FLAME RETARDANTS
Figure 4 - PP specimen ( a ) & intumescence after first ( b ) & second ( c ) flaming for 10s in UL94 test
Chemical recycling , in which the polymer is depolymerised in order to synthesise a new polymer , consumes a lot of energy and additives in the waste material can cause problems . In mechanical recycling , the waste is ground up and reused . The properties of these materials can vary significantly and improvements in sorting are needed . If the waste stream is homogeneous , recycling is easier and several applications with recycled materials are already in the market .
Waste material that contains FRs can be reused . In a PINFA-funded project at Fraunhofer LBF in Darmstadt , Germany , several processing cycles of a PP with an intumescent FR system , showed no negative effect on the mechanical properties and FR performance ( Figure 4 ). 4 It was also confirmed that FR dispersion is as important to achieving a good FR performance and mechanical properties , since several extrusion cycles showed an improvement in mechanical properties without any effect on FR performance .
Figure 3 - Pictures after migration test of coated and uncoated intumescent systems
In the case of oven-ageing , a decrease was observed but this was explained by the oxidative degradation of the polymer . The use of additives after the fifth cycle in a model system demonstrated an increase of oxidation stability for the following cycles . Another approach to using recycled material is up-cycling by fabricating FR compounds . So far , limited data are available but first trials with post-consumer waste indicated the feasibility of this approach . Further research is needed to improve the resulting compounds and secure the quality .
Conclusion
FRs play a major role in our daily lives and are gaining further importance due to the digitalisation and electrification of the transportation sector . NHFRs offer already a good solution regarding sustainability in comparison with halogenated FRs . Regarding the recycling of polymers containing NHFRs , several studies have been conducted and have confirmed the potential to reuse resources and close the loop . Nevertheless , increasing requirements in terms of environmental and toxicological aspects make improvements of existing and developments of new FRs necessary . •
* - BUDIT is a registered trademark of Budenheim
References :
1 : J . Troitzsch , E . Antonatus , Plastics Flammability Handbook 4th Edition 2021 , 23-53
2 : T . Futterer , SCM , July / August 2006 , 34-36
3 : https :// www . pinfa . eu / wp-content / uploads / 2020 / 01 / Pinfa _ Newsletter _ Issue _ 109 _ FRIP _ 2020 . pdf
4 : https :// www . pinfa . eu / mediaroom / mechanicalrecycling-of-pin-fr-polymers /
Dr Tobias Moss
MANAGER INNOVATION AND APPLICATION DEVELOPMENT - MATERIAL SCIENCE DIVISION
CHEMISCHE FABRIK BUDENHEIM KG k + 49 6139 89863 J tobias . moss @ budenheim . com j www . budenheim . com
56 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981