Sanitary napkins are considered as the most personal feminine hygiene products. Competing brands of women’s sanitary napkins variously promote claims of “ultra-thin”, “high capacity” and “speed absorption” which can ease the users over their monthly periods, without embarrassment and discomfort due to leakage. However, a Consumer Council test on 45 models of sanitary napkins found slight leakage in 2 models. Further, whether the sanitary napkins still stay surface dry after absorbing multiple doses of fluid is also a vital factor for consideration. In the multiple absorption test, 3 models failed to complete the entire test process. The remaining models in the multiple absorption test were found to vary widely in the acquisition time (length of time to absorb the dose). A day-use/night-use model, took nearly 30 minutes to fully absorb the testing fluid. Sanitary napkins that absorb speedily with only slight amount of re-infiltration, and stay dry without any leakage not only can make the users comfortable and set their mind at ease, but also reduce the risk of infection arising from prolonged contact of the genital area with the wet surface of the sanitary napkin.
Included in the 45 models were 21 models purportedly suitable for day use and regular menstrual flow (claimed length of 23-25cm); 10 models for day/night use (claimed length 26-29cm); and 14 models for overnight use (claimed length 29-42.5cm). All models were with wings.
The test made reference from the Mainland’s mandatory standard GB 15979-2002 “Hygienic Standard for Disposable Sanitary Products” and recommended standard GB/T 8939-2008 “Sanitary Absorbent Pads (including panty liners)”, and also Taiwan’s Standard on Feminine Sanitary Napkins CNS 9324, in conjunction with the laboratory to jointly devise a test method for evaluation of the product performance from different aspects, based on a simulated usage of the products.
Sanitary napkin’s structure
In general, a sanitary napkin consists of 3 layers made with different materials: a permeable top layer, an absorbent layer and an impermeable bottom layer. Its performance is affected by the design and the materials used.
The Top Layer: which is in direct contact with the skin and the genital area, its main function is to allow the menstrual flow to be instantly absorbed and isolated to ensure dryness of the skin and to avoid discomfort due to prolonged contact with the soaked napkin. The top layer is usually made of non-woven cotton-like material or pure cotton, both are soft to the touch. Also some are made of polyethylene material to create a mesh layer which has the advantage of lesser degree of liquid attachment and higher degree of surface dryness.
The Absorbent Layer: whose function is to absorb the fluid and then store and retain it. The layer is commonly made of the material super absorbent polymer (SAP) or SAP-containing paper. These polymer particles will expand rapidly once coming into contact with water thus can effectively absorb and then retain fluid. Other materials used include fluff pulp, pulp, wood pulp or cotton.
The Bottom Layer: whose main function is to prevent leakage, is generally made of low-density polyethylene to prevent fluid from seeping through the layer staining clothes.
Test findings
On a scale of 5 points, 29 out of 45 models scored 4 points or above in the rating, a good overall performance. But 3 of the models received only 2.5 points, 2 of them, were intended for both day and night use, scored in the multiple absorption and surface dryness tests, a mere 1 point, a rather dismal performance. Among the different types of tested models, the models for overnight use fared the best – nearly 80% (11 models) were rated favorably with 4 points or above. Two-third (14 models) of the day-use samples were rated also with 4 points or above.
Leakage test
In reference to the Taiwan’s Standard on Feminine Sanitary Napkins, the results showed slight leakage in 2 models. In the re-test, 1 of these models, a day-use model absorbed with10ml of colored solution was found to have slight leakage along its edge after being pressurized, and as to the other - a model for day/night use, the colored solution seeped through and stained the surface of the wings but not did not reach the filter paper placed below the sample. Manufacturers are urged to strengthen quality control in their production, and to address the leakage problem.
Absorption tests
In the run-off test to assess products’ instant absorption performance, 41 models were found able to almost fully absorb the 5ml artificial menstrual fluid within a short time, indicating good overall absorption performance. The remaining 4 models could absorb, however, only 3.1g to 3.6g of the artificial menstrual fluid though still in compliance with the Mainland’s standard.
In the actual circumstance, menstrual bleed could flow continuously. Women with heavier flow will need products that can absorb swiftly to avoid the risk of spill-over. In the multiple absorption test, the models were found to vary vastly, in particular, the models for day/night use which were the least satisfactory.
2 models for day use/night use, on their very first round of the multiple absorption test (10ml artificial menstrual fluid), became so saturated that they were not able to absorb the second and third doses. Their performance in this aspect was most unsatisfactory amongst the models. For the remaining 8 models for day use/night use which completed the 3-round absorption test (a total of 30ml artificial menstrual fluid), the requisition time measured for absorption varied from some 3 min (189 sec) to nearly 30 min (1,754 sec), an eight-fold difference. Among the 14 models for overnight use, 1 could not complete the multiple absorption test (a total of 30ml artificial menstrual fluid); whereas the remainder took about 3 min (186 sec) to nearly 22 min (1,342 sec) to absorb 3 doses, a six-fold difference. As regards models for day use, the acquisition time measured for completing the multiple absorption test (a total of 15ml artificial menstrual fluid) was between 98 sec and 626 sec, a variation of fivefold.
Some brands described themselves as “speed absorption” / “speed clean”. Tests were conducted respectively on a model claimed as “speed clean” and another model without such a claim under the same brand for comparison. It was found that the day-use model with the claim of “speed clean” completed the multiple absorption test (involving 3 rounds of absorption) in 101 sec. while the day use model without such claim took 626 sec to absorb the same volume of liquid and complete the test, a difference of 5 times. On the other hand, it was also found that that some other tested models even bearing no “speed absorption” claims could also absorb fluid within a short time indicating good performance in absorption speed.
Consumers should also pay heed to product claims of “ultra thin” with only thickness in “0.08 cm”, “0.09cm” and “1mm”. In fact, they refer to the thickness of the absorbent layer, and not that of the whole piece of sanitary napkin.
Furthermore, the test measured the water absorption rates of the models by weighing them before and after immersion in water, so as to assess the total efficacy of absorption. The results showed all models were in compliance with the minimum requirement on absorption rate be 7 times or above under the Mainland Standard.
Rewet assessment tests
In reference to the Taiwan’s standard, the results of the rewet assessment test showed that 6 models performed well with a rewet amount of 0.01g or below, and all of their top layers were made of a mesh material. 12 other models were measured with a rewet amount of 0.1g or below, among them many of their top layers were of non-woven or cotton-like soft materials. On the other hand, in the assessment of the rewet of the outer layers of the samples, it was found that the multiple absorption test showed that the speed in absorption may not necessarily go hand in hand the efficacy of keeping surface dry. Manufacturers are urged to improve their product design in order that both qualities could be achieved in the same sanitary napkins.
The attention is drawn to the following:
- Wash hands thoroughly before changing napkins to avoid contamination by micro-organisms;
- Choose napkins according to the flow of menstruation and there is no need to use models for heavy flow for extended period of time;
- Change napkins every 2 or 3 hours to ensure hygiene;
- It is not advisable to store sanitary napkins in the bathroom or a humid environment;
- Some sanitary napkins are individually packed but not necessarily airtight. So always store them properly when carrying around with you to avoid contamination.