Basic knowledge and mechanical property test of hydrogel

2022-02-25   admin666

Hydrogel as in the field of polymer material testing products, with good biocompatibility, physical and chemical properties, high water absorbability, high water retention and other characteristics, is gradually being soft tissue engineering, biological medicine, electronic and other industries development and application, especially in the area of biomedical materials, hydrogel as drug carrier, tissue adhesive, wound dressings and other good used.


一、What is hydrogel

    Hydrogel is a gel with water as the dispersion medium. It is a crosslinked polymer in which a part of hydrophobic groups and hydrophilic residues are introduced into the water-soluble polymer with a network crosslinked structure. The hydrophilic residues are combined with water molecules to connect the water molecules in the network, and the hydrophobic residues are expanded by water. As a material with a three-dimensional polymer network structure, hydrogel is soft but retains a certain shape and can absorb large amounts of water.

二、Hydrogel application and types

 Material properties, with high water absorption, Gao Baoshui hydrogel is widely used in many fields, such as drought, drought region in cosmetics mask, clinical cooling gel and analgesic paste, building condensation of preventing agent, wet agent, water plugging in oil chemical dehydrating agent dispensing, crude oil or refined petroleum products, mining in dust suppression agent, food antistaling agent, thickening agent, Drug carrier in medical treatment, agricultural film in agriculture, etc. However, it is worth noting that different application fields should use different polymer raw materials to meet different application needs. According to different classification standards, hydrogels can be divided into the following types:

1. Network bonding

Hydrogels can be divided into physical gels and chemical gels according to different network bonding. Physical gel is formed by physical forces, such as electrostatic action, hydrogen bond, chain winding, etc. This gel is non-permanent and can be transformed into a solution by heating the gel, so it is also called pseudo-gel or thermally reversible gel. Chemical gels, on the other hand, are three dimensional network polymers formed by chemical bonds, which are permanent and also known as true gels.

2. Fold sizes and shapes

According to the different size and shape, hydrogels can be divided into macrogel and microgel (microsphere). According to the different shape, macrogel can be divided into columnar, porous spongy, fibrous, membrane, spherical, etc. Microgel (microsphere) can also be divided into micron and nanometer scale.


3. External stimuli

Hydrogels can be divided into traditional hydrogels and environmentally sensitive hydrogels according to their response to external stimuli. Traditional hydrogels are not sensitive to environmental changes such as temperature or pH. Environmental sensitive hydrogel is a kind of polymer gel that can sense the tiny changes or stimuli of the external environment (such as temperature, pH, light, electricity, pressure, etc.) and produce the corresponding changes in physical structure and chemical properties or even mutations.

4. Synthetic materials

According to the different synthetic materials, hydrogels are divided into synthetic polymer hydrogels and natural polymer hydrogels. Due to its better biocompatibility, environmental sensitivity, abundant source and low price, natural polymer hydrogels are attracting more and more attention and applications. However, natural polymer materials also have disadvantages such as poor stability and easy degradation.

三. Test of mechanical properties of hydrogel

As a material of biomedical grade, hydrogels must undergo strict performance evaluation and testing before design and use. The performance test of hydrogels includes physical properties, biological properties and chemical properties, among which the physical and mechanical properties are a very important performance index of polymer materials like hydrogels.

The mechanical properties of hydrogels are generally characterized by elastic modulus. In the process of elastic deformation, the proportional relationship between stress and strain is the elastic modulus, which is the main mechanical characterization parameter. The larger the elastic modulus is, the less likely the material is to deform. At present, the methods for measuring elastic modulus of hydrogel are not fixed, mainly including tensile method, compression method and indentation method, etc. Appropriate test methods can be selected according to the actual situation.

Taking tensile method as an example, tensile method is under the conditions of specified experimental temperature, speed and humidity, using electronic universal testing machine to apply static tensile load along the longitudinal axis of the sample until the sample is pulled off, in this process, the equipment will automatically generate the stress-strain curve of the sample deformation. The tensile strength, tensile fracture stress, tensile yield stress and tensile elastic modulus can be obtained from the stress-strain curve.

Universal testing machine microcomputer control electronic universal testing machine has the characteristics of compact structure, simple and easy to use, can be applied to tensile, compression, bending, shear, peel, tear and other force testing. The beam in the main engine is guided by high-precision guide rod, with high rigidity and good linear motion characteristics. Load sensors with different ranges can provide accurate measurement data for small to micron fiber, large to full load structural parts and other samples. In addition, the rich fixture, deformation measurement and other accessories, can almost meet all the needs of customers. The flexible and easy-to-use TestPilot software makes testing easier for users. Test solutions cover plastics, metals, automotive industry, building materials, textiles, paper and cardboard, food and packaging, composite materials, etc.


Electromechanical universal testing machine


Test grips

In addition to the mechanical properties, water gel test and antibacterial test, cytotoxicity test, rheology test, optical test, etc., through the layers of detection, can help us to understand and reflect the performance characteristics of the product, for application of hydrogels in the fields of production, design, and use to provide technical support, to further promote the optimization and upgrading of products To promote the healthy and sustainable development of hydrogel industry, which is also the mission and responsibility of WANtao as a material mechanical properties testing solution provider.