Flexible Gel Packs

Flexible gel packs are reusable packs containing a thick aqueous gel that maintains flexibility when frozen. These packs are used for thermal regulation in a variety of applications, including food packaging, shipping, pain relief, and first aid. While applications can differ greatly, all flexible gel packs contain three main ingredients: a freeze point depressant, a thickener, and water. The selection of these ingredients ultimately determines their physical properties and product quality.

Freeze Point Depressants

Thickeners

Thickeners Used in Gel Packs

Two main types of thickeners are used in flexible gel packs: superabsorbent polymers and cellulose ethers, such as carboxymethyl cellulose. These two families of thickeners provide advantages and disadvantages when used in flexible gel pack applications.

Superabsorbent Polymers

Superabsorbent polymers (SAPs) have a high affinity for water and are used to absorb large quantities of water to form a gel. Most superabsorbent polymers are composed of sodium polyacrylate and are commercially available in granular form. The amount of water absorbed by an SAP depends on the ionic concentration of the aqueous solution and the cross-link density of the polyacrylate polymer. SAPs are used in gel packs when a lower viscosity or thinner consistency is required.

Advantages

• Inexpensive
• Highly efficient; absorbs up to 300 times its weight in water
• Forms gels quickly

Disadvantages

• Gels will leak if gel pack is punctured
• Sensitive to pH and ionic concentration
• Not biodegradable

 

TEXTURECEL^™ Cellulose Ethers

TEXTURECEL^™ cellulose ethers are sodium carboxymethyl cellulose polymers that are highly efficient thickeners. High–molecular weight TEXTURECEL^™ carboxymethyl cellulose grades are ideal thickeners for flexible gel pack applications and provide several distinct benefits over other thickeners, such as SAPs.

Particularly, gels formed with TEXTURECEL^™ carboxymethyl cellulose have a firm texture and will not leak if a pack is punctured or ruptured. Additionally, TEXTURECEL^™ sodium carboxymethyl cellulose polymers are comparatively safe for the environment and food contact applications. If a punctured or ruptured gel pack’s contents are dumped down the drain, it is considered drain safe and will not pose a problem for disposal. Furthermore, TEXTURECEL^™ is nontoxic to the environment and animals. TEXTURECEL^™ GA, PA, and PPA grades also have food contact approvals, making them perfect for gel pack applications in close contact with food products.

Advantages

• Gel will not leak if pack is punctured
• Nontoxic to the environment and animals
• Will prevent clogging if the gel is poured down the drain
• Stable over a wide pH
• Less sensitive to salt concentration
• Food contact safe

Disadvantages

• More expensive than SAPs
• Can be difficult to hydrate

 

TEXTURECEL^™ Grades for Gel Pack Applications

Selecting the appropriate grade of TEXTURECEL^™ carboxymethyl cellulose depends on the desired physical properties of the gel pack. As a guideline, as the molecular weight of the TEXTURECEL^™ carboxymethyl cellulose polymer increases, so does the viscosity of the corresponding solution. In some cases, selecting the highest–molecular weight grade available reduces the amount of thickener required to achieve the desired gel consistency. Granular grades of TEXTURECEL^™ sodium carboxymethyl cellulose are typically recommended over powder grades because they are easier to hydrate and form gels faster.

Recommended Grades

 

Formulating Gels with TEXTURECEL^™

The amount of TEXTURECEL^™ carboxymethyl cellulose required to formulate a gel for flexible gel packs varies depending on the desired consistency and physical properties of the gel. Generally, typical usage rates range from 0.5% to 3%. When using TEXTURECEL^™ carboxymethyl cellulose as a thickener, it is recommended to fully disperse it in the water-soluble freezing point depressant prior to hydrating with water. This will form a smooth gel free from lumps. Once the gel is formed, any other additives can be incorporated. The formulation listed below is typical of a hot or cold gel pack.

Typical thickeners used to create a thick consistency in gel packs, such as superabsorbent polymers (SAPs), are economical but are not environmentally friendly, safe for food contact, or drain friendly. TEXTURECEL^™ carboxymethyl cellulose is an ideal gel pack thickener because it is nontoxic to animals and the environment, will not clog if poured down drains, and carries food contact approvals. Furthermore, they prevent gel pack leakage if punctured and present fewer considerations when formulating, making gel pack manufacturing easier.

Contact us below to discuss your next flexible gel pack project and request a sample of TEXTURECEL^™.