Lamination is the process of manufacturing a material in multiple layers, so that the combined physical and mechanical characteristics of each layer make for a stronger, more resilient composite material.
The earliest examples of lamination made use of natural adhesives such as beeswax, gums, tar and substances derived from animal bones. As technology progressed, we discovered the use of sealing wax as the first hot-melt adhesive. In the 1930s a wet lamination process (with the use of solvents) was used to bond shirt collars (a woven fabric) with cellulose acetate. This process was deemed inconvenient, and by 1948 progress was made in dry lamination using polyvinyl acetate plasticized with dibutyl phthalate.
Nonwovens lamination, in particular, is the process of bonding two or more layers, at least one of which is a nonwoven fabric, with the objective of obtaining improved strength, stability, sound insulation, appearance, or other properties. Although less expensive to manufacture, nonwoven fabrics tend to be weaker than woven ones, and the lamination process comes into play just when there is the need to strengthen this nonwoven material for a variety of uses.
The bonding is typically done with the use of adhesives (or heat) and pressure, making it possible to manufacture nonwovens products, equipped with a waterproof layer, that are breathable, soft, comfortable and suitable for printing.
Shortly after the beginning of the industrial production of disposable diapers, nonwoven laminated products, such as the textile backsheet, appeared. From the early days of dry lamination various adhesives were produced, including hot-melt powders.
Breathability was an issue with lamination in the early days, but the processes used today are capable of producing breathable, porous materials that maintain their waterproof properties.
Nonwovens Lamination main areas of application
The use of nonwoven laminates has grown over the past few decades to include many industries, such as agriculture, clothing (interlinings, fillings, etc.), household, transportation and environmental. While there are many uses across various industries, the following make the most use of nonwoven laminates.
The medical industry is one of the most prominent users of nonwoven laminates. With the need to have sterile, disposable materials, there are a number of key uses for this material in medicine. Nonwovens lamination creates breathable materials that allow moisture to easily pass out of the garment, while preventing liquids from entering. The nonwoven composite material can also have an anti-microbial surface treatment to further enhances its protective properties. The outer layer of nonwoven fabric is soft to the touch, strong and durable.
Nonwovens lamination produces a variety of garments and items for protection in a medical environment, such as:
-Surgical gowns and drapes
-Hair and shoe covers
-Bandages and adhesive bandages
Remember that all surgical gowns, masks, and protective coverings must be lightweight and fit snuggly, while allowing freedom of movement.
Read more: A.Celli Nonwovens in support of the Chinese health emergency
Hygiene is another industry that widely uses nonwoven laminated products. Again, the focus is on the availability of sterile, disposable products featuring air and water vapor permeability and water resistance like:
-Adult and Baby diapers
-Feminine hygiene products
-Patient bathing products
Filtration is used in many industries, including beverage and automotive. The filtration of air and liquids requires filters made using nonwoven lamination with the capability of filtering various sizes of particles, depending on the type of filter and intended use.
A coffee filter, for example, only has to filter out the coffee grounds and allow the water to pass through. In contrast, an air filter must be capable of filtering out the tiniest particles of dust and other contaminants to ensure purification. Here are examples of filters made using nonwoven lamination:
-Vacuum cleaner filters
-Air filtration systems
The construction industry relies on materials made with nonwoven lamination primarily for insulation and waterproofing. The types of products used by the construction industry includes things like:
-Roof insulation material
-VCI or metal protection wrap
Nonwovens Lamination techniques and advantages
The most suitable lamination method depends on the required properties of the final composite which, depending on the specific application, might need to be:
-Impermeable to contaminants
-Soft and comfortable
As for the techniques that can be used in nonwoven lamination, these can be divided into four categories:
1. Adhesive Lamination
When it comes to adhesive nonwovens lamination, there are a number of different methods:
Hot melt adhesives
Dry bond laminating
Wet bond laminating
Using hot melt adhesives is the leading method, replacing older ones like mechanical fastening, cold glue and wet lamination. This method uses microscopic dots to create bonds between the layers in order to form a composite. It offers several advantages, including the ability to:
Bond two materials with very different properties
Use a variety of adhesive application methods, including bead patterns, spirals, meltblown, sinusoidal and the point bonding technique, which minimizes points of contact and offers a more permeable composite with less use of adhesive
Perform high-precision bonding
Maintain the properties (breathability, flexibility, etc.) of the original material
Manufacture products at high speed
2. Thermal Lamination
Thermal lamination uses pressure and heat to adhere layers together, using a thermoplastic layer that can be a hot melt, fiber, film, or powder. There are a few different thermal bonding options that can be used, including the following:
Area Bonding – produces stiff, thin, strong composites
Point Bonding – produces composites that can range in their level of strength, elasticity, softness and flexibility
3. Ultrasonic Lamination
Ultrasonic lamination is the most environmentally friendly method, since no chemicals or adhesives are required. It relies on the use of high-frequency sound vibration to generate heat locally, which in turn causes thermoplastic fibers to melt and bond. Aside from the sustainability of the process, the advantages of ultrasonic lamination are many, including the ability to:
Laminate as many as seven layers in a single pass
Bond materials with different characteristics (physical strength, melting temperatures, etc.)
Produce incredibly uniform composites in which the individual materials remain fully intact
Use point bonding technique to minimize the bonded surface in permeable materials
Ensure precision bonding to meet specific needs (such as pattern, location and frequency)
Obtain a product that is more durable and will hold up to extreme heat better than those created through chemical bond
4. Extrusion Coating
Extrusion coating is a process in which a molten polymer is applied as a thin coating on one or both sides of one or more nonwoven layers.
This coating makes the nonwoven material waterproof, printable, antistatic and flame-resistant. In addition to this, the Extrusion Coating allows to contain the costs of raw materials and improve the structural stability of the material.