Test Method for Water Vapor Permeability Performance of the Medical Hydrogel

Abstract: The primary application of hydrogel in the medical field is the wound dressing. As the closest biological functional material to living tissues, hydrogel can make direct contact with human tissues, prevent external microbial infection, effectively prevent the loss of body fluids, and transmit oxygen and promote wound healing. At the same time, as a drug release carrier, because of its good permeability to low molecular solutes, it also gives the function of hydrogel drug transport system. In this paper, the principle of cup method is used to test the water vapor transmission rate of hydrogel, and introduces the test principle, the parameters and applicable scope, the test process and other contents of W3/062 Water Vapor Transmission Rate Test System, which can be used for reference by enterprises and related institutions in testing the water vapor permeability performance of similar medical hydrogel products.

Keywords: wound dressing, hydrogel, water vapor permeability, moisture resistance performance, water vapor transmission rate, water vapor transmission rate test system, cup method, weighing method, inverted-cup method

1. significance

As an organ covering the surface of the human body, the skin is vulnerable to a variety of external injuries. The large area skin defect is difficult to repair due to the difficulty of skin in the defect area, the recovery period is long and the operation itself would bring injury. Therefore, the treatment would be difficult.

Medical hydrogel contains a large amount of water (up to 90%), which has soft texture. Its physical properties are similar to biological tissue with excellent biocompatibility, and adjustable mechanical properties. Therefore, it is an excellent biological material. Hydrogel has a good effect on the traumatic surface. Hydrogel on the wound surface can prevent wound infection and promote wound healing, conducive to the early wound recovery. Common medical hydrogel is semi-permeable, which has the effect of blocking bacteria, preventing wound infection, and allowing oxygen and water to pass through.

Therefore, the water vapor performance of the hydrogel is very important, which is related to the recovery process of the injured. This paper introduces a test method for the water vapor permeability performance of medical hydrogel.

Figure 1. Common Medical Hydrogel

2. Test Sample

A certain hydrogel was used as the test sample.

3. Test basis

This paper evaluates the water vapor transmission rate of a sample by testing the water vapor permeability. The test process adopts the cup method principle stipulated in YY/T 0471.2-2004, Test Method of Contact Wound Dressing, Part 2: Water Vapor Transmission Rate of Breathable Film Dressing, and tests based on the requirements of the water vapor transmission rate of liquid contact wound dressing in its 3.3.

4. Test Equipment

W3/062 (Figure 2) Water Vapor Transmission Rate Test System was used for the test, which was independently developed and produced by Labthink Instruments Co., Ltd.

Figure 2. W3/062 Water Vapor Transmission Rate Test System

4.1 Test Principle

W3/062 works according to the test principle of the water vapor permeable cup weighing method, a specific humidity difference is formed on both sides of the sample at a certain temperature, and the water vapor passes into the dry side through the sample in the permeable cup. By measuring the change of the weight of the permeable cup over time, the water vapor transmission rate and other parameters of the sample is obtained. The test cell is the dry side for the weight reduction method and the wet side for the weight increase method. According to whether the material has direct contact with water in the actual process of use, it can be divided into regular cup method and inverted cup method. Between them, the former is contact between water vapor and sample, and the latter is direct contact between water and sample.

4.2 Equipment Parameters

l  The test range is 0.1 – 10,000 g/(m2 24h) (weight reduction method); 0.1-2500 g/(m2 24h) (weight increase method).

l  The test accuracy is 0.01 g/(m2 24h);

l  The simultaneous test of 6 test samples can be realized, that is, the test results of 6 test samples can be obtained once;

l  The test temperature range is 15 to 55℃, and the temperature control accuracy is ±0.1℃;

l  Test humidity: weight reduction method: 90% RH ~ 70% RH, weight increase method: 10% RH ~ 98% RH, humidity control accuracy is ±1%RH;

l  The purge flow speed is 0.5 ~ 2.5 m/s, which can ensure the constant humidity difference inside and outside the permeable cup;

l  Two fast calibration methods of reference film and standard weight to ensure the accuracy and versatility of the detection data;

The system adopts the cylinder lifting mechanical structure design and intermittent weighing measurement method, which effectively reduces the system error;

Compatible to LystemTM Laboratory Data Management System to manage in an unified way of test results and test reports;

4.3 Scope of Applications

(1) Suitable for water vapor permeability test of all kinds of plastic film, plastic composite film, paper-plastic composite film, geomembrane, coextrusion film, aluminum foil, aluminum foil composite film, waterproof breathable film and other film materials.

(2) Suitable for water vapor transmittance tests of all kinds of engineering plastics, rubber, building materials (construction waterproof materials) and other sheet materials, such as PP sheet, PVC sheet, PVDC sheet, etc.

(3) Suitable for the test of water vapor transmission rate tests of paper, aluminum foil, paper and cardboard.

(4) It is suitable for the test of water vapor permeability of waterproof and breathable fabrics, non-woven fabrics diapers, non-woven fabrics for sanitary products, and non-woven fabrics.

(5) The equipment can also be extended to the water vapor transmission rate tests of artificial skin, medical supplies and accessories, LCD display film, solar backplane, paint film, cosmetics, biodegradable film, etc.; it can also be used for inverted cup method test.

(6) It meets many national and international standards, such as GB 1037, GB/T 16928, ASTM E96, ASTM D1653, TAPPI T464, ISO 2528, DIN53122-1, JIS Z0208, and YBB00092003.

5. Test Process

In this test, the inverted cup method is used to test the water vapor transmission performance of the samples when contacting the liquid.

(1) Cut out 6 uniform and intact samples.

(2) Add a certain amount of distilled water to the permeable cup, put the sample, and then clamp the permeable cup cover to ensure that the permeable cup and the sample is well sealed without leakage.

(3) Put the permeable cup on its holder of the equipment, close the test cell door, set the sample name, test temperature, humidity, test mode and other parameter information on the control software, click Test button, and conduct the test according to the set parameters.

(4) After the test, the computer software shows the test process curve and the results.

Figure 3. Sample Clamping Process

Figure 4. W3/062 is in test

6. Test Results

Considering the large amount of sample passing through and the range of the equipment, in order to ensure the accuracy and reliability of the data, we only put one sample at a time for testing. The test conditions were 38℃ and 90% RH, and the arithmetic mean value of the test results of the 6 samples was taken as the water vapor transmission rates of the samples. The water vapor transmission rate of the antibacterial dressing samples tested in this test was 17981.4950 g/(m2 24h).

7. Conclusions

Water vapor permeability is an important performance of medical hydrogel and has an important influence on the healing of wound sites. In This paper’s test, hydrogel samples was tested on W3/062 Water Vapor Transmission Rate. The test process is simple and the equipment is easy to operate with accurate temperature and humidity control and high test efficiency compared with the traditional oven control and weighing, the test method has automatic timing, automatic weighing, higher intelligence, less human interference. Moreover, the permeation and weighing are carried out in the same environment, and the weighing process has no impact on the osmosis balance, and the test results are more accurate and reliable, which can truly reflect the water vapor transmission performance of the dressing. Labthink Instruments Co., Ltd. is a professional manufacturer engaged in packaging testing equipment research and development, production and packaging testing services. In addition to W3/062, Labthink also has a number of other types and principles of testing equipment that can be used for water vapor permeability, gas permeability performance test. To learn the relevant equipment information, please visit: www.labthink.com. The more you understand, the more you trust! Labthink is looking forward to enhancing technical communication and cooperation with enterprises and institutions in the industry.