With the advent of a low-carbon economy worldwide, laundry products are progressively developing toward low-temperature, water-saving, concentrated, and safe directions. Concentration is a significant development direction for enhancing the sustainability of laundry products. Compared to regular laundry detergents, concentrated formulations can reduce the amount of chemical and packaging materials, lower energy consumption during production, reduce consumption in transportation processes, and decrease waste generation in disposal stages . Laundry pods align with the industry trend toward concentration, effectively reducing environmental pollution and promoting structural adjustments and industrial upgrades in China’s laundry industry. Laundry pods can be classified into single-chamber and multi-chamber forms. Multi-chamber laundry pods available on the market may have two, three, four, or five chambers, forming different shapes by adjusting the chamber sizes and colors of the liquid. With advancements in multi-chamber packaging technology, incompatible materials are separated by water-soluble membranes. For example, combining sodium percarbonate particles with concentrated liquid in solid-liquid pods achieves functions unattainable by traditional laundry detergents, realizing multifunctional laundry pods. This provides a larger formulation space, incorporating ingredients with functions such as long-lasting fragrance, long-term antibacterial effects, fabric softening, anti-static, color protection, and anti-color-bleeding into different chambers to form new laundry pod products.

This paper analyzes laundry pod products, briefly describing their characteristics in terms of safety, packaging film, and contents.

1. Safety of Laundry Pods

Colorful and crystal-clear laundry pods resemble candy or jelly, posing a risk of accidental ingestion by children. In December 2021, China’s Ministry of Industry and Information Technology issued the light industry standard “Laundry Pods” (QB/T 5658—2021), mandating the addition of bittering agents that are safe for both the environment and humans in water-soluble membranes. To prevent accidental ingestion by children, a volume restriction was set, with individual pods required to contain no less than 10 ml. The outer packaging of laundry pods should be non-transparent to reduce children’s curiosity about the product, and clear warning labels stating “Keep away from children” should be affixed to the packaging. Additionally, designs that are difficult for children to open should be adopted, further reducing the likelihood of children coming into contact with the product.

2. Packaging Film of Laundry Pods

The mechanism of laundry pods involves releasing detergent upon contact with water, dissolving the polyvinyl alcohol (PVA) packaging film. The water-soluble outer film has long been a key technical issue affecting laundry pod development. The film’s barrier properties can effectively prevent the liquid in laundry pods from oxidizing with oxygen in the air and reduce the volatilization of fragrance. Although quicker dissolution is theoretically better, safety concerns dictate that to prevent rapid dissolution in cases of accidental ingestion by infants, industry standards specify that laundry pods should take at least 25 seconds for the film to break. Additionally, a compressive strength of over 300 N is required to prevent the pod from breaking when bitten, reducing the risk of accidental ingestion. If the PVA film leaves residues on clothes after washing, it greatly affects the user experience. Based on market feedback, consumers expect no residue from quick-wash modes, which requires laundry pods to dissolve well under low temperatures and low-water conditions. During transport and storage, high temperatures may affect the solubility of the film, so factors like single film dissolution time, film breakage time after pod formation, and solubility performance under extreme storage conditions such as high temperature and humidity should be considered .

Since PVA film is particularly sensitive to moisture, proper storage and usage conditions are crucial for laundry pods. PVA film is sensitive to bleach, which, if present in the ingredients as sodium hypochlorite, can affect the storage stability of laundry pods. In detergents, polyvinyl alcohol also serves as an anti-residue agent, being environmentally friendly and easily degradable. The polyvinyl alcohol solution generated after using laundry pods can be decomposed by bacteria in the soil within 180 days, ultimately degrading into carbon dioxide and water.

The general production process of laundry pods is as follows: a layer of water-soluble film is used as the base layer, vacuum-formed to fit the mold, and then filled with the required amount of contents. Another layer of water-soluble film serves as the top layer, which is heat-sealed or moistened at the edges to ensure a secure seal, creating a fully enclosed laundry pod. The entire sheet of laundry pods is then cut into individual pods.

3. Contents of Laundry Pods

The base formula of laundry pods generally consists of a small amount of water, surfactants, laundry aids, organic solvents, enzymes, antibacterial agents, fragrances, colorants, etc. It is crucial to examine the compatibility between PVA water-soluble film and the ingredients in the formula. The water content in the formula is a key factor, as the water content should be controlled below 10%; too much water softens the film, while too little makes it hard and brittle. To ensure intact packaging film and high active ingredient content (over 45%) during storage, meeting requirements directly by simply increasing the active ingredient content using traditional raw materials is challenging.

3.1 Surfactants

Current methods for detecting active ingredients exhibit poor resistance to solvent interference. When tested according to the “Test Methods for Surfactants in Detergents” (GB/T 13173—2021), the repeatability of active ingredient content results is low. Industry standards for laundry pods do not specify total active ingredient content but state that when the concentration is one-fourth of standard laundry detergent, the detergent power of laundry pods on three types of standard test fabric must be greater than or equal to that of standard laundry detergent. Laundry pods can be considered as four times more concentrated than regular laundry detergents. The main components responsible for cleaning in laundry pods are surfactants, typically a combination of anionic and nonionic surfactants, which work synergistically to enhance cleaning power. During use, laundry pods are diluted in a large volume of water, which may cause them to enter a gel phase. Under extreme conditions (such as low temperatures), the detergent may gel, so it is essential to select and combine surfactants carefully.

Anionic surfactants are excellent in cleaning performance, have strong detergency, good biodegradability, and low cost, with notable efficacy on particles, proteins, and oily stains. The formula may include common raw materials such as amine salts of fatty acids, sodium lauryl ether sulfate (AES), sodium fatty alcohol ether carboxylate (AEC), α-olefin sulfonates (AOS), methyl ester sulfonate (MES), or monoethanolamine salts of dodecylbenzene sulfonic acid (MEA salts). Due to the low water content in the formula, monoethanolamine or triethanolamine should be selected for the formation of amine salts. Amino acid-type surfactants are currently popular as they are mild, non-irritating, derived from widely available bio-based materials, and have good biodegradability. In laundry pod formulas, anionic surfactant content is around 10%, and because the overall water content needs to be low, low-water-content anionic surfactants should be used as much as possible.

Nonionic surfactants also play an important role in the formula. In some respects, they outperform ionic surfactants. They are stable in solution, unaffected by strong electrolytes, pH values, or inorganic salts, and are compatible with other types of surfactants. In laundry pod formulations, the content of nonionic surfactants is about 30%, often using materials such as fatty alcohol polyoxyethylene ether (AEO), isomeric fatty alcohol polyoxyethylene ether (ICEO), alkyl polyglucosides (APG), cocamidopropylamine oxide (CAO), fatty acid methyl ester ethoxylate (FMEE), or modified oil ethoxylates (SOE). The EO content in AEO affects the product’s performance, with 9EO enhancing detergency and 7EO improving penetration and wetting. Compared with AEO series, isomeric alcohol ether nonionic surfactants have a lower pour point, narrower gel range, faster dissolution, stronger wetting power, lower foaming, and easier rinsing, with good compatibility with anionic surfactants, lowering foam, reducing rinse times, and saving energy. FMEE offers excellent calcium soap dispersion, hard-water cleaning performance, oil removal, low-temperature fluidity, and a narrow gel region, making it suitable for laundry pods. SOE is a new polyoxyethylene-type nonionic surfactant derived from natural oils, with excellent surface activity, biodegradability, low irritation, low foaming, and good low-temperature fluidity. It also has comparable cleaning power to AEO-9 and does not form a gel when mixed with water, making it ideal for laundry pods .

3.2 Laundry Aids

Common laundry aids include chelating agents, stabilizers, anti-redeposition agents, and fluorescent whitening agents. Tap water contains calcium and magnesium ions, as well as transition elements such as iron and manganese, which can affect the effectiveness of surfactants. Therefore, small amounts of high-efficiency chelating agents are added to the formula to chelate these metal ions. Chelating agents include sodium citrate, disodium EDTA (ethylenediaminetetraacetic acid), GLDA (glutamic acid diacetic acid tetrasodium salt), and MGDA (methylglycinediacetic acid). Widely used carboxyl-based chelating agent EDTA has long been considered environmentally unfriendly due to its low biodegradability. GLDA, a newer chelating agent derived from MSG (monosodium glutamate), is 48% bio-based from plant products and is biodegradable, achieving a biodegradability rate of over 80% within 28 days .

Stabilizers, such as cocamide, hydrogenated castor oil, sodium xylene sulfonate, alkyl diphenyl ether disulfonate, and urea, are primarily used to improve and increase the viscosity of the fluid, maintain its stability at different temperatures, and offer emulsifying, stabilizing, or suspension properties. By adding stabilizers, the micelle structure of surfactants can be altered to prevent gelation, allowing it to transition from a liquid crystal to a more easily flowing and dissolvable spherical or rod-shaped micelle. Urea is typically added in amounts of 2% to 10% in laundry pods; it has a solubilizing effect that reduces the viscosity of the formulation and enhances transparency.

Anti-redeposition agents are often high-molecular-weight polymers that help prevent hydrophilic particle and oil-based soil from resettling on fabrics. Common anti-redeposition agents include polyacrylic acid, polyethyleneimine, polyvinyl alcohol, and polyvinylpyrrolidone. Copolymers of acrylic acid and styrene are compatible with many systems, providing solubilizing effects and excellent calcium and magnesium chelation to prevent dyes from redepositing on other fabrics, thereby enhancing cleaning power. On one hand, polymers can prevent the deposition of non-water-soluble salts, such as calcium carbonate, on fabrics through chelation and crystal surface modification, especially under high-temperature and hard-water washing conditions. On the other hand, the anionic component of acrylate adsorbs onto stain particles, giving them a negative charge that repels similarly charged fabric surfaces, effectively suspending the stain and preventing redeposition, which helps maintain fabric brightness and softness after multiple washes.

Ordinary laundry detergents often contain fluorescent whitening agents, which are both dyes and functional aids that can resolve fabric yellowing caused by factors such as partial loss of whitening agents during dyeing and finishing stages. Relevant national standards permit two types of fluorescent whitening agents for fabric detergents but do not explicitly require laundry detergents to declare the presence of fluorescent whitening agents. Most high-active laundry pods do not contain fluorescent whitening agents, although some products include them to keep fabrics vibrant and enhance the cleaning power of the formula.

3.3 Organic Solvents

Organic solvents help address the gelation and stratification issues that can arise in high-active ingredient formulations. Unlike water, most surfactants are more soluble in organic solvents. Common solvents include ethanol, ethylene glycol, propylene glycol, butylene glycol, glycerin, diethylene glycol, diglycol, sorbitol, polyethylene glycol-200, and ethoxylated benzyl alcohol, with an addition rate generally controlled between 15% and 25%. Some lower-end products use a large amount of inexpensive solvents to reduce costs, which can affect product quality and raise safety concerns. Diethylene glycol is a prohibited substance under the “Cosmetic Safety Technical Specification,” with impurity levels in raw materials not exceeding 0.1%. Diethylene glycol is toxic to the kidneys and nervous system and can cause a range of symptoms when ingested, often leading to acute renal failure with potential metabolic acidosis . If laundry pods containing diethylene glycol are accidentally ingested, they may cause bodily harm, so its use should be avoided in formulations. Notably, polyethylene glycol-200’s highest historical usage in rinse-off cosmetics is 15%, while ethanol concentrations above 24% are classified as hazardous under the Ministry of Emergency Management’s hazardous chemicals list.

3.4 Enzymes

Laundry pod products are increasingly using biological enzyme technology, where enzymes work in tandem with other formulation ingredients to achieve efficient cleaning and fabric care functions. Enzymes are efficient, green cleaning agents and include protease, lipase, cellulase, amylase, and mannanase, with some formulas also incorporating enzyme complexes for synergistic effects. Enzymes effectively remove stains that surfactants cannot, providing high-efficiency biological catalysis and automatic decomposition of dirt. Enzymes in laundry pods tend to be more stable than in regular liquid detergents, as the large amount of organic solvent in laundry pods helps preserve enzyme activity. National standard soiled fabric JB-01, which contains carbon black oil stains, shows improved cleaning when cellulase is added, as it removes damaged fibers from the fabric’s surface. JB-02, which has protein stains, demonstrates enhanced cleaning performance when protease is added. JB-03, which has synthetic sebum stains, generally does not respond to single enzymes but shows improved cleaning potential when enzymes are combined. Mannan, often used as a thickener and conditioner in food and cosmetics, is challenging to remove due to its sticky properties, and residual mannan can easily attract colored particles from daily environments, causing secondary pollution. Even at low doses, mannanase can significantly enhance the cleaning effect on such stains in laundry pod detergents, showing improved specificity and efficiency.

3.5 Antibacterial Agents

As new additives, antibacterial agents serve important functions in maintaining environmental cleanliness and human health. There are numerous types of antibacterial agents, some of which are highly corrosive, toxic to humans, or harmful to the environment. Such side effects severely restrict their applications. LAE (lauric arginate) hydrochloride, discovered in Europe, is an amino acid surfactant and has the advantages of being renewable, environmentally friendly, low in cytotoxicity, biodegradable, and highly effective against bacteria, making it widely used as a broad-spectrum antibacterial agent . Additionally, commonly used antibacterial agents include chloroxylenol (PCMX), polyhexamethylene biguanide (PHMB), and benzalkonium chloride. However, compatibility with other ingredients or multi-chamber packaging technology to separate antibacterial agents should be considered during formulation.

4. Conclusion

With the improvement of living standards, fully automatic washing machines have become increasingly popular, and the time spent on laundry has gradually decreased, leading to new laundry consumption habits. Quick and convenient “one-click” laundry has become a strong market demand. Laundry pods were initially designed to meet consumers’ needs for a faster, more convenient laundry experience. Over the past decade, as the economy has transformed and living standards have risen, consumers have placed greater emphasis on products with eco-friendly, energy-saving, and emission-reduction features. Laundry pods can reduce the amount of plastic packaging and lower energy consumption during production and transportation, aligning better with sustainable development principles .

The structural design of chambers allows laundry pods to depart from the industrial style of laundry powder or detergent products and introduce more fashionable aesthetics. Adding cultural elements, such as designs resembling Tai Chi, zodiac signs, or constellations, could significantly enhance the perceived quality of cleaning products in consumers’ minds, increasing the added value of detergent products. For instance, Tide’s classic three-color yin-yang laundry pod and Liby’s Wi-Fi-shaped laundry pod both showcase creative designs and unique shapes, leaving a deeper impression on consumers and enhancing repurchase rates.

The entire industry should work together to promote the advantages and significance of laundry pods, helping consumers experience the convenience they bring to daily life and understand the importance of these products in energy-saving, emission reduction, and environmental protection. Raising public awareness and acceptance of concentrated pod products will help drive the development of the laundry pod market.