1. Material chemical properties: inherent advantages of molecular structure
Polyurethane polymer chain design
Soft and hard segment microphase separation: Polyurethane is composed of flexible soft segments (polyether/polyester) and rigid hard segments (isocyanate) alternating to form a microphase separation structure. This structure gives the material the characteristics of high elasticity and high strength, while effectively resisting chemical erosion.
High crosslinking density: The urethane bonds in the hard segment form a three-dimensional network structure, which significantly improves solvent resistance and creep resistance, and reduces molecular chain breakage caused by oils or acids and alkalis.
Key to oil resistance: Chemical inertness of polyester polyurethane
The ester bond of polyester polyurethane has high polarity and poor compatibility with mineral oil and lubricating oil, so it is not easy to swell or dissolve. Experiments show that its volume change rate after immersion in engine oil for 1000 hours is less than 5%, which is much lower than that of rubber materials (chloroprene rubber can reach 20%).
Adding oil-resistant additives (such as fluorocarbon compounds) can further block the penetration of oil molecules and extend the service life.
2. Anti-aging mechanism: multiple protective barriers
Anti-ultraviolet (UV) and ozone
The UV absorbers (such as benzotriazoles) in PU materials can absorb ultraviolet rays with a wavelength of 290-400nm to prevent photo-oxidative degradation. After 10 years of outdoor use, its tensile strength retention rate is still >80%.
The saturated bond structure in the polyurethane molecular chain is not sensitive to ozone (O₃), avoiding the common cracking problem of rubber.
Heat aging resistance
The decomposition temperature of polyurethane is usually >200℃, and it can withstand high temperatures of 110℃ in a short period of time. By adding heat stabilizers (such as hindered phenols), high-temperature oxidation reactions can be inhibited, so that the mechanical property attenuation rate of the material is <1%/year when it works continuously at 80℃.
Hydrolysis resistance (polyether type advantage)
The ether bond (-C-O-C-) of polyether polyurethane is more resistant to hydrolysis than the ester bond of polyester type, and the hydrolysis rate is reduced by more than 50% in a humid environment, which is suitable for high humidity conditions.
3. Process and structural enhancement: a breakthrough from laboratory to industrial level
Reinforcement layer design
Glass fiber/steel wire core: As a tensile layer, it bears the main mechanical stress and protects the polyurethane matrix from molecular chain breakage caused by continuous stretching. For example, the tensile strength of glass fiber reinforced PU synchronous belt can reach 2000MPa, extending fatigue life.
Surface coating technology: Some high-end products use PTFE (polytetrafluoroethylene) coating, which reduces the friction coefficient to 0.1, reduces wear and blocks oil and dirt adhesion.
Manufacturing process optimization
Thermosetting molding process: Through high temperature and high pressure curing, the polyurethane molecular chain is more thoroughly cross-linked, and the density and chemical stability are improved.
Precision tooth processing: The meshing error between the tooth surface and the pulley is less than 0.1mm, which reduces material fatigue caused by local stress concentration.
- Daily inspection and cleaning
Weekly inspection items:
Surface condition: Check for cracks, cuts, oil accumulation or abnormal wear.
Tooth integrity: Check whether the teeth are deformed, missing or excessively worn (calipers can be used to measure tooth height changes).
Tension condition: Use a tension meter to detect, and refer to the manufacturer's manual for standard tension values (usually 3-5% elongation).
Cleaning method:
Oil cleaning: Wipe with a neutral solvent (such as isopropyl alcohol) to avoid strong acid/alkali detergents corroding the PU material.
Dust removal: Blow with compressed air (pressure ≤ 0.3MPa) to prevent particles from embedding in the tooth grooves.
Prohibited operations:
Use a wire brush or sharp tool to scrape to avoid damaging the belt teeth.
Rinse directly with water (may cause rust or hydrolysis of the core wire).
- Tension adjustment and centering calibration
(1) Tension control
Overtightening: Increases bearing load, causing belt body stretching deformation (life shortened by more than 30%).
Overloosening: Causes tooth skipping, slipping, and reduced transmission accuracy.
Adjustment method:
Use a tension meter to measure, or press the middle of the belt body, the sinking amount should be 1.5-2% of the belt width.
Recheck after running for 30 minutes. Thermal expansion and contraction may cause tension changes.
(2) Alignment
The laser alignment instrument detects the parallelism of the pulley, and the deviation must be less than 0.1mm/m.
Visual inspection: When the belt body deviates, adjust the pulley position or install a guide flange.
- Lubrication and anti-aging measures
(1) Lubrication recommendations
General working conditions: Polyurethane synchronous belts usually do not require lubrication (self-lubricating design).
High load/high speed scenarios: PTFE spray can be applied to reduce friction, but avoid the tooth surface.
Prohibited lubricants:
Grease (cause PU swelling)
Silicone oil-containing products (adsorb dust and accelerate wear)
(2) Anti-aging protection
Ultraviolet protection: Outdoor equipment is equipped with a protective cover or a carbon black filled PU belt is selected (UV resistance is improved by 50%).
High temperature environment: When >80℃, it is recommended to use heat-resistant polyurethane.
- Storage and replacement standards
(1) Storage conditions
Environmental requirements: temperature 10-30℃, humidity <60%, away from ozone sources (such as motors, transformers).
Placement method: hanging or laying flat (no folding), avoid long-term compression and deformation.
(2) Replacement standards
The synchronous belt needs to be replaced immediately in the following situations:
Tooth root crack: length > 2mm or depth > 1mm.
Core wire exposure: glass fiber/steel wire core wire is exposed.
Permanent deformation: elongation > 10% or the original tooth shape cannot be restored.
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