PLA-rayon

Fig. 18.18 Tensile properties of uncoupled PLA-rayon composites as a function of fiber content (from Ganster and Fink [30] with permission from CRC press)...

Fig. 18.21 SEM cryo fracture micrographs of PLA-rayon composites with strong left), moderate middle), and weak right) interphase...

Fig. 18.23 Selected mechanical properties of PLA-rayon composites with designed interphases...

Fiber Property Nylon 6 PET Acrylics PLA Rayon Cotton Silk Wool... 

PLA is the most commonly used biodegradable polymer found in fibre form. PLA fibre properties compare favourably with both PET and rayon fibres. Potential PLA fibre applications include apparel, bedding, carpet, furnishings, personal care, nonwovens and industrial textiles. 

In the present chapter, rayon and other man-made cellulose fibers wUl be introduced in terms of properties and stracture. The compounding method to obtain the composites will be described briefly. PP-rayon composites will be considered in more detail as the practically most relevant class of this type of material at present arousing interest from the automotive industry. In another section rayon composites with poly(lactic acid) (PLA) and polyhydroxyalkanoates (PHA) will be studied as a promising bio-based and biodegradable alternative to conventional materials in durable applications, transport, and automotive industry. Finally, some concluding remarks will be given concerning future prospects of rayon reinforced thermoplastics and the problems to be tackled in future work. 

Being 100% cellulose, rayon is completely bio-based and biodegradable. Thus, it is an obvious choice for bio-based and/or biodegradable matrices such as PLA or PHA. Compared to natural fibers, the compact structure and the well-defined and constant properties as well as the availability on an industrial scale and ease of handling are advantageous. 

One of the disadvantages of PLA for many applications is its brittleness (20 kJ/m and 2 kJ/m for unnotched and notched Charpy, respectively). Instead of using common impact modifiers which reduce strength and stiffness, rayon fibers generate improved impact properties both in the unnotched and notched testing modes, as demonstrated in Fig. 18.19. Again, with wood or natural fibers, such a behavior caiuiot be generated [30]. 

Fig. 18.25 Selected mechanical properties of PLA (black) and its rayon composites with standard (blue) and weak green) interphase in comparison to glass fiber reinforced PP (red)...

Natural fibers, such as cotton, kenaf, coir, jute, flax, sisal, hemp, and wood, etc., become the first choice due to their biodegradabihty. Some synthetic biodegradable fibers have also been used for nonwoven apphcations, including cellulose esters such as cellulose acetate, rayon, lyoceU, etc., polyesters such as poly(lactic acid) (PLA), poly(caprolactone) (PCL), poly(hydroxybutyrate) (PHB), poly(hydroxybutyrate-co-valerate) (PHBV), Biomax, Biopol, polytetramethylene adipate-co-terephthalate (PTAT), etc., and water solubles such as poly(vinyl alcohol) (PVA), etc. 

One of the main applications today is in the fibre sector. In Table 6.2, the properties of PET and rayon fibres are compared with those of PLA fibre. 

The initial development efforts for large scale PLA applications has been in fibres. PLA is not necessarily biodegradable as a fibre due to its crystallinity. Table 6.3 compares PLA fibre properties with those of PET and rayon, two materials that it may displace. 

Arrieta MP, Fortunati E, Dominici F, Rayon E, Ldpeza J, Kenny JM. Multifunctional PLA-PHB/cellulose nanocrystal films processing, structural and thermal properties. Carbohydr Polym 2014 107 16-24. 

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