It is as strong and durable as thermosetting plastics, but as moldable and recyclable as thermoplastics. Therefore, microcrystalline powder is a "variable thermosetting plastic", which poses a challenge to the current situation of the composite material industry. A startup company founded by some pioneer inventors of this technology is developing a malleable CFRP to shorten the production cycle.
For more than 50 years, synthetic polymers have been divided into two categories: thermosetting materials that have excellent mechanical properties but must be irreversibly cured; thermoplastics, which can be melted and reprocessed, but have poor thermal and mechanical properties. This characteristic allows thermoplastics to be molded relatively quickly for mass production using techniques such as injection molding. In addition, these materials can be recycled through melt processing. On the downside, most thermoplastics are prone to mechanical deformation and creep at high temperatures. Therefore, they do not have sufficiently stable dimensional stability at high temperatures. In addition, commercial thermoplastics are generally more expensive than similar thermosetting resins.
Although thermosetting resins have obvious performance advantages over thermoplastic thermosetting resins, thermosetting resins have a longer curing time and are therefore not suitable for mass applications such as automobiles. In addition, since thermosetting resins cannot be reprocessed after curing, these materials are difficult to repair and reshape.
Recently, the emergence of ductile thermosetting materials (also called vitrifiers) has challenged this tradition.
The researchers said: Polymers crosslinked by covalent bonds, such as thermosetting plastics, but its distinguishing feature is that the chemical bonds in the network are exchangeable. Usually, the resin formulation contains a catalyst. When the material is heated above the glass transition temperature, the catalyst can carry out the bond exchange reaction. When the silica is heated to a ductile state, their total crosslink density remains constant, but the bond exchange The rate increases with increasing temperature because all chemical reactions run faster at higher temperatures. This results in a gradual decrease in viscosity with temperature, which is different from the relatively sudden viscosity decrease associated with the melting transition of thermoplastic materials. The enamel agent is reversible and can weld, mold, shape, and recycle fully cured materials. Look at this picture: the temperature-dependent stress relaxation behavior of the trimer shows that the plastic flow of the trimer is related to the reaction rate of bond exchange.
The stress curve with temperature change shows that the plasticity flow is related to the bond exchange reaction rate
This company invented the first known glass material, which does not require catalysts and behaves like traditional thermoset plastics under environmental conditions. The catalyst-free micropowder only exhibits malleable behavior when heated above the glass transition temperature (Tg) of a given formulation, which means that below the glass transition temperature, the polymer network is frozen, so it is different from the traditional There is no difference in thermosetting materials. The vitreous polyimide platform is also easy to handle. For example, a formula can be used to adjust the Tg from below room temperature to above 200°C.
What is the difference between this new composite material and thermoset plastic?
Microcrystalline polymers represent a new class of polymers based on polymer networks linked by dynamically exchangeable imines. Like thermosetting plastics, micronized polymers are highly cross-linked network polymers. However, unlike thermosetting plastics that permanently maintain a fixed form after curing, products produced by chemical methods can be reshaped. When heated above the glass transition temperature, the fully cured network polymer undergoes rapid dynamic covalent bond exchange within the polymer network. This makes it easy to handle thermoset materials so that they can be heated and reshaped after they are fully cured. After cooling, the material maintains mechanical properties similar to thermosetting. What does this mean for composite materials?
The team has shown that when vitrified resin is used to make structural composites, such as carbon fiber reinforced plastic (CFRP), there are some clear advantages.
First, unlike traditional thermosetting plastics, glassy composite materials can be reprocessed after curing. The fully cured material can be heated, reshaped and reshaped without losing its original strength.
Second, these composite materials can be thermally welded together to form an integrally cured multilayer laminate.
Finally, CFRP made of glassy resin can be easily recycled in a solution-based process, where fiber and resin can be separated, recycled and reused to their original strength
This company is using new technology to develop a new type of "precured prepreg laminate (prepreg)", which will affect current prepreg users and the current high-capacity production that relies on rapid-curing resin transfer molding (RTM) processes商 resin.
The envisioned pre-cured prepreg malleable composite material can be cured as a single laminate in a roll-to-roll manner upstream of the manufacturing process and stored indefinitely at room temperature. In order to manufacture composite parts, any number of layers can be heated to a specific formula Tg of the material, placed in a mold to the desired thickness, and then consolidated by compression molding to form the final part. Pre-cured matrix prepreg: It takes 3 minutes for the mold to stay in the production of the parts. Within 1 to 3 minutes, the molded parts can be demolded and processed immediately, and full rigidity will appear after cooling. The waste can be further used to form other parts, or it can be recycled in a solution-based process, in which the fiber and resin material can be recycled and reused.
Essentially recyclable Due to the reversible crosslinking chemistry in the new composite material, the cured resin can be depolymerized using the chemical precursor of the resin itself. In this way, resin and fiber can be recycled and reused. This process can be carried out at room temperature to achieve energy neutral recovery. Mild heat (30°C) can be applied to quickly depolymerize.