Creating Easy Peel Longitudinal Seals in a Mono-PP Film without Additives in the Sealant Layer using Ultrasonic Sealing on a HFFS System

Current trends show that mono-material films are replacing complicated multi-material films in the packaging industry. These mono-material films are more suitable for recycling. However, achieving the same functionalities like easy pealing and sufficient barrier properties is a challenge. This research investigates two topics, namely the creation of an easy peel seal and damage to the barrier layer while sealing mono-materials with the ultrasonic sealing process.
This research is executed by creating mono-PP (BOPP-PP-EVOH-PP) packages on an Omori HFFS system with an ultrasonic longitudinal seal and conduction transverse seal. The speed of the machine was set to 80 packs/minute. The longitudinal seal was created with a 35kHz Herrmann Ultraschall LSM with the amplitude ranging from 70 – 100% and the pressure from 0,1 – 2,3 bar.
The seal strengths are measured using the KOPP Labormaster HCT 3000. The results confirm that it is possible to create an easy peel seal with ultrasonic sealing with material where no controlled contamination has been applied in the sealant layer. An explanation is found in the heat generation of ultrasonic sealing.
Cross-sections of seals have been investigated using the Keyence VHX 7000 digital microscope. It is found that the barrier layer might be disrupted while sealing a mono-material with ultrasonic sealing.