I. Project Background

A well-known cosmetics client plans to upgrade its lipstick product line and has set forth specific technical requirements for the packaging bottle’s applicator component: the material must possess— High transparency, excellent resilience, extremely low odor and can be compatible with the PE substrate of the bottle body. Strong and reliable rubber-coated bonding This component comes into direct contact with the user’s lips; therefore, both the sensory experience and safety and reliability are of paramount importance.

 

II. Material Selection and Systematic Testing Process

To meet our customers’ comprehensive requirements, we have established a dedicated task force and developed a multi-stage testing plan that spans from initial screening to in-depth validation.

Round 1 Testing: Screening of Basic Transparent Series Materials

• Test model ES40A-GT-9
• Test results After injection molding, tiny bubbles are uniformly distributed inside the product, affecting its visual consistency.
• In-depth analysis Preliminary assessment indicates that the material absorbed moisture prior to storage or processing, and under the customer’s high-speed injection molding process, this moisture vaporized, forming bubbles. At the same time, the melt flowability of the material does not adequately match the venting design of the mold.
• Conclusion The test was terminated because the requirements for a flawless appearance could not be met.

Round 2 Testing: Verification of High-Transparency, High-Fluidity Materials

• Test model ES45B-28
• Test results The bubble issue persists, and slight flow marks appear at the edges of the product; transparency has not yet reached its optimal level.
• In-depth analysis Although this model improves fluidity, it may compromise melt strength and trap air when coating PE substrates. Its thermal stability may also be slightly insufficient under the specified processing conditions.
• Conclusion : The core visual defect remains unresolved and is therefore not applicable.

Round 3 Testing: Optimizing Formability and Odor Control

• Test model ES40A-XY-10
• Test results The molding process has a wide processing window, excellent stability, no bubbles, and outstanding odor performance. However, the finished products exhibit unacceptable... The base color is yellowish. Phenomenon.
• In-depth analysis The yellowish tint may result from color changes in antioxidants or stabilizers within the material system when exposed to heat, which conflicts with the “water-white” clarity required for cosmetic packaging.
• Conclusion The color indicator was ruled out for use in high-end transparent packaging.

Round 4 Testing: Customized Solution — ES45B-CGPZ

Based on the profound insights gained from the first three rounds of testing, we have launched a targeted development initiative. ES45B-CGPZ (Code definitions: C—Clear and transparent; G—Excellent encapsulation; P—Rapid prototyping; Z—Low odor.)

• Test Results and Optimization Measures ：
• Transparency issues It features a carefully selected base rubber with a higher degree of hydrogenation and special transparent additives, completely eliminating yellowing and achieving crystal-clear transparency.
• Bubble and Coating Issues The viscoelastic properties of the material have been adjusted to give it... Moderate liquidity (Flow index: 9 g/10 min) — this ensures rapid mold filling while also maintaining sufficient melt strength to effectively vent gases and tightly encapsulate the PE substrate. At a coating temperature of 200°C, the bonding interface is strong and seamless.
• Odor control The raw materials are purified using molecular distillation technology and combined with a reactive odor adsorbent, enabling the material to pass stringent VOC and sensory odor tests.
• Comprehensive Property Confirmation ：
  • The hardness is precisely controlled at 45 Shore A, delivering a flexible tactile feel.
  • Tensile strength: 4 MPa; elongation at break: 550%. This ensures that the material is unlikely to undergo permanent deformation or rupture during use.
  • Tear strength: 22 kN/m, meeting the service life requirements for repeated opening and closing.
• Conclusion ： The ES45B-CGPZ fully meets the four key performance criteria—transparency, moldability, encapsulation strength, and low odor—and has thus gained customer approval.

III. Key Issue Resolution and Summary of Core Material Advantages

1. The balance between “transparency” and “bubble-free” By precisely designing the molecular weight distribution and optimizing the formulation with additives, we have addressed the common molding defects associated with highly transparent materials.
2. Balancing “Adhesion” and “Efficiency” The specially designed functional groups ensure strong physicochemical bonding with the nonpolar surface of PE, while the optimized processing window enhances mass-production efficiency.
3. Guarantee of “Performance” and “Safety” Under the premise of meeting mechanical performance requirements, enhance sensory indicators (visual and olfactory) to cosmetic-grade standards.

IV. Conclusion and Project Value

ES45B-CGPZ The successful development and implementation not only solved the specific challenges of this lipstick tube nozzle project but also established a set of guidelines tailored to... High-transparency, rubber-coated PE, low-odor elastomer components a systematic solution. This case demonstrates the ability to translate customer needs into successful products through scientific material design, systematic problem analysis, and iterative testing. Currently, this material has achieved stable mass production and is being expanded for use in other high-end transparent packaging and consumer electronics sealing applications.

Material Notes The ES45B-CGPZ has become our company’s benchmark product in the field of transparent overmolding applications, and its development approach has provided valuable experience for subsequent customer-specific projects.