A complete analysis of antibacterial fabrics

Types of antimicrobial agents

Antibacterial agents for antibacterial fabrics are mainly divided into three categories.

• Silver-based antibacterial agents. Silver ion antibacterial therapy is currently the most effective and widely used antibacterial solution. Silver ions can destroy bacterial cell membranes and DNA, has a broad antibacterial spectrum, and is effective against both Gram-positive and Gram-negative bacteria. Silver ion antibacterial products can be added at the spinning grade and have good durability. The downside is the high cost.
• Zinc-based antibacterial agents. Zinc ions have milder antibacterial effects than silver ions, but are much less expensive. Zinc is an essential trace element for the human body and is very safe. Zinc-based antimicrobial products are commonly used in antibacterial solutions for mid- to low-priced products.
• Organic antibacterial agents. Quaternary ammonium salts, biguanidins, and other organic antibacterial agents. There are many types and flexible costs, but their durability and heat resistance are generally inferior to inorganic antibacterial agents.

Natural antibacterial fibers

There is also a category of products that do not require additional antibacterial agents—the fibers themselves have antibacterial properties.

Hemp-type fibers (Hemp, flax) have natural antibacterial and deodorizing effects.

The structure of hemp fiber contains certain antibacterial components, and its good moisture absorption and sweat-wicking properties reduce the environment for bacterial growth.

The antibacterial effect of linen fabrics does not diminish with washing, but their antibacterial strength is usually not as strong as additive-type antibacterial fibers.

Bamboo fiber It is also promoted for its natural antibacterial properties.

But in reality, most of the natural antibacterial components in bamboo fiber are chemically removed during production. The real antibacterial effect comes from the recycled bamboo fiber with added antibacterial agents, not the bamboo fiber itself.

When purchasing when encountering advertisements claiming “natural antibacterial bamboo fiber,” it is necessary to confirm the source of the antibacterial effect—whether it is the natural properties of the bamboo fiber itself or the antibacterial agents added during processing.

Chitosan fiber It is a natural antibacterial material extracted from shrimp and crab shells, with biocompatibility and biodegradability, and high safety.

The antibacterial effect of chitosan is relatively mild, and its durability depends on the chitosan content in the fiber and the processing technology.

Differences in strains: If it’s not antibacterial, it can kill any bacteria

“Antibacterial” is a general term. In fact, different products test different types of bacteria, resulting in different antibacterial effects.

The three most commonly used bacteria in textile antibacterial testing are: Staphylococcus aureus (representing Gram-positive bacteria), Escherichia coli (representing Gram-negative bacteria), and Candida albicans (representing fungi).

A piece of fabric that passes these three bacterial tests can be considered to have broad-spectrum antibacterial capabilities.

However, the application scenarios for antibacterial fabrics are much more complex than those of these three types of bacteria.

• The main types of sweat odor bacteria are Staphylococcus and Corynebacterium.
• The main bacteria for foot odor are Bacillus subtilis and Staphylococcus epidermidis.
• The main strain of elderly odor (aged odor) is: Moraxella —This bacterium can break down fatty acids on the skin surface, producing 2-nonenal, which is the main source of elderly odor. Mora is not a mandatory strain for routine antibacterial testing, so many products labeled as antibacterial have no effect on elderly odor. Antibacterial fabrics targeting elderly odor require additional testing for Moraxia inhibitory effects beyond conventional strains.

When reviewing the inspection report, buyers should carefully check which strains are listed and what their antibacterial rates are. Listing only one strain, Staphylococcus aureus, does not prove that the product has broad-spectrum antibacterial capabilities.

The difference between spinning grade and finishing

Spinning-grade antibacterial properties During the fiber spinning stage, antibacterial agents are mixed into the polymer; the antibacterial ingredients remain inside the fibers and cannot be washed off. Spinning-grade antibacterial products can withstand over 50 washes, with some products rated up to 100 cycles. The key to the quality of spinning-grade antibacterial is the uniformity of dispersion of the antimicrobial agent within the fiber—poor dispersion results in poor local antibacterial effects, and may even affect spinning stability.

Post-finishing is antibacterial After the fabric is knitted, a layer of antibacterial agent is applied to the garment, as if spraying a layer of disinfectant. The post-finishing antibacterial process is simple, low-cost, and flexible in order size. But the problem is poor durability—generally, after 10 to 20 washes, the antibacterial rate drops below the standard line.

There is also a compromise called the “Compromise.” Stock solution addition method — Add antibacterial agents to the working solution during fabric dyeing or styling. This method falls between spinning grade and post-finishing; its durability is slightly better than post-finishing but worse than spinning grade, but it is flexible to operate and does not require specialized antibacterial masterbatch.

5A、7A、10A

An A-grade rating for antibacterial fabrics corresponds to the number of washes. The larger the number before A, the more times the test is washed.

According to the current industry standard, 5A corresponds to testing antibacterial rate after 50 washes. 7A corresponds to 70 washes before detection, 10A corresponds to 100 washes before detection. In other words, a fabric labeled as 10A antibacterial can still detect antibacterial effects even after 100 washes in the lab.

But there are two issues here that require procurement attention.

• Differences in washing conditions A rating only means “antibacterial rate tested after so many washes,” not “so many washes under uniform strict conditions.” Water temperature, detergent type, stirring intensity, drying method—these conditions are set by the submitting party themselves. For the same fabric, using gentle or strict washing conditions can result in significantly different antibacterial rate data after 50 washes. The number of Grade A grades between different brands cannot be directly compared, as testing conditions may vary.
• A rating and the strength of antibacterial efficacy are two different things A product with 99% antibacterial rate after 50 washes and a product with 90% antibacterial rate after 50 washes can both be labeled 5A—because 5A only specifies “after 50 washes,” not “how much antibacterial rate must be achieved after washing.” When looking at the A-level rating, procurement must also look at the specific antibacterial rate value.

One of the improvements in this regard is that the new standard standardizes washing conditions more widely, reducing the room for prosecutors to choose their own conditions.