History

Despite its current use in various industries, nylon’s discovery began as a side experiment in the early 1930s. By 1938, significant funds were allocated to its research, and the first version—nylon 66—was introduced to the mainstream market. Practical applications soon followed, with toothbrushes featuring nylon-based bristles being the first nylon product to reach the market.

Properties

The term nylon is used to describe any synthetic plastic material that belongs to the family of high molecular weight polyamides. These polymers are composed of monomers linked through amide groups (–CONH–). While natural polyamides can be found in materials such as silk and wool, synthetic polyamides include materials such as Kevlar and nylon. What distinguishes these materials and gives them their unique properties are the structure of the monomer, i.e., the individual unit that is sequentially bonded during polymerization, and the average number of units in a macromolecule—also referred to as the degree of polymerization. Nylon is obtained synthetically from the reaction of diamines with petroleum-derived dicarboxylic acids, although methods to obtain nylon from castor oil, a more sustainable process than fossil-based ones, have been reported. Since its production is based on step polymerization, the degree of polymerization is dictated by the reaction time, with longer times leading to higher molecular weights.

Versitility

The versatility of this material allows its use for a range of applications, as it can be shaped into fibers, bristles, sheets, or even molded into forms. The characteristics of the material can be fine-tuned to meet the specifications of different applications; this can be achieved by adjusting polymer composition, additives, and processing techniques. 

• Discovered in the 1930s, nylon is a synthetic polymer linked via amide groups (–CONH–), typically obtained from reacting petroleum-based dicarboxylic acids with diamines.
• The monomer (individual unit of the polymer) and average number of units per macromolecule determine the characteristics of the material; further fine-tuning of the characteristics can be achieved through additives and processing techniques.

Resistance

Nylon is considered to have moderate corrosion resistance to weak acids and bases but may degrade if exposed to strong acidic conditions or oxidizing agents, leading to a decline in the material’s mechanical strength. When organic solvents and oils are considered, nylon demonstrates excellent resistance. However, prolonged exposure to strong solvents, such as formic acid, may lead to degradation. Water, and more specifically hydrolysis, represents a significant weakness in nylon’s profile: continued exposure to steam or hot water can break down the polymer chains, thus leading to a loss of strength and toughness. While nylon is moisture-resistant, due to its hygroscopic nature—the ability to absorb moisture from the environment—its long-term performance can be impacted in wet or humid conditions. Changes in dimension, increased flexibility, and reduced tensile strength are the main characteristics affected by moisture absorption. While water will not cause corrosion in the traditional sense (as with metals), it can increase nylon’s vulnerability to mechanical stress. 

• Nylon is resistant to most organic solvents, fuels, oils, weak acids and bases but is susceptible to degradation by strong acids and oxidizing agents.
• While the material is moisture-resistant, prolonged exposure may affect its strength, stability, and long-term performance. Additionally, hot water/steam may also cause degradation.

Melting Point

Nylon can have a relatively low melting point, thus limiting its use in high-temperature environments. Moderate temperature will typically not affect the material’s characteristics; however, long exposure times or high temperatures may accelerate the degradation process, weakening the material and causing it to eventually melt, deform, or degrade. Additionally, low temperatures may cause the material to become more brittle. It is important to note that at high temperatures, thermal oxidation may occur (providing oxygen is present) with the same net effect.

UV Stability

Repeated or continual exposure for long periods to UV radiation causes nylon to lose its mechanical properties and become brittle. This issue can be addressed through the addition of UV stabilizers or the use of protective coatings. 

• Nylon has moderate thermal stability: at low temperatures, it may become brittle, while high temperatures may cause it to melt, deform, or degrade.
• Nylon is susceptible to UV-induced degradation in the absence of UV stabilizers.

Tensile Strenght

Nylon is exceptionally strong and demonstrates high tensile strength, making it particularly suitable for mechanical application due to its excellent resistance to abrasion, friction, and impact. This increased wear resistance contributes to its corrosion resistance and enhances its durability. Its toughness and semi-crystalline structure help absorb and dissipate the energy during impact, leading to mild deformation rather than fractures, a characteristic that makes nylon highly suitable for dynamic or load-bearing applications. Despite its strength, nylon is a lightweight material, making it ideal for lightweight fabrics and fishing lines. 

• Nylon is exceptionally strong and exhibits high tensile strength, as well as high wear and impact resistance.
• The material is durable and lightweight, giving it a great strength-to-weight ratio.

Flexibility

While the amide linkages of the polymer give nylon its inherent flexible nature, this characteristic is often balanced out with the strength of the material—higher flexibility is typically accompanied by lower tensile strength. Moreover, nylon is elastic; it can stretch and return to its initial shape when the external stress is removed, making it suitable for applications such as textiles, fibers, parachutes, and seatbelts. 

• Nylon is flexible and elastic.
• Its flexibility is balanced out with strength; higher flexibility is typically accompanied by lower tensile strength.

Cost 

While nylon remains a popular choice for mass-produced goods due to its relatively low cost of production and its numerous advantages discussed above, it is important to consider the environmental impact of this material. As a synthetic polymer derived from petroleum, its manufacturing process is energy-intensive, and since the material is non-biodegradable, proper management is crucial to minimize its contribution to plastic pollution. As industries shift towards more sustainable practices, these factors are increasingly being addressed to balance nylon’s benefits with environmental responsibility. 

• The low cost of production makes nylon a popular choice for mass-produced goods.
• Effective management of production and waste is essential to balancing nylon’s benefits with environmental responsibility.