Elongation , %
3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00
0 % 10 % 20 % 30 % 40 % 50 % 60 %
Figure 3 – Mechanical properties of GF-PBT containing Exolit OP 1260
Elongation at break
Recylate content
GF-PBT Exolit OP 1260 BFR / ATO
‣ Flame-retarded polyesters
Polyesters are very versatile and are used in a wide range of applications from plastics to fibres to thermoplastic elastomers . Engineering plastics like PBT and PET are increasingly used in electrical and electronic ( E & E ) applications , such as connectors for devices and electrical components . Both impart good strength and stiffness , as well as dimensional stability in moulded parts . PBT tends to crystallise somewhat faster than PET ; both exhibit good insulation properties . Exolit FRs based on organic phosphinates are compatible with polyesters in E & E applications and provide an excellent balance of flame retardancy with mechanical and electrical properties . Exolit OP 1260 is a new FR that can be in used in both unfilled and GF PBT and in PET . Besides providing excellent flame retardancy , it also exhibits better melt flow and elongation in polyesters . Another significant advantage is the lower density it imparts to GF PBT compared to traditional FRs . Furthermore , Exolit OP grades retain critical electrical and thermal properties in GF PBT . For instance , the CTI can be maintained around 600 V , similar to the non-flame retarded PBT , while traditional halogenated FRs fail to meet this criterion .
Recycling GF PBT
Clariant has teamed up with others to seek ways of converting plastic litter into components that are flame retarded for E & E applications . 2 Exolit FRs provide efficient flame retardancy in these recycled components and maintain the mechanical properties . In post-industrial recycling ( PIR ), the thermal stability of the FR and the flowability and mechanical properties of the flame retarded compounds are crucial . In post-consumer recycling , process properties can be improved with further additives . This cannot normally be done in PIR , where no compounding step is applied . Clariant has carried out a similar investigation with flame retarded polyesters . In this study , PBT compounds with 30 % glass fibres with and without FRs were moulded with the addition of 10 %, 30 % and 50 % recycled material . This was simulated using moulded parts made of fresh compound , ground and added to the neat compound on a twinscrew compounding system .
References :
1 : C . Schultheis , E . Metz-Zilligen & R . Pfaendner , Kunststoffe International , 8 / 2018
2 : S . Hörold & Y . Lavergne , Kunststoffe International , 5 / 2020
It is common in injection moulding to add sprues and other waste after grinding and sieving in the moulding process . Typically , up to 25 % of ground sprues can be added for GFR plastics . For comparison , a typical polymeric brominated FR ( BFR ) with antimony trioxide synergist was tested as well . All of the PBT formulations retained their flame retardancy standard UL 94 V-0 at 0.8 mm thickness at all levels of recyclate being added . Even the afterburning times were not significantly affected . The mechanical properties of GFR PBT with Exolit OP 1260 , including elongation , remained unchanged as well . The study shows that , under the conditions used in the test , Exolit OP 1260 can be used as a drop-in replacement to BFRs . This allows the moulders of flame retarded polyesters to add reground waste from production when producing moulded parts and thus reduce waste in their process . •
Sebastian Hoerold
HEAD OF TECHNICAL SERVICE - FLAME RETARDANTS FOR PLASTICS
CLARIANT PLASTICS & COATINGS ( DEUTSCHLAND ) GMBH
k + 49 821 479 2506 J sebastian . hoerold @ clariant . com j www . clariant . com
38 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981