PET film faces unique technical challenges as a substrate for silicone release agents, and these fundamental problems limit its popularity in large-scale industrial applications. PET (polyethylene terephthalate) is a crystalline polymer material with low surface energy and strong chemical inertness, which makes it difficult for silicone release agents to form a strong bond. In practical applications, PET and silicone coatings are prone to peeling, especially in high temperature and high humidity environments, and the stability of the bonding force is difficult to ensure. This inherent interfacial incompatibility forces R&D personnel to develop special adhesion-enhancing technologies, such as using methylphenyl alkoxysilane, silane coupling agent with epoxy group and silane coupling agent with aminopropyl group to react to prepare adhesion enhancers, and then compounding with high-transmittance silicone resin to form special coatings. Although these technical solutions partially solve the bonding problem, they significantly increase material costs and process complexity, weakening the market competitiveness of PET substrates.


From the perspective of coating process, the production of PET release films faces many technical barriers. Unlike paper, PET film cannot withstand high-temperature curing conditions (usually below 150°C), which limits the application of traditional heat-curing silicone oils6. To solve this problem, the industry has to adopt alternative technologies such as UV curing or electron beam curing, but these methods require expensive special equipment and the processing cost is 1-2 times that of heat curing. For example, UV curing silicone oil requires a UV lamp system and nitrogen protection device, while the investment in electron beam curing equipment is even larger, and it is reported that only one foreign-funded enterprise in China has such a production line6. In addition, PET film is prone to static electricity during high-speed coating, resulting in uneven coating and increased defects, which are less common in paper coating. The complexity of the process directly pushes up the production cost of PET release film, making it difficult to compete with paper-based products in the price-sensitive mass market.


The stringent performance requirements further increase the technical difficulty of PET release film. High-end PET release films for optical and electronic die-cutting industries need to have high light transmittance, low haze, excellent dimensional stability and cleanliness4. Most domestic companies use ordinary coating machines for production, which have problems such as organic solvent volatilization, uneven resin cross-linking and much dirt, and the products are difficult to meet high-end application standards4. In contrast, paper substrates have no requirements for optical properties, and the surface fiber structure can cover some coating defects, and the process tolerance is higher. In response to the special requirements of PET substrates, leading companies have developed silicone resin systems based on highly transparent monomers such as methylphenylsiloxane, methylphenylcyclosiloxane and trapezoidal polysilsesquioxane, which can meet the optical performance requirements through rare earth solid superacid catalytic polymerization. This high technical threshold has blocked many small and medium-sized enterprises from the PET release film market, resulting in high industry concentration and insufficient innovation vitality.


Cost structure differences are the key economic factor limiting the application of PET. The price of PET resin itself is higher than that of paper, and the complex coating process and expensive curing equipment make the final product cost high. Market data shows that the price of high-quality PET release film can reach 3-5 times that of ordinary release paper. This price gap is difficult to be accepted by end users in most application scenarios unless there is an irreplaceable performance advantage. At present, PET release films are mainly limited to a few fields such as high-end electronic die-cutting and optoelectronic display. These applications have extremely high requirements for material thickness accuracy, dimensional stability and cleanliness, which paper substrates cannot meet4. Even in areas where PET has a relative advantage, such as protective films and release films, domestic products still find it difficult to compete with international brands, resulting in a heavy reliance on imports in the high-end market4. This market structure further inhibits the enthusiasm of domestic companies to invest in PET release film technology, forming a vicious circle.


The problem of recycling and reuse constitutes a bottleneck for the sustainable development of PET substrates. Although PET materials are theoretically recyclable, there are many challenges in actual recycling and treatment. Silicon-coated PET films are more difficult to recycle because the silicone coating will affect the melt processing performance and product quality of recycled PET6. In contrast, paper-based release materials have obvious advantages in recycling and treatment, especially plastic-free release paper can directly enter the pulp recycling system. With the increasingly stringent global environmental regulations and the popularization of the concept of circular economy, material recyclability has become an important purchasing consideration. If PET release films cannot effectively solve the recycling problem, they will be in a more disadvantageous position in the wave of sustainable development. Currently, the industry is exploring advanced recycling technologies such as chemical depolymerization, but cost-effectiveness remains a major challenge.


The limitations of application areas also restrict the market expansion of PET release films. PET substrates are mainly used in special scenarios that require transparency, high strength or temperature resistance, such as optical film materials, electronic component process protection, etc.4. However, paper-based solutions are generally used in packaging, labels, sanitary products and other fields that occupy the largest market share of release materials. This application differentiation makes it difficult for PET release films to achieve economies of scale, and the unit cost remains high. It is worth noting that even in areas where PET has performance advantages, such as flexible display and touch screen processes, new paper-based materials are constantly penetrating, improving performance through surface treatment and composite technology, further squeezing PET's market space. In the future, PET release films may be increasingly limited to a few high-end professional applications, and it will be difficult to shake the dominant position of paper in the mainstream market.


In general, the technical bottlenecks, process challenges, cost disadvantages and recycling problems faced by PET substrates in the application of silicone release agents have jointly restricted its market development. Although it still maintains an irreplaceable position in the high-performance field, it is difficult to compete with paper-based products in the mass market. In the future, breaking through existing technological limitations through material innovation and process innovation may be the key path to expanding the application scope of PET release films.