EXPERIMENTAL - Project1

2. EXPERIMENTAL

2.1. Materials

PBAT with MFI 3.3- 6.6g/10min (at 190°C; 2.16 Kg); density 1.25-1.27g/cm³, melting point 110°C-115°C supplied by M/S BASF Japan Ltd was used as base matrix. Four types of nanoclays i.e Na⁺MMT (unmodified having CEC 92.6meq/100g clay), Cloisite 20A, (C20A, modified by 2M2HT: dimethyl, dihydrogenated tallow, quaternary ammonium having CEC of 95meq/100g clay), Cloisite 30B,( C30B,modified by MT2EtOT: methyl tallow bis-2-hydroxy ethyl quaternary ammonium salt and CEC of 90 meq / 100g clay) procured from M/S Southern clay Products Inc, USA and Bentonite (B109) obtained from M/S Elementis UK were used as nanoreinforcement to fabricate PBAT nanocomposites. Maleic anhydride (MA) and benzoyl peroxide (BPO) of analytical grade were purchased from E-Merck, India and used without further purification.

The organoclays and unmodified clay (Na⁺MMT) were dried under vacuum at 80°C for 5 hrs and the PBAT pellets were dried at 40°C for 30 minutes, prior to melt blending and fabrication of bio-nanocomposites.

2.2. Preparation of PBAT Bio-nanocomposite hybrids

The bio-nanocomposite hybrids of PBAT with various organically modified nanoclays and natural Na⁺MMT was prepared using melt blending technique in a co-rotating twin screw extruder (Haake rechord 9000, Germany). PBAT biopolymer was melt mixed with Na⁺MMT, C30B, C20A and B109 nanoclays at different weight percentage (1, 3, 5 wt%) at a temperature difference from feed to die zone between 165° C- 180°C and screw speed of 60-70 rpm.

In an attempt to improve the interfacial region between PBAT and nanoclays, maleic anhydride grafted PBAT (MA-g-PBAT) bio-nanocomposite hybrids were prepared using C30B, C20A and B109 nanoclays at 3wt% of clay loading through a two steps reactive extrusion process. In the first step, free radical grafting of PBAT using MA (3wt% by PBAT) was carried out using (BPO) (0.5wt% by PBAT) at a temperature of 165°C-180°C and screw speed of 60-80 rpm.

In the second step, MA-g-PBAT was melt blended with various organically modified nanoclays using the same optimized temperature and speed. Subsequently the extrudate was pelletized to granules.

2.3. Preparation of PBAT Bio-nanocomposite films

The extrudate pellets of various bio-nanocomposite hybrids were predried at 60°C for one hour prior to introduction into the blown film unit (Haake 9000, Germany) attached to the extruder. The temperature range between feed zone to die zone were varied from 145°C to 170°C with a screw speed between 60 - 85 rpm to produce the films of approximately 0.07mm thickness.