Oil-Based and Bio-Derived Thermoplastic Polymer Blends and Composites 249
50
0
50
100
LLDPE 100
PLLA
LLDPE/PLLA/LLDPE-g-MA 80/20/4
LLDPE/PLLA/ 80/20
LLDPE-g-MA
100 150 200 250
Temperature (°C)
Weight (%)
300 350 400 450 500
Figure 8.5Thermal analysis results for low-density polyethylene/PLA blend with 4 phr of low-density
polyethylene-graft-maleic anhydride. Singhet al. 2011 [28]. Reproduced with permission of Springer.
Singhet al. [28] analysed linear low-density polyethylene and PLA blends in order
to develop a film with good mechanical properties and biodegradability under specific
conditions. On facing the problem of immiscible blends, they decided to introduce
low-density polyethylene-graft-maleic anhydride as compatibilizer. Analysing different
ratios of polymer amount and compatibilizer, they stated that 80 wt% of LLPE, 20 wt% of
PLLA and 4 phr of compatibilizer was the best blend in terms of mechanical properties,
thermal stability and biodegradability. An example of their results is given for thermal
analysis in Figure 8.5.
Interesting studies for medical applications have been done by Ploypetcharaet al. [29]
blending together different ratios of polypropylene and poly(lactic acid) with 3 wt% of
polypropylene-grafted-maleic anhydride as compatibilizer.
Important properties of water vapour permeability were observed: PLA increased
water vapour permeability of the blend, indicating that PP biodegradability might be
improved.
Nayak [30] proposed a work based on TPS, blended with polybutylene adipate-co-
terephthalate (PBAT) and nanoclay C30B at 3 wt% with and without the addition
of maleic anhydride-grafted-polybutylene adipate-co-terephthalate (PBAT-g-MA)
to optimize the blend. C30B is Cloisite 30B: natural montmorillonite organically
modified with methyl tallow bis-2-hydroxy ethyl quaternary ammonium salt with
cation exchange capacity (CEC) 90 meq/100 g. SEM analysis (Figure 8.6) displays an
improved interface of TPS in PBAT thanks to PBAT-g-MA and addition of 3% of
nanoclays, reducing size domains of TPS.
Both nanoclays and PBAT-g-MA increased the mechanical properties of PBAT–TPS
blend, especially elongation at break. Another important effect of the improved
compatibilization was the higher thermal stability of the blend thanks to both compati-
bilizer agents. A synergic effect of both methods of compatibilization was evident: both
nanoclays and MA alone improved the properties of the blend, but their simultaneous
interaction allowed to obtain a better blend (Table 8.9).
