I. Project Background
In medical settings, patients have extremely stringent requirements for the performance of shoe insoles. Whether it’s a rehabilitation patient taking their first steps after prolonged bed rest or a patient with mobility impairments who relies on assistive devices, shoe insoles must possess excellent cushioning properties, snug fit, and hygienic antibacterial characteristics to relieve pressure on the feet, promote blood circulation, and prevent bacterial growth that could lead to infections. Traditional shoe insole materials, such as ordinary rubber and EVA, have limitations when it comes to meeting the complex demands of medical applications. The emergence of TPE material ES35A - XND provides an ideal solution for upgrading medical shoe insoles.
II. ES35A - XND Material Properties
Ultra-soft and Highly Elastic: The ES35A - XND has a Shore A hardness of only 35A, offering an exceptionally soft touch that closely conforms to the contours of the foot and evenly distributes pressure across the foot. Its highly elastic properties effectively absorb the impact forces generated during walking, acting like a soft, resilient “protective cushion” for the feet. In simulated walking tests, the peak pressure experienced by feet wearing ES35A - XND insoles was reduced by 30% compared to those wearing conventional insoles, significantly alleviating foot fatigue—making it particularly suitable for individuals with sensitive feet or those suffering from foot pain.
Outstanding breathability: The material features a unique micro-porous structure internally, with tiny pores interconnected to form efficient air channels. Testing has shown that the ES35A - XND boasts a breathability rate 40% higher than that of conventional insole materials, enabling it to quickly wick away moisture and heat generated by the feet, keeping the shoe interior dry and comfortable. This feature is crucial for preventing foot bacterial growth and fungal infections, making it especially suitable for individuals with extremely high foot hygiene requirements—such as diabetic foot patients.
Excellent biocompatibility: After undergoing rigorous biocompatibility testing, ES35A - XND meets the standards for medical-grade materials and exhibits no irritation or allergic reactions to human tissues. During prolonged contact with the skin, it does not cause discomfort such as redness, swelling, or itching, thereby ensuring both safety and comfort for patients. For example, in clinical trials, hundreds of patients wore shoe insoles made from this material continuously for one month without experiencing any adverse skin reactions.
Excellent antibacterial performance: The material is infused with nano-silver ion antibacterial agents, which effectively inhibit the growth and reproduction of common harmful bacteria such as Escherichia coli and Staphylococcus aureus. The antibacterial rate exceeds 99%, and even in humid environments, the antibacterial effect can be maintained for an extended period, creating a clean and healthy environment for the feet. This feature significantly reduces the risk of complications caused by foot infections in patients.
Excellent processing performance: It exhibits excellent flowability, enabling rapid and precise filling of mold cavities during injection molding, thus facilitating the production of insoles with complex shapes. At the same time, it demonstrates outstanding adhesion to a variety of upper materials, such as leather and textiles. With appropriate process treatment, it ensures that the insole is firmly bonded to the shoe upper, preventing easy detachment. In actual production, when ES35A - XND is used to manufacture insoles, the yield rate of qualified products can exceed 98%.
III. Key Design Points for Medical Shoe Insoles
Ergonomic Design: Based on the unique foot characteristics of different patient groups—such as age-related skeletal deformities in the elderly and morphological changes in diabetic patients caused by peripheral neuropathy—we offer personalized ergonomic designs. The arch-supporting area of the inner insole features a specially designed curved shape that effectively supports the arch of the foot, reduces pressure on the arch, and helps prevent aggravation of conditions like flatfoot. The heel area has been thickened to enhance cushioning and minimize impact on the heel during walking.
Thickness and Density Distribution: Based on the stress distribution across different regions of the foot, the thickness and density of the insoles are rationally designed. In areas that bear significant loads, such as the ball of the foot and the heel, the thickness is appropriately increased to enhance cushioning performance. In the arch area, a moderate thickness and density are used—providing sufficient support without excessively compressing the arch. For example, the thickness in the ball-of-the-foot and heel regions is typically designed to be 8–10 mm, while the arch area is designed to be 5–7 mm thick.
Edge Design: The inner padding edges feature a rounded, smooth design to eliminate sharp corners and prevent scratching the skin on your feet. At the same time, the transition area where the edges meet the shoe upper has been specially treated to ensure maximum comfort when worn and minimize discomfort caused by friction.
Color and Markings: Given the unique characteristics of medical environments, shoe insoles typically feature light-colored designs—such as white or pale blue—to convey a sense of cleanliness and hygiene. At the same time, the surface of the insoles can be printed or molded with clear size markings, usage instructions, and medical warning labels, making them easy to use for both healthcare professionals and patients.
4. Production Process
Raw material preparation
ES35A - XND Preprocessing: Dry the ES35A - XND raw material in an oven at 60℃ for 3–4 hours to remove moisture from the material, thereby preventing defects such as bubbles and silver streaks in the molded products caused by moisture evaporation during injection molding.
Additive Mixing: The nano-silver ion antibacterial agent, antioxidants, and other additives are thoroughly mixed with the ES35A - XND raw material in a high-speed mixer according to precise proportions, ensuring that the additives are uniformly dispersed throughout the raw material to guarantee consistent product performance.
Injection Molding Process Parameters
Injection Molding Temperature: For ES35A - XND, the injection molding temperature is typically maintained within the range of 170–190℃ to ensure thorough melting of the material and excellent flowability. In actual production, the temperature can be adjusted appropriately based on factors such as mold design, product dimensions, and the performance of the injection molding machine. For instance, for thin-walled products, the injection molding temperature can be slightly increased to 180–200℃; whereas for thick-walled products, the temperature can be slightly reduced to 160–180℃.
Injection Pressure and Speed: The injection pressure is determined based on the product’s shape, size, and mold structure, typically ranging from 60 to 100 MPa. The injection speed should be moderate, controlled between 20 and 50 mm/s, to avoid issues such as material jetting or air pocket formation caused by excessively high injection speeds, while ensuring that the material fills the mold cavity quickly and uniformly.
Holding Pressure and Holding Time: The holding pressure is typically 50% to 70% of the injection pressure. The holding time is determined based on the product thickness, generally ranging from 3 to 10 seconds. The purpose of holding pressure is to replenish material into the mold cavity during the cooling and shrinkage process of the product, thereby preventing defects such as sink marks and deformation. For products with greater thickness, the holding time can be appropriately extended; for products with thinner walls, the holding time can be slightly shortened.
Cooling Time: The cooling time is determined by the product thickness and the efficiency of the mold cooling system, typically ranging from 10 to 20 seconds. During the cooling process, it’s crucial to ensure that the product cools sufficiently and sets properly without deforming when demolded. By optimizing the mold cooling system—such as adopting circulating water cooling or increasing the number of cooling channels—cooling time can be effectively reduced, thereby improving production efficiency.
Post-processing technology
Trimming and Finishing: After injection molding, the shoe insoles need to be trimmed along the edges to remove excess flash and burrs, ensuring a neat and tidy appearance. At the same time, the product surface must be refined to guarantee smoothness and the absence of any defects.
Antimicrobial Performance Enhancement Treatment: Place the trimmed and prepared shoe insoles into an antimicrobial treatment solution for soaking, thereby further enhancing their antimicrobial performance. The typical soaking time is 10 to 15 minutes. After soaking, remove the insoles, allow them to air dry, or dry them in a low-temperature oven.
Quality Inspection: Each shoe insole undergoes rigorous quality inspection, including visual inspection, dimension measurement, elasticity testing, and antimicrobial performance testing. The visual inspection primarily checks the product surface for defects such as bubbles, flow marks, or material shortages. Dimension measurement ensures that the product dimensions meet the design specifications, with dimensional tolerances controlled within ±0.5 mm. The elasticity test simulates real-world conditions such as compression and stretching to evaluate the product's elastic recovery performance. Antimicrobial performance testing employs specialized methods, such as the inhibition zone assay, to ensure that the product’s antibacterial rate meets the standard requirements.
V. Quality Control
Raw Material Quality Control: Establish a rigorous supplier screening system to ensure the consistent quality and stability of ES35A-XND raw materials and additives. Each batch of raw materials must undergo comprehensive quality testing upon arrival at the facility, covering indicators such as hardness, elasticity, fluidity, and antimicrobial performance. Only raw materials that pass the tests are permitted for use in production.
Process Quality Monitoring: During the production process, multiple quality monitoring points are established to conduct real-time monitoring of injection molding process parameters, product appearance, dimensions, and other relevant factors. Advanced sensor technology and automated control systems are employed to ensure the stability of process parameters. Online inspection equipment is used to perform rapid and accurate checks on product appearance and dimensions. Once a quality issue is detected, process parameters are promptly adjusted or production is immediately halted for corrective actions.
Finished Product Quality Spot Check: For insoles that have been fully manufactured, a spot check of finished product quality is conducted according to a specified sampling ratio. In addition to routine inspections covering appearance, dimensions, and performance, tests for biocompatibility and aging resistance are also carried out. Biocompatibility testing employs methods such as cytotoxicity assays and skin sensitization tests to ensure that the product is safe and harmless to humans. Aging resistance testing involves subjecting the products to accelerated aging experiments under simulated conditions—such as light exposure, temperature, and humidity—that closely resemble real-world usage environments, thereby assessing how the product’s performance changes over extended periods of use. Any batch of products failing the spot check will be entirely reworked or scrapped.
VI. Cost Analysis
Material Cost: The ES35A - XND material has a relatively moderate price. Although slightly higher than that of conventional insole materials, its superior performance can effectively reduce after-sales maintenance costs and the frequency of replacements. By optimizing product design and appropriately controlling the thickness and weight of the insoles, we can further reduce material usage and thereby lower material costs. For example, while maintaining the same product performance, reducing the insole thickness from the original 10 mm to 8 mm can cut material consumption by approximately 20%.
Mold Costs: The design and manufacture of molds for medical shoe insoles are relatively complex and thus come with higher costs. However, by collaborating with professional mold manufacturers, leveraging advanced mold-design software and manufacturing processes, optimizing mold structures, and extending mold service life, it’s possible to spread out the mold costs. Moreover, as production volumes increase, the proportion of mold costs in the overall cost structure will gradually decrease. For instance, using hot-runner molds can reduce material waste, boost production efficiency, and lower the overall cost of mold usage. Additionally, selecting high-quality mold steels—such as NAK80—can enhance the wear resistance and service life of molds, thereby reducing the frequency of repairs and replacements.
Production efficiency and cost: The ES35A - XND material boasts excellent machinability and reasonably set injection molding process parameters, which can enhance production efficiency, shorten the production cycle, and reduce labor costs as well as equipment energy consumption costs. By optimizing the production process and reducing the defect rate, we can also effectively lower overall production costs. For example, by fine-tuning the injection molding process parameters to increase the yield of good-quality products from 95% to 98%, the per-unit production cost can be reduced by approximately 3%. Additionally, adopting automated production equipment—such as automatic injection molding machines and automatic trimming devices—can further boost production efficiency and cut labor costs.
VII. Market Prospects
As public attention to healthcare continues to rise and aging societies intensify, the market for medical shoe insoles is experiencing rapid growth. The ES35A-XND material has garnered widespread attention in the medical industry thanks to its unique advantages in medical shoe insole applications—such as ultra-softness, high elasticity, breathability, antibacterial properties, and excellent biocompatibility. It holds great potential for use in medical settings including hospitals, rehabilitation centers, nursing homes, and the home-care market. Meanwhile, with ongoing technological advancements and further reductions in costs, the ES35A-XND material is poised to expand its applications into other medical products, such as knee braces, wrist supports, and orthotics, presenting enormous market potential.