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Choosing a Forming Agent (Blowing Agent) for Plastics and Rubber: Match Decomposition Temperature to Your Process
A forming agent (also called a blowing agent or foaming agent) is a compound that stays stable at room temperature, then breaks down at a known temperature and releases gas that expands a polymer into a cellular structure. The most common selection error is a decomposition temperature that does not fit the processing window. Get that match right and most foam problems (coarse cells, surface blisters, collapse, unstable density) become much easier to control.
What a forming agent does in practice
Chemical blowing agents are added to thermoplastics and rubbers to reduce density. Patent literature describes them as stable at room temperature and decomposing during processing to produce the gas that forms the foam. Typical end uses include foamed wall coverings, artificial leather, floor coverings, insulation, footwear, automotive parts, cable insulation and packaging. Manufacturers pursue foaming for lower weight, better thermal and acoustic insulation, better shock absorption and fewer sink marks in injection molding.
Two families matter for grade selection:
- Exothermic agents (azodicarbonamide, sulfonyl hydrazides) release heat as they decompose and give high gas pressure at low dosage. Once triggered, the reaction cannot be stopped, so temperature control matters.
- Endothermic agents (bicarbonates, citrates) absorb heat and give gentler, more controllable gas release, usually at higher loadings.
How the main chemistries compare
The figures below are typical published ranges. Actual behavior shifts with particle size, activators, heating rate and pressure, so treat them as a starting point for trials rather than a specification.
| Blowing agent | Type | Typical decomposition range | Gas yield (approx.) |
|---|---|---|---|
| Azodicarbonamide (ADC) | Exothermic | 200–230 °C (lower with activators) | up to ~220 ml/g |
| OBSH | Exothermic | 140–165 °C | ~125 ml/g |
| TSH | Exothermic | ~105–140 °C | ~120 ml/g |
| Sodium bicarbonate | Endothermic | 150–230 °C | ~165 ml/g |
Sources: a foam-molding patent lists decomposition ranges and gas yields for ADC, TSH, OBSH and sodium bicarbonate (US 9,080,023); a second patent notes that TSH starts decomposing at about 105 °C (US 11,926,722).
Jinli Chemical grades at a glance
Jinli publishes decomposition temperature (measured at 5 °C/min in air), gas volume and other checkpoints on each product page. The three grades below are the ones with clean, consistent data on the site as of the update date above.
| Grade | CAS No. | Decomposition temp. | Gas volume in air | Other checkpoints |
|---|---|---|---|---|
| Benzene sulfonyl hydrazide (BSH) | 80-17-1 | 143–147 °C (min) | 120–130 ml/g | Water ≤0.5%; ash 0.1%; pH 3.0–7.0 |
| 4,4'-Oxybis(benzenesulfonyl hydrazide) (OBSH) | 80-51-3 | 152–162 °C | 125 ml/g | Purity ≥98%; water ≤0.5%; pH 5–8 |
| P-Toluenesulfonyl semicarbazide (RA/TSSC) | 10396-10-8 | 228 °C (min) | 140–150 ml/g | Purity ≥98%; water ≤0.5%; ash 0.5% |
The catalog also lists P-Toluenesulfonhydrazide (TSH), Zinc P-Toluenesulfinate Salt (ZTS/TM) and Benzenesulfinic acid zinc salt (BM/ZBS). For these, request the current certificate of analysis before you fix a formulation.
A practical selection guide
Start from your process, not from the agent. The goal is for gas to release while the material is soft enough to expand but not so early that the gas escapes. Technical literature suggests the melt-processing temperature is usually set roughly 20 °C above the agent's decomposition temperature, though this varies with conditions.
| If your process runs at… | Consider | Watch out for |
|---|---|---|
| Low temperature (roughly 140–160 °C), such as many rubber and flexible-foam compounds | BSH or OBSH | Scorch or premature gas release if residence time is long |
| Medium temperature (roughly 160–200 °C) | OBSH near the upper end, or a blend with an endothermic agent | Cell size drift when barrel temperatures fluctuate |
| High temperature (above about 220 °C), such as engineering polymers | RA/TSSC (decomposition min 228 °C) | Polymer degradation at the required temperature; confirm resin stability |
| Need for gentle, controllable gassing | Blend an exothermic agent with an endothermic one | Higher total loading and balancing two decomposition curves |
Blending is a recognized strategy. One patent describes flexible insulation foams made by combining OBSH with an endothermic agent (US 10,696,811). Treat the table as a shortlist; a small lab trial decides the final choice.
Process details that decide foam quality
- Dispersion: Powders can agglomerate, and clumps cause voids and uneven density. Industry sources recommend breaking up agglomerates and pre-dispersing the agent in a carrier or masterbatch (US 10,279,361).
- Moisture: Jinli's specs cap water at 0.5% for the listed grades. Wet powder can cause caking and inconsistent metering, so keep containers sealed.
- Activators: Activators can lower the working decomposition temperature. In ADC systems, additives can bring it down from 200–220 °C to as low as about 125 °C, though practical rates are usually reached only at 140 °C and above (EP 3431535). Change one variable at a time.
- Heating rate: Decomposition figures on a datasheet come from a fixed heating rate. Your extruder or press will behave differently, so run a density ladder at several temperatures.
- Storage and handling: Jinli's product pages advise storing in a dry, cool, well-ventilated place away from ignition sources and oxidizing agents, and avoiding dust inhalation and skin or eye contact. Follow the safety data sheet for your grade.
A simple trial plan before scale-up
- Fix the resin, filler and stabilizer system first.
- Run three or four temperature steps around the expected window, keeping dosage constant.
- Measure density, then check cell structure in a cross-section.
- Adjust dosage in small steps; change the agent or add an activator only if temperature and dosage cannot fix the problem.
- Repeat with a second production lot to confirm consistency.
About Jinli Chemical (experience and credentials)
Jiaxing Jinli Chemical Co., Ltd. was established in 2002 and relocated in 2011 to the harbor region of Jiaxing, Zhejiang, on a site of 22,000 square meters with a stated annual output of 19,000 tons. According to its company profile, it is a national high-tech enterprise, holds ISO 9001, ISO 14001 and ISO 45001 certification, and runs industry-university-research cooperation with Zhejiang University of Technology and Jiaxing University. Its products are sold in the USA, the EU, Korea, Japan and Southeast Asia. Learn more about its technology and R&D or browse more industry news.
Beyond blowing agents, Jinli supplies related sulfonyl chemistry, including plasticizers and intermediates such as 4,4'-Oxybis(benzenesulphonyl chloride) (OBSC), benzenesulfonyl chloride and P-toluene sulfonyl chloride (PTSC). Having these upstream materials in the same portfolio helps buyers who want fewer suppliers to qualify.
Frequently asked questions
Are "forming agent," "blowing agent" and "foaming agent" the same thing?
In industrial use, yes. The terms are interchangeable, and Jinli lists them together in one category.
Does higher gas volume always mean a better foam?
No. Gas volume sets how much you need to hit a density target. Cell uniformity depends more on temperature match, dispersion and polymer melt strength.
Can I use the datasheet decomposition temperature as my processing temperature?
Only as a starting point. Measurement conditions differ from real processing, so validate with trials.
How do I get a sample or a certificate of analysis?
Use the contact page or call 0086-573-85580888. Share your resin, process temperature and target density so the recommendation is specific.
