If you’ve ever had to ship a pallet of fragile glass bottles, roll of canvas, or 50-pound bag of powder, chances are you’ve relied on paper tubes to keep your products intact. As a supplier of these tubes, I get asked this question almost every day by new customers: “What’s the shear strength of paper tubes?” It’s not a simple yes-or-no answer—shear strength depends on everything from the raw material we use to how the tube is manufactured and tested. Let me break this down in plain, practical terms, not just textbook jargon, because I know when you’re buying tubes, you need real numbers you can count on, not abstract research. Paper Tube
First, let’s make sure we’re on the same page about what shear strength means for paper tubes. Shear strength is the maximum amount of parallel force a tube can resist before the layers of paper that make up the tube start sliding apart. It’s different from tensile strength, which is the force that pulls the tube apart end-to-end. For most of our customers, shear strength matters most when you’re stacking heavy loads on top of tubes, or when you’re winding a tight material (like film or fabric) around the tube that exerts side-to-side force. If the shear strength is too low, the tube will collapse at the layers, not split cleanly or snap in half. That’s a failure you don’t want mid-shipment or mid-production run.
So how do we measure it? We don’t just guess. We use a standard test method called the “edge crush test” or, more accurately for shear, the “interlaminar shear strength test.” This test places a short section of tube between two supports and applies force along the side, parallel to the layers of paper, until the layers delaminate (slide apart). The result is measured in pounds per square inch (PSI) or, for metric customers, megapascals (MPa). For most industrial paper tubes we supply, standard shear strength ranges from 15 PSI to 40 PSI. But wait— that’s a wide range, and that’s where customers need to specify their exact needs. A tube for a small craft spool needs way less shear strength than a tube for holding a 100-pound roll of insulation.
Now, let’s talk about what factors actually change that shear strength number, because that’s where my experience as a supplier comes in. I’ve worked with hundreds of clients over 12 years in this business, and I can tell you the top three variables that determine shear strength: paper grade, wall thickness, and the adhesive we use to bond the layers.
First, paper grade. Not all paper is the same. We use different paper for different tubes. For low-shear applications, like mailing tubes for posters, we might use a 200-pound test (lb/test) kraft paper— that’s a lightweight, flexible paper that’s cheap and easy to cut. Its interlaminar shear strength is around 15-20 PSI, which is enough for sending a rolled-up poster via USPS. But for high-shear applications, like core tubes for winding aluminum foil, we use 500 lb/test or even 700 lb/test heavy-duty kraft paper. Those thick, dense papers have longer wood fibers that bond together better, so their shear strength jumps to 30-40 PSI. I learned this the hard way 8 years ago, when a food packaging client asked for tubes to wind 50-pound rolls of plastic wrap. They initially ordered our standard 250 lb/test tubes, and when they ran the wrap, the tubes delaminated mid-run. We had to rework the order with 500 lb/test paper, and that fixed their problem entirely. That’s the kind of on-the-ground experience you don’t get from a textbook.
Second, wall thickness. The wall of a paper tube is made by winding multiple layers of paper around a steel mandrel. The more layers, the thicker the wall—and the higher the shear strength. Let’s be clear: it’s not a perfect linear relationship, but it’s close. A 3/8-inch wall tube with 5 layers of 500 lb/test paper has a shear strength of about 25 PSI. A 5/8-inch wall tube with 10 layers of that same paper jumps to 35-40 PSI. We also make heavy-duty “super wall” tubes for extreme applications, like lifting 1,000-pound rolls of steel. Those can have up to 20 layers, with shear strength over 50 PSI. One of our biggest clients is a lumber company that uses our 12-inch diameter, 1-inch wall tubes to hold long pine wood planks. Those tubes don’t just need shear strength to hold the weight of the wood—they need to resist the side force when the planks are being loaded onto trucks. If the wall was any thinner, the tube would crack at the layers and drop a $2,000 plank. We’ve never had a failure on that line, and that’s all because we matched the wall thickness to their shear requirement.
Third, adhesive. This is the secret sauce that most customers don’t think about, but it’s make-or-break for shear strength. When we wind the layers of paper around the mandrel, we apply a food-grade, water-based adhesive between each layer. If the adhesive is too weak, it won’t bond the fibers together, and the layers will slide apart at even low force. If it’s too strong, it might make the paper brittle, which causes the tube to snap instead of shear. We use a modified corn starch adhesive for most standard tubes—it’s strong enough for general use, flexible, and non-toxic, which is perfect for food packaging. For high-shear applications, we switch to a synthetic acrylic adhesive that has 2x the bonding strength of our standard adhesive. That’s why our heavy-duty tubes have such high shear strength. Last year, a construction company was making concrete pipes that needed core tubes resistant to wet cement. Their old supplier used a standard adhesive, and the tubes delaminated when exposed to water. We switched them to our acrylic adhesive, and not only did the tubes resist delamination—their shear strength increased by 12 PSI, which let them cut costs by using thinner walled tubes for their new projects. That’s the kind of value we bring as a supplier, not just selling a tube, but solving a problem.
Now, I want to address a common misconception: shear strength isn’t the only number that matters. A tube with high shear strength but low tensile strength will snap when pulled, and a tube with high tensile strength but low shear will collapse when stacked. That’s why we always ask customers to tell us not just what they’re using the tube for, but the conditions: weight of the product, how it’s being shipped or stored, side force during winding, and even temperature or humidity. Paper tubes are porous, so high humidity can soften the adhesive and lower shear strength by up to 30%. We once had a customer in Florida order our standard tubes, but their warehouse had 85% humidity. The tubes arrived and failed within a week. We adjusted the adhesive to a moisture-resistant formula, and that fixed it. That’s why we don’t just give a one-size-fits-all answer for shear strength—we work with each client to customize their tubes.
So, what’s the shear strength you can expect when you order from us? Let’s break it down by common applications, based on 12 years of data from our production floor and customer projects:
- Mailing tubes (posters, documents): 15-20 PSI. Lightweight, low side force, standard humidity.
- Core tubes for fabric, carpet, or foil: 25-35 PSI. Medium to heavy side force during winding.
- Heavy-duty tubes for construction, lumber, or industrial products: 35-50 PSI. High weight and side force, variable humidity.
- Custom tubes for extreme applications (1,000+ pound loads): 50+ PSI, up to 60 PSI for specialized orders.
I also want to mention that we test every batch of tubes before they leave our facility. We run 10 shear tests per production run, checking that each tube meets our specified strength. If a batch falls below the required PSI, we don’t ship it. That’s a promise I make to every customer—no cutting corners on quality, because I know a failed tube costs you time and money, which is bad for business for both of us.
At the end of the day, the shear strength of paper tubes isn’t just a technical number—it’s a measure of reliability. Whether you’re winding packaging material, storing long items, or shipping fragile products, you need a tube that will hold up when you need it. As a supplier, I don’t just sell tubes; I partner with you to find the right shear strength for your specific needs. If you’re tired of dealing with tubes that fail mid-production or mid-shipment, let’s talk. I can walk you through our material options, test specs, and even provide a custom sample to verify the shear strength for your application. Reach out to us to discuss your project, and let’s make sure your next tube order is one you can count on.
Magnetic Box References
ASTM International. Standard Test Method for Interlaminar Shear Strength of Paper and Paperboard Using a Short-Beam Method. ASTM D2344/D2344M-16.
TAPPI Press. Physical Testing of Paper and Paperboard, Volume 2. 2nd Edition. 2012.
Hearst Business Media. Industrial Packaging Materials: Properties and Applications. 5th Edition. 2020.
Shenzhen Jinyida Printing & Packaging Co., Ltd.
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