Natural Kraft and SUS papers and boards are among packaging designers and brands managers favorite materials to foster packaging innovation and pursue sustainability goals, combining high strength, high tear resistance, 100% recyclability and a positive image among consumers.
The Kraft process (the industrial process involved in producing pulp for Kraft papers and boards) is a chemical pulping process (different from thermo-mechanical pulping) that produces a stronger pulp than other chemical pulping processes thanks to a lower degradation of cellulose. Sulfite process used for instance to produce SBS and SUS boards requires an acidic environment that affects a bit more the cellulose but remove almost entirely the lignine from the fiber for a better stiffness. The Kraft process can use a wide range of fiber source including resinous woods especially pine renowned for the length of its fibers, fiber length impacting directly the strength of the paper or the board.
Natural Kraft boards proposed for packaging purpose are sold under different acronyms depending on their features. UUK (Uncoated unbleached kraft), CUK (Coated unbleached Kraft) or CNK® (Coated natural kraft) … Some are specially engineered for an increased resistance in cold (and wet) environments for beverage carton packaging. Natural Kraft boards could also be coated with polyethylene (PE) resin for wet strength food packaging.
We can find on the market very good Natural Kraft boards with an attractive natural brown appearance and outstanding printability, even if uncoated. Unbleached and uncoated boards are a good packaging material for brands promoting a natural product, with no chemical additive and a sustainable development. It is also a smart way of differentiation especially in markets where SBS ultrawhite boards are considered as a norm.
SUS board has a better stiffness than any other board with the same caliper.
|lbs / 3000 ft2||Stiffness CD mNm||Stiffness MD mNm|
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