I. Project Background

A well-known trendy toy brand plans to launch a series of innovative stress-relief toys. These products pose extremely challenging and comprehensive requirements for TPE materials:

1. Outstanding mechanical durability It must pass a rigorous tensile test with a force of 15 pounds (about 6.8 kilograms) and ensure that it can withstand repeated squeezing. Bounce more than 10,000 times And without undergoing permanent deformation or fracture.
2. A unique sensory experience : The finished product must have Extremely low hardness (target Shore C 10) It offers a uniformly smooth,细腻 and soft touch, providing a top-notch stress-relieving feel.
3. Good post-processing performance The components need to be able to be bonded and assembled using common adhesives to meet the design requirements of complex structures.

 

II. Systematic Development and Testing Iteration Process

Faced with the contradictory demands of ultra-soft, high-rebound, and high-strength properties, we assembled a dedicated technical team and embarked on a step-by-step materials research and development effort.

Phase 1: Identifying the Core Bottleneck—Tackling Resilience and Durability

The initial plan focuses on meeting the most stringent requirement: “ten thousand bounces.”

• Test model TST1500-7, TST00A-RH-10
• Test results In initial hand-feel tests, both materials showed a soft texture; however, in the specialized fatigue-rebound testing machine, neither material reached 10,000 cycles. Typically, after 5,000 to 7,000 cycles, these materials begin to exhibit signs of slowing rebound speed, reduced height, or the formation of subtle local creases.
• In-depth analysis and adjustment ：
  • Problem Diagnosis Preliminary analysis suggests that traditional ultra-soft TPE formulations, in their pursuit of low hardness, heavily rely on plasticizers and soft segment structures, which to some extent compromise the strength of the molecular chain’s elastic recovery network. Under continuous dynamic stress, molecular chain slippage or hysteresis-induced heat generation leads to structural relaxation.
  • Direction adjustment Recognizing that we must abandon the simplistic approach of merely adjusting the proportion of plasticizers, we need to take a more comprehensive view starting from the polymer chains themselves. Topological Structure Design Start by building on an extremely soft foundation to create something more stable and fatigue-resistant. Dynamic crosslinked network 。

Phase 2: Balancing Key Performance—Tackling the Challenges of Strength and Stability

After clearly defining the structural design direction, the next-generation materials need to simultaneously tackle two major challenges: unstable tensile strength and rebound.

• Test model TST1501A, TST1502A, TST1503A
• Test Results and Progress ：
  • TST1501A The number of rebound cycles has been increased to approximately 8,000; however, the tensile strength exhibits significant fluctuations (0.8–1.3 MPa), resulting in an unstable pass rate for tensile tests.
  • TST1502A Tensile strength stability has improved somewhat, but the hardness has risen to around Shore C 15, sacrificing the “ultra-soft” feel that the customer was seeking.
  • TST1503A We attempted to strike a balance between softness and strength, but the material exhibited uneven surface gloss during injection molding, compromising the visual and tactile requirements for “uniform softness.”
• In-depth Analysis and Breakthrough ：
  • Problem Diagnosis The root cause of unstable intensity lies in... Heterogeneity of the microphase-separated structure In the ultra-soft system, the hard-segment microdomains serve as physical crosslinking points; their size distribution and uniformity directly determine the stability of the material’s strength. Meanwhile, the impact of processing techniques on the final structure is amplified.
  • Technological breakthrough We have introduced Reactive compatibilization technology and precise shear control process The novel compatibilizer promotes finer and more uniform dispersion of the hard-segment microdomains within the soft-segment matrix. At the same time, the material’s rheological properties have been optimized (melt flow index: 52 g/10 min), ensuring that even during high-flow-rate rapid molding, the internal structure remains highly homogeneous.

Phase 3: Comprehensive Solution Validation—The Success of TST15A-WJ

Integrating all the experience from the first two phases, we have ultimately developed... TST15A-WJ  (Code definitions: W—Toy Application; J—Extreme Durability.)

• Comprehensive test results ：
• Mechanics and Durability ：
  • Tensile test The tensile strength remained stable at 1 MPa and successfully passed both static and dynamic tests under a 15-pound tensile force.
  • Rebound test We have successfully completed 10,000 fatigue rebound tests on dedicated equipment, with minimal performance degradation—far exceeding industry standards.
• Sensory and Processability ：
  • Tactile sensation The hardness is precisely controlled at Shore C 10, resulting in a finished surface that is smooth and细腻, with a soft and even texture that feels neither sticky nor oily.
  • Formability High fluidity ensures rapid mold filling and efficient production, eliminating defects such as flow marks and insufficient material.
  • Adhesiveness The surface polarity of the material has been moderately adjusted, ensuring excellent compatibility with commonly used assembly adhesives and providing strong, reliable bonding.
• Core Property Confirmation ：
  • With an elongation at break of up to 900%, the toy is guaranteed not to become brittle and fracture even under extreme stretching.
  • With a specific gravity of only 0.865, it achieves lightweight design while maintaining high performance.

III. Summary of Core Technology Innovation and Problem Solving

1. Molecular Design for “Ultra-Soft” and “High-Elastic” Materials By constructing Multiscale dynamic physical crosslinking network By introducing moderately strong and uniformly distributed reversible interaction points between molecular chains, the material achieves both extreme softness and rapid recovery capability, as well as excellent fatigue resistance.
2. Process Assurance for "Strength" and "Stability" By precisely controlling reactive technologies and processing techniques, we have addressed the common challenges associated with ultra-soft materials. Microstructural inhomogeneity The issue thus achieved highly stable mechanical performance.
3. The perfect integration of “feel” and “function” In the formulation design, the interactions among various components have been finely balanced, ultimately achieving a harmonious combination of a smooth surface, internal flexibility, and reliable performance—fully meeting the sensory and functional requirements of high-end stress-relief toys.

IV. Conclusion and Project Value

TST15A-WJ The successful development not only perfectly solved the specific technical challenges associated with this stress-relief toy from Xiongjin/BubbleMall, but its significance goes even further:

• Technology benchmark It has set a new benchmark for the performance of ultra-soft TPE materials, balancing low hardness, high resilience, high strength, and excellent processability.
• Solution A systematic materials design and problem-solving methodology has been developed for “ultra-soft, high-durability” elastomer applications.
• Market Expansion This material has become an ideal choice for applications in areas such as stress-relief toys, high-end footwear materials, and comfortable wearable devices, demonstrating its broad application potential.

Material Notes The TST15A-WJ has now achieved scalable and stable production. Its successful case provides a valuable technical roadmap and instills confidence for the subsequent development of customized TPE products that meet specific mechanical and sensory requirements.