4,4'-Oxybis(benzenesulfonyl hydrazide), universally shortened to OBSH (CAS No. 80-51-3), is one of the most widely used organic chemical blowing agents in the polymer processing industry. It belongs to the sulfonyl hydrazide family of foaming agents and is prized for decomposing at relatively low temperatures while releasing nitrogen gas cleanly, without leaving behind the more persistent by-products associated with some competing agents.

1. Identification and Molecular Structure

OBSH's molecular formula is C12H14N4O5S2, consisting of two benzenesulfonyl hydrazide groups (–SO2NHNH2) joined through a central oxygen (ether) bridge. This structure means two sulfonyl hydrazide functional groups are attached to a central oxygen atom, and the compound appears as a white crystalline solid. It is moderately soluble in polar solvents but has poor solubility in water, which is relevant when selecting dispersion methods for masterbatch or compound production.

Because both sulfonyl hydrazide arms are chemically equivalent and mirror-symmetric around the oxygen bridge, OBSH decomposes in a fairly narrow, predictable temperature window — a property that makes it easier to control cell structure in a foamed part than agents with broader or less predictable decomposition ranges.

2. Physical and Chemical Specifications

Commercial-grade OBSH is typically supplied as a fine white powder meeting the following technical specifications, based on manufacturer quality-control data:

These specifications — white powder appearance, minimum 98% purity, maximum 0.5% water content, a decomposition temperature of 152–162°C under a 5°C/min heating rate in air, a gas volume of 125 ml/g, and a pH between 5 and 8 — represent the typical quality benchmark for industrial-grade OBSH, as published in the technical datasheet from Jinli Chemical's OBSH product page. When comparing suppliers, purity and decomposition temperature range are the two figures worth scrutinizing most closely, since both directly affect foam cell uniformity and scorch safety during processing.

3. Decomposition Behavior: Why OBSH Works as a Blowing Agent

OBSH's usefulness comes down to one core reaction: on heating past roughly 150°C, the sulfonyl hydrazide groups decompose and release nitrogen gas (N2), along with small amounts of water vapor and sulfur dioxide derivatives. Upon heating, OBSH decomposes and releases nitrogen gas, which forms bubbles within the polymer, creating a cellular structure that reduces the material's density. This is the same fundamental mechanism used by other chemical blowing agents, but OBSH's decomposition onset is lower than azodicarbonamide (ADCA, which typically decomposes near 200–215°C), making OBSH the preferred choice when a polymer or rubber compound cannot tolerate higher processing temperatures without degrading.

Because the decomposition window is comparatively narrow (roughly a 10°C spread), OBSH gives processors tighter control over cell nucleation timing — an important factor in achieving fine, uniform cell structures rather than coarse or collapsed foam.

4. Industrial Applications

OBSH is a multi-industry material. Its four primary application areas are:

• Polymeric foaming (blowing agent): It is incorporated into polymer matrices such as polyolefins, styrenics, and elastomers to generate a lightweight, foamed product, reducing part weight without sacrificing structural performance.
• Rubber industry: OBSH is used as a foaming agent for producing rubber products with improved cushioning properties, enabling closed-cell foam rubbers used in gaskets, seals, and vibration dampeners.
• Polyurethane foams: OBSH is used in the synthesis of polyurethane foams for applications requiring high insulating properties, producing foams with excellent thermal insulation suitable for construction, refrigeration, and automotive industries.
• Thermal insulation components: The insulation capabilities of OBSH-blown foams are widely used in construction and automotive sectors for lightweight, thermally efficient parts such as doors, panels, and engine components.

Beyond these four core categories, OBSH is also commonly specified in wire-and-cable jacketing compounds and shoe-sole (EVA/rubber) foams, where its low decomposition temperature and low odor profile compared to older sulfonyl-hydrazide agents give it an edge in indoor-air and workplace-comfort considerations.

5. OBSH vs. Other Common Blowing Agents

Suppliers such as Jinli Chemical also produce related sulfonyl hydrazide agents including Benzenesulfonyl hydrazide (BSH, CAS 80-17-1) and P-Toluenesulfonylhydrazide (TSH), which sit at different points on the decomposition-temperature spectrum — useful if a formulation needs an even lower or slightly higher onset than OBSH provides.

6. Handling, Storage, and Safety Notes

OBSH is generally regarded as one of the lower-hazard chemical blowing agents relative to older nitroso- and azo-based alternatives, but standard industrial-chemical handling practices still apply:

• Store in a cool, dry, well-ventilated area away from direct sunlight and oxidizers, since decomposition is temperature-triggered.
• Keep containers sealed to protect against moisture uptake, which can affect the water-content specification and gas-yield consistency.
• Use standard dust-control PPE (gloves, dust mask, eye protection) during weighing and compounding, as with most fine chemical powders.
• Always request a current Safety Data Sheet (SDS) from the manufacturer before first use, and follow local chemical-handling regulations.

7. Manufacturer Profile: Jinli Chemical

Jiaxing Jinli Chemical Co., Ltd. was established in 2002 and relocated to the Zhejiang Province Zhapu Economic Development Park in the Jiaxing port area in 2011 — a site on the north bank of Hangzhou Bay, roughly 105 km from Shanghai and 110 km from Hangzhou, covering an area of 22,000 square meters. The company has been recognized as a national high-tech enterprise and a Zhejiang Province small-and-medium science-and-technology enterprise, and it has obtained ISO 9001, ISO 14001, and ISO 45001 quality-system certifications, with products sold into the USA, EU, Korea, Japan, and Southeast Asia.

For buyers evaluating an OBSH supplier, this kind of certification and export track record is a reasonable proxy for manufacturing consistency — worth checking regardless of which vendor you ultimately choose. Full company background is available on Jinli's About page, and the complete blowing-agent range can be browsed on the Forming Agent & Blowing Agent product category page.

8. Frequently Asked Questions

What does OBSH stand for?
OBSH is the common abbreviation for 4,4'-Oxybis(benzenesulfonyl hydrazide), CAS No. 80-51-3.

Is OBSH the same as OBSC?
No. OBSC (4,4'-Oxybis(benzenesulphonyl chloride)) is a related sulfonyl chloride intermediate used, among other things, in the synthesis of OBSH itself — it is a precursor, not the same finished blowing agent. See Jinli's OBSC intermediate page for details.

What gas does OBSH release?
Primarily nitrogen gas, generated as the sulfonyl hydrazide groups decompose under heat.

Why choose OBSH over ADCA?
OBSH decomposes at a notably lower temperature, making it better suited to heat-sensitive rubber and PU foam formulations where ADCA's higher decomposition range would risk scorching or premature curing.

OBSH (CAS 80-51-3) remains a workhorse chemical blowing agent precisely because its decomposition chemistry is well understood and well controlled: a narrow 152–162°C decomposition window, a clean nitrogen-gas release, and broad compatibility across rubber, polyurethane, and polyolefin systems. For sourcing, prioritize suppliers who publish full specification sheets and hold recognized quality certifications. Jinli Chemical's OBSH product datasheet is a useful reference point, and their Contact page is the direct channel for specification confirmation, sample requests, or bulk quotations.