Sterilization of propylene/ethylene random copolymers: Annealing effects on crystalline structure and transparency as influenced by polymer structure and nucleation

Abstract

Abstract. An extensive investigation of three different series of isotactic ethylene/propylene (EP) random copolymers was performed to understand the factors influencing the change in optical properties in the steam sterilization of extrusion cast films from such materials. Different analytical methods (differential scanning calorimetry (DSC), X-ray diffraction and electron microscopy) were employed to elucidate structural changes determining film optics, and in addition to the polymer structure parameters also nucleation and processing effects were studied. The findings clearly show that a combination of homogeneously randomized comonomer distribution and nucleation can partly inhibit lamellar thickening in sterilization, thus preserving high transparency even after a heat treatment. In detail, attention has to be paid to the combined effects of primary and secondary post-crystallization, which both are affected by the chain regularity.

Designing polymer crystallinity: An industrial perspective

“…All of these changes are relevant for packaging‐related processes like steam sterilization and sealing/welding. For PP it clearly depends on polymer structure, nucleation and processing history . It is obvious that relatively stronger changes occur in quenched structures even at ambient temperature.…”

Heterophasic copolymers of polypropylene: Development, design principles, and future challenges

“…The combination of a high impact strength and rigidity allows the packaging solution to withstand transportation and storage unscathed, and it protects the contents. The development of heterophasic PP, which shows high transparency and gloss also after sterilization, has allowed the use of such materials for flexible packaging solutions such as stand‐up pouches . The development of high‐purity PP and the debate concerning the adverse effects of plasticizers in plasticized poly(vinyl chloride) (PVC) increased the use of very soft heterophasic PP copolymers in health care applications, such as in medical infusion bags and in packaging for medical instruments.…”

Modeling and analysis of the process of polymeric film cooling on the drum with a liquid cooling agent

“…Articles [20,21] contain results of research in influence of temperature of the cooling drum on properties of a polypropylene film.…”

“…An analysis of publications on the production of flat polymeric films [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] showed that majority of them are devoted to numerical and experimental modeling of separate stages of their production process. The focus on the process of preparation of polymer melt in the extruder [7][8][9][10], as well as the process of orientation of semi-finished film on the section from the extrusion head to the cooling drum [11][12][13][14][15][16].…”