## 3 Results & Discussion
### TGA--Thermograimetric Analysis
Maximum degradation temperature of PBA is defined at T\({}_{\text{dmax}}\) = 385.1 \({}^{\circ}\)C [39] which is aligned with the TGA results shown in Table 3. The presence of multi-component nature for PHB226 commercial formulation containing organic additives and polyesters has been also corroborated by further authors such as [PERSON] et al. [40]. Different residual weights remaining at 800 \({}^{\circ}\)C can be found for the three matrices being higher for P3 HB-co-P4 HB blends than for P3 HB. Usually, two inorganic fillers are commonly used in polymers as nucleating agents to reduce crystallization rates: Mg\({}_{3}\)Si\({}_{4}\)O\({}_{10}\)(OH)\({}_{2}\) and CaCO\({}_{3}\)[41; 42]. Complementary EDS was used for the elemental analysis of the final residues revealing their correspondence to talc. In addition, the final amount of inorganic residue found for the bio-nano-composites developed, reveals an effective dosage of the nanoclays load introduced. The thermal degradation of Sepiolite and montmorillonite nanoclay additives was characterised in order to better understand the effect these have over the final bio-nano-composites. The T2 thermograph (Figure 2a) shows a typical curve for non-modified sepiolite. T1 thermograph shows a few deviations from respect to T2 due to the modification through organosilanes containing amine groups [25; 27]. Our TGA results are in concordance with the aminosilane grafted Sepiolite (T1) characterisation made by [PERSON] et al., in previous publication [43]. In particular, four degradation steps are appreciated for T1. The clay presents degradations around 74, 232 and 305 \({}^{\circ}\)C. In addition, a less defined degradation phase is observed at 349-495 \({}^{\circ}\)C. To try to better define this area and separate the overlap of peaks, the heating rate was lowered from 10 to 5 \({}^{\circ}\)C/min. The first loss corresponds to mainly methanol, probably used as a solvent for the modification of the clay, followed by dehydration of water: moisture and zeolitic water (below 180 \({}^{\circ}\)C). The volatilization of the modifier takes place in two steps, the first one related to adsorbed molecules (non-grafted) at 215-250 \({}^{\circ}\)C. The grafted modifier is likely to volatilize over 400 \({}^{\circ}\)C. The grafted groups are very stable, being eliminated by heating at temperatures above 400 \({}^{\circ}\)C. In this way, the characteristic hydrophilic surface of Sepiolite becomes organophilic and the fibrous clays can then be easily dispersed in low-polar polymers [44]. The last loss observed approximately at 750 \({}^{\circ}\)C has been described in the literature to be related to a complete oxidation of the carbonaceous residue formed during previous thermal oxidation of the grafted molecules [45]. T3 (Na-MMT) presents a chemical structure modified with a quaternary alkyl ammonium surfactant which has a noticeable effect on the thermal stability of the organoclay itself. Analysing its thermal degradation behaviour, it can be observed that T3 DTG shows a water/solvent release at 68 \({}^{\circ}\)C and at 116 \({}^{\circ}\)C. In addition, two small mass loss peaks are found for 295 \({}^{\circ}\)C and for 526 \({}^{\circ}\)C, and finally an accentuated peak corresponding to 674 \({}^{\circ}\)C. According to the literature ([PERSON] et al. [46] and [PERSON] et al. [47]) free water loss in MMT nanoclays containing hydroxyl groups in the alkylammonium anion, shows free water loss at around 80 \({}^{\circ}\)C. Peaks in at 200-600 \({}^{\circ}\)C are attributed not only to structural water but also to the decomposition of the alkylammonium ions. In particular, peaks found at 297 and 528 \({}^{\circ}\)C are associated to the following chemical species for this organoclay sample: H\({}_{2}\)O, CO\({}_{2}\), alkanes, alkenes, CHO's, COOH's, amines [47]. Finally, peaks attributed between 610 and 674 \({}^{\circ}\)C are attributed to some further structural water release.