The Evolution of Core Designs

core design

From the first disposable baby diaper by CHUX, now Johnson & Johnson, in 1949 to Kimberly Clark’s introduction of adult diapers in 1984, the disposable hygiene industry has come a long way! These products have changed the world. They have transformed how people live. And now, as manufacturers explore and experiment with new disposable hygiene core designs, the future for these products is even more exciting. 

In the beginning

Early disposable diaper designs were very simple—yet they were still considered luxurious. The core was a stack of 15 to 25 sheets of tissue paper. They could hold an estimated 100 ml of fluid, which meant they needed to be changed after every use. Plus, they did not have the features we see today, like elasticized waistbands, leg cuffs, re-fastenable ear tabs and wetness indicators. 

But parents came to love disposable diapers, and their popularity grew. Competition among manufacturers grew as well. Just one year after the original tissue-core diaper was released, the first fluff core (made of cellulose wadding) by Paulistrom was introduced. It was cut, sized and put in reusable panties to help with fluid absorption and distribution, as well as improved performance.

Superabsorbent polymer becomes the game changer

Disposable hygiene made another big leap in the 1980s with superabsorbent baby diapers. This began when Unicharm introduced superabsorbent polymer (SAP) in Japan. 

Compared to an all-fluff core, SAP could hold greater volumes of fluid, even under pressure. But SAP alone tends to absorb and wick fluid slowly, so fluff had to stay for absorption speed and wicking. To increase absorption, manufacturers began to add greater amounts of SAP to the fluff in the core matrix. 

Core designs today 

Currently, there are two sets of fluff to SAP ratios used by most manufacturers, and adhesives are critical for both:

50% fluff to 50% SAP 

At this ratio, the fluff fibers are entangled to create a pad that keeps the SAP in place and supports core integrity. To improve core integrity even more, a core wrap that goes around the fluff/SAP and sealed with a core adhesive can be used. 

70% SAP to 30% fluff 

Manufacturers find themselves facing more challenges at this ratio. At 70% SAP, a core wrap and a core adhesive are needed to prevent the loss of SAP powder. Bostik has seen that a core at this ratio that does not use an adhesive will immediately fail the Conditioned Core Cracking Test because there is too much loose SAP powder. The core adhesive helps keep the SAP in place to improve core performance.

The future of fluff-free cores

As product producers look toward fluff-free core options, with new SAP that has better wicking and absorption speed, SAP stabilization is more important and adhesives become even more critical. No fluff means there are no fibers to hold the SAP powder in place. For manufacturers looking to create a fluff-free option, re-thinking the design is critical, and a channel core is one to consider.

If exploring new core designs is in your future, Bostik strongly recommends involving core adhesive experts like us in the early stages of development. By leveraging our expertise, we can quickly help identify the nonwoven adhesive solutions that best meet your design needs.

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