Chemical blowing agents are reactive additives that liberate gases during the processing of thermoplastics. They thus make it possible to produce foamed plastics for a wide variety of applications. A thermally activated decomposition reaction of the additives contained in the blowing agents results in gases being eliminated and hence to the production of a stable, defined plastic foam.
There are two main groups of blowing agents, which differ fundamentally according to their reaction mechanism:
- Endothermic (heat consuming) and
- Exothermic (heat releasing) blowing agents
Blowing agents are mainly employed in order to reduce density, which leads to a weight reduction in the end product and a decrease in costs. Additional or enhanced product characteristics are another advantage of using chemical blowing agents.
Examples of this are:
- Improved heat and noise insulation
- Improved dielectric properties
- Improved shock-absorbing properties
- Avoidance of sink marks during injection moulding
- Decorative effects
Endothermic blowing agents
When heat is added, these blowing agents decompose and generate environmentally neutral gases. Often these gases are carbon dioxide and water vapour – the most well-known active ingredients are carbonates and carboxylic acids. As heat is consumed in order to initiate and propagate the reaction, the substances are referred to as endothermic blowing agents. Their advantage lies in the fact that when the heat supply is interrupted, gas production comes to a standstill and resumes if further heat input is provided. Consequently, endothermic blowing agents are easy to manage during processing. Many of the endothermic blowing agents that we employ are approved for use with food and can thus be included in many packaging solutions.
After an initiation process using radiation, heat or other forms of energy, exothermic blowing agents liberate heat and gases such as nitrogen, carbon dioxide or ammonia when they decompose. The decomposition reaction then continues running independently due to the liberated heat and cannot be stopped by simple cooling measures. In contrast to endothermic blowing agents, significantly higher gas yields can be achieved with exothermic blowing agents. Using supplementary additives we are able to influence the starting energy and hence the initial decomposition temperature.
Our know-how in process engineering makes us one of the leading suppliers of blowing agents. This is because blowing agents impose high demands on development and production due to their latent tendency to decompose when incorrectly handled in powder form. Our individually prepared solutions of endothermic and/or exothermic blowing agents cater to all wishes for modifications.
In addition to the combinations of endothermic and exothermic blowing agents, we also supply chemical blowing agents as a nucleation agent for physical and chemical foaming. If especially fine and even foam structures are required, nucleation is the best strategy.
You can obtain further information from our product brochure.