Spray process to styrene grafting onto polyethylene film surface

Scientists found a versatile process to perform grafting reactions on PE surfaces. Therefore a Polyethylene film was modified by grafting styrene using a spray method. PE paintability was enhanced by a combination of surface hydrophilicity increment and roughness and thermal degradation temperature are incremented.

Th scientists modified polyethylene (PE) film surface in order to improve its paintability performance. Source: Franz Pfluegl – Fotolia.com. -

A direct and fast post-processing method to modify polyethylene (PE) film surface is proposed in order to improve its paintability performance without changing its bulk properties. This goal is achieved by grafting styrene onto the PE film surface using a macrocarbocationic copolymerization reaction where both catalysts and reagents are sprayed directly on softened film respectively. Pure styrene as grafting molecule and aluminium chloride suspended in n-heptane as catalyst are used. Grafting reaction occurrence was assessed by analyzing the reacted film surface before and after extraction of non-grafted reaction products.

Potential application in continuous film production

The results confirmed by three independent analytical techniques evidence reaction occurrence. A graft-copolymer layer remains onto the PE film surface even when physically adhered reaction products were extracted. This layer enhances PE film water-affinity and paintability either with water or acrylics paints because of the grafted aromatic group and roughness increase. Besides, this modification increments PE thermal degradation temperature giving another beneficial effect for future film applications. The proposed modification film methodology has potential application in continuous film production as reagents spraying onto softened films could be applicable in a cast film extrusion line.

The study is published in: Progress in Organic Coatings Volume 117, April 2018, Pages 91-101.

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