Next Article in Journal
Morphological and Structural Study of a Novel Porous Nurse’s A Ceramic with Osteoconductive Properties for Tissue Engineering
Next Article in Special Issue
Biomineralization of Engineered Spider Silk Protein-Based Composite Materials for Bone Tissue Engineering
Previous Article in Journal
Fabrication of Wood-Rubber Composites Using Rubber Compound as a Bonding Agent Instead of Adhesives
Previous Article in Special Issue
Room Temperature Consolidation of a Porous Poly(lactic-co-glycolic acid) Matrix by the Addition of Maltose to the Water-in-Oil Emulsion
Article Menu
Issue 6 (June) cover image

Export Article

Open AccessArticle
Materials 2016, 9(6), 473;

Recyclability of PET/WPI/PE Multilayer Films by Removal of Whey Protein Isolate-Based Coatings with Enzymatic Detergents

National Research Council, Institute for the Chemical and Physical Processes UoS Pisa, Via G. Moruzzi 1, Pisa 56124, Italy
Department of Civil and Industrial Engineering, University of Pisa, Via Diotisalvi 2, Pisa 56122, Italy
Fraunhofer Institute for Process Engineering and Packaging IVV, Giggenhauser Strasse 35, Freising 85354, Germany
Chair of Food Packaging Technology, Technische Universität München, Weihenstephaner Steig 22, Freising 85354, Germany
Innovació i Recerca Industrial i Sostenible (IRIS), Parc Mediterrani de la Tecnologia, Avda. Carl Friedrich Gauss 11, Castelldefels 08860, Spain
Authors to whom correspondence should be addressed.
Academic Editor: Marek M. Kowalczuk
Received: 23 March 2016 / Revised: 30 May 2016 / Accepted: 6 June 2016 / Published: 14 June 2016
(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)
Full-Text   |   PDF [2389 KB, uploaded 14 June 2016]   |  


Multilayer plastic films provide a range of properties, which cannot be obtained from monolayer films but, at present, their recyclability is an open issue and should be improved. Research to date has shown the possibility of using whey protein as a layer material with the property of acting as an excellent barrier against oxygen and moisture, replacing petrochemical non-recyclable materials. The innovative approach of the present research was to achieve the recyclability of the substrate films by separating them, with a simple process compatible with industrial procedures, in order to promote recycling processes leading to obtain high value products that will beneficially impact the packaging and food industries. Hence, polyethyleneterephthalate (PET)/polyethylene (PE) multi-layer film was prepared based on PET coated with a whey protein layer, and then the previous structure was laminated with PE. Whey proteins, constituting the coating, can be degraded by enzymes so that the coating films can be washed off from the plastic substrate layer. Enzyme types, dosage, time, and temperature optima, which are compatible with procedures adopted in industrial waste recycling, were determined for a highly-efficient process. The washing of samples based on PET/whey and PET/whey/PE were efficient when performed with enzymatic detergent containing protease enzymes, as an alternative to conventional detergents used in recycling facilities. Different types of enzymatic detergents tested presented positive results in removing the protein layer from the PET substrate and from the PET/whey/PE multilayer films at room temperature. These results attested to the possibility of organizing the pre-treatment of the whey-based multilayer film by washing with different available commercial enzymatic detergents in order to separate PET and PE, thus allowing a better recycling of the two different polymers. Mechanical properties of the plastic substrate, such as stress at yield, stress and elongation at break, evaluated by tensile testing on films before and after cleaning, were are not significantly affected by washing with enzymatic detergents. View Full-Text
Keywords: whey protein isolate; enzymatic detergents; recyclability; protease; multilayer films; polyethylene terephthalate (PET); polyethylene (PE) whey protein isolate; enzymatic detergents; recyclability; protease; multilayer films; polyethylene terephthalate (PET); polyethylene (PE)

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

Share & Cite This Article

MDPI and ACS Style

Cinelli, P.; Schmid, M.; Bugnicourt, E.; Coltelli, M.B.; Lazzeri, A. Recyclability of PET/WPI/PE Multilayer Films by Removal of Whey Protein Isolate-Based Coatings with Enzymatic Detergents. Materials 2016, 9, 473.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics



[Return to top]
Materials EISSN 1996-1944 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top