What Is OBSH Blowing Agent? Uses, Properties, and Applications

OBSH blowing agent is a chemical blowing agent based on 4,4′-oxybis(benzenesulfonyl hydrazide), commonly identified by CAS No. 80-51-3. When heated in a suitable polymer or rubber compound, OBSH decomposes and releases gas that creates a cellular structure, reducing density and producing foam. I use the term “OBSH” for the active chemical, while the actual processing behavior depends on grade, particle size, formulation, and molding conditions.

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OBSH is mainly considered for PVC, rubber, EVA, polyolefin, and other thermoplastic or elastomeric systems that require controlled foaming. Commercial data commonly describe decomposition in the approximate range of 150–160°C, but buyers should confirm the exact activation temperature and gas evolution from the supplier’s current technical data sheet. PubChem identifies the material as 4,4′-oxydibenzenesulfonyl hydrazide and provides its chemical identity and molecular information for reference.

Source: U.S. National Library of Medicine, PubChem.

How OBSH Blowing Agent Works

In a polymer compound, OBSH is dispersed through the base material before or during processing. Heat activates the decomposition reaction, and the resulting gases expand the softened polymer or rubber matrix. The final cell structure depends not only on OBSH dosage but also on melt viscosity, nucleation, pressure release, cooling rate, and mold design.

Core functions of OBSH

• Density reduction: Gas generation can create a lighter cellular product when the foam is properly stabilized.
• Cell formation: The decomposition gas supports the formation of closed-cell or partially open-cell structures, depending on the formulation and process.
• Material saving: Lower density may reduce the amount of polymer or rubber required per unit volume, although the actual saving must be measured by product design.
• Processing adjustment: OBSH can be combined with activators, nucleating agents, plasticizers, and stabilizers to adjust foaming behavior.

OBSH is not a universal replacement for every blowing agent. Its suitability must be confirmed against the resin’s processing temperature, the required foam density, odor requirements, mechanical properties, and regulatory expectations for the finished article.

OBSH Blowing Agent Properties and Key Specifications

Buyers should evaluate OBSH by measurable specifications rather than by the name alone. The most important parameters are chemical purity, decomposition temperature, gas evolution, moisture, particle size, appearance, and packaging stability. A consistent specification is particularly important when the product is used in continuous extrusion or in high-volume molded parts.

The values in this table are screening references, not a universal product specification. Gas evolution may be reported in milliliters per gram, while decomposition temperature can change according to heating rate, test method, formulation, and the presence of activators. I recommend requesting a current TDS, SDS, certificate of analysis, and test-method description before approving a grade.

Source: Buyers can compare chemical identity and hazard information with the European Chemicals Agency chemicals database and the relevant supplier SDS or TDS. Commercial technical sheets should be treated as grade-specific evidence rather than as proof that every OBSH product has identical performance.

Uses and Application Scenarios

Rubber and elastomer products

OBSH may be used in rubber compounds for profiles, seals, sheets, grips, insulation components, and other lightweight elastomeric products. It can be considered when the compound requires a chemical blowing agent activated within the rubber-processing window. The compounder must still confirm scorch safety, compression set, cell uniformity, odor, and compatibility with the selected curing system.

PVC foam products

In PVC formulations, OBSH can support the production of foam sheets, profiles, gaskets, flooring components, and related products. Processing may involve stabilizers, lubricants, plasticizers, and activators, so the blowing-agent dosage cannot be selected independently from the whole formulation. A laboratory trial should measure density, expansion ratio, surface appearance, dimensional stability, and mechanical strength.

EVA, polyolefin, and thermoplastic compounds

OBSH may also be evaluated for EVA and selected thermoplastic systems where the processing temperature and melt strength are suitable. The key risk is a mismatch between gas release and polymer softening: gas released too early may escape, while gas released too late may produce insufficient expansion. For this reason, I recommend comparing the OBSH decomposition profile with the actual extrusion or molding temperature profile.

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Industrial foaming and specialty formulations

Other possible uses include lightweight molded components, insulation-related products, footwear compounds, and specialty elastomer formulations. The final application must be reviewed for odor, emissions, worker exposure, food-contact status, electrical performance, and end-of-life requirements. “Suitable for foaming” does not automatically mean suitable for a regulated finished product.

OBSH Grade and Material Options

Suppliers may offer OBSH in different purity levels, particle-size distributions, and treatment forms. A fine-particle grade can improve dispersion in some compounds, while a treated or activated grade may be designed to modify processing behavior. These options are formulation-dependent, so the correct grade should be selected from comparative trials rather than from particle size alone.

Common selection categories

• Standard OBSH: Suitable for initial laboratory screening and general-purpose formulation development.
• Fine-particle OBSH: Considered when dispersion and surface quality are priorities.
• Activated or modified OBSH: Evaluated when the compound requires a changed activation profile or improved process matching.
• Masterbatch or pre-dispersed form: May simplify dosing and dispersion, subject to carrier compatibility and minimum order requirements.

These categories are not interchangeable commercial standards. I advise buyers to request the active content, carrier information, particle-size data, decomposition test method, gas-evolution method, storage conditions, and recommended dosage for each option.

How to Select OBSH Blowing Agent for a Project

1. Define the target product

Start with the required density, thickness, hardness, cell structure, surface appearance, and dimensional tolerance. For example, a flexible rubber profile and a rigid PVC sheet may require different activation behavior and dosage control. The target should be written as measurable limits, such as density in kilograms per cubic meter, thickness in millimeters, and hardness in Shore units.

2. Match the thermal window

Compare the OBSH decomposition range with the compound’s mixing, extrusion, molding, and cooling stages. A material processed at 170°C may behave differently from one processed at 190°C, even if both are described as thermoplastic applications. The supplier should explain whether the quoted temperature is a peak decomposition temperature, an onset temperature, or a range from a defined test method.

3. Confirm formulation compatibility

Review the interaction between OBSH and lubricants, plasticizers, fillers, pigments, stabilizers, curing agents, and other additives. In my experience as a materials supplier, small changes in dispersion and melt strength can affect foam quality as much as the nominal OBSH dosage. A controlled trial should change one major variable at a time.

4. Test finished-product performance

Measure density, expansion, cell size, compression behavior, tensile or tear strength, odor, surface defects, and aging performance. Where applicable, test at least three production-relevant temperatures and several dosage levels rather than relying on one laboratory condition. The results should be recorded with batch number, mixing history, equipment, heating rate, and cooling conditions.

Buyer Checklist for an OBSH Supplier

• Can the supplier provide a current SDS and TDS?
• Is the CAS number clearly identified as 80-51-3?
• Does the certificate of analysis include purity, moisture, appearance, and relevant thermal data?
• Are gas-evolution values linked to a named test method and unit, such as mL/g?
• Can the supplier provide particle-size information in micrometers or a defined mesh specification?
• Are packaging, storage temperature, shelf life, and batch traceability documented?
• Can the supplier support sample testing before a larger purchase?
• Are MOQ, lead time, export documents, and packaging options stated clearly?

OBSH should be stored and handled according to the supplier’s SDS, with attention to heat, contamination, dust control, and incompatible materials. Chemical blowing agents must be evaluated under the workplace and product regulations applicable in the destination market. The U.S. Occupational Safety and Health Administration provides general hazard communication requirements that buyers and processors should consider when managing chemical additives.

Source: U.S. Occupational Safety and Health Administration, Hazard Communication.

Summary Insights

• OBSH is 4,4′-oxybis(benzenesulfonyl hydrazide), commonly identified as CAS No. 80-51-3.
• It is a heat-activated chemical blowing agent used in selected rubber, PVC, EVA, and thermoplastic formulations.
• Commercial references often place decomposition near 150–160°C and gas evolution near 140–150 mL/g, but these values must be confirmed for the selected grade and test method.
• Purity, moisture, particle size, dispersion, melt strength, and processing temperature all influence foam quality.
• The correct purchase decision should be based on TDS and SDS review, laboratory trials, finished-product testing, and supply reliability.

Conclusion: Is OBSH the Right Blowing Agent?

OBSH blowing agent can be a practical option when a formulation needs a chemical blowing agent that activates within an approximately 150–160°C processing range and can produce controlled gas generation. It is most appropriate for buyers who can evaluate the complete compound, rather than selecting an additive by name alone. The final decision should consider product density, cell structure, odor, mechanical performance, safety documentation, and processing stability.

My recommended next step is to send the supplier your polymer or rubber type, processing temperature, target density, product dimensions, current additives, and expected monthly volume. At Shitong, I can support an initial OBSH grade review, documentation comparison, sample evaluation, and application-focused quotation based on your actual formulation requirements. Request the relevant TDS, SDS, sample quantity, MOQ, packaging details, and lead time before moving to commercial production.

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