According to the report of the UN, it is estimated that in 2045, more than 6 billion people in the world will be concentrated in urban areas, forming a large-scale urban life circle, and the diversified needs necessary in big cities, including transportation, medical care, housing, food, water, etc., will become indispensable services and resources.

However, while pursuing a better life, human beings have also brought about the existential crisis of climate change and environmental pollution. For example, the mobility convenience brought by cars has created the growth of the industrial economic chain, but it is also the main source of energy consumption and pollutant emissions.

In the face of these major issues, people begin to find solutions to achieve the goal of sustainable environment by reducing carbon emissions, paying attention to the management of natural resources, and the sustainable reuse of resources and other paths, and in these solutions, materials play a key role.

In order to cope with the environmental and energy shortage problems brought by the automobile industry, countries have formulated strict regulations to limit the fuel consumption and greenhouse gas emissions of automobiles, including the European Union in 2021 stipulated that the annual carbon emissions must be reduced to 95g/km, the United States stipulated that the 2025 must be reduced to 97g/km, and relevant research results show that every 100Kg reduction in car weight, It can directly save fuel about 0.3~0.5L/(100km), and carbon emissions can be reduced by about 8~11g/(100km).

Therefore, enterprises continue to achieve lightweight vehicles through the use of structural design, lightweight materials, and green manufacturing processes, thus effectively reducing the impact of the overall industry on the environment.

In the formulation of thermoplastic composite materials, glass fiber is often used as a resin reinforcement material to improve the mechanical properties or heat resistance of formed products, and the general traditional technical method is to use the extruder to melt and mix the glass fiber tow directly with the resin base material for granulation, and the glass fiber tow is chopped under the friction and shear action of the screw and the cylinder. The obtained reinforced resin granules with glass fiber length <1mm.

Such a material after the next molding process, the glass fiber is broken again, so in the end products, most of the glass fiber retention length is actually far below the effective critical length, the glass fiber itself has not been fully played out, so how to improve the fiber retention length, will become composite materials in the field of terminal application, The key to taking it to the next level.

New selection of lightweight materials

Long Fiber Reinforced Thermoplastics (LFRT or LFT) is a class of high-performance composite materials that has developed rapidly in recent years. Special processes and equipment are used. The continuous glass fiber is fully soaked and coated with molten resin, and the rubber strip is cooled and then cut into long stick-like pellets of a specific size.

The length of a single pellet is about 5~25mm, and the length of the glass fiber covered in it is equal to the length of the rubber pellet (5~25mm). Because the length of the glass fiber contained in LFRT exceeds the critical length (Lc), It can show the advantages of the original strong performance of the glass fiber.

In the finished products using injection molding of long glass fiber reinforced materials, the substantial length retention rate of glass fiber is high, so there is enough length between the fibers to bond with each other, forming a three-dimensional 3D mesh structure, which is interleaved in the matrix resin as a reinforced skeleton.

Compared with general thermoplastic reinforcing materials, LFRT can withstand greater stress and load. And effectively absorb energy, so that the finished product has high specific strength, high rigidity, high impact resistance, high dimensional stability, temperature resistance, low warping, creep resistance, low thermal expansion coefficient and many other advantages.

According to the formula and performance evaluation of LFRT, the mechanical properties of different glass fiber lengths (12mm, 25mm) were compared. The experimental results showed that the longer the length of the contained glass fiber, the higher the relative impact resistance.

The same shape can also be observed from the fracture surface of the test sheet, and the interlacing mesh glass fiber in the resin forms a tight structure. Thus, the material can withstand more damage stress, especially when the fiber length reaches 25mm, even if the test piece has been broken, but by the internal fiber in sufficient length, the formation of 3D overlap effect between each other, still can maintain partial integrity of the test piece appearance.

From the research data point of view, LFRT can greatly improve the mechanical safety performance of products, in terms of specific strength, it is very close to metal materials, plus LFRT can be quickly formed with molds, making complex shapes, and materials can be recycled and reused, with the world's advanced countries towards environmental protection, energy saving, lightweight trend.

The industry has set off the trend of "replacing steel with plastic", and LFRT has become one of the new lightweight material choices to replace metal.