Expert Guide: What Are Sanitary Napkins Made Of? The 4 Core Materials Explained

Abstract

An examination of the modern disposable sanitary napkin reveals a sophisticated, multi-layered composite engineered for optimal fluid management, comfort, and discretion. The product’s efficacy hinges on the specific materials and structural arrangement of its four primary components. A topsheet, typically made from a non-woven fabric like polypropylene, provides a soft, dry interface with the skin. Beneath this lies an acquisition distribution layer, designed to rapidly wick moisture away from the surface and spread it evenly. The central component is the absorbent core, a matrix of cellulosic fluff pulp and superabsorbent polymer (SAP) particles, which chemically locks fluid into a gel state to prevent leakage and rewetting. Finally, a waterproof yet often breathable backsheet, usually a polyethylene or microporous film, serves as the ultimate barrier. Understanding the material science behind each layer is fundamental for appreciating the technological advancements in menstrual hygiene products and for making informed choices regarding performance, skin health, and environmental considerations.

Key Takeaways

• A sanitary napkin is a multi-layered product engineered for fluid absorption.
• The topsheet is the soft, skin-contact layer designed for quick fluid passage.
• The absorbent core, with superabsorbent polymer (SAP), is key for locking in fluid.
• Understanding what sanitary napkins are made of helps in choosing the right product.
• The backsheet is a waterproof barrier that prevents any leakage onto clothing.
• Breathable materials in the backsheet enhance comfort by reducing heat and humidity.
• Eco-friendly options use materials like organic cotton and biodegradable polymers.

Table of Contents

• Deconstructing the Familiar: The Hidden Complexity of a Simple Product
• The Anatomy of a Modern Sanitary Napkin: A Layer-by-Layer Exploration
• Beyond the Core Four: Innovations and Enhancements in Menstrual Pads
• The Material Spectrum: From Conventional Polymers to Sustainable Alternatives
• From Blueprint to Product: The Manufacturing and Quality Assurance Journey
• Frequently Asked Questions (FAQ)
• Conclusion
• References

Deconstructing the Familiar: The Hidden Complexity of a Simple Product

To hold a sanitary napkin in one’s hand is to hold an object of profound simplicity and, simultaneously, remarkable technological sophistication. Its purpose is straightforward: to manage menstrual fluid discreetly and effectively, enabling individuals to navigate their daily lives with confidence and comfort. Yet, beneath its unassuming, soft exterior lies a marvel of material science and structural engineering, a carefully orchestrated system of layers, each with a distinct role and composition. The terms “sanitary napkin,” “sanitary pad,” and “menstrual pad” are often used interchangeably, reflecting regional linguistic preferences rather than functional differences; in the United States, “pad” is most common, while “napkin” has historical roots and persists in other English-speaking regions like Great Britain childsea.com. Regardless of the name, the fundamental product is the same childsea.com.

The inquiry into what sanitary napkins are made of is not merely a matter of listing materials. It is an exploration into the physics of fluid dynamics, the chemistry of polymers, and the human-centered design principles that prioritize comfort, security, and health. Why does one pad feel softer than another? How can something so thin hold a surprising amount of fluid without feeling wet? What makes a pad “breathable”? The answers to these questions are embedded in the very fibers, films, and polymers from which the product is constructed.

Thinking about a sanitary napkin as a high-performance system can be a helpful mental exercise. Imagine it not as a single piece of material, but as a team of specialists working together. The first specialist’s job is to greet the fluid and guide it inward, away from the body, as quickly as possible. The second specialist must then take this fluid and rapidly spread it out, preventing a bottleneck. The third, the powerhouse of the team, has the task of absorbing and securely locking away this fluid so it cannot escape. Finally, a fourth specialist acts as a security guard, ensuring nothing gets past the final boundary. Each member of this team corresponds to a layer within the sanitary napkin, and the team’s overall success—the pad’s performance—depends on how well they cooperate. This exploration will journey through each of these layers, examining the materials used, the scientific principles at play, and the thoughtful design choices that culminate in the modern menstrual product.

The Anatomy of a Modern Sanitary Napkin: A Layer-by-Layer Exploration

The effectiveness of a sanitary napkin is not derived from a single material but from the synergistic interplay of its distinct layers. Each layer is meticulously designed and chosen to perform a specific function in the overall process of fluid management. We will now dissect the typical disposable sanitary napkin, moving from the surface that touches the skin down to the final barrier that adheres to undergarments.

The Topsheet: The First Point of Contact

The topsheet is the gateway to the entire system. Its dual mandate is to feel soft and comfortable against the skin while allowing menstrual fluid to pass through it rapidly and completely, leaving the surface feeling as dry as possible. This “dry-feel” property is paramount for user comfort and for minimizing skin irritation. To achieve this, manufacturers primarily use non-woven fabrics.

What exactly is a “non-woven” fabric? Unlike traditional textiles like cotton or linen, where threads are woven or knitted in an orderly pattern, non-woven fabrics are made from a web of fibers bonded together through mechanical, chemical, or thermal means. The most common polymers used for these fibers are polypropylene (PP) and polyethylene (PE). These materials are naturally hydrophobic, meaning they repel water. This might seem counterintuitive for a product meant to handle liquid. The genius lies in the treatment and structure. The fabric is treated with surfactants, which are compounds that act as wetting agents, creating a hydrophilic (water-attracting) path through the material. The fluid is thus drawn into the pad rather than sitting on the surface.

There are two dominant styles of topsheets:

1. Spunbond or Thermal-Bonded Non-wovens: These have a soft, cloth-like feel that many users prefer for its perceived gentleness on the skin. The fibers are randomly oriented, creating a plush texture.
2. Perforated Films or Apertured Films: Often marketed under brand names like “Dri-Weave,” these are essentially thin plastic sheets with tiny, funnel-shaped holes. The wider end of the funnel faces the body, allowing fluid to pass through easily, while the narrow end on the other side makes it difficult for the fluid to return to the surface. This design provides an exceptionally dry feel but can be perceived by some as more “plasticky” and less soft than non-woven fabric topsheets.

The choice between these types represents a classic design trade-off between the sensation of softness and the performance of dryness.

The Acquisition Distribution Layer (ADL): The Unsung Hero

Immediately beneath the topsheet lies a layer that is often overlooked but is absolutely vital for a high-performing pad: the Acquisition Distribution Layer, or ADL. Its name perfectly describes its function. When menstrual fluid passes through the topsheet, it tends to be concentrated in one area. If this fluid were to hit the main absorbent core directly, that spot could become saturated too quickly, creating a risk of leakage before the full capacity of the core is utilized.

The ADL prevents this by acting as a temporary reservoir and a rapid distribution network. It quickly acquires the fluid from the topsheet and wicks it horizontally, spreading it out over a larger surface area of the absorbent core below. This ensures that the core can absorb the fluid more evenly and efficiently. Think of it as the traffic management system of the pad, preventing jams and ensuring a smooth flow to all available absorption zones.

Materials used for the ADL are typically bulky, porous non-wovens, such as through-air bonded fabrics or airlaid paper. These materials have a more open structure than the topsheet, allowing them to move liquid quickly via capillary action. Often, this layer is visibly distinct, appearing as a colored (frequently blue or green) rectangle in the center of the pad.

The Absorbent Core: The Heart of the Matter

This is where the primary work of absorption and retention happens. The absorbent core is a sophisticated composite material designed to soak up and lock away many times its own weight in fluid. The evolution of this core is what has allowed sanitary napkins to transform from bulky, mattress-like pads to the ultra-thin products common today childsea.com. The core is typically a blend of two key materials: fluff pulp and superabsorbent polymer (SAP).

• Fluff Pulp: This is a type of cellulose fiber derived from softwood trees. It is processed to create a fluffy, cotton-like material that is naturally absorbent. Fluff pulp creates a fibrous matrix that provides structure to the core and helps to wick fluid throughout its volume. In older or less advanced pads, the core might consist almost entirely of fluff pulp, which is why they were so thick. While it absorbs well, it can also release fluid back under pressure (a phenomenon known as “rewet”).
• Polymère superabsorbant (SAP) : This is the game-changing ingredient. SAPs are typically granules of sodium polyacrylate, a polymer with an incredible capacity for absorbing aqueous liquids. Through the process of osmosis, a single gram of SAP can absorb hundreds of grams of water, swelling to form a stable gel. When menstrual fluid, which is mostly water, comes into contact with SAP granules, it is drawn into the polymer structure and chemically locked away. This gel formation is the key to preventing rewet; once the fluid is absorbed by the SAP, it cannot be easily squeezed back out, even under the pressures of sitting or movement.

The combination of fluff pulp and SAP creates a synergistic effect. The pulp provides the structure and wicking capability to transport the fluid to the SAP particles, while the SAP provides the high-capacity, high-retention absorption. The ratio of pulp to SAP is a key design parameter that manufacturers can adjust to create pads of varying absorbency levels and thicknesses.

Material Feature	Fluff Pulp (Cellulose)	Superabsorbent Polymer (SAP)
Primary Function	Wicking, structure, initial absorption	High-capacity fluid retention, rewet prevention
Mechanism	Capillary action within cellulose fibers	Osmosis, forming a stable hydrogel
Absorbency Capacity	Moderate; absorbs about 10x its weight	Extremely high; absorbs up to 300x its weight
Rewet Performance	Poor; releases fluid under pressure	Excellent; locks fluid into a gel chemically
Contribution to Bulk	High; requires significant volume for capacity	Low; enables ultra-thin designs
Type de matériau	Natural polymer (from wood)	Synthetic polymer (sodium polyacrylate)

The Backsheet: The Final Barrier

The final layer is the backsheet, which faces the underwear. Its primary, non-negotiable function is to be waterproof to prevent any leakage. For decades, this was achieved with a simple, solid film of polyethylene—the same type of plastic used in many shopping bags. While effective at containing fluid, this non-breathable barrier also trapped heat and moisture vapor, which could lead to a feeling of stuffiness, humidity, and discomfort.

Modern advancements have led to the widespread use of “breathable” backsheets. These are typically microporous films. They are engineered to have microscopic pores that are large enough for water vapor (a gas) to escape, but far too small for liquid water droplets to pass through. This allows air to circulate and moisture vapor from the skin to evaporate, significantly reducing the buildup of heat and humidity. The result is a cooler, drier, and more comfortable wearing experience. You can think of it like the technology in high-performance rain gear, which keeps rain out but lets sweat vapor escape.

Finally, on the outside of the backsheet is the positioning adhesive—the strips of glue that hold the pad in place. This is a specially formulated hot-melt adhesive designed to stick securely to fabric but be removed without leaving significant residue. This adhesive is covered by a strip of silicone-coated release paper, which is peeled off before use.

Beyond the Core Four: Innovations and Enhancements in Menstrual Pads

While the four-layer structure forms the foundation of what sanitary napkins are made of, manufacturers continually introduce additional features and materials to improve performance, comfort, and user experience. These innovations address everything from a more secure fit to odor control and specialized skin care.

Wings, Contours, and Anatomical Shaping

One of the most significant functional improvements in pad design was the introduction of “wings.” These are flaps that extend from the sides of the pad and fold around the edges of the underwear. They serve two purposes: they help to anchor the pad more securely, preventing it from shifting or bunching during movement, and they provide an extra barrier along the sides to catch any lateral leakage.

Beyond wings, pads are now designed with a greater understanding of the human body. Contoured and anatomical shapes, often wider at the front and back and narrower in the middle, are intended to provide a better fit against the body’s curves. This improved conformity not only enhances comfort but also reduces gaps where leaks could potentially occur. Different shapes and lengths are also offered for day versus night use, with overnight pads being significantly longer and often having a flared back for extra protection while lying down.

Odor Control Technologies

Menstrual fluid itself is largely odorless, but when exposed to air and natural skin bacteria, it can begin to develop an odor. Many modern sanitary napkins incorporate technologies to manage this. While some pads use light fragrances to mask odors, a more sophisticated approach involves neutralization. This can be achieved in several ways:

• pH-Balancing Materials: Some cores include materials that help maintain a slightly acidic pH on the pad’s surface, which can inhibit the growth of odor-causing bacteria.
• Absorbent Neutralizers: Specialized molecules can be embedded within the absorbent core that trap and neutralize odor-causing compounds.
• Activated Carbon or Charcoal: Some pads include a thin layer containing activated carbon. Known for its highly porous structure and vast surface area, carbon is extremely effective at adsorbing a wide range of organic molecules, including those responsible for odor.

Functional Chips and Specialized Additives

In some markets, particularly in Asia, it is common to find sanitary napkins that feature a “functional chip” or “anion strip” embedded in the center of the pad childsea.com. These strips are purported to release negative ions (anions) upon contact with moisture. Proponents claim a variety of health benefits, such as reducing bacteria, alleviating cramps, and improving energy levels. Other additives, such as graphene, nano-silver, or magnetic elements, are also marketed with similar claims of antibacterial or therapeutic properties. It is worth noting that while these features are popular with some consumers, the scientific evidence supporting many of the associated health claims is often limited or debated within the broader medical community. The primary verifiable function of many of these materials, like nano-silver, is their antimicrobial effect, which can contribute to odor control.

The Material Spectrum: From Conventional Polymers to Sustainable Alternatives

The conversation around what sanitary napkins are made of has expanded significantly in the 21st century to include pressing questions about health and environmental impact. The conventional disposable pad, while highly effective, is largely composed of petroleum-derived plastics and non-biodegradable materials. A single pad can take hundreds of years to decompose in a landfill. This reality has spurred a growing demand for more sustainable and “natural” menstrual products.

The Environmental Question of Conventional Pads

A typical sanitary napkin is composed of a polypropylene topsheet, a polyethylene backsheet, and a core of wood pulp and SAP. The wrappers and release papers add more plastic and silicone-coated paper to the mix. The sheer scale of use means that disposable menstrual products contribute a significant amount of plastic waste globally. Furthermore, the bleaching process for wood pulp has historically been a source of concern. While modern methods have moved away from elemental chlorine, which could produce harmful dioxin byproducts, consumers are increasingly seeking products explicitly labeled as “Totally Chlorine-Free” (TCF).

Exploring Eco-Friendly and Organic Alternatives

In response to these concerns, a new category of sanitary napkins has emerged, utilizing alternative materials focused on biodegradability, compostability, and natural origins.

• Topsheet: The most common alternative is organic cotton. It is chosen for its softness, breathability, and hypoallergenic properties. For consumers with sensitive skin, a 100% cotton topsheet can reduce the risk of irritation. The “organic” certification ensures the cotton was grown without the use of synthetic pesticides and fertilizers.
• Noyau absorbant : The focus here is on sustainable pulp and alternatives to petroleum-based SAP. This includes using Totally Chlorine-Free (TCF) wood pulp or pulp from more rapidly renewable sources like bamboo. The challenge has been finding a biodegradable replacement for SAP that offers comparable performance. Emerging options include plant-based biopolymers derived from cornstarch, which can provide superabsorbent properties while being compostable under the right conditions.
• Backsheet: The plastic backsheet is replaced with a bioplastic film, often made from polylactic acid (PLA), a polymer derived from plant starches (like corn). These films are designed to be commercially compostable, breaking down into water, carbon dioxide, and organic matter in an industrial composting facility.

Product Layer	Conventional Material	Eco-Friendly/Organic Alternative	Key Benefit of Alternative
Topsheet	Polypropylene/Polyethylene (PP/PE) Non-woven	100% Organic Cotton	Hypoallergenic, soft, pesticide-free, renewable
Noyau absorbant	Chlorine-bleached Fluff Pulp, SAP	TCF Pulp (Wood/Bamboo), Biopolymer SAP	Chlorine-free, rapidly renewable, compostable
Backsheet	Polyethylene (PE) Film	Bioplastic Film (e.g., PLA from cornstarch)	Compostable, derived from renewable resources
Wrapper	Plastic Film	Compostable Bioplastic or Paper	Reduces plastic waste, compostable

It is important to understand that terms like “biodegradable” and “compostable” have specific meanings. A product might biodegrade over a very long time, but for it to be truly beneficial, it should be “compostable,” meaning it breaks down within a specific timeframe in a controlled composting environment without leaving toxic residues. The performance and cost of these eco-friendly options can also differ from their conventional counterparts, presenting a trade-off that consumers and brands must weigh.

From Blueprint to Product: The Manufacturing and Quality Assurance Journey

Understanding the materials is only half the story. The process of bringing these disparate layers together into a cohesive, reliable product is a feat of high-speed, precision manufacturing. This process, along with rigorous quality control, is what ensures that every pad performs as expected.

The Assembly Line: A Symphony of Machines

The production of a sanitary napkin happens on a long, automated assembly line. The process generally follows these steps:

1. Core Formation: Fluff pulp, often delivered in large rolls, is shredded and broken down in a “hammermill.” It is then mixed with SAP granules and vacuum-formed into the desired core shape on a moving screen.
2. Layering: The continuous sheet of absorbent core material moves down the line. The ADL, topsheet, and backsheet materials are unrolled from massive spools and laminated together with the core in the correct order. Adhesives are precisely applied to bond the layers.
3. Cutting and Sealing: The long, continuous strip of layered material is then cut into individual pad shapes using a rotary die cutter. Heat and pressure are often used to seal the edges, encapsulating the core.
4. Feature Application: At this stage, wings are folded, and the release paper is applied over the positioning adhesive on the backsheet.
5. Folding and Packaging: The individual pads are folded, often tri-folded, and then individually wrapped for hygiene and portability. Finally, they are counted and packed into their final bags or boxes by automated systems.

This entire process occurs at incredible speeds, with modern machines capable of producing hundreds or even thousands of pads per minute.

The Role of an OEM/ODM Partner

For many brands, developing the expertise and infrastructure to manufacture such complex products is prohibitive. This is where Original Equipment Manufacturer (OEM) and Original Design Manufacturer (ODM) partners play a vital role. A specialized company, such as a dedicated wholesale supplier of sanitary napkins, provides the manufacturing capabilities.

• Un OEM relationship involves the partner manufacturing a product based on the brand’s specific design and material specifications.
• Un ODM relationship is more collaborative, where the manufacturing partner also provides the design and engineering expertise. A brand can choose from a portfolio of existing designs or work with the manufacturer to develop a new one.

Working with an experienced partner like Mer d'enfants allows a brand to leverage existing knowledge of material science, supply chains, and manufacturing processes. It enables customization of every aspect of the pad—from the softness of the topsheet and the SAP concentration in the core to the breathability of the backsheet and the design of the packaging. This partnership is key to creating high-quality serviettes hygiéniques jetables tailored for specific consumer needs and market positions.

Ensuring Safety and Performance

Quality assurance is a continuous process that runs parallel to manufacturing. It involves a battery of tests to ensure every batch meets safety and performance standards.

• Absorbency Tests: Standardized tests, such as the “Syngina” (Synthetic Gynecological Fluid) test, measure how much fluid a pad can hold, how quickly it absorbs it (the strike-through rate), and how well it prevents the fluid from returning to the surface under pressure (the rewet test).
• Adhesive Tests: The peel strength of the positioning adhesive is tested to ensure it will hold the pad securely but can be removed cleanly.
• Material Safety: Raw materials are tested to ensure they are free from harmful substances. This includes checking for contaminants like heavy metals, phthalates, and residual chlorine byproducts. Finished products are also tested for skin irritation and sensitization.

This rigorous testing provides the final assurance that the product is not only effective but also safe for its intended intimate use.

Frequently Asked Questions (FAQ)

1. Are “sanitary napkins” and “sanitary pads” the same thing? Yes, the terms refer to the exact same product: an absorbent item worn externally for menstrual fluid management. “Sanitary pad” or “menstrual pad” are the more common terms in the United States, while “sanitary napkin” is still widely used in other parts of the world, including Great Britain childsea.com.

2. What is Superabsorbent Polymer (SAP) and is it safe? Superabsorbent Polymer, or SAP, is typically sodium polyacrylate, a material that can absorb and retain extremely large amounts of liquid relative to its own mass, turning it into a gel. It is the key ingredient in modern thin pads. Decades of research and use have shown SAP to be safe for external use in products like pads and diapers. It is non-toxic and has a very low potential for skin irritation as it is held within the core of the pad (Farage & Miller, 2011).

3. Why do some pads feel “plasticky” while others feel soft? This difference comes from the topsheet material. A “plasticky” feel is often associated with a perforated or apertured film topsheet, which is designed for maximum dryness by funneling liquid away from the surface. A softer, cloth-like feel comes from a non-woven fabric topsheet, typically made of polypropylene fibers, which prioritizes a gentle texture against the skin.

4. What exactly makes a sanitary napkin “breathable”? A “breathable” pad uses a microporous film for its backsheet (the bottom layer). This film has microscopic pores that are large enough for air and water vapor to pass through but too small for liquid water droplets. This allows heat and humidity to escape, leading to a cooler and more comfortable experience compared to a traditional non-breathable polyethylene film.

5. Are organic cotton pads more absorbent than regular pads? Not necessarily. Absorbency is primarily determined by the absorbent core, specifically the amount and quality of the Superabsorbent Polymer (SAP) and fluff pulp. While an organic cotton topsheet provides benefits in terms of softness and being hypoallergenic, the core’s composition is what dictates the pad’s fluid capacity. An organic pad and a conventional pad with identically constructed cores would have similar absorbency.

6. What does “chlorine-free” mean when talking about fluff pulp? This refers to the bleaching process used to whiten the wood pulp. “Totally Chlorine-Free” (TCF) means the pulp was bleached using oxygen-based compounds (like hydrogen peroxide) instead of any chlorine compounds. “Elemental Chlorine-Free” (ECF) uses chlorine dioxide instead of elemental chlorine gas, a process that significantly reduces the formation of harmful dioxin byproducts. TCF is considered the most environmentally friendly bleaching method.

7. How do I choose the right type of sanitary napkin? Choosing the right pad depends on your menstrual flow, daily activities, and personal preference for materials childsea.com. Consider absorbency levels (light, regular, super, overnight) based on your flow. Think about your activity level; pads with wings offer more security. Finally, consider your skin sensitivity; if you are prone to irritation, a pad with a soft, non-woven or organic cotton topsheet and a breathable backsheet may be more comfortable.

Conclusion

The journey through the layers of a sanitary napkin reveals an object far more intricate than its simple form suggests. It is a product born from a deep understanding of fluid mechanics, polymer chemistry, and human-centered design. From the hydrophilic-treated non-woven topsheet that welcomes fluid inward, to the rapid-transit ADL, the high-capacity SAP-infused core that forms a stable gel, and the final, breathable backsheet that ensures security, each component is a testament to decades of scientific innovation. The inquiry into what sanitary napkins are made of is therefore an appreciation of the silent, sophisticated technology that millions of people rely on every day. As material science continues to advance, we can anticipate future generations of products that are even more comfortable, effective, and sustainable, continuing the evolution of menstrual care to better serve the needs of individuals and the health of our planet.

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