TPE Material Selection Engineering Case: Application of TO7002-MTDQ Dedicated Material in Toilet Seat Gaskets
Time of issue:2026-01-19
I. Core Customer Needs
Bonding performance: Peel strength to PP substrate > 3.5 N/mm
Weathering requirements: 5-year resistance to yellowing (ΔE < 2.0, ISO 105-B02); resistance to 84 disinfectant/toilet cleaner (no cracking after 500 hours of immersion).
Material Specification: Hardness 60 ± 5 Shore A, hydrolysis resistance (tested at 85℃/85% RH for 1000 hours).
Hygiene and Safety: Odor level < Grade 3 (VDA 270 standard), dirt-resistant and easy to clean (contact angle > 90°).
II. Sample Preparation Process
First trial sample: ES65A-MW-3 (Chemical resistance NG)
Test conditions: Injection molding coating on a PP substrate at 190℃, followed by immersion in 84 Disinfectant (undiluted, 40℃).
Failure phenomenon: Surface swelling and cracking occurred within 72 hours (weight increase of 12%); peel strength was only 2.1 N/mm (40% below the standard).
Root Cause Analysis: The molecular chains contain ester bonds (detected by FTIR at the 1730 cm⁻¹ peak); penetration of the disinfectant causes the molecular chains to break (SEM reveals crack origins).
Second test sample: TV65A-SP (Adhesion NG)
Improvement: Adopt a fully polyolefin structure (no polar groups).
Test result: Chemical resistance passed (no abnormalities after immersion in disinfectant for 500 hours).
Fatal defect: Peel strength with PP is 1.8 N/mm (interfacial separation).
Failure mechanism: The non-polar surface leads to poor interfacial compatibility (contact angle of 105°), and during injection molding, the temperature difference between the melt and the substrate is too large (interfacial temperature < 160℃).
Third test sample: TO7002 (adhesion does not meet the standard)
Technical Adjustment: Introduction of Maleic Anhydride Grafting (Improved Polarity)
Test data: Excellent chemical resistance (passed disinfectant testing); yellowing ΔE = 1.2 (equivalent to 5 years of accelerated aging).
Key shortcoming: Peel strength of 2.9 N/mm (still 17% below the standard).
Fourth test sample: TO7002-MTDQ (fully compliant)
Core technology breakthrough:
Molecular Structure Design: Controlled Grafting Technology (maleic anhydride grafting rate: 0.8 wt%), with the addition of hydrogenated C5 tackifying resin (interface diffusion coefficient increased by a factor of 3).
Weathering Resistance System: Composite Antioxidant (Synergistic Effect of Phenolic and Phosphite), Nano-Cerium Oxide Anti-Yellowing Agent (UV Shielding Rate > 99%)
Mass-production validation: Peel strength of 4.2 N/mm (20% above the standard); no change after immersion in disinfectant for 1,000 hours (weight change rate of 0.3%); accelerated yellowing test over 5 years yields ΔE = 1.5 (customer standard: ΔE < 2.0).
III. Core Engineering Experience
Bonding-Chemical Resistance Balance Principle:
Lessons from failures: ES65A-MW-3: Polar groups lead to chemical attack vulnerabilities; TV65A-SP: Non-polar structural interfaces fail in adhesion.
Success Path: "Gradient Polarity" Design—The matrix remains inert to polyolefins, while the surface features controllable grafting of polar functional groups (with a grafting rate of 0.8% serving as the critical threshold).
Key technologies for long-term weather resistance:
Dual anti-yellowing mechanism: Nano-cerium oxide reflects ultraviolet light (shields wavelengths below 400nm), while phenolic antioxidants scavenge free radicals (extending the induction period to up to 5 years).
Hydrolysis-resistant guarantee: Molecular chains contain 0% ester bonds (no characteristic peaks detected by FTIR), and feature a closed-cell structure design (water absorption rate < 0.01%).
Encapsulation process window formula: Mold temperature T_mold ≥ Substrate temperature T_substrate - 15℃ (for PP substrates: substrate temperature 175℃ → mold temperature 160℃). Injection molding speed V (mm/s) = 0.2 × Peel strength (4.2 N/mm → V = 0.84 mm/s).
Technology transfer outcomes:
Medical Device Handle: TO7002-1-MD (USP Class VI Certified)
Outdoor sealing ring: TO7002-1-OS (-40℃~120℃ weather-resistant)
TEL: +86-0752-6768128 FAX: +86-0752-6768088 MAIL: sales@tpe-sp.com WEB: en.tpe-sp.com
ADD: Huangxi Industrial Park, Shiwan Town, Boluo County, Huizhou City, Guangdong Province，China