The Main Factors Affecting the Strength and Toughness of Nylon 66

Whether nylon 66 exhibits brittleness or toughness is related to its own structure, such as chemical structure, secondary structure, etc., as well as external conditions, such as temperature, humidity and strain rate. The main factors that affect the strength and toughness of nylon 66 are discussed below.

The Influence of Nylon 66 Chemical Structure

The destruction of polymer is nothing more than the breakage of chemical bonds on the main chain of polymer or the destruction of the interaction between polymer chains, so the strength of nylon 66 comes from the interaction between the main chain chemical bonds and molecules. The strength of the material can be improved by increasing the polarity of polymer or generating hydrogen bonds. Nylon 66 has hydrogen bonds, and its tensile strength can reach 60-83Mpa. The higher the hydrogen bond density, the higher the strength of the material. However, if the polar groups are too dense, which hinders the mobility of polymer segments, the strength will be improved, but the material will become brittle.

Effects of Additives of Nylon 66 

Plasticizer

Generally speaking, after adding plasticizer into high polymer, the interaction force between high polymers is weakened, which will lead to the decrease of the breaking strength of the material. The decrease of the strength is proportional to the amount of plasticizer added, and it can also reduce the yield strength of the material, thus improving the toughness of the material. It is a plasticizer for nylon 66 with hydrophilic groups in the water polymer chain. After absorbing water, the touch and strength of nylon 66 decrease obviously, while the elongation at break and impact strength increase. However, excessive water absorption of nylon 66 will seriously deform and affect its dimensional stability, that is, after the water absorption exceeds a certain critical value, not only the strength will decrease, but also the toughness will deteriorate.

Solid Filler

The strength of nylon 66 composite is related to the strength of filler itself and the affinity between filler and nylon 66. One is the inert filler used to reduce the cost, which only plays a dilution role, and it will reduce the strength of nylon 66; The other kind is active filler whose main purpose is to improve the strength of nylon 66. For example, the glass fiber developed today has become a widely used fiber reinforced filler because of its high strength and low price.

Influence of Copolymerization and Blending

Copolymerization and blending of polymers is one of the important means to improve the properties of polymers. Copolymerization and blending can improve the application performance, improve the processing performance or reduce the cost, which has attracted wide attention. In nylon 66 blend composites, different components are mainly combined by physical action. When melted and mixed under strong shear action, the shear action may lead to chain breaking of macromolecules, resulting in a small amount of free radicals, resulting in block or graft copolymer, or adding compatibilizer into the blend, or introducing a small amount of chemical bonding. The modification effect of mechanical properties of nylon 66 by graft copolymerization, block copolymerization and blending is related to the chemical composition and structure of matrix nylon 66 and dispersed phase, the content of dispersed phase, particle size and grafting ratio.