What can I use to modify viscosity in hot-melt adhesives?

How to Modify Viscosity in Hot-Melt Adhesives: A Deep Dive into Polyethylene Wax

Hot-melt adhesives have become a cornerstone in various industries—including packaging, automotive, textiles, woodworking, and more—because of their rapid setting times, strong bonding capabilities, and solvent-free formulations. Yet formulators often encounter a key challenge when working with these adhesives: controlling or modifying viscosity. If you’re asking yourself, “What can I use to modify viscosity in hot-melt adhesives? Polyethylene wax” is often one of the most practical and effective solutions. This article explores the science, application methods, and latest innovations surrounding the use of polyethylene wax (sometimes called PE wax, polyolefin wax, or low molecular weight polyethylene) in hot-melt adhesive formulations. We will delve into the complexities of viscosity, the role of various additives, why polyethylene wax has gained traction as a primary modifier, and how global market trends are steering formulators toward more innovative, sustainable solutions.

Understanding Viscosity in Hot-Melt Adhesives

Hot-melt adhesives are thermoplastic materials that melt upon heating and solidify upon cooling. Their performance depends on a series of formulation parameters:

• Base Polymer: Common hot-melt base polymers include ethylene-vinyl acetate (EVA), polyolefins (e.g., metallocene polyolefin), styrene block copolymers (SBCs), or polyamides.
• Tackifiers: These components improve adhesion to various substrates by modifying the adhesive’s glass transition temperature and compatibility.
• Fillers: Sometimes used for cost reduction or to adjust mechanical properties.
• Plasticizers or Waxes: Typically used to reduce melt viscosity, improve flow, or influence the open time and set time of the adhesive.

Viscosity—a measure of a fluid’s resistance to flow—is one of the most critical parameters to get right. Formulations with excessively high viscosity can be difficult to process, requiring higher temperatures or more energy. Conversely, if the viscosity is too low, the adhesive may not develop the necessary cohesive strength or may spread uncontrollably, leading to defective bonds.

Viscosity impacts processing, pumpability, coating weight, bond line thickness, and even final appearance.

In many manufacturing settings, consistency in viscosity is important for achieving uniform bead application or even film coverage. Changes in temperature also directly affect the viscosity of hot-melt adhesives, so manufacturers must carefully balance all factors to maintain quality and production efficiency.

The Role of Additives in Controlling Viscosity

To tailor viscosity in hot-melt systems, formulators typically work with various additives. While some adjust the tack or color, others specifically target the flow characteristics or melt temperature. Below are a few categories of additives that can influence viscosity:

• Waxes (Paraffin, Polyethylene, Microcrystalline)
• Plasticizers
• Tackifiers
• Reactive modifiers

Among these, polyethylene wax has emerged as a standout performer. Paraffin wax is common in certain applications, but it may not always provide the thermal stability or mechanical properties desired. Polyethylene-based waxes, however, often deliver consistent, predictable performance across a range of temperatures and formulations. This consistency makes them particularly attractive for high-volume industries such as packaging or hygiene products.

Why Polyethylene Wax is a Powerful Viscosity Modifier

Polyethylene wax is produced by polymerizing ethylene under specific conditions to yield a lower molecular weight polymer—essentially a wax-like substance rather than a high-strength plastic. Here are some reasons why PE wax is especially well-suited to hot-melt adhesives:

1. Thermal Stability

   • Polyethylene waxes generally have higher melt points compared to paraffin waxes, offering more stability under the high processing temperatures typical of hot-melt adhesives.
   • They maintain consistent viscosity profiles across a broad temperature range, reducing fluctuation in the adhesive during continuous production runs.

2. Compatibility

   • Many hot-melt formulations, particularly those using EVA, polyolefins, or certain tackifiers, exhibit excellent compatibility with polyethylene wax.
   • This compatibility extends the working window and makes it easier to fine-tune the final adhesive properties.

3. Low Volatility

   • Low molecular weight polyethylene waxes are less prone to evaporation or degradation during processing, ensuring minimal smoke or odor and extending equipment life.
   • This characteristic also contributes to better worker safety and cleaner production lines.

4. Improved Wetting and Flow

   • By lowering viscosity, PE wax helps the adhesive flow more readily over substrates, improving coverage and penetration.
   • This can be essential in applications like bookbinding, where uniform adhesive penetration is needed for binding strength.

5. Enhanced Mechanical Properties

   • Despite reducing viscosity, polyethylene wax can also contribute to the hardness and block resistance of the final adhesive film.
   • The adhesive’s resistance to discoloration or degradation may also improve depending on the grade and formulation.

Different Types of Polyethylene Wax

Within the realm of polyethylene waxes, variations exist based on polymerization methods, molecular weight distribution, and other chemical modifications. Below is a brief overview of the most common types:

Each wax type presents unique benefits. For example, oxidized polyethylene wax can improve polarity and dispersion in certain formulations, making it appealing for specialized hot-melt adhesives that require compatibility with polar substrates or fillers. On the other hand, high-density polyethylene wax might be better for high-temperature applications because of its higher melt point.

Mechanisms for Viscosity Reduction

When you add polyethylene wax to a hot-melt adhesive, you are typically looking to lower the overall viscosity. This happens primarily through:

• Dilution Effect
  The wax, being relatively low in viscosity at melt temperatures, dilutes the base polymer, resulting in a lower overall viscosity.
• Crystallinity Introduction
  Polyethylene wax tends to have high crystallinity, which can help control the flow at elevated temperatures while also enhancing the cohesive strength upon cooling.
• Improved Flow at Higher Shear
  Many hot-melt adhesives exhibit non-Newtonian behavior, meaning their viscosity changes under shear. The addition of wax can alter shear-thinning characteristics, making the adhesive easier to pump and apply.

It’s worth noting that while waxes generally reduce viscosity, the final outcome depends on other formulation parameters such as polymer content, tackifier selection, and processing temperatures. Formulators often use a range of lab tests—like Brookfield or rotational rheometry—to measure viscosity at different shear rates and temperatures before scaling up to production.

Can Polyethylene Wax Increase Viscosity?

Interestingly, under certain circumstances, adding polyethylene wax could increase the viscosity of the final formulation, especially if you are using a wax with a higher molecular weight or if the wax crystallizes quickly and forms a structured network with other components. In most hot-melt adhesive formulations, however, PE wax primarily acts as a viscosity reducer, especially if it’s a low molecular weight grade. Still, it’s crucial to choose the right type of polyethylene wax based on the specific application requirements.

Advantages of Using Polyethylene Wax Over Other Options

If you’ve looked into ways to modify viscosity in hot-melt adhesives, you might have come across other waxes or plasticizers as well. Below is a quick comparative look:

1. Paraffin Wax

   • Pros: Widely available, economical, easy to blend.
   • Cons: Lower thermal stability, more prone to smoke or odor, can cause blooming or exudation in certain adhesives.

2. Microcrystalline Wax

   • Pros: Good flexibility, improved tack, higher melt point than paraffin.
   • Cons: May be less compatible with certain polymers, might not always achieve the precise viscosity control needed.

3. Polyethylene Wax

   • Pros: Superior thermal stability, consistent melt flow, good compatibility with a wide range of base polymers and tackifiers.
   • Cons: Typically more expensive than paraffin wax, selection of the correct grade may require testing and validation.

4. Plasticizers (e.g., Mineral Oil or Phthalates)

   • Pros: Significant viscosity reduction, enhanced flexibility and open time.
   • Cons: Potential for migration, may not be suitable for food packaging or medical applications, regulatory concerns with certain phthalates.

In summary, PE wax stands out for its balance of thermal stability, compatibility, and consistent performance, making it one of the top choices for modifying viscosity in hot-melt adhesive formulations aimed at demanding applications or high-volume production.

Real-World Applications of Polyethylene Wax in Hot-Melt Adhesives

Hot-melt adhesives are ubiquitous in countless industries, and many of these applications benefit from the properties imparted by polyethylene wax:

• Packaging and Labeling

  • Manufacturers often rely on hot-melt adhesives for carton sealing, labeling, and flexible packaging. Polyethylene wax can help the adhesive flow smoothly on automated lines, reduce application temperatures, and maintain strong bond integrity.

• Bookbinding

  • In publishing, consistent adhesive flow is crucial to ensure a uniform spine and page alignment. The low viscosity made possible by polyethylene wax simplifies the binding process and helps produce durable books.

• Automotive Interiors

  • Modern vehicles often feature complex interior assemblies bonded with hot-melt adhesives for trims, headliners, and other components. By using PE wax, manufacturers can achieve reliable adhesion at lower temperatures while ensuring a stable, cohesive bond.

• Woodworking and Furniture

  • Hot-melt adhesives are used for edge banding, laminating, and various woodworking joints. Polyethylene wax reduces the risk of scorching or charring, allowing more precise adhesive application on wood-based substrates.

• Nonwoven and Hygiene Products

  • In products like diapers, sanitary napkins, and medical drapes, adhesives must be gentle yet secure. PE wax often plays a role in achieving lower viscosity and better wetting on delicate substrates while maintaining necessary bond strength.

Current Market Trends and Innovations

The global hot-melt adhesive market continues to evolve, driven by emerging technologies, sustainability goals, and regulatory frameworks. Recent innovations related to polyethylene wax in hot-melt adhesives include:

• Bio-Based and Renewable Feedstocks

  • There is a growing push toward bio-based polyethylene waxes derived from renewable sources such as sugarcane ethanol. This aligns with consumer and industry demand for more eco-friendly formulations.

• Higher Performance Grades

  • New polymerization techniques yield polyethylene waxes with narrower molecular weight distributions, providing enhanced consistency and tailored melt points for specialized applications.

• Sustainability and Circular Economy

  • Governments worldwide are introducing strict measures to reduce carbon footprints and improve recyclability. Polyethylene wax can support these goals by enabling lower application temperatures (reducing energy usage) and, in some cases, improving compatibility with recyclable substrates.

• Advanced Dispersion Technologies

  • Dispersing polyethylene wax uniformly in certain polymer matrices can be challenging. Recent innovations in reactive extrusion and specialty compounding methods are addressing this issue, resulting in adhesives with more stable viscosity profiles.

Global studies indicate that the hot-melt adhesives market is poised for continued growth, with an expected increase in demand for low-odor, sustainable, and high-performance formulations.
Incorporating advanced polyethylene wax additives is often a straightforward route to achieving these emerging requirements, thus maintaining a competitive edge.

Sustainability Considerations

As environmental awareness increases, industries are looking for ways to develop adhesives that are less harmful to people and the planet. Polyethylene wax supports some sustainability objectives:

• Lower Application Temperature

  • By reducing overall viscosity, polyethylene wax can help hot-melt adhesives flow at lower temperatures, saving energy and reducing greenhouse gas emissions.

• Reduced Volatile Organic Compounds (VOCs)

  • Hot-melt adhesives are generally solvent-free and low in VOCs. Polyethylene wax, especially grades with minimal volatiles, further reduces the possibility of harmful emissions.

• Recycling Compatibility

  • In some packaging applications, using compatible polyethylene wax grades may improve the recyclability of the product, ensuring that the adhesive does not contaminate the recycling stream.

• Extended Equipment Life

  • Cleaner-running adhesives containing stable waxes are less likely to cause fouling in application equipment, reducing downtime and waste from equipment maintenance or replacement.

While polyethylene wax alone is not a comprehensive sustainability solution, it is often part of a broader strategy to reduce environmental impact, improve energy efficiency, and meet stringent regulatory requirements for safe consumer products.

How to Use Polyethylene Wax in Hot-Melt Adhesives

Incorporating polyethylene wax into a hot-melt adhesive formulation typically involves:

• Selection of the Right Grade

  • Consider melt point, molecular weight, density, and oxidation level. The choice depends on your target application—whether you need short open time for fast-setting adhesives or a higher melt point for durability under stress.

• Optimal Dosage

  • Dosage rates can vary from 2% to 20% or more, depending on how much you need to adjust viscosity and other properties.
  • Too little may not achieve the desired viscosity reduction, while too much could compromise adhesive strength or lead to brittleness.

• Processing Temperature

  • Adjust the melting and mixing temperatures to ensure complete dispersion of the wax into the polymer matrix.
  • Overheating can degrade the wax or cause undesirable side effects like gelling or char formation.

• Mixing Protocol

  • A well-thought-out mixing sequence is essential. Generally, you melt the base polymer first, then incorporate the tackifiers, followed by the wax.
  • Proper agitation and time at temperature are critical to ensuring a homogeneous blend.

• Quality Control Tests

  • Monitor viscosity, color, and stability tests. Use standardized methods (e.g., Brookfield viscometer or capillary rheometer) to confirm the adhesive meets specification across the intended temperature range.

Practical Formulation Example

Below is a hypothetical example of a hot-melt adhesive formulation to illustrate how PE wax might be included. Please note that real-world formulations require extensive lab testing and validation:

• Processing Notes:
  1. Heat the EVA to around 160–180°C.
  2. Add the hydrogenated tackifier slowly to ensure complete melt.
  3. Introduce the polyethylene wax in small increments, allowing each portion to fully disperse before adding the next.
  4. Incorporate the antioxidant package to preserve long-term performance.
  5. Monitor viscosity and color throughout the process.

This formulation is just an example and may be adjusted based on specific equipment, application methods (slot die, spray, roll coater), and performance needs (open time, set speed, heat resistance).

Real-World Case: Packaging Line Optimization

A medium-sized packaging company producing corrugated boxes faced efficiency challenges due to frequent adhesive clogging and inconsistent bead application. Their existing hot-melt adhesive had a relatively high melt viscosity, requiring application at around 190°C. This led to:

• Higher energy consumption.
• Frequent nozzle blockages.
• Irregular bonding, occasionally resulting in open seams.

By reformulating the adhesive with a polyethylene-based wax, the manufacturer successfully lowered the recommended application temperature to around 170°C. The viscosity improved, leading to:

• Reduced Downtime: Fewer clogging incidents and less frequent cleaning.
• Energy Savings: About a 10% reduction in heating costs for the adhesive melter.
• Improved Throughput: A more consistent and controllable bead application allowed for higher line speeds.

Over one fiscal quarter, the company reported a noticeable return on investment through combined savings in energy, labor, and reduced scrap.

Table: Common Hot-Melt Adhesive Additives and Their Typical Functions

To put PE wax in the broader context, here’s a table outlining various additive types and their general roles:

Notice how polyethylene wax typically falls into the 5–20% range in many formulations, though this can vary based on the specific adhesive requirements.

Conclusion: The Strategic Role of Polyethylene Wax in Adhesive Formulations

To effectively modify viscosity in hot-melt adhesives, polyethylene wax offers unmatched benefits, including thermal stability, improved flow, and enhanced mechanical properties. By selecting the right grade and formulation approach, industries such as packaging, automotive, and hygiene can achieve consistent adhesive performance while optimizing energy efficiency and sustainability. As global markets shift towards advanced, eco-friendly solutions, leveraging polyethylene wax in hot-melt adhesives remains a key strategy for improving production efficiency and long-term product reliability.

Top FAQs: Expert Answers to Your Common Queries

1. How can I modify viscosity in hot-melt adhesives for better processing and performance?

Viscosity in hot-melt adhesives can be modified using various additives, but polyethylene wax (also known as PE wax, polyolefin wax, or low molecular weight polyethylene) is one of the most effective options. It reduces melt viscosity, enhances flow, and ensures smoother application. By incorporating polyethylene wax, manufacturers can optimize adhesive properties for different substrates, improve processing efficiency, and lower energy consumption. Adjusting the wax concentration and selecting the right grade (e.g., oxidized PE wax for improved polarity) ensures compatibility with different adhesive formulations.

2. What are the benefits of using polyethylene wax over paraffin or microcrystalline wax in hot-melt adhesives?

While paraffin wax is cost-effective and microcrystalline wax offers flexibility, polyethylene wax provides superior thermal stability, lower volatility, and consistent viscosity control. Unlike paraffin wax, which can cause blooming, polyethylene wax ensures long-term adhesive performance without degradation. Additionally, polyethylene wax can withstand higher temperatures, making it ideal for packaging, automotive, and woodworking adhesives. Recent innovations in bio-based polyethylene wax also make it a more sustainable alternative.

3. How does polyethylene wax improve hot-melt adhesive performance in packaging applications?

In packaging, adhesives must maintain strong bonding, fast setting times, and stable viscosity across various conditions. Polyethylene wax enhances adhesive flow, ensuring uniform application on corrugated boxes, labels, and flexible packaging materials. It also helps manufacturers reduce application temperature, lowering energy costs and minimizing production downtime due to clogged nozzles. As e-commerce growth increases packaging demands, polyethylene wax ensures adhesives remain cost-efficient, high-performance, and eco-friendly.

4. Can polyethylene wax help reduce the environmental impact of hot-melt adhesives?

Yes, polyethylene wax contributes to sustainability by lowering application temperatures, reducing carbon footprint, and improving recyclability of adhesive-coated materials. Some manufacturers now offer bio-based polyethylene wax derived from renewable sources, making it an even greener choice. Additionally, low-volatility PE waxes reduce VOC emissions, ensuring compliance with stricter environmental regulations in industries like food packaging and medical adhesives.

5. What is the ideal dosage of polyethylene wax in hot-melt adhesive formulations?

The optimal dosage of polyethylene wax varies based on adhesive type and application. Generally, it ranges between 5% and 20% of the total formulation. A higher concentration is used for low-viscosity adhesives requiring fast flow, while a lower percentage is preferred when minimal viscosity adjustment is needed. Formulators must conduct viscosity tests (Brookfield or rheometry analysis) to fine-tune dosage levels and ensure desired adhesive properties.

6. How does polyethylene wax influence the thermal stability of hot-melt adhesives?

Thermal stability is crucial for ensuring adhesives maintain viscosity and bonding strength under fluctuating temperatures. High-density polyethylene wax (HDPE wax) is particularly beneficial in high-temperature applications, as it prevents adhesive degradation and oxidation. Compared to paraffin wax, polyethylene wax maintains a consistent viscosity profile, reducing risks of scorching, gelling, or premature setting during application.

7. What industries benefit the most from using polyethylene wax in hot-melt adhesives?

Industries that require fast-setting, high-strength, and thermally stable adhesives benefit the most from polyethylene wax. These include:

• Packaging & Labeling (carton sealing, flexible packaging, food-safe adhesives)
• Automotive (interior trims, sound dampening, wire harness adhesives)
• Woodworking & Furniture (laminating, edge banding, veneer bonding)
• Bookbinding (spine adhesives for durability and uniformity)
• Hygiene & Medical (diapers, surgical drapes, nonwoven adhesives)

With increased focus on sustainability and performance, industries are shifting toward polyethylene-based formulations to improve efficiency and reduce waste.

8. What are the latest trends in hot-melt adhesive technology, and how does polyethylene wax fit in?

Recent innovations in hot-melt adhesives focus on sustainability, bio-based materials, and energy-efficient formulations. Trends include:

• Bio-Based Polyethylene Wax: Derived from renewable sources to reduce carbon footprint.
• Low-Temperature Application Adhesives: Reducing energy consumption by using polyethylene wax to lower melt viscosity.
• Smart Packaging Adhesives: Enhancing performance for e-commerce-ready packaging and temperature-sensitive labels.
• Recyclable Adhesives: Improving recyclability by selecting PE waxes that align with circular economy goals.

These advancements position polyethylene wax as a key component in next-generation hot-melt adhesives.

9. Can polyethylene wax increase the viscosity of hot-melt adhesives instead of reducing it?

Yes, under certain conditions, polyethylene wax can increase viscosity instead of reducing it. This occurs when using high molecular weight PE wax or functionalized polyethylene wax, which enhances structural integrity and cohesive strength in adhesives. Some formulations leverage this characteristic to create heat-resistant adhesives for automotive or industrial applications. However, in most cases, polyethylene wax primarily acts as a viscosity reducer, enabling better flow and application consistency.

10. What is the best method for incorporating polyethylene wax into a hot-melt adhesive formulation?

To effectively blend polyethylene wax into a hot-melt adhesive, follow these steps:

1. Melt the base polymer (e.g., EVA, polyolefin) at 160–180°C.
2. Slowly add tackifiers to improve adhesion.
3. Introduce polyethylene wax in small increments, ensuring even dispersion.
4. Incorporate antioxidants to prevent oxidation and extend adhesive lifespan.
5. Conduct viscosity tests to confirm the desired flow and set time.

By controlling temperature, mixing speed, and ingredient sequencing, formulators can achieve stable, high-performance adhesives optimized for industrial use.

11. How do you increase the viscosity of adhesive?

To increase viscosity in adhesives, formulators typically add high molecular weight polymers, structured fillers, or specific waxes that enhance cohesion. In hot-melt adhesives, increasing viscosity can be achieved through:

• Using high molecular weight polyethylene wax: Unlike standard PE wax, certain high-density or oxidized polyethylene waxes create stronger intermolecular interactions, increasing viscosity.
• Incorporating higher molecular weight base polymers: Adhesives based on ethylene-vinyl acetate (EVA), polyolefin, or styrene block copolymers (SBCs) can achieve greater viscosity by increasing polymer chain length.
• Adding thixotropic agents: These materials, such as fumed silica or clay-based rheology modifiers, can improve shear-thinning properties, allowing adhesives to maintain viscosity while still being spreadable under force.
• Reducing plasticizers or low-viscosity waxes: If too many low-viscosity components (e.g., mineral oils, short-chain hydrocarbons) are present, replacing them with structured polymers or crystalline waxes can increase the adhesive’s overall thickness.

For applications requiring a thicker adhesive layer, such as construction adhesives, industrial bonding, or bookbinding, optimizing viscosity ensures better gap-filling ability and stronger adhesion under stress.

12. What is the viscosity of hot-melt adhesive?

The viscosity of hot-melt adhesives (HMA) varies significantly based on the base polymer, wax content, and formulation additives. In general, viscosity is measured in centipoise (cP) at a specific temperature, typically 160°C (320°F) to 180°C (356°F).

• Low-viscosity hot-melt adhesives: (~500 – 2,000 cP)
  • Used for spray applications, light packaging, and bookbinding.
• Medium-viscosity hot-melt adhesives: (~2,000 – 10,000 cP)
  • Common for carton sealing, woodworking, and labeling.
• High-viscosity hot-melt adhesives: (>10,000 cP)
  • Preferred for industrial bonding, automotive applications, and high-strength assemblies.

Example: A typical EVA-based hot-melt adhesive for packaging has a viscosity of 2,500–4,000 cP at 160°C, whereas a polyolefin-based adhesive might have a lower viscosity of 800–1,500 cP at the same temperature.

Formulators use Brookfield viscometers or capillary rheometers to test viscosity under different conditions, ensuring adhesives meet processing and application requirements.

13. How do you make glue less viscous?

Reducing the viscosity of an adhesive is essential for improving flow, penetration, and application efficiency. The following methods help make glue less viscous:

• Adding polyethylene wax or paraffin wax: These reduce melt viscosity, allowing the adhesive to spread more easily. Low molecular weight polyethylene wax (e.g., polyolefin wax) is especially effective in hot-melt formulations.
• Incorporating plasticizers: Materials like mineral oil, phthalates, or polybutene soften adhesives and improve flow.
• Raising processing temperature: Heating the adhesive to a higher application temperature (e.g., 180–200°C) reduces viscosity, making it easier to apply. However, excessive heat may degrade components over time.
• Using reactive diluents: Some UV-curable or solvent-based adhesives include reactive diluents that temporarily lower viscosity but later integrate into the cured adhesive matrix.

Industry Example: Nonwoven hygiene adhesives (e.g., diaper production) require low-viscosity adhesives for fast application and even distribution, often achieved using low-viscosity PE waxes.

14. What is an alternative to hot-melt adhesive?

While hot-melt adhesives are widely used due to their solvent-free, fast-setting, and strong-bonding properties, some applications require alternative adhesive solutions based on specific performance needs:

1. Water-Based Adhesives

• Best for: Paper, packaging, woodworking, and textiles
• Advantages: Non-toxic, eco-friendly, and cost-effective
• Example: Polyvinyl acetate (PVA) glue, used in bookbinding and carton sealing

2. Solvent-Based Adhesives

• Best for: Industrial bonding, automotive, and aerospace applications
• Advantages: High strength, excellent adhesion to difficult surfaces
• Example: Neoprene-based adhesives for rubber and leather bonding

3. Reactive Adhesives (Epoxy, Polyurethane, Cyanoacrylate)

• Best for: Structural bonding, electronics, and medical devices
• Advantages: High durability, chemical resistance, long-lasting bonds
• Example: Epoxy adhesives for metal-to-metal bonding

4. UV-Curable Adhesives

• Best for: Glass, medical, and electronics industries
• Advantages: Fast curing under UV light, no heat required
• Example: Acrylic UV adhesives for smartphone screens

Why Hot-Melt Adhesives Remain Popular:
Despite the availability of alternatives, hot-melt adhesives remain dominant in industries like packaging, woodworking, and hygiene products due to their instant bonding, cost-effectiveness, and solvent-free nature. However, sustainability trends are driving the development of bio-based and low-temperature hot-melt adhesives to reduce environmental impact and energy consumption.