parent material, which is better than PVC welding.
Environmental protection and economy
Recyclability: It can be crushed and re-extruded, which complies with the EU RoHS environmental protection directive;
Cost-effectiveness: The price is only 1/5 of stainless steel welding materials, and the service life is up to 20-30 years.
Specific application areas
Chemical and environmental engineering:
HDPE tank and container welding: HDPE tanks used to store corrosive media such as sulfuric acid, hydrochloric acid, and alkali. Welding rods can repair tank cracks, leakage at the pipe joints, or lining damage. The joint strength meets the long-term corrosion resistance requirements (acid and alkali resistance is consistent with the parent material).
Ventilation ducts and exhaust gas treatment components: In the chemical, electroplating and other industries, HDPE welding rods are used to repair sand holes or interface cracks in ventilation ducts to avoid environmental pollution or safety hazards caused by leakage.
Filter plates and separators: HDPE filter plates used in sewage treatment and oil-water separation equipment. Welding rods can repair damaged holes on the surface of the filter plates to restore filtration accuracy and chemical resistance.
Water treatment system:
HDPE pipe and joint repair: HDPE pipes used to transport pure water, sewage or chemical agents. Welding rods can repair cracks caused by installation scratches, aging or external forces to ensure system sealing and durability (stronger water hammer resistance than PVC pipes).
Water tank and water tower parts: HDPE welding rods are used for welding and repairing water tank linings, support frames or joints. Their water resistance and non-toxic properties meet the drinking water hygiene standards (such as GB/T 17219).
Agriculture and irrigation fields:
Agricultural water pipeline repair: HDPE main pipes and branch pipes used in farm irrigation systems. Welding rods can quickly repair cracks caused by agricultural machinery rolling or frozen soil expansion and restore water delivery efficiency (excellent resistance to soil stress corrosion).
Drip irrigation belt and sprinkler irrigation parts: HDPE welding rods are used for welding and repairing drip irrigation belt joints or local repairs of sprinkler irrigation pipes. Their chemical resistance and flexibility can adapt to the complex environment of farmland.
Plastic products processing industry:
Large storage tank and container manufacturing: In the production of large HDPE storage tanks in the chemical and food industries, welding rods are used for edge welding of multi-layer plates or embedded welding of reinforcement ribs to ensure structural strength and sealing.
Injection molded parts welding: Used to fix the metal inserts (such as bolts and nuts) of HDPE injection molded parts to improve the mechanical connection strength of the parts (such as the reinforcement welding of pallets and turnover boxes).
Food and medical equipment:
Food processing pipeline repair: HDPE welding rods that meet FDA standards are used to repair damaged parts of food delivery pipelines to prevent plastic debris from contaminating food and ensure production safety (grease and high-temperature steam resistance is better than PP).
Laboratory equipment welding: Used for welding and repairing HDPE culture dishes, reagent bottles or fume hood parts. Its chemical resistance and non-toxic properties meet the requirements of laboratory environments (such as repairing cell culture box seals).
