Can Diapers Achieve Both "Breathability" and "Leak-Proof" Performance? — The Science Behind Microporous Backsheet Technology

II. Process Balance Between Breathability and Leak-Proofing — How to Prevent "Breathable Pores" from Becoming "Leak Channels"?

Since breathable films are covered with micropores, how do we ensure that urine isn't "squeezed" out under pressure? This involves three key process balances.

The first is pore size distribution control. During backsheet production, more than 95% of micropores must be concentrated within the 0.5–1.5 micrometer range to prevent individual "oversized pores" from becoming leak channels. The second is hydrophobic modification treatment. Hydrophobic additives are typically incorporated into the backsheet material during blow molding or casting processes, reducing the film's surface energy and further increasing resistance to liquid water penetration — even under mechanical pressure, droplets cannot deform sufficiently to enter the micropores. The third is core-backsheet synergy. No matter how strong the backsheet is, it cannot withstand localized liquid pooling caused by the core "rewetting" large amounts of fluid. Therefore, high-performance diapers must ensure a synergistic relationship between the core's liquid-locking capability and the backsheet's breathability — the core locks it in, and the backsheet lets it out. When core rewet values are controlled at ≤10g and the backsheet WVTR exceeds 3,000 g/(m²·24h), even under firm pressure, urine will not find its way through the micropores. This is precisely the technical foundation that allows premium diapers to maintain both a "dry top layer" and a "non-leaking outer backsheet" throughout 8–12 hours of wear.