The material selection logic for personal care flexible packaging differs fundamentally from that of food packaging: the contents are mostly not afraid of oxidation, but rather fear moisture, solvents, and migration and leakage caused by prolonged contact. The outer bag of laundry detergent pearls must work hard to prevent moisture, while wet wipe bags need to prevent moisture from slowly escaping under the zipper flap. Refill packs must withstand the bending stress from repeated emptying. When customizing packaging for personal care clients, Huashu Packaging always starts by identifying the product’s failure points before determining the structure. This article breaks down the four most common failure points—leakage, moisture loss, fading, and seal contamination—step by step to help you determine where to invest your money in each layer of the packaging.
Three Special Requirements for Cosmetic Contents in Packaging
The first is resistance to content erosion. Surface active agents, alcohol-based solvents, and fragrance components penetrate ordinary PE film much more easily than water or oil in food systems. Prolonged contact causes these substances to migrate from the inner layer to the outer layer, leading to blistering on the bag’s printing surface in mild cases, or creating channels in the sealing edge in severe cases. For inner layers of personal care packaging, it is often necessary to select films with better chemical resistance or increase the thickness by one grade. The second is fragrance retention. Half of the shelf competitiveness of personal care products comes from fragrance. Fragrance components are complex with a wide range of molecular weights. Low molecular weight esters and aldehydes can slowly penetrate ordinary PE, resulting in insufficient fragrance retention. Products with inadequate barrier properties will experience a noticeable decline in fragrance within six months. The third is mechanical requirements based on usage scenarios. Personal care packaging often needs to withstand high humidity environments in bathrooms, repeated opening and closing, and emptying actions. This determines the selection of sealing edge width, cover film adhesion, and bag bottom structure.
Point of Failure One: Leaking and Moisture Absorption of Laundry Pods
Laundry detergent pearls are one of the most demanding categories in personal care flexible packaging, as the contents themselves are sensitive to both moisture and humidity. The outer membrane of the pearls is a polyvinyl alcohol (PVA) water-soluble film, which dissolves upon contact with water. Therefore, the outer packaging must effectively prevent moisture ingress throughout the entire transportation and storage process. Once the outer bag fails to meet moisture barrier requirements, the PVA film may become damp and sticky prematurely, causing the entire bag of pearls to clump together on the shelf, which is the most common type of customer complaint in this category. Conversely, the pearl contents have a high moisture content (typically around 10% in the formula). If the outer bag lacks sufficient moisture barrier properties, slow moisture migration can lead to weight loss of the pearls and degradation of the PVA film.
The common practice in material selection is to use a high moisture barrier structure for the outer bag, with typical configurations such as PET//AL (pure aluminum foil)//PE or PET//metalized film//high barrier PE, aiming to reduce moisture transmission rate to below 1 gram per square meter per day, with aluminum foil structures achieving even lower values. Meanwhile, the inner PE film in direct contact with the condensate should be confirmed for resistance to surfactants to prevent slow leakage of contents, which could cause an oily feel on the bag surface. The filling process is equally critical: residual water vapor inside the bag after filling condensate and liquid residue at the filling nozzle can create weak areas at the seal, leading to contamination. Therefore, the sealing of condensate bags is typically combined with alcohol detection or water vapor purging processes. To understand why the barrier data is set this way, refer to this article.Interpretation of Oxygen Transmission Rate and Moisture Transmission Rate Test DataThe article explains the meaning of the indicators in detail.
Failure Point 2: Emptying Stress of the Refill and Edge Fatigue
Soft pouch refill packs for laundry detergent and fabric softener face the core challenge of lightweight packaging accommodating large volume contents. During the emptying process of a 2kg refill pouch, the bag undergoes dozens of repeated folds, with the folding points concentrated at the bottom and side seams. If the PE layer lacks sufficient fatigue resistance, it will develop fine cracks and eventually lead to leakage. In terms of material selection, large-volume refill packs commonly use thickened PE inner layers or PA/PE structures to enhance anti-folding performance. The bottom is also die-cut with rounded corners to reduce stress concentration.
Another decision point for the refill option is the cap type. The cost of the suction cap is significantly higher than that of the flat edge bag, but it offers two experience upgrades: emptying cleanly and standing upright for storage, making it suitable for products with large single-use quantities that need to be hung near the washing machine. The flat edge bag with a tear notch has a lower cost and is suitable for single-use refills. Details about the pouring experience (cap type, mouth size, and drip prevention) can be found on the Huashu Packaging Station website.Nozzle Bag Cap Type SelectionThere is a dedicated section for elaboration. Cost-sensitive procurement can be compared accordingly.Number of Layers and Structural Diagram of Composite Packaging BagsDetermine whether you need to add a three-layer structure for the supplement.
Failure Point 3: Moisture Retention and Repeated Opening of Wet Towel Bags
Wet wipes are a typical category where the contents are less sensitive to damage but the packaging is prone to moisture loss. The liquid content of wet wipes usually ranges between 180% to 250%. Once the moisture content drops below 100%, the wiping experience declines dramatically. Therefore, the moisture barrier requirements for wet wipe packaging are among the highest in all personal care categories. The mainstream structure is PET//AL//PE or PET//high barrier metallized film//PE, with a moisture transmission rate controlled below 0.5 grams per square meter per day.
However, the real challenge of wet wipe bags lies in repeated opening and closing: the sealing tape on the lid is torn and pressed back dozens of times daily. After the adhesive loses its effectiveness, the moisture permeability at the edge of the lid can be significantly higher than the designed value of the film material. When selecting the material, three details should be considered: the durability of the lid adhesive (a good lid adhesive should maintain sealing performance even after hundreds of opening and closing cycles), the flatness of the lid’s adhesion to the bag surface (wrinkles are a shortcut for moisture permeation), and the match between the lid size and the bag width. The industry standard practice is to use the overall moisture permeability of the sealed bag as the acceptance criterion, rather than just relying on the moisture permeability report of the film material—once the lid is installed, the performance of the entire bag differs from the data of the bare film.
Failure Point 4: Fading and Ink Migration
Cosmetic products displayed under store lights and near bathroom windows are exposed for much longer periods than food items, making color fading more pronounced. There are three strategies to address this issue: first, select ink with higher UV resistance, especially for the main visual colors; second, switch surface printing to reverse printing (back printing), so the ink is sandwiched between layers and not directly exposed to light; third, add a UV-blocking layer or use a film with UV absorption properties in the structure. Additionally, fragrance can extract plasticizers from the ink, so the bonding strength of reverse-printed composite materials should be regularly tested to prevent interlayer separation caused by extraction. This issue is most commonly seen in packaging for liquid soaps and shampoos with high fragrance content.
FAQ
Why must the outer packaging of laundry detergent pearls use an aluminum foil structure?
Because the PVA skin film of the microcapsules dissolves upon contact with water, the outer bag must maintain an extremely low moisture permeability throughout the entire shelf life. Aluminum foil is the only conventional material that can approach zero moisture permeability. The combination of metallized film and high barrier PE is commonly used in cost-sensitive products, but shelf-life performance must be verified through sample testing.
What can be done if the bottom of the flexible bag tends to crack after emptying?
Bottom cracks result from repeated bending fatigue. The solution is to thicken the inner layer or switch to a PA/PE structure to improve flexibility, while also making rounded corners with die-cutting at the bottom to reduce stress concentration, and ensure the filling volume does not exceed the designed capacity.
What is the minimum moisture permeability required for wet wipe bags?
Main requirements call for a moisture transmission rate below 0.5 grams per square meter per day, and this must be measured after the bag is sealed with the lid film. The degradation of the lid film’s adhesion is the primary cause of water loss in wet wipes. Meeting the film material data does not necessarily mean the entire bag meets the standard.
How to prevent fading in cosmetic packaging?
Three-pronged approach: using oil inks with higher UV resistance, employing inner printing to keep the ink away from direct light, and adding a UV-blocking layer in the structure. For products with high fragrance content, regular inspection of composite strength is necessary to prevent interlayer separation caused by fragrance extraction.
Are the sealing strength standards for cosmetic packaging bags the same as for food?
Core testing methods are the same, but acceptance values are typically higher because surfactants and solvents in daily chemical contents continuously erode the seal during shelf life. When customizing, the content formula should be provided to the factory for compatibility testing rather than directly using the acceptance values from food applications.
Should you choose a suction mouth bag or a flat edge bag for the supplementary pack?
Refer to the usage instructions. For products that require frequent access and need to be stored upright, choose a valve bag for easy dispensing and clean emptying. For single-use refills, select a flat-bottom bag with a tear notch for lower cost. For guidance on choosing between different lid types and mouth sizes, refer to the dedicated article on valve bags within the site.