October 16, 2024 – Polypropylene, a Standout in the Synthetic Resin Industry, Seeks Transparency Enhancements
Polypropylene, a leading synthetic resin with a consumption rate accounting for approximately 30% of the global synthetic resin total, finds widespread application in various industries such as automobiles, home appliances, electronics, packaging, and building materials and furniture. However, its crystalline nature poses limitations on its use in transparent products, making research into transparent modification of polypropylene particularly crucial.
Optical properties serve as a key indicator for measuring the transparency of polypropylene, with light transmittance and haze being two important parameters. Light transmittance, which represents the percentage of light flux passing through an object relative to the incident light flux, directly reflects the degree of transparency of polypropylene. Haze, on the other hand, describes the proportion of light intensity deviating from the incident light direction after passing through an object. The higher the haze, the poorer the transparency of the polypropylene.
According to Color Masterbatch Industry Network, three primary methods are currently employed to enhance the transparency of polypropylene. The first involves the use of metallocene catalysts to polymerize transparent polypropylene. The second method entails obtaining transparent polypropylene through random copolymerization. The third approach involves modifying conventional polypropylene by adding nucleation agents, which is a simple and effective modification technique.
The poor transparency of polypropylene is primarily attributed to its crystalline structure within the aggregated state. The crystalline regions of polypropylene consist of large polycrystalline spherulites, which cause light rays to undergo refraction and reflection during propagation, resulting in light haze and reduced transmittance. Therefore, controlling the size of the spherulites is crucial for improving the optical properties of polypropylene. Nucleation agents, acting as “impurities,” can promote heterogeneous nucleation and inhibit homogeneous nucleation in polypropylene, thereby reducing crystal size, increasing crystallinity, and lowering light scattering and refractive index at crystal interfaces. Ultimately, this enhances the transparency of polypropylene.