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Effects on Oxygen‐barrier Properties of Pretreating Paperboard with a Starch–Poly(Vinyl Alcohol) Blend before Polyethylene Extrusion
Author(s) -
Javed Asif,
Ullsten Henrik,
Järnström Lars
Publication year - 2017
Publication title -
packaging technology and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.365
H-Index - 50
eISSN - 1099-1522
pISSN - 0894-3214
DOI - 10.1002/pts.2210
Subject(s) - plasticizer , materials science , coating , extrusion , starch , composite material , polyethylene glycol , polyvinyl alcohol , chemical engineering , vinyl alcohol , paperboard , pullulan , polymer chemistry , polymer , chemistry , organic chemistry , polysaccharide , engineering
Polyethylene (PE) extrusion coating was performed on paperboard pre‐coated with water‐borne barrier coatings based on starch–poly(vinyl) (PVOH)–plasticizer blends in order to investigate that how the addition of a plasticizer to the pre‐coating affects the oxygen‐barrier properties of the board after PE extrusion coating. The plasticizers used were glycerol, polyethylene glycol (PEG) and citric acid (CA). Photomicrographs showed that the barrier coating layers were rather smooth, but defects were observed in the starch–PVOH layers when a plasticizer was added. Starch–PVOH layers had oxygen‐barrier properties similar to those of pure PVOH without plasticizers. When a sufficient number of layers (four layers) were applied to cover defects, the starch–PVOH layers containing CA showed oxygen transmission rate (OTR) values similar to those of starch–PVOH layers without plasticizer. The adhesion of PE to pre‐coated paperboard decreased when a plasticizer was added to the pre‐coating recipes. PE extrusion coating resulted in a reduction in the OTR in the case of pre‐coating formulations containing plasticizers. A lower OTR after polyethylene extrusion was observed with PEG as plasticizer than with CA as plasticizer. This could be explained by the increase in brittleness due to cross‐linking under the high temperature load during the extrusion process. Dynamic mechanical analysis of the films showed a substantial increase in storage modulus between 100°C and 200°C for CA‐containing starch–PVOH films. The contact angle of diiodomethane on the pre‐coating layer decreased when a plasticizer was added to the coating recipe indicating an increase in wetting of the PE melt. Addition of PEG to the pre‐coating led to a greater wetting than the addition of CA, and this may have sealed some defects in the pre‐coating leading to lower OTR values.