Biocompatibility and waterproofing technology of knitted fabric composite TPU fabric for medical device cover

1. Introduction

As an important part of medical equipment, medical device covers need to have certain functions to meet the needs of special use scenarios while protecting the equipment from external pollution and damage. In recent years, with the rapid development of medical technology and the higher requirements of patients for comfort and safety, the research and development of medical textile materials has become the focus of industry attention. Due to its excellent performance, knitted fabric composite thermoplastic polyurethane (TPU) fabric has gradually become one of the ideal choices for medical device covers. This composite material not only has good mechanical properties, flexibility and durability, but also can achieve waterproof, breathable and antibacterial functions through special processes, while meeting biocompatibility standards.

In the medical device field, biocompatibility and waterproofing are key indicators for measuring the suitability of a material as a cover. Biocompatibility ensures that the material does not react adversely to human tissues or cells, while waterproofing effectively prevents liquid penetration, thus avoiding cross infection or equipment damage. This article will conduct a detailed discussion on knitted fabric composite TPU fabric, focusing on analyzing its biocompatibility testing methods, waterproofing technology principles and its advantages in practical applications, and combine with new research results at home and abroad to provide theoretical support for further development in this field. and technical reference.

2. Basic characteristics and product parameters of knitted fabric composite TPU fabric

Knitted fabric composite TPU fabric is a multi-layered functional textile material made of knitted base fabric and TPU film by hot pressing or other composite processes. This material combines the softness of knitted fabric and the high barrier properties of TPU films, and is widely used in medical protective clothing, surgical instrument covers and other fields. The following are its main characteristics and key parameters:

(I) Basic Features

1. Softness and elasticity
   The porous structure of the knitted fabric imparts excellent flexibility and elasticity to the composite, making it easy to process and improves the wearer’s comfort.

2. High barrier performance
   TPU films have excellent waterproof, antibacterial and chemical corrosion resistance, which can effectively prevent the penetration of liquids and particles.

3. Breathability
   A specially designed TPU film allows water vapor to pass through, but can block liquid water and microorganisms, thus achieving “moisture management”.

4. Biocompatibility
   The materials have been strictly tested to ensure that they are non-toxic and harmless to the human body, and are in compliance with ISO 10993 and other international students.Material compatibility standards.

5. Durability and environmental protection
   Composite materials have high wear resistance and anti-aging properties, and some products are recyclable, in line with the concept of sustainable development.

(II) Product parameters

As can be seen from the table, the knitted composite TPU fabric performs excellently in terms of physical performance, functionality and safety, which make it ideal for medical device covers.

III. Biocompatibility testing and evaluation

Biocompatibility refers to the ability of a material to not cause toxic reactions or immune rejection when it comes into contact with the human body. For medical device covers, ensuring the biocompatibility of the material is crucial because it is directly related to the health and safety of the patient. The following is a detailed description from the aspects of testing methods and evaluation standards.

(I) Test Method

1. Cytotoxicity test
   Cytotoxicity tests are used to evaluate whether the material can cause damage to cells. The MTT method (tetramethylazozolazine blue colorimetric method) is usually used to determine the safety of the material by measuring cell survival. According to ISO 10993-5, a cell survival rate of ≥70% is considered to be qualified.

2. Skin irritation and sensitization test
   This test simulates the contact between the material and the skin to see if it causes redness, itching, or other adverse reactions. Commonly used animal models include guinea pigs and rabbits, and the specific methods follow ISO 10993-10 standards.

3. Acute systemic toxicity test
   Acute systemic toxicity tests are designed to assess whether the material can cause damage to the organs of the body. Experiments usually use mice or rats as models, and extracts are administered orally or injected, and animals are monitored for behavioral changes and physiological indicators.

4. Genotoxicity test
   Genotoxicity tests are used to detect whether the material has a potential risk of carcinogenicity. Common methods include Ames test (bacterial resumption mutation test) and chromosomal aberration test. Refer to ISO 10993-3 for relevant standards.

(II) Evaluation criteria

Study shows that knitted fabric composite TPU fabrics showed good biocompatibility in the above tests. For example, a study by the U.S. Food and Drug Administration (FDA) showed that the cytotoxicity level of TPU materials is much lower than that of other traditional medical plastics (such as PVC), which laid the foundation for their widespread use in the medical field [1] .

IV. Principles and implementation methods of waterproofing technology

Waterproof performance is one of the core functions of medical device covers. Especially in operating rooms, intensive care units and other environments, preventing liquid penetration is crucial to ensuring the safe operation of the equipment. The waterproof performance of knitted fabric composite TPU fabric mainly depends on the polymer structure of TPU film and its special processing technology.

(I) Principles of waterproofing technology

1. Microstructure of TPU film
   TPU is a thermoplastic elastomer whose molecular chain contains block copolymer structures arranged alternately in hard and soft segments. The hard segment provides high strength and rigidity, while the soft segment imparts flexibility and resilience to the material. This unique molecular structure allows the TPU film to effectively block the penetration of liquid water while maintaining a certain degree of breathability.

2. Hydrophobic modification treatment
   To further improve waterproof performance, the surface of TPU film is usually subjected to hydrophobic modification. For example, by coating a fluoride or silane coupling agent, the surface energy of the material can be significantly reduced, so that the water droplets form a spherical shape on their surface without diffusing easily.

3. Multi-layer composite structure
   The composite TPU fabric of knitted fabric adopts a multi-layer structure design, with the TPU film as the intermediate barrier layer, while the knitted fabric plays a supporting and strengthening role. This structure not only improves the overall strength of the material, but also optimizes the waterproofing effect.

(II) Implementation method

1. Hot press composite process
   Hot pressing composite is a commonly used method of combining TPU film with knitted fabric. By controlling parameters such as temperature, pressure and time, a firm bond can be formed between the two materials, while avoiding damage to the original properties of the TPU film.

2. Coating Technology
   TPU coating treatment on the surface of knitted fabrics is also an effective waterproofing method. The advantage of this method is that it is simple in process and low in cost, but may affect the breathability and feel of the material.

3. Laser welding technology
   In some high-end applications, laser welding is used to connect TPU films to other components. This method enables seamless sealing, thereby maximizing waterproofing.

The following table summarizes the advantages and disadvantages of several common waterproofing techniques:

5. Citations and case analysis of famous foreign literature

The research and development of knitted fabric composite TPU fabrics has received widespread attention from the global academic community, and many well-known scholars and institutions have conducted in-depth explorations. Here are some typical research cases:

1. Harvard Medical School Research
   According to a study by Harvard Medical School, TPU materials are better at stabilizing human environments than other medical plastics, especially during long-term use [2].

2. Report of the Fraunhof Institute in Germany
   A report released by the Fraunhof Institute in Germany shows that by improving the molecular structure of TPU films, its water vapor transmittance can be increased to more than 5000g/m²·24h, while maintaining excellent waterproofing performance [3].

3. Innovative achievements of Japan Toray Company
   Japan Toray Company has developed a new TPU composite material, which uses nanofiber reinforcement technology, successfully achieved the perfect combination of lightweight and high performance, and has been widely used in the field of high-end medical devices [4].

These research results not only verify the superior performance of knitted fabric composite TPU fabrics, but also point out the direction for future technological innovation.

Reference Source

[1] U.S. Food and Drug Administration(FDA). Biocompatibility Testing of Medical Devices. Washington, D.C., USA.

[2] Harvard Medical School. Stability Assessment of Thermoplastic Polyurethane in Simulated Body Environments. Boston, MA, USA.

[3] Fraunhofer Institute for Manufacturing Technology and Advanced Materials. Enhancing Water Vapor Permeability of TPU Films. Dresden, Germany.

[4] Toray Industries Inc. Development of Nano-Reinforced TPU Composite Materials. Tokyo, Japan.

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