DMA, TC, BT - Project1

2.6. Dynamic Mechanical Analysis (DMA)

The samples were studied using Dynamic Mechanical Thermal Analyzer (NETZSCH DMA 242, Germany), at fixed frequency of 1Hz and heating rate of 10°C/min using specimens of dimensions 25mm x 5mm x .07mm in a temperature range of –150°C to 200°C.

2.7. Thermal Characterization

The melting, crystallization and thermal stability of virgin PBAT and the nanocomposite samples have been studied using Differential Scanning Calorimetry (Perkin-Elmer Diamond DSC, USA) and Thermogravimetric Analysis (Perkin –Elmer Pyris-7 TGA, USA), respectively. The samples for DSC analysis (5-10 mg) were initially scanned from -80°C to 200°C under nitrogen atmosphere at a heating rate of 10°C/min, to erase the previous thermal history. Subsequently, the sample was held at 200°C for 5 minutes and cooled to -80°C and rescanned from -80°C to 200°C. Corresponding glass transition temperature, melting temperature, heat of fusion and crystallization temperatures were recorded.

The thermal stability of the PBAT and PBAT bio-nanocomposite hybrids was determined using TGA with samples ≤ 5mg weight, scanned from 50°C to 600°C at a heating rate of 10°C in nitrogen atmosphere. The initial and final degradation temperature and corresponding percentage weight loss for the samples were noted.

2.8. Biodegradation test

The biodegradability of the bio-nanocomposite hybrid and PBAT matrix was determined as per ASTM D 5338; by measuring the total Biological oxygen demand (BOD) in an aerobic compost medium. Rectangular samples of dimensions 2 cm x 2 cm, were taken as the specimen for biodegradation test.

2.8.1. Test procedure as per ASTM D5338

1. The test material was added to one of the three composting vessels, the second one was kept as blank with the third one as reference (cellulose) to ensure the viability of the innoculum.

2. The composting vessels (innoculum + test material / reference/ blank) are incubated in the dark and the vessel temperature was maintained at 58° C.

3. The test was started by bubbling free air (O2) in the solution at a rate of 50 to 100 ml/ min per flask for a period of 180 days (as per ASTMD 6400).

C + O2 ----------> CO2

4. The amount of CO2 produced passed through the Ba(OH)2 solution which is precipitated as BaCO3.

Ba(OH)2 + CO2 --------------> BaCO3 + H2O

5. The CO2 liberated was calculated by titrating the remaining Ba(OH)2 with 0.05N HCl.

Ba (OH)2 + 2 HCI ------------------> BaCl2 + 2 H2O

% CO2 evolved = 1.1 * ml HCl * 12* 100 /44 * y

Where

y = mg CO2 charged to flask

6. The percentage of biodegradation was calculated using the following equation:

% Biodegradation = Mean Cg (test) – mean Cg (blank) / Ci

Where:
Cg =amount of gaseous carbon produced, g, and

Ci = Theoretical amount of carbon in test compound in the sample, g

The theoretical oxygen demand was calculated from the composition and structural formula of the PBAT copolymer with the assumption that the degraded products were completely mineralized to CO_2.