Flexible Packaging

followed perhaps by an LDPE/foil layer and finally an LDPE/heat seal layer.

EMBOSSING IS BOSS For applications where an attractive, high impact visual appearance is needed such as cosmetic packaging certain grades of PET are being used. The film lends itself to a variety of decorative finishes including embossing and holographic designs. However, as mentioned earlier packaging is not necessarily the only area where filmic materials can be used. PET and polyamide films are known for their ability to withstand heat and for the ability to maintain di-electric properties at high temperatures, depending upon material selection temperatures as high as 240 degrees centigrade can be confidently achieved, making them ideal for coil winding insulation and for the manufacture of motors. Poly-ether-ether-ketone or PEEK can be used for applications that require a film that can function at temperatures in excess of 260 degrees centigrade, at the same time providing resistance to solvents, chemicals and even fire and smoke. In terms of packaging, one of the most

prominent areas for flexible packaging is snack foods and/or ready to eat foods and drink. For this reason let’s look at this application area briefly. Films have provided an enormous creative opportunity for marketer and brand owners using flexible plastic films and laminates. Generally regarded as impulse purchases snack food producers; their print and converting suppliers, the marketers and designer must strive not only for initial maximum visual impact, frequent design changes are often required in order to gain shoppers attention and keep interest going in the brand. Selecting the most appropriate film for the application is not always clear-cut. Packaging technologists, manufacturers and converters have to take into account film slip properties, dimensional stability, elasticity and hardness, for example. The dictates of the application narrow

down the selection. Many snack foods have low moisture content but high fat content. Watchfulness is very much a key requirement for everyone involved in snack food package selection and production process. The presence of unsaturated fatty acids from cooking oils, albeit in trace amounts is spread over the product contents and interior of a package surface can, when exposed to air and oxygen lead to rancidity. When selecting packaging structure for snack foods the packaging professional and film supplier must ensure that packaging is free from the smallest pinhole and that the seal prevents aroma leakage while minimising the risk of air or moisture seeping in and possibly compromising product quality. Bi-axially oriented films are often used,

particularly in Europe for snack food items. Oriented polypropylene (OPP) may form October 2018 31

part of a structure as it provides good clarity, offers excellent puncture and abrasion resistance. Sealability can be achieved via extrusion with co-polymers of polyolefin or by coating with PvdC. Polyesters provide good gas barrier resistance, PP on the other hand and EVOH or ethyl vinyl alcohol may be selected if resistance against moisture is high on the agenda. Of course there are many other issues to consider such as printability. Because colour has such a powerful influence, much time and effort is placed on ensuring it is accurately reproduced and that elements such as design, graphics, text and other value added decorative enhancements are in agreement. Achieving colour accuracy on press is not always easy; equally it can be trying at times for the ink formulator. Paper and foils do not require the variety of ink types necessary for films. As far as the ink formulator is concerned, polypropylene is arguably the material with the greatest potential for variance owing to the presence of antioxidants, stabilisers and slip compounds.

COLOUR COMMUNICATION Proofing and colour communication devices such as the FlexiProof and variants FlexiProof UV and FlexiProof LED UV enable users and producers of flexographic inks to ensure colour accuracy, determine printability and trial unfamiliar substrates/consumables, etc. Printing, proofing, curing, evaluating and resolving colour and ink issues off of the production press minimises on press waste and reduces downtime. Over the last decade the requirements of production, particularly down gauging and

the processing of ultra-thin filmic materials at high speed and the deposition of ultra thin coatings has placed greater demands on printing and converting machines. To address many of the processing and production requirements a new generation of quality control, product monitoring and pilot coating/printing and laminating systems have been developed and have come on stream. The VCM is one of RK Print Coat

Instruments most ambitious product concepts to date. Each system is custom configured to meet the specific and known needs of the converting or manufacturing customer. The VCM is designed and built under the strictest of customer confidentiality agreements. There is no typical user, however, it is often the case that purchasers have been unable to obtain a standard commercially available system that can meet their needs. The VCM can be used for developing new coating formulations; testing substrate/ink receptivity, quality control purposes, trialling (pilot runs) and the specialised production of high tech items, security and other products. Users can select from a wide range of print/coat and laminating technologies. Coating systems include hot melt, reverse roll, gravure-offset (printing and coating), knife over roll, meter bar and much more. The VCM can be employed to determine

how different substrates and consumables such as inks and coatings perform over a period of time, especially useful when products have been developed but prior to full-scale production and commercial commitment.

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