Smart Molding International 2-2025

31 www.smart-molding.com molding technologies • The processing temperature for PET exceeds 270 °C, significantly greater than that of HDPE (<200 °C); • PET crystallises much more slowly than HDPE, and its glass transition temperature is very close to the cap’s operating temperature. Impact on TCO and life cycle assessment The higher melting point of PET compared to HDPE inevitably demands more energy to melt and subsequently cool the material to a demoulding temperature. PET cap production requires a cycle time up to 70% longer than that of HDPE caps (due to higher processing temperatures, slower crystallisation, and lower thermal diffusivity), and it also requires dedicated moulds because of differing material properties (such as shrinkage and elastic modulus). Performance is similar to that of HDPE caps, with two important considerations: • PET is highly sensitive to elevated temperatures, which must be factored into the logistics and storage of the finished product; • For equivalent performance, a PET cap weighs around 20% more than an HDPE cap — its theoretical strength is offset by high moisture absorption, which, according to tests, can reduce its mechanical properties by up to 60%. Efforts to reduce wall thickness (e.g. approximately 0.4 mm in HDPE caps) face technological constraints during moulding, such as mechanical tolerances, stress-induced crystallisation, etc. Sacmi's approach included a highly detailed LCA analysis, carried out by an independent laboratory. The results of the analysis, covering 19 parameters (including climate change, resource use, water, soil, etc.) in accordance with the international standards, underscored the importance of conducting such evaluations before launching the project to confirm tangible environmental benefits. The regulatory context must also be considered. On the one hand, the European PPWR (Packaging and Packaging Waste Regulation) promotes the adoption of mono-material, returnable, and similar packaging solutions, supporting this development in principle. On the other hand, it pushes for an overall reduction in packaging weight, a target not yet attainable with the PET alternative. The SACMI approach The design and development of the new PET cap comply with the international standards regarding cap performance requirements. In addition, SACMI’s process avoids the use of additives and dyes that could interfere with subsequent recycling: the PET used is standard PET or rPET suitable for bottles. With regard to cap production and application technologies, SACMI deliberately avoided introducing special capping equipment, testing the production on its own CCM (continuous compression moulding) presses. In-line cutting and folding were also adopted, along with integrated quality control. The entire process was tested on a pilot line consisting of a humidification unit, extruder, adapted compression moulding unit, cutting and folding line, and quality control using CVS systems. Technology: the support of the SACMI Lab Reduced cycle times and high cavitation are key market demands that SACMI has addressed with the recent launch of the new CCM64MD press. Boasting outstanding performance, the machine can produce up to 2,850 caps per minute (171,000 caps per hour) in HDPE, using just 64 moulds and a cycle time of only 1.35 seconds. This is achieved alongside a 50% reduction in footprint and a 15% reduction in specific energy consumption compared to the previous generation, at 0.43 kWh per kilogram of HDPE processed. In this context, any potential shift from HDPE to PET would require consideration o f several factors : comparab l e performance (especially regarding storage temperatures, transportation, etc.), higher TCO, LCA assessments tailored to specific environmental and production scenarios, etc. The SACMI Laboratory is available to support customers in developing customised early adoption solutions. SACMI www.sacmi.it All pictures: SACMI 64 molds for 2.850 caps/min. in 53 m 2