Blends 4 Innovation
Polymer blends can be of great interest for processing in textiles and composites,since a remarkably broad spectrum of properties can be obtained without having to,develop a new polymer. By blending, it can be possible to outperform the existing,homopolymers or develop materials with tailored properties. In addition, introducing,a cheaper polymer may reduce the cost of the final product.
In the Blends4Innovation project, focus was given to PP/PET, PP/PA6 and PET/PA6 blends. The PP based blends were studied both for textiles and composites, while the PET/PA6 blend was only of interest for textile applications.
It was already proven in the previous Cornet project Fibriltex that PP/PET blends are very promising. Therefore, Blends4Innovation further elaborated on this interesting polymer combination. The presence of PET microfibrils in PP can increase the modulus of the monofilaments, certainly when a compatibiliser is added. High PET concentrations can easily be added during monofilament extrusion, but this higher PET content did not result in an additional positive effect. Shrinkage and creep of the monofilaments did not further decrease when increasing the PET concentration above 30%. PP multifilaments reinforced with PET microfibrils can be dyed using disperse dyes resulting in deeply dyed filaments with a good water and light fastness.
When processed to composites, a PP plate with PET microfibrillar reinforcement is produced, having properties in the same range as self-reinforced composite materials. For unidirectional composites, an optimum is reached at 50% PET, while for
bidirectional composites, the highest performance is realised at 30% PET.
In general PP/PA6 blends showed to be less promising than PP/PET blends. Presence of PA6 microfibrils inside PP does not lead to an increase in mechanical properties. A decrease in shrinkage compared to neat PP was realised, but the effect was smaller than for blends with PET. Yet, the presence of PA6 in PP can reduce the hydrophobicity of PP filaments. Also PP/PA6 blends results in dyeable PP filaments, but the obtained light fastness is lower. PA6 based blends with a small amount of PP, aiming to a cost reduction, can be processed to multifilaments, but only in presence of a compatibiliser, which again increases the cost. The knowledge obtained on the processing of PP/PA6 blends is of high interest for the re-processing of recycled waste, since this often contains multiple polymer types.
Microfibrillar reinforced composites out of PP/PA6 are possible, but results are also in this application less promising than PP/PET blends. Yet, the presence of PA6 does lead to an improved water absorption and fibre adhesion, in case also a second reinforcement such as glass fibre is added.
Finally, also for PET/PA6 blends, it was proven that they can be easily processed
to textile filaments, without affecting the mechanical properties. Again, this shows the potential for the easy recycling of plastic waste. Moreover, the addition of PA6 to PET improves the dyeability of PET and might have a positive influence on the wearability. For this blend combination, the full textile processing chain has been evidenced going from filament extrusion, through textile processing (twistingknitting-weaving) and finally to dyeing,
In conclusion, the use of polymer blends can be an interesting route to improve the properties of yarns and composites and can give valuable insights for the reprocessing of plastic waste. This knowledge has been transferred to the industrial target groups and will be further disseminated. The positive feedbacks and cooperation of the companies during the User Committee meetings already showed the clear interest of companies to evaluate the blend technology in their applications.