1. Introduction

With the increasing demand for sustainable development and environmental protection, the research and development of high - performance bio - based polyurethane have attracted extensive attention. Traditional polyurethane is mainly synthesized from petroleum - based raw materials, which are non - renewable and can cause environmental pollution. In contrast, high - performance bio - based polyurethane uses renewable bio - based raw materials, such as bio - based polyols and bio - based isocyanates, to replace part or all of the petroleum - based raw materials. This not only helps to reduce the dependence on petroleum resources but also has better environmental friendliness. At the same time, achieving high performance is crucial for its wide - spread application in various fields.

2. Preparation of High - performance Bio - based Polyurethane

2.1 Selection of Bio - based Raw Materials

• ​​Bio - based Polyols​​
  • ​​Sources​​: Common bio - based polyols are derived from renewable resources such as soybean oil, castor oil, and lignocellulosic biomass. Soybean oil - based polyols are obtained by modifying soybean oil through reactions such as transesterification and epoxidation. Castor oil, rich in hydroxyl groups, can be directly used as a raw material for synthesizing bio - based polyols after appropriate treatment. Lignocellulosic biomass can be converted into bio - based polyols through processes such as hydrolysis and chemical modification.
  • ​​Properties​​: The properties of bio - based polyols, such as hydroxyl value, functionality, and molecular weight, have a significant impact on the performance of polyurethane. For example, a higher hydroxyl value can lead to a higher cross - linking density of the polyurethane, resulting in better mechanical properties.
• ​​Bio - based Isocyanates​​
  • ​​Research Progress​​: Although the research on bio - based isocyanates is still in the early stage, some progress has been made. Bio - based isocyanates can be synthesized from natural products such as amino acids and sugars. For example, some researchers have explored the synthesis of bio - based isocyanates from lignin - derived compounds.
  • ​​Challenges​​: The synthesis of bio - based isocyanates faces challenges such as low yield, high cost, and difficult control of reaction conditions. Currently, in some cases, a small amount of bio - based isocyanates is used in combination with traditional petroleum - based isocyanates to prepare high - performance bio - based polyurethane.

2.2 Synthesis Process

• ​​One - shot Method​​
  • ​​Principle​​: The one - shot method involves mixing all the raw materials, including bio - based polyols, bio - based isocyanates, catalysts, additives, and chain extenders (if necessary), at one time and then carrying out the reaction to form the polyurethane. This method is simple and has a short production cycle.
  • ​​Advantages and Disadvantages​​: The advantage is its simplicity and low equipment requirements. However, it is difficult to control the reaction process accurately, which may lead to uneven product quality.
• ​​Pre - polymer Method​​
  • ​​Principle​​: In the pre - polymer method, bio - based polyols and bio - based isocyanates are first reacted to form a pre - polymer, and then other additives and chain extenders are added to the pre - polymer for further reaction. This method allows for better control of the reaction process and product quality.
  • ​​Advantages and Disadvantages​​: The advantage is that it can produce high - quality polyurethane with more stable performance. However, the process is relatively complex and requires more equipment and time.

3. Performance Study of High - performance Bio - based Polyurethane

3.1 Mechanical Properties

• ​​Tensile Strength and Elongation at Break​​
  • ​​Research Findings​​: Studies have shown that the mechanical properties of high - performance bio - based polyurethane can be comparable to or even better than those of traditional petroleum - based polyurethane. By adjusting the type and content of bio - based raw materials and the synthesis process, the tensile strength and elongation at break of the polyurethane can be effectively controlled. For example, increasing the cross - linking density can improve the tensile strength, while maintaining a certain degree of flexibility can increase the elongation at break.
• ​​Hardness and Modulus​​
  • ​​Influence of Raw Materials and Process​​: The hardness and modulus of high - performance bio - based polyurethane are also affected by the type of bio - based polyols and isocyanates, as well as the synthesis process. Different bio - based polyols can result in different hardness levels of the polyurethane. For example, polyols with higher functionality can lead to a higher hardness of the polyurethane.

3.2 Thermal Properties

• ​​Thermal Stability​​
  • ​​Thermal Decomposition Temperature​​: The thermal stability of high - performance bio - based polyurethane is an important performance indicator. Research has found that the thermal decomposition temperature of bio - based polyurethane can be improved by using bio - based raw materials with high thermal stability and optimizing the synthesis process. For example, some bio - based polyols derived from lignocellulosic biomass can improve the thermal stability of the polyurethane.
• ​​Glass Transition Temperature​​
  • ​​Effect on Performance​​: The glass transition temperature (Tg) of high - performance bio - based polyurethane affects its flexibility and hardness at different temperatures. By adjusting the type and content of bio - based raw materials, the Tg of the polyurethane can be controlled. A higher Tg generally indicates a harder and more brittle polyurethane, while a lower Tg indicates a more flexible and elastic polyurethane.

3.3 Environmental Performance

• ​​Biodegradability​​
  • ​​Degradation Mechanism​​: One of the significant advantages of high - performance bio - based polyurethane is its biodegradability. Under appropriate environmental conditions, such as in soil or compost, the bio - based polyurethane can be decomposed by microorganisms into carbon dioxide and water. The biodegradability of the polyurethane is affected by factors such as the type of bio - based raw materials and the cross - linking structure.
• ​​Environmental Friendliness​​
  • ​​Reduction of Environmental Pollution​​: The use of renewable bio - based raw materials reduces the dependence on petroleum resources and the emission of greenhouse gases during the production process. At the same time, the biodegradability of the polyurethane also reduces the environmental pollution caused by waste disposal.

4. Application Prospects

• ​​Aerospace and Automotive Industries​​
  • ​​Lightweight and High - performance Requirements​​: High - performance bio - based polyurethane can be used in the aerospace and automotive industries to manufacture lightweight and high - performance components. Its high strength - to - weight ratio and good mechanical properties can help reduce the weight of vehicles and aircraft, improving fuel efficiency and reducing emissions.
• ​​Construction and Building Materials​​
  • ​​Insulation and Protection​​: In the construction industry, high - performance bio - based polyurethane can be used as insulation materials, coatings, and adhesives. Its good thermal insulation performance, waterproof performance, and durability can improve the energy efficiency and service life of buildings.
• ​​Medical and Health Fields​​
  • ​​Biocompatibility​​: Due to its good biocompatibility, high - performance bio - based polyurethane can be used in the medical and health fields to manufacture medical devices, wound dressings, and tissue engineering scaffolds.