Polymer Alloys: Development and Innovation from Preparation to Industrial Applications

Polymer alloys, also known as polymer blends, refer to new materials formed by combining two or more polymer materials through physical or chemical methods. This technology can integrate the advantages of each component and弥补 the shortcomings of a single material, thus obtaining composites with more excellent properties. At present, polymer alloys have been widely used in automobiles, electronics, packaging, medical and other fields, and have become an important part of modern material engineering.

1. Preparation methods of polymer alloys

The preparation of polymer alloys requires scientific methods to make different polymer materials work together to achieve the best performance. Its preparation is mainly divided into physical blending and chemical modification.

(1) Physical blending

Physical blending is the mixing of different polymers through methods such as melt blending, solution blending, or mechanical blending. This method is simple to operate, but phase separation is likely to occur between incompatible polymers, affecting material properties.

Melt blending is the most commonly used physical blending method in industrial production. Polymers are mixed through equipment such as screw extruders in a molten state, which is efficient and low-cost. Solution blending is to mix polymers by dissolving them in solvents, which is suitable for some polymer materials that are difficult to melt. Mechanical blending mixes polymers through mechanical forces, and the operation is relatively simple, but the mixing effect is not as uniform as the previous two methods.

(2) Chemical modification

Chemical modification improves the interface bonding between different polymers by adding compatibilizers or performing graft copolymerization. Compatibilizers can improve the compatibility of two originally incompatible polymer materials and make them better integrated.

For example, in the PP/EPDM system, dynamic vulcanization technology is used to vulcanize the rubber phase through chemical reactions and disperse it in the polypropylene matrix, which can significantly improve the mechanical properties of the material and make the material have both the rigidity of polypropylene and the elasticity of rubber. Graft copolymerization is to attach a chain segment of another polymer to the molecular chain of one polymer, so that the two polymers are connected through chemical bonds, thereby improving compatibility.

(3) Nanocomposite technology

Nanocomposite technology further improves the strength, heat resistance, or functionality of materials by introducing nano-fillers (such as silicon dioxide, carbon nanotubes, etc.) into the blending system. Nano-fillers have small size, large specific surface area, and can fully contact with polymer materials to form strong interactions, thus significantly improving material properties.

Adding carbon nanotubes can make polymer alloys conductive, and adding silicon dioxide can improve the hardness and heat resistance of the material. This technology provides more possibilities for the performance upgrade of polymer alloys, enabling them to be used in more high-end fields.

2. Classification of polymer alloys

According to the compatibility between components, polymer alloys can be divided into fully compatible systems, partially compatible systems, and incompatible systems, each with its own characteristics.

(1) Fully compatible system

In a fully compatible system, component molecules can be uniformly mixed at the molecular level to form a homogeneous structure. For example, some PS/PPO blends, the molecules of the two polymer materials can be perfectly interwoven, so that the material has uniform properties. The properties of polymer alloys in this system are relatively stable, but there are relatively few combinations of polymer materials that can form such a system.

(2) Partially compatible system

In a partially compatible system, there is limited compatibility between the components, forming a micro-phase separation structure. Most practical polymer alloys belong to this category. This micro-phase separation structure allows the material to take advantage of the advantages of different components. For example, in some rubber-toughened plastic alloys, the rubber phase is dispersed in the plastic matrix in the form of tiny particles, which not only improves the toughness of the material but also does not affect its rigidity.

(3) Incompatible system

In an incompatible system, the compatibility between components is very poor, and the interface bonding needs to be improved by adding compatibilizers, such as PC/ABS alloys. After adding compatibilizers, originally incompatible PC and ABS can form a relatively stable structure and give play to their excellent properties.

3. Typical polymer alloys and their applications

(1) PC/ABS alloy

Polycarbonate (PC) and acrylonitrile-butadiene-styrene copolymer (ABS) alloy is one of the most successful commercial polymer alloys. PC provides high impact strength and heat resistance, can maintain structural stability when subjected to external impact, and is not easily deformed in a high-temperature environment; ABS improves processing fluidity and reduces costs, so that the material can be processed into various complex shapes.

This material is widely used in the shells of electronic devices (such as laptops, mobile phones), which can protect the internal components of electronic devices from external damage and have a good appearance. It also plays an important role in the field of automotive interior parts (such as instrument panels, door handles), meeting the multiple requirements of automobiles for material strength, heat resistance, and aesthetics.

(2) PP/EPDM thermoplastic elastomer

Polypropylene (PP) and ethylene-propylene rubber (EPDM) blends are prepared by dynamic vulcanization technology, which not only retains the rigidity of PP to provide stable structural support for components but also obtains the elasticity of EPDM, with good flexibility and impact resistance.

This material is mainly used for automotive bumpers and can effectively absorb impact energy during a collision to protect the vehicle and the safety of personnel. It can also be used for automotive sealing strips, which can closely fit the body to play a role in waterproofing, dustproofing, and sound insulation, creating a comfortable environment for the interior of the vehicle. Its excellent weather resistance and impact resistance make it an ideal material for automotive components.

(3) PA/PPO alloy

Polyamide (nylon, PA) and polyphenylene ether (PPO) alloys have excellent heat resistance, dimensional stability, and low moisture absorption. In a high-temperature environment, many materials will experience performance degradation and deformation. The PA/PPO alloy can maintain stable performance.

This alloy is particularly suitable for manufacturing components around automotive engines. The temperature around the engine is high, and the material has extremely high heat resistance requirements. The PA/PPO alloy can work stably in this environment for a long time. It is also widely used in the field of electronic connectors. When electronic devices work, they generate a certain amount of heat. The alloy can ensure the dimensional stability of the connector and ensure the stable transmission of electronic signals.

(4) Degradable PLA/PBAT alloy

Polylactic acid (PLA) is a biobased degradable plastic derived from renewable plant resources, with good biocompatibility and degradability, but it has the disadvantages of brittleness and poor heat resistance. Polybutylene adipate terephthalate (PBAT) has good flexibility and processing properties. By blending PLA with PBAT, the flexibility and processing properties of PLA can be significantly improved, and the resulting degradable PLA/PBAT alloy combines the advantages of both.

This type of degradable alloy is currently mainly used for environmentally friendly packaging materials, such as food packaging bags, shopping bags, etc. After use, it can be decomposed by microorganisms in the natural environment, reducing white pollution. It is also popular in the field of disposable tableware and contributes to environmental protection.

4. Development trends of polymer alloys

With the advancement of materials science, polymer alloy technology is moving in multiple directions, continuously expanding the performance boundaries and application fields of materials.

(1) High performance

Researchers are developing new compatibilizers and optimizing nanocomposite technologies to continuously develop alloy materials with higher strength and better heat resistance. Higher strength means that the material can withstand greater external forces without damage, and better heat resistance allows the material to work in more extreme temperature environments.

For example, by introducing new nano-fillers and improving compatibilizers, the polymer alloys prepared have strength comparable to some metal materials, while having the advantage of light weight, and are expected to be used in aerospace, high-end equipment manufacturing, and other fields, providing more powerful material support for the development of these fields.

(2) Functionalization

Functionalization is an important direction for the development of polymer alloys. Researchers are committed to giving materials special functions such as conductivity, thermal conductivity, and flame retardancy. Conductive polymer alloys prepared by adding carbon nanotubes can be used for conductive components and sensors in electronic devices to achieve the transmission and detection of electrical signals. Polymer alloys with thermal conductivity can quickly dissipate heat and can be used for heat dissipation components of LED lamps and electronic chips to improve the service life of equipment. Flame-retardant polymer alloys can suppress combustion during a fire and reduce the losses caused by the fire, and have important application value in construction, transportation, and other fields.

(3) Greening

In the context of increasing global environmental awareness, the development of more alloys based on biodegradable polymers has become a trend to reduce reliance on oil-based plastics. Oil-based plastics are difficult to degrade, and long-term accumulation will cause serious pollution to the environment. Biodegradable polymer alloys are derived from renewable resources and can be degraded in the natural environment after use without burdening the environment.

In addition to degradable alloys, researchers are also studying the use of recycled polymer materials to prepare alloys, improve resource utilization, reduce waste generation, and practice the concept of green development.

(4) Intelligence

Intelligence is a cutting-edge direction for the future development of polymer alloys. Researchers are studying intelligent polymer alloys with environmental response characteristics, such as temperature-sensitive and light-sensitive materials. Temperature-sensitive polymer alloys can change their properties based on temperature changes. For example, they become soft when the temperature rises and hard when the temperature drops. They can be used for intelligent valves, temperature sensors, etc. Light-sensitive polymer alloys can respond to light and change their properties under light, which can be used in light-controlled switches, optical storage, and other fields.

These intelligent polymer alloys bring new development opportunities to the fields of intelligent devices, biomedicine, and so on.

5. Conclusion

Polymer alloy technology has achieved the optimization and innovation of polymer properties through reasonable material design. From daily electronic products to high-end automotive components, from traditional industrial applications to emerging environmental protection fields, polymer alloys are constantly expanding their scope of applications, bringing about huge changes in life and industrial production. With the deepening of research, more high-performance, environmentally friendly new polymer alloy materials will be developed in the future, providing more powerful material support for the sustainable development of human society.