Improving diaper performance while saving money
Exactly one year ago, I shared a short article entitled “Short Fibers and the Paradox of Pad Integrity, Myth or Reality?”. That text was viewed by thousands of professionals in the diaper industry and was later translated into other languages by a pulp manufacturer. In it, I discussed the benefits of using short fibers, such as eucalyptus fluff, to increase pad capillarity, improve wicking, reduce diaper thickness, lower packaging costs, and enhance perceived softness. I also debunked some myths surrounding short fibers and pad integrity that have accompanied the industry for nearly six decades. Many people contacted me requesting guidance on how to apply these concepts and, above all, a simple guideline that could be used during manufacturing. Below, I share some suggestions on how to leverage these benefits, explaining why this is a concrete opportunity to save money while improving diaper performance.
Diaper softness has gone from being merely a differentiator to becoming one of the most important attributes demanded by consumers worldwide. To meet this demand, new nonwoven technologies have had to be implemented and continue to evolve. Generally, softness is improved by replacing the backsheet with softer materials, using higher lofts or higher-GSM materials, and applying 3D textures that create a soft feel. However, high-loft materials may pose risks, such as fiber shedding, which can detach and reach babies’ mouths.
What is not always well known is that softness can be significantly improved simply by making the absorbent core softer. Many may have already noticed a slight improvement when replacing the core wrap with a nonwoven material while keeping the rest of the construction unchanged. Now imagine the impact of softening the entire core, not just its wrap. That said, simply reducing block density without changing the ingredients is not a good solution: it increases packaging costs and may compromise pad integrity. Moreover, this approach runs counter to important current market trends, as I will explain below.
A more effective solution for improving softness is to blend eucalyptus fibers into the core. The ideal amount depends on the type of final product. Products designed for low capacity, such as feminine hygiene pads or booster pads, can be manufactured without blending with pine. Products not subjected to intense movement, such as underpads and pet pads, can also use eucalyptus fluff without the need to combine it with pine fluff. However, products that require greater structural integrity, such as baby diapers, pants (especially when used by children), or adult disposable underwear, should use a blend of short and long fibers to achieve softness without sacrificing stability.
Adult pants produced on double-drum formers present an additional advantage: they can benefit from the density gradient created by the combined use of pine and eucalyptus fibers in separate layers. It is possible to increase fiber content and pad density by using more eucalyptus, resulting in a more compact and softer core, without the need for high investments in backsheet upgrades.
The global trend toward thinner products is evident. In mature markets, consumers prefer slimmer diapers, seeking better ergonomics, a more comfortable fit, and improved aesthetics. For adults, this need is even more critical: they demand more discreet products that preserve dignity and are easy to carry while traveling or commuting. In this context, thinner products are also more economical, as they reduce logistics and packaging costs. However, an important question arises: how far can diaper thickness be reduced?
After analyzing hundreds of consumer reviews and participating in home-use tests in the United States, I found that fluff-free cores tend to leak earlier, especially after the second insult. Preventing early leaks in fluff-free cores requires extremely advanced engineering, which is difficult to implement for most factories. In my experience, unless these fluff-free cores are balanced with the correct amount of cross-linked fibers (such as curled fibers) or receive a higher-basis-weight ADL, it is not uncommon for diapers with a small percentage of fluff to outperform fluff-free designs, especially under certain body positions. For this reason, I do not see many brands pursuing specialized fluff-free diaper machines, despite a few reference examples in the industry. Blending short and long fibers offers natural advantages without requiring the complete elimination of traditional fluff.
To maximize the capacity of an absorbent core, it is necessary to increase pad utilization efficiency. Increasing the ADL can help, but it is an expensive solution and, when applied too broadly, may promote edge leakage. Therefore, ADL should remain a patch rather than a continuous layer. Increasing core capillarity without raising costs is a more efficient alternative, and this is precisely where blending with eucalyptus outperforms pine alone. By reducing the spacing between fibers and increasing core density, capillarity improves. This is a well-known phenomenon in fluid dynamics: it is not the fibers themselves that retain liquids, but the spaces between them. For this reason, cores using short fibers tend to exhibit higher efficiency — something that may not always be evident in laboratory tests but becomes clear in maximum capacity before leakage (MCBL) measurements using mannequins or real-use tests.
Another important consumer demand is the use of sustainable materials. It is widely recognized that eucalyptus is an environmentally more advantageous alternative than pine for carbon capture. Young trees capture CO₂ at higher rates than mature trees, making eucalyptus’s shorter harvesting cycle even more favorable from a climate perspective. Using more eucalyptus allows the harvesting cycle to be reduced to one-third of the time, ensuring more replanting and increasing net carbon sequestration. I also believe that, in the coming years, post-consumer diaper recycling will become viable, with components being recycled instead of sent to landfills or incinerators. When this happens, disposable diapers may achieve an even lower carbon footprint, outperforming alternatives such as biodegradation, incineration, or even cloth diapers.
In summary, cost savings can be achieved by blending eucalyptus fluff at the mill. However, it is essential to adjust debulking on the production line. For 50% eucalyptus and pine blends, a thickness reduction of 15% to 20% is estimated. In 100% eucalyptus blends, this reduction can reach 25% to 30%, depending on pulp moisture and plant conditions. Due to the natural resilience of the pad, the physical reduction in gap may not correspond exactly to the final thickness reduction, so a margin of error must be considered. Even so, under conservative estimates, a 15% volume reduction can result in net savings of at least 2% when considering packaging and distribution, potentially even higher when pine blending is not required.
It is also essential to evaluate pad integrity after changing the composition. If necessary, institutions such as Diaper Testing International, in Houston, can perform independent testing at affordable costs. Integrity hot-melt adhesives may also be used as an additional resource. For 50% blends, the use of such adhesives tends to be minimal or unnecessary. For blends with higher eucalyptus content, compensation with specific adhesives may be required, similar to what occurred in the industry when SAP usage increased from 40% to 60%. Cores with 100% eucalyptus will likely also require slightly thicker ADLs due to the reduced absorption speed expected in denser pads. Nevertheless, this additional cost is expected to be lower than the savings achieved through reduced packaging and distribution, in addition to the benefits gained in softness, absorption, and sustainability.
Finally, do not believe theoretical assumptions — not even mine — without validating them on your own production line. Every factory operates under unique conditions. Test, measure, and validate under real conditions. This is probably the best advice I can offer today.