I. Project Background

Recently, the client plans to develop a new type of sports mouthguard and requires the material to have: Ultra-high transparency (to facilitate observation of oral fit) and Soft and comfortable touch At the same time, the inner PP/PE material of the dental guard needs to be encased with a rubber coating on its fixed bracket to ensure a secure fit. The customer had previously tried a transparent TPU material but abandoned it due to insufficient transparency and its tendency to yellow during molding. There is an urgent need for a thermoplastic elastomer that balances optical performance, bonding strength, and safety.

II. Analysis of Technical Challenges

1. Achieving ultra-high transparency
   Conventional TPE tends to fog easily due to differences in the refractive indices of its components, and its light transmittance typically falls below 85%. Dental guards require a light transmittance of ≥90% and a haze level of ≤5%. To achieve these specifications, it is necessary to carefully design the refractive index match between the base material and the oil-filled system, and to strictly control impurities and gelation points.
2. Balance between low hardness and tactile feel
   Dental guards need to have appropriate softness (Shore A 50–60) to cushion the biting force, while also maintaining sufficient resilience to prevent permanent deformation. If too soft, they’re prone to tearing; if too hard, their comfort level will decline.
3. Reliability of PP/PE Coated Materials
   PP/PE are nonpolar materials with significant polarity differences from TPE, making it difficult to achieve a strong bond using conventional formulations. It is necessary to introduce polar-modified components or compatibilizers to ensure that the peel strength is ≥2.5 N/mm and that the material exhibits resistance to saliva and to aging under humid and hot conditions.
4. Safety and Weather Resistance
   Oral contact materials must comply with FDA 21 CFR 177.1210 or equivalent food-contact standards and must not leach or discolor upon prolonged contact with sweat or saliva.

III. Material Recommendations and Validation

Based on the above requirements, we recommend the self-developed... ES40A-YDHC Ultra-High Transparency TPE Modified Material , its core features are as follows:

Technical Highlights ：

• Optical optimization By matching the refractive indices of the substrate and the hydrogenated resin, interfacial scattering is eliminated, achieving high transparency and low haze.
• Polar grafting Maleic anhydride is grafted onto the SEBS main chain to enhance interfacial compatibility with PP/PE, and during delamination, it exhibits cohesive failure.
• Anti-precipitation system High-molecular-weight silicone oil is used as a slip agent to prevent the migration of small molecules that could cause hazing.

IV. Customer Onboarding Process

1. Internal simulation test
2. Mold validation The customer-provided dental guard mold (with one mold cavity and two cavities, featuring a slender flow channel) was used. The injection molding temperature was set at 240℃, the injection pressure at 80 MPa, and the holding pressure maintained for 5 seconds. As a result, a transparent sample was successfully molded without any flow marks or bubbles.
3. Rubber-coating strength test Injection molding over a PP substrate with overmolding; the 180° peel test showed that the failure mode was cohesive failure within the TPE, with no interfacial delamination.
4. Bite Resistance Test After simulating masticatory forces (500 N, 1,000 cycles), the sample’s permanent deformation was less than 3%.
5. Customer pilot production
6. Transparency Consistency Continuous production of 200 molds yielded random samples with a light transmittance of ≥91% and haze of <5%, with no batch-to-batch variation.
7. Rubber-coating stability After assembling the dental guard with the PP bracket, it was immersed in artificial saliva at 37℃ for 72 hours, during which no delamination or whitening occurred.
8. User experience Ten athletes tested the fit and provided feedback: The material is soft and conforms well to the mouth, has no odor, and its transparency allows for easy observation of oral conditions.

V. Conclusion

ES40A-YDHC by virtue of 92% light transmittance, Shore A 55 softness, strong encapsulation PP/PE performance And FDA compliance The project successfully replaced the customer’s original solution and enabled mass production of sports mouthguards. This case demonstrates the feasibility of highly transparent TPE in medical-grade sports protective products, providing a valuable reference for the subsequent development of applications such as oral care products and transparent wearable devices.