Author: The Engineering Team at Jiaxing Trustworthy Import And Export Co., Ltd
If you're a compounder, a process engineer, or a product developer in the polymer industry, you know this problem. You need to reduce weight, improve cushioning, or lower dielectric properties. The obvious answer is to create a cellular structure—to foam the material.
The go-to "workhorse" for many is Azodicarbonamide (ADC). It's cheap, it's effective, and it's powerful. But then come the trade-offs. The yellowness. The residue. The potential for odor.
This is where, as engineers, we have to look past the workhorse and find the specialist. For us, and for many of our partners, that specialist tool is 4,4'-Oxydibenzenesulfonyl Hydrazide, or as we all know it, OBSH (CAS 80-51-3).
This isn't a sales pitch. This is a technical breakdown of why OBSH exists, where it solves problems ADC can't, and how to use it properly.
OBSH is a sulfonyl hydrazide. Its job is to decompose under heat and release gas, primarily nitrogen ($N_2$). But the devil is in the details.
Decomposition Temperature: Unactivated, OBSH has a decomposition temperature in the range of 150°C - 160°C. This gives it a sweet spot. It's stable during typical low-temperature mixing (like on a two-roll mill) but activates reliably during high-temperature processing like extrusion, molding, or curing.
The Gas: It releases nitrogen ($N_2$). This is clean, inert, and efficient.
The Residue: This is the most critical part. Unlike ADC, which can leave a yellow-tinted residue, OBSH decomposes into a non-staining, non-discoloring polymeric residue.
This last point is the key. The core technical problem OBSH solves is discoloration.
You don't use OBSH just to make foam. You use OBSH to make clean foam.
If you are manufacturing any of the following, you’ve likely faced the limitations of other agents:
White or Light-Colored Products: This is the number one application. Think white EVA foam for athletic shoe midsoles, light-colored PVC flooring, or white rubber seals. Using ADC here is a non-starter; the product will come out with a yellow or orange tint. OBSH gives you a bright, pure white foam.
Wire & Cable Insulation (XLPE, PE): In high-frequency data and communication cables, foaming the insulation (like PE or XLPE) is a classic trick. It lowers the dielectric constant, improving signal speed and integrity. OBSH is perfect here because it's clean (no conductive residue) and non-staining, so the color-coding of the wires remains true.
High-Temperature Processing & Rubbers: OBSH is robust. It's used heavily in EPDM, SBR, and other rubber compounds for automotive weather stripping and seals. It can survive the mixing process and activates cleanly during the vulcanization/curing stage.
Food-Contact Applications: OBSH is often cited as a preferred blowing agent for polymers in food-contact applications (subject, of course, to final regulatory approval by the end-user). Its odorless and clean-residue profile makes it a much safer and more stable choice.
A data sheet only tells you half the story. As a factory that works with this material every day, here are our practical notes on usage.
1. Dispersion is Everything
OBSH is a powder. If it's not perfectly dispersed in your polymer matrix, you will not get a uniform cell structure. You will get large voids and defects. You must ensure you have a high-shear mixing process (like a Banbury, high-speed mixer, or twin-screw extruder) to break it down. For some partners, we've even developed pre-dispersed masterbatches to eliminate this problem entirely.
2. It’s a System, Not a Single Ingredient
You almost never use OBSH "naked." Its decomposition temperature can be (and should be) fine-tuned with activators.
Activators: Zinc oxide ($ZnO$), stearic acid, and urea are common activators. By adding small amounts (e.g., 0.5 - 2.0 PHR), you can lower the "kick-off" temperature. This gives you precise control, so the foam expands when you want it to—for example, as it exits the die, not inside your extruder barrel.
Dosage: This depends on your target foam density. For low-density foams, you might go as high as 5-10 PHR. For microcellular applications, you might be as low as 0.5 PHR. Start with your technical data sheet's recommendation and titrate from there.
3. The Processing Window
Your processing temperature profile is critical. Your compound temperature must rise above the activated decomposition temperature of the OBSH at the exact right moment. If you heat it too early, you lose your gas before the part is formed. If you heat it too late, you get incomplete foaming. This is where process engineering and good formulation work hand-in-hand.
We are a Chinese chemical manufacturer. We know there are suppliers all over the world. But we believe our model offers a distinct advantage, and we want to be sincere about it.
Technical Advantage: Our advantage isn't just in synthesis. It's in consistency. We focus heavily on controlling particle size and purity. A batch with a tight, small particle size distribution will disperse better and give you a finer, more uniform cell structure. A high-purity batch ensures no side reactions or unexpected odors. We test this constantly because we are engineers, too.
Cost Advantage: Let's be honest. Our position in China gives us access to a highly efficient and mature supply chain for raw materials. We run large, efficient production lines. This doesn't just mean "cheaper"—it means stable. We can offer stable pricing and a reliable supply chain that isn't subject to the wild swings seen in other markets.
Service Advantage: This, for us, is the most important. A data sheet is not enough. You cannot solve a complex foaming problem by email. Our service is built on communication. We want to talk to your engineers. We want to see your formulation, understand your polymer, and know your processing equipment.
We've had partners come to us saying "OBSH doesn't work," only to find they were fighting a dispersion issue or using the wrong activation package. We helped them fix it. That's the partnership we offer.
OBSH is a precision tool. When you need to lightweight a part without compromising its color or structural integrity, it’s often the best tool for the job.
If you're working on a new compound or are frustrated by the limitations of your current blowing agent, let's have a technical-to-technical conversation. Send us your specs. Let's solve the problem.
