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While it inherently offers these advantages, flexible packaging is highly engineered to optimally fulfill other performance requirements of food and consumer goods packaging. These include providing an effective barrier between the environment and product, facilitating print such that brand owners can drive growth and recognition, and enabling high-throughput production and finishing of the package. Since the plastic films that constitute flexible packaging are, in some cases, detrimental to achieving the functionality mentioned, specialized coating formulations are required to apply on these films. LUDOX® colloidal silica is a performance additive widely used in various coating formulations. It provides significant benefits to packaging coatings.
Another characteristic of plastic packaging films that presents a manufacturing challenge is their tendency to have low surface energies. This means that water-based ink formulations, which have surface tensions higher than the surface energy of the packaging films, will not wet and level easily. Wetting and leveling are essential to creating a good appearance on films, such that brand information, designs, and nutritional information are appealing and presented clearly. To overcome this, primers or coatings are typically applied to the films to promote adhesion. LUDOX® can be used to formulate primers and coatings, which help increase ink receptivity when applied to packaging films. The mechanism by which this is achieved is thought to come from interactions of the silanol groups on the silica particles and the hydroxyl groups or polar moieties on dyes and pigments.
LUDOX® can even provide benefits to the flexible packaging manufacturing process far upstream of the steps described so far. When packaging films are freshly manufactured, they have a propensity to block or stick together when wound up into rolls for shipping. Simply put, this occurs because the newly made film layers are chemically identical, quite warm, and experience high amounts of pressure. Prior to winding, LUDOX® helps reduce blocking by being applied as a coating. While imperceptible to the naked eye, the nano-sized silica particles impart a degree of surface roughness that reduces the surface area of the films’ interface. This mechanism is very similar to the one in which LUDOX® is used as an anti-slip coating for paper packaging. The surface roughness applied to these films allows them to be easily unwound without sacrificing visual quality. When these films are used to manufacture packaging, this surface roughness also helps to provide easier separation between the film and heated plates used to seal films together.
Grade
|
Particle size (nm)
|
Silica content (%)
|
Surface area (m2/g)
|
pH
|
Stabilizing counterion
|
---|---|---|---|---|---|
LUDOX® SM | 7
|
30
|
345
|
6.8
|
Sodium
|
LUDOX® HS-40 | 12
|
40
|
220
|
9.7
|
Sodium |
LUDOX® AS-30 | 12 |
30
|
220
|
9.4
|
Ammonium
|
LUDOX® AM | 12 |
30
|
220
|
9.0*
|
Sodium
|
LUDOX® TM-50 | 22
|
50
|
135
|
9.0
|
Sodium |
LUDOX® CL | 12 |
30
|
220
|
4.0
|
Chloride
|
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