Microflute and Paperboard, Updated

Recent inquires to the Ask the Experts link have sought thoughts on the robust and resilient aspects of both “conventional” and small-flute corrugated. There have also been questions on F flute. As a follow-up to the last article on warp and digital printing, here is an updated refresher on the strength characteristics of small-flute corrugated.

Tom Weber and I facilitated a three-hour forum at the 2018 AICC Spring Meeting on the merging of microfluted products (E, F, N, and O) with solid-fiber paperboard substrates such as solid bleached sulfate, coated recycled board, and uncoated recycled board applications for folding carton and rigid box.

Six exceptionally qualified presenters, AICC member panelists, and facilitators had over 141 years of combined experience in the production and conversion of E flute, F flute, and thinner flutes for creative solutions that can run directly through offset presses in some cases and now on digital presses as flat sheets (no warp).

One example was a 33/23F/33 combination to replace a rigid-box construction, and this new alternative carton ended up having 30% more top-to-bottom compression than needed. It was robust and resilient. Machine direction and cross-direction Taber stiffness tests were also performed. So, next time even lighter-fluted alternatives will likely be combined to engineer the best and most economical fit for carton use.

F flute is becoming more available from sheet feeders and trade finishers. E/F combined board has some promising opportunities at replacing conventional 40# and 44# ECT grades.

There have been testing methods to directly relate fluted products with paperboard, but they have been widely unknown to many converters. Testing fluted materials under the solid fiber protocols used for paperboard, such as block compression, Taber stiffness, and corner crush, will give folding carton and rigid plants the opportunity to compare and quantify the results for different substrates. These comprehensive test methods will take the guesswork out of the conversion and allow for a documented, repeatable, and statistical rationale to be presented to all internal and external stakeholders involved.

What were the key drivers identified by our audience?

• Digital and direct print onto fluted substrates.
• Making certain microflutes are mold- and bacteria-free for indirect food contact and pharmaceuticals.
• Lightweights—browns are increasing, although 9# and 10# are used today, 20# uncoated whites are coming, and paper grades are always available.
• Ongoing issues with SBS—less than 10-point availability domestically.
• Paperboard mills have closed, and merchant “open-market” tonnage is disappearing into integrated companies.
• E-commerce and its need to reduce the amount and weight of packaging.
• Warehouse clubs constantly change the retail experience.
• More seasonal product changes and more product offerings (SKU proliferation).
• Modern corrugators have many new capabilities to tightly control sheet warp with process controls that can adjust moisture, heat, and actual starch applications.
• Asitrade machines can meter adhesives through conventional anilox rolls and grooved rod metering systems that can apply different application rates for each particular flute profile as needed.
• Lastly, how do we know what microflute profiles and material compositions to change to from paperboard to fluted products? Is there a method we can depend on to communicate to our clients, to ensure that success is built into our conversions?

There were recommendations regarding die cutting from the single-face or double-face printed side of the sheet and the use of counter plates. If this or score-cracking has become an issue with you, contact us for referrals. One of the presubmitted questions involved the use and amount of biocide in food-grade and pharmaceutical packaging. Chemistry keeps evolving. There is a difference between starch-line and glue-line dosings.

All panelists, facilitators, and audience members were reminded that the two distinctly unique product lines of microflute and paperboard are not mutually exclusive replacement strategies, but they are additive and additional opportunities to advance packaging sales into markets that are perhaps not being currently served. We believe much progress has been made. It was proven without a doubt that, within AICC member organizations, we have the technical, converting, and personnel expertise to support any member’s decision to take the next steps.  

Ralph Young is the principal of Alternative Paper Solutions and is AICC’s technical advisor. Contact Ralph directly at askralph@AICCbox.org about technical issues that impact our industry.