Crack analysis of barrier coatings based on starch and starch-PVOH with and without plasticizer

• Barrier coatings based on starch and starch-PVOH plasticized with glycerol and without plasticizer were applied to two different paperboard substrates, a triple coated board and duplex board, in order to investigate the tendency for cracks to develop in the barrier coating layers during creasing and folding. Tensile properties of films based on the starch and starch-PVOH blend were determined to investigate the relationship between the flexibility of the films and the cracking in the barrier coating layers. Furthermore, the oxygen transmission rate through the barrier-coated paperboard was measured before and after creasing and folding. The oxygen transmission rate through the barrier-coated samples was over the measurable range i. e. OTR > 10000 cm 3 / m 2 day\text{OTR}>10000\hspace{0.1667em}{\text{cm}}^{3}/{\text{m}}^{2}\hspace{0.1667em}\text{day} after creasing and folding, which indicated failure in the barrier coating layers. Optical microscopy revealed small cracks in the barrier coating layers, probably related to an increase in flexibility of the barrier coating layers. It was observed in scanning electron micrographs that cracks in the barrier coating layers seemed to follow the fibers when the barrier coating was applied on the rear side of the duplex board. Scanning electron micrographs and surface profiler images revealed that cracks in the barrier coating layers might have originated from the mineral coating layer when the starch and starch/PVOH coating layers were applied on the mineral-coated side of the triple coated board. An increase in the thickness of the barrier coating layer did not seem to increase the resistance to failure.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Kemiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Chemical Engineering (hsv//eng)

Nyckelord

barrier coatings

creasing

folding

glycerol

mechanical properties

starch

Cracks

Nanofiltration membranes

Oxygen

Oxygen permeable membranes

Paperboards

Plasticizers

Reinforced plastics

Scanning electron microscopy

Coated paperboard

Crack analysis

Oxygen transmission rates

Scanning electron micrographs

Surface profilers

Coatings

Vapor Barriers

Chemical Engineering

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