PA6T

High-transparent nylon represents one of the most remarkable developments in advanced engineering plastics in recent years. Compared with conventional nylon, it not only requires excellent mechanical strength and heat resistance but also demands a delicate balance between high light transmittance and low birefringence at the molecular level. Achieving this balance relies on the regularity of molecular chains, controlled crystallinity, and extremely low impurity content. Traditional nylons often suffer from optical scattering due to the refractive index difference between crystalline and amorphous regions, which limits transparency. To overcome this, researchers have modified monomer structures, introduced copolymer units, and adjusted crystallization kinetics to optimize optical performance at the molecular scale. During the optical design phase, high-transparent nylon typically adopts aliphatic and cycloaliphatic copolymer structures to reduce intermolecular polarity and suppress crystallization. The incorporation of cycloaliphatic rings enhances molecular rigidity and minimizes birefringence during light transmission. As a result, transmittance in the visible spectrum can reach 88–92%, comparable to PMMA and PC. At the same time, nylon’s superior toughness and thermal stability enable it to maintain optical performance under high temperature and impact, giving it unique advantages in automotive, electronic, and optical applications. Processing conditions play a decisive role in determining transparency. Since crystallinity strongly affects optical clarity, precise control of cooling rate and mold temperature is essential during injection molding. Rapid cooling suppresses crystallization and increases the amorphous fraction, improving transparency, though overly fast cooling may induce internal stress. Hence, temperature zoning and gradual cooling are often employed. Proper drying before molding is also critical, as moisture can disrupt hydrogen bonding and cause optical defects. Today, transparent nylon is widely used in optical lenses, automotive lamp covers, sensor windows, and 3D-printed optical components. Especially in automotive lighting, it is gradually replacing PC and PMMA due to its excellent heat aging resistance and impact strength. Future research will focus on orientation-controlled amorphous transparent nylon, low-hygroscopicity grades, and recyclable bio-based transparent nylons, aiming to achieve a balance between optical performance and sustainability.