Second-Grade vs. First-Grade Baby Diapers: What Performance Differences Actually Exist?

3. Core Integrity: No Structural Defects, Only Minor Unevenness

Core integrity encompasses whether the core exhibits fractures, clumping, or agglomeration. Grade A cores require uniform distribution of SAP and fluff pulp, maintaining a flat structure after multiple absorptions. The most common downgrade reasons for Grade B in this metric include: slight local deviations in SAP application (such as slightly less at the edges) or core compression thickness marginally exceeding the standard central value. However, these deviations are far from causing core fracture or severe agglomeration. In practical use, Grade B cores may show mild uneven swelling after absorption, but structural collapse or adhesive leakage that could compromise safety does not occur.

4. Summary: Downgrade Reflects Cosmetic or Minor Parameter Deviations, Not Functional Failure

Synthesizing the above indicators, the core distinction between Grade A and Grade B is that Grade A pursues "all indicators within the ideal range," while Grade B has "some indicators at the edge of the qualified range." The absorption speed gap is a few seconds, the rewet difference is a few grams, and the core integrity variation is merely a subtle degree of uniformity. None of these gaps renders the product unusable or harmful to infant skin. The downgrade of Grade B is essentially a compromise on "extreme parameter consistency," not a concession on "basic functional performance." For purchasers, selecting the appropriate grade based on actual usage scenarios—such as change frequency and single-use duration—is a completely reasonable commercial decision.