Medical hot melt pressure-sensitive adhesive is a category of medical hot melt adhesive widely used in the processing and production of medical and sanitary products such as medical tape, infusion patches, and wound dressings. It possesses both hot melt properties and pressure-sensitive properties, requiring specialized equipment for heating and melting during the production of adhesive products, demonstrating its hot melt nature. Products made with medical hot melt pressure-sensitive adhesive, such as medical tape and wound dressings, exhibit adhesive properties upon tearing and can be adhered by finger pressure, showcasing its pressure-sensitive nature.
Hot melt pressure-sensitive adhesives used in the medical tape market not only require suitable coating workability and thermal stability but also need to have characteristics such as non-itchiness, adhesion, and breathability.
Coating Workability As mentioned earlier, hot melt pressure-sensitive adhesive can be applied to various special substrates using special dies or rollers. However, hot melt pressure-sensitive adhesives for medical tapes typically have high fluidity, making them prone to overflow into porous substrates, causing adhesive leakage. Additionally, many substrates used for medical tapes cannot withstand high temperatures and may experience elongation, deformation, or even damage during adhesive application. To address these challenges, manufacturers often first apply hot melt pressure-sensitive adhesive to release paper that can withstand high temperatures and then transfer the adhesive onto various substrates.
Non-itchiness Solvent-based adhesives commonly used in medical tapes can cause skin allergies, requiring the addition of zinc oxide powder to the adhesive. Zinc oxide serves two purposes: reducing the allergenicity of solvent-based adhesives on the skin and enhancing the adhesive's moisture absorption or sweat-absorbing capacity.
Adhesion Since natural tackifying resins such as rosin or esterified rosin are not suitable for medical tapes, adhesion to the skin relies on the flexibility and wetting properties of the hot melt pressure-sensitive adhesive itself, known as cohesive elasticity. When designing hot melt pressure-sensitive adhesives for medical tapes, particular attention should be paid to the flowability on the human skin. After the tape is applied to the skin, it should continuously wet and adhere to the skin surface, ideally remaining securely in place even during joint movement and bending.
Breathability To prevent skin irritation, hot melt pressure-sensitive adhesives used in medical tapes typically do not contain polar substances (hydrophobic high polymers). This is because polar substances cannot absorb moisture or sweat. To achieve appropriate breathability, pinholes can be created in the tape substrate along with the adhesive, either by perforating the tape after adhesive application or by using specialized coating equipment to create non-full coverage, forming breathable holes on the coated surface. Both methods can provide some degree of breathability to medical tapes.
Other Physical Properties The adhesive target for medical tapes is the human skin, which typically has a surface temperature ranging from 30 to 35°C at any time and space. Therefore, besides considering whether the hot melt pressure-sensitive adhesive will cause adhesive overflow due to excessively high fluidity during storage and transportation, medical hot melt pressure-sensitive adhesives do not require special attention to heat resistance and cold resistance, unlike tapes and labels for other purposes. However, variations in individual skin dryness and oiliness may result in users experiencing different levels of adhesion and tackiness.
