Speciality Chemicals Magazine SEP / OCT 2023 | Page 59

FLAME RETARDANTS

As well as CO6010-EX , Nofia homopolymer HM1100 can also be used for PFAS-free FR PC with V-0 at 1.6 mm ( Figure 3a ). As indicated , Joncryl * ADR 4400 , a polymeric chain extender with a medium epoxy equivalent weight that reacts with the chain ends of polycondensation polymers , significantly improved the NI and FR .

The epoxy group on the Joncryl can react with the chain ends of both HM1100 and PC to compatibilise the blend and increase its melt viscosity , which could help with dripping . Attention should be paid during compounding to minimise the exposure of pre-dried HM1100 to ambient air to avoid moisture reabsorption .

PFAS-free FR PC with V-0 at 0.8mm or below can also be made with Nofia polyphosphonate with excellent impact properties ( Figure 3b ). The addition of impact modifiers restored the NI to PC level , while the use of phosphazene reduced the total loading of FR in the formulation .

The ultimate optimised formulation could include other FRs acting as synergists , such as RDP and BDP , impact modifiers , chain extenders and stabilisers , which could further reduce the total FR loading and thus cost . Although in these examples the HDT has not been measured , the high glass transition temperature ( Tg ) of polyphosphonate will ensure an HDT much higher than other traditional small molecule FRs , as shown in commercial formulations based on Nofia .

In FR PC-PBT & PC-PET blends - PFAS-free

In addition to FR PC , Nofia FR can also be used to make PFAS-free formulations for PC blends ( Figure 4a ). All three impact modifiers evaluated not only improved NI to 100 % ductile break , but also reduced overall dripping and flaming drips . Two eliminated the dripping entirely and increased the FR to V-0 at 1.6 mm ; Lotader AX8900 even helped achieve V-0 at 0.8mm .

Another advantage is that the torque for PTFE-free formulations was relatively low compared to the PC- PBT blend with PTFE . Although data are not presented here , both FRX and its customers have noted improved chemical resistance because of the addition of Nofia FR . Customers have reported a comparative tracking index for FR PC-PBT blend based on Nofia FR as high as 600V .

A similar phenomenon was observed for FR PC-PET blends based on Nofia FR ( Figure 4b ). The addition of the two impact modifiers improved both NI and FR . V-0 at 1.6mm and 0.8mm was achieved without PTFE while achieving 100 % ductile NI for a Paraloid * EXL-2690 based formula .

PC , PBT , PET and polyphosphonate are incompatible polymers . The interactions between them , especially the transesterification reaction , are important for compatibilisation , which in turn directly affects processing and properties . The addition of impact modifiers , some of them carrying reactive groups , adds another level of interaction .

The selection of impact modifiers is therefore crucial to making PFAS-free FR PC or its blends based on Nofia . For example , for PC-PET based on Nofia , Paraloid EXL-2690 appears to be a better option than Lotader AX8900 , contrary to the case of FR PC-PBT blend ( Figure 5 ). For PFAS-free FR PC using Nofia copolymer CO6010-EX , Metablen S-2130 is a better choice than Lotader AX8900 ( Figure 2 ).

Work on PFAS-free PC-ABS blends based on Nofia FR is currently under

Figure 3 - Application of Nofia HM1100 in PFAS-free FR PC for V-0 at 1.6mm ( a ) & 0.8 mm ( b )

Dried materials used 230629-2 23629-5 230629-6 220725-6 PC , Lexan 141R 66 % 78 % 77.5 % 84.5 % Nofia CO6010-EX 32 %

Nofia HM1100 20 % 20 % 10 %

Phosphazene , SPB-100 3 % Metablen S-2130 2 % 2 % 2 % Lotader AX8900 2 % Joncryl ADR 4400 0.5 % 0.5 %

Total 100 % 100 % 100 % 100 % P content 2.10 % 2.10 % 2.10 % 1.45 %

Compounding temp . setting , ° C , feed to die

200 / 265 / 265 / 260 / 260 / 260 / 260 / 260

NI at 3.2mm , J / m 790 690 820 855

Dried materials used 161110-3 230629-7 220725-4 220725-5 PC , Lexan 101 ( MFI 6 ) 76.45 % PC , Lexan 141R ( MFI 10 ) 60 % 74.5 % 79.5 %

Nofia HM1100 20 % 35 % 20 % 15 %

Phosphazene , SPB-100 3 % 3 % 3 % Lotader AX8900 5 % 2 % 2 % Joncryl ADR 4400 0.5 % 0.5 % 0.5 % Irganox 168 0.05 % P content , % 2.51 % 3.71 % 2.51 % 1.98 %

Compounding Temp . setting , ° C , feed to die

200 / 250 / 250 / 250 / 250 / 245 / 240 / 240C

NI at 1.6mm , J / m 960

200 / 275 / 275 / 270 / 265 / 260 / 260 / 260

NI at 3.2mm , J / m 765 810 835

SEP / OCT 2023 SPECCHEMONLINE . COM

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