Custom Paper Cups

Why Paper Cups Don’t Tear When Exposed to Water

One of the common questions that comes to the mind of the customers is why paper-based cups do not tear when exposed to water. The reason for this is simple and lies largely in the manufacturing process and the additives used to strengthen the paper. The reason why cups remain intact when exposed to water is as follows:

• Fiber-modifying chemistries
• Cross-linking resins
• Paperboard manufacturing process

We use the following processes to give you disposable paper cups water resistance:

Internal Sizing

Alkenyl Succinic Anhydride (ASA) and Alkyl Ketene Dimer (AKD) are commonly used internal sizing agents. They are added during the wet end of the paper-making process to modify the cellulose fibers. The addition of these sizing agents makes the fiber hydrophobic and reduces the water uptake. ASA is quite reactive and forms surface-active anhydrides that coat the fiber and lower the surface energy, and ultimately reduce the water molecules’ tendency to stick to the fiber surface.

AKD, on the other hand, offers more durable sizing because it forms a covalent ester bond with the hydroxyl groups of the fiber. We make sure to add a proper concentration of the sizing agents to effectively maintain fiber-to-fiber hydrogen bonding. Usually, 0.1 percent to 0.2 percent of sizing is added based on pulp weight.

Wet-Strength Resins

Polyamidoamine-epichlorohydrin (PAE) and polyethyleneimine (PEI) are common wet strength resins that form covalent bonds with cellulose and create a cross-link network. This network exhibits fiber swelling and separation. During the curing process of paper, active functional groups on these react with the hydroxyl group on cellulose and preserve 20 to 30 percent of dry strength when the paper is fully saturated with water molecules. Chitosan or starch derivatives are natural alternatives to PAE and PEI that augment the hydrogen bond strength. However, natural alternatives are less durable than synthetic ones.

Barrier Coating

Aside from the application of sizing agents, barrier coatings such as low-density polyethylene (LDPE) and aqueous polymer dispersion are applied to the branded paper cups. These coatings are applied in a thin layer of 8–20 g/m² that forms an impermeable film protecting the paper from direct liquid contact. In extrusion coating, the polymer is melted and pressed onto the paper to yield a seamless coverage. However, aqueous coatings contain food-grade emulsions that deposit barrier polymers without adding plastic water to the fiber network.

Polyethylene

This coating is applied via extrusion at 8–20 g/m² onto the paper. Polyethylene creates a continuous hydrophobic barrier that prevents liquid penetration and provides heat-sealable surfaces for side seams and button insertion. This coating is an excellent option for hot as well as chilled drinks. Aside from this, PE resists grease and maintains the structural integrity. Although the addition of this coating reduces the recyclability of the paper, separating the polymer film from the paper can make recycling easy.

Polylactic Acid

Polylactic acid is a derivative of starch that is obtained from the fermentation process. This coating is one of the best options for custom compostable cold cups. It degrades easily. This coating gives barrier properties similar to polyethylene, but it is slightly costly than that of polyethylene.

Aqueous Coatings

Aqueous coatings are not only sustainable but also contain food-grade polymers and natural minerals that give strength to custom hot paper cups. Methacrylate emulsion is one of the common aqueous coatings that is gaining traction due to the consumer and regulatory demands for sustainable options. The application of this coating is slightly expensive, but it is easy to recycle without the need of de-inking.

High-Quality Board

As a paper cup supplier, we only use quality raw materials to manufacture the cups. Paper of high basis weight, such as 170–350 g/m², and a multi-ply fiber blend are combined with the fibers for strength and stiffness. This thickness of the paper has a dense fiber network that, even if the barrier is compromised in quality, the dense fiber network resists water molecules and maintains the shape of cups even under hot and cold loading.

Materials

For custom hot paper cups, we use multiple paperboards that are a mixture of mechanical and chemical pulp. This paper has a grammage as low as 170 g/m 2 to as high as 350 g/m 2 that ensures sufficient rigidity of the material to retain the shape under hot and cold liquids.

The chemical pulp component is manufactured via the kraft process, in which lignin is removed to yield long and strong cellulose fibers. These fibers form strong hydrogen-bond networks that give paperboard its tear resistance and stiffness. Adding mechanical pulp gives the paper bulk and opacity without affecting the print quality.

We use two types of chemicals to enhance the brightness and smoothness of the paper; these two options are calcium carbonate and kailin. They enhance the printability of the paper and make it a perfect option for custom printed paper cups. All our raw materials are obtained from FSC-approved forests that are sustainably managed and do not contribute to excessive deforestation. On the whole, our material has the following qualities:

High Heat Resistance

The material used in the manufacturing of custom paper cups is resistant to high temperatures up to 100 degrees Celsius. This feature of the cups makes them ideal for serving hot beverages. So when you serve hot beverages, the heat-resistant feature of the cups prevent them from melting and retaining their shape foir extended period of time. Moreover, it also ensures that the material is cool enough from the external side so that the user can easily hold the cups.

Food-Grade Certification

Another very useful feature of the materials is that they are food-safe and comply with international standards for food packaging, such as FDS and EU regulations. These certifications ensure that the material is non-toxic and odor-free, and you can use it for liquids without any hitch.

Polyethylene Inner Coating

Though the raw material used for the manufacturing of the cups has excellent durability. However, the liquids can seep through them. To prevent such a loss we are using internal and external coatings which enhance the compatibility of apper board material with hot liquids.

Superior Print Surface

Material studies and food gardens are undoubtedly the best features of the packaging. However, the material must be compatible with the printing processes so that you can easily promote your brand. Our printing material has a smooth surface that is easy to print on.