Application of reactive extrusion in nylon polymerization and modification

Nylon (PA) is a multi-variety thermoplastic semi-crystalline polymer. Due to its good processing properties and excellent strength, it has been widely used in high-demand engineering applications and can even replace metal parts in many cases. .

Among them, PA66 and PA6, the most widely used, are petroleum-based products and are often used to make fibers or films; PA11 is a bio-based material (derived from castor oil) with the lowest melting point among PAs; PA12 comes from petroleum or renewable resources. It has the smallest relative density among all engineering plastics; PA11 and PA12 have the lowest water absorption among all commercially available PAs.

Reactive extrusion refers to a technology that uses a screw extruder as a continuous reactor to complete chemical reactions and extrusion processing at the same time during the processing.

Applications of reactive extrusion

1.Extrusion polymerization 

Reactive extrusion polymerization is an intensive process that maximizes reaction rates at maximized monomer and initiator/catalyst (if present) concentrations. It also allows polymerization reactions to be carried out at higher temperatures without the need to take measures to prevent solvent evaporation or to work under pressure. 

2. PA6 chain extension and branching Tuning

polymer melt rheology and chain relaxation dynamics can make polymers easier to process and have wider applications. The molecules of the PA6 chain have active amine and carboxylic acid groups at the chain ends, which can react with other functional groups of organic/inorganic materials. In particular, acid anhydrides or epoxy groups can actively react with the terminal amine groups of the PA6 chain, and the rheological properties can be controlled through chain extension and branching of PA6. 

3. Compatibilization and blending 

The main difficulty in blending PA with polyolefins lies in the inherent incompatibility between polymers. Reactive extrusion technology is widely used in polymer blending because it combines efficient mixing and flexibility of reaction conditions in a continuous process. modified. High-shear mixing provides the possibility of micron or even nanoscale compatibilization blending, and PA can even form nanoscale blend structures with fluoropolymers. 

4. Material toughening

ABS is a thermoplastic polymer material with high strength, good toughness, and easy processing. The combination of PA6 and ABS can maximize its strengths and avoid weaknesses, overcoming the weaknesses of PA6 such as poor impact performance and high water absorption. 

5. Flame retardant modification

The flame retardant level of pure PA is low. For example, the vertical combustion of PA6 without flame retardant can only reach UL94V-2 level, and the limiting oxygen index (LOI) is about 24%. During the combustion process, dripping will occur and cause fire. 

6. Recycling and recycling

Plastic recycling is an important way to solve the problem of white pollution and is even more environmentally friendly than using bioplastics. Compared with landfilling, incineration and chemical treatment, polymer recycling is more economical and more environmentally friendly.