October 13, 2024 – The transparent polypropylene industry in China has been witnessing robust growth in recent years, with its production and sales consistently expanding. It has emerged as one of the fastest-growing segments within polypropylene products. The continuous introduction of new processes and varieties has led to an expansion in the production scale, efficiency, product range, and application areas of transparent polypropylene.
Transparent polypropylene, renowned for its exceptional transparency and gloss, rivals typical transparent materials such as PET, PVC, and PS. It finds wide application in household items, packaging, and medical fields. Its products not only exhibit high toughness, rigidity, and heat resistance but also demonstrate outstanding chemical resistance. To enhance the market value of polypropylene (PP), transparent modification plays a crucial role.
According to AsiaMB, numerous factors influence the transparency of polymer materials, with refractive index, crystallinity, crystal size, and surface roughness being the primary ones. For transparent polypropylene, reducing crystallinity and crystal size is key to improving its transparency. Currently, the main methods to enhance PP’s transparency include adding transparency agents, synthesizing random copolymers, using metallocene-catalyzed synthesis, blending for increased transparency, and process control.
In the case of adding transparency agents, incorporating them into PP effectively reduces the size of spherulites, thereby enhancing the resin’s transparency. Transparency agents act as crystal nuclei, increasing the number of crystal nuclei within the crystallization system. This results in a higher number of microcrystals, a decrease in spherulite count, and finer crystal sizes. Among these, sorbitol-based nucleating agents are the most widely used in PP transparent modification. When the content of DMDBS is between 0.2% and 1%, PP’s transparency significantly improves with the increase of DMDBS.
Synthesizing random copolymers is another effective method to enhance PP’s transparency. During PP synthesis, the addition of ethylene as a second monomer to copolymerize with propylene disrupts the regularity of the PP molecular chain, reducing crystallinity and improving the transparency of PP products. Meanwhile, metallocene-catalyzed synthesis of transparent PP represents a new technology, with the transparent PP resin produced using metallocene catalysts achieving a light transmittance of up to 94%, comparable to PS.
Blending for increased transparency is yet another method, but it requires good compatibility and similar refractive indices among the two or more base materials. Blending modification allows for the integration of performance advantages from each component, resulting in polymer materials with excellent overall performance. However, this method has seen slow development, with limited research currently being conducted.
In terms of process control, processing temperature and cooling temperature are the main process conditions affecting PP’s transparency. Lowering these temperatures enhances transparency. Additionally, controlling molding orientation is crucial for improving transparency, as proper orientation can minimize birefringence and light scattering, thereby increasing light transmittance.
In summary, the transparent polypropylene industry in China continues to grow and thrive. To enhance market competitiveness, the industry should focus on the development of advanced catalysts, efficient transparency nucleating agents, and advanced processing technologies and equipment. It should also emphasize technological innovation and product development to meet the ever-changing market demands.