SOT (Stay-on Tab) and RPT (Ring Pull Tab) are two well-known forms of aluminum can LIDS, and their primary differences are structural strength, opening techniques and manufacturing costs. Let’s consider SOT as an example. Its pull ring and can lid are formed in one piece, and the material thickness is generally 0.30 millimeters. It needs to have a tensile strength above 300 Newtons. But RPT adopts a split pull ring structure with the thickness reduced to 0.25 millimeters, but with higher requirements on the ductility of aluminum alloy (breaking elongation should be ≥20%). Based on the 2022 data of Ball Corporation in the United States, SOT’s production cost was 8%-12% higher than that of RPT, primarily caused by the 2 added stamping processes and the rise in the aluminum material loss rate from 4.5% of RPT to 6.2%. Yet SOT’s rate of consumer safety complaints is only 0.003%, far lower than 0.015% of RPT, owing to the fact that its pull ring will not come off easily and lead to the risk of accidental ingestion.
As for market application, SOT aluminum can lid is more compatible with high internal pressure situations such as carbonated beverages. Its sealing surface is 1.2 millimeters in width and has the capacity to withstand an internal pressure of 7 bar. Since the pull ring is set to be torn apart in RPT, the RPT sealing surface is narrowed to 0.9 millimeters and the ultimate pressure tolerance value is 5.5 bar. An example is Red Bull. SOT was adopted by 98% of the world’s Red Bull production lines in 2023. Due to the carbon dioxide level of the product being 12 g/L, it requires greater structural stability. On the other hand, RPT gains 65% market share in Japan, with more than 30% of the consumers being elderly, due to the opening force of the pull ring requiring only 15-20 Newtons (SOT requires 25-30 Newtons). According to the statistics of the International Aluminium Institute, among 180 billion aluminium cans produced globally each year, SOT and RPT occupy 58% and 42% of the market respectively. However, RPT’s growth rate in Southeast Asia has reached 7.5%, far exceeding SOT’s 2.3%.
In terms of recyclability and sustainability, the SOT aluminum can lid, which has an intact overall structure, leads to a fragment residue rate of <0.1%, while the RPT separating pull ring makes 0.8% metal impurities enter the recycling stream, and the purity of recycled aluminum decreases from 99.7% to 99.2%. A 2021 study by the European Aluminum Foil Association shows that the energy consumption in tank regeneration by SOT is 8 MJ/kg, 12% lower than RPT, and carbon dioxide emissions are 9.3 g per tank lower. RPT is, nevertheless, closing the gap through structural optimization. For instance, the V2 version of RPT, which Yamatsu Can of Japan launched in 2023, increased the number of pull ring connection points from the original 3 to 5, achieving a recycling completeness rate of 98.5%. At the same time, it reduced the aluminum usage by 6% (from 2.1 grams to 1.97 grams, the weight of a can lid), saving over 4 million US dollars in raw material costs annually.
Technologically, SOT aluminum can lid sealing requires more accuracy, and the rolled edge overlapping ratio of it requires ≥45% (RPT is 35%), which translates to a 30% increase in equipment maintenance frequency. But Industry 4.0 technology is changing the game: In 2022, Carlsberg had an AI quality inspection system installed at its plant in Hungary. By examining 500 frames of images per second, it reduced the SOT roll seal defect rate from 0.07% to 0.005%, while also increasing the speed of the production line to 3,400 cans per minute, 22% faster than the traditional RPT production line. In contrast, RPT’s most important innovation is in user experience. For instance, Coca-Cola’s 2024 tactile feedback pull TAB with a micron-level concave and convex texture design (50-80 microns in height) has enhanced the opening success rate to 99.9% and achieved a 73% consumer preference rate in blind testing.