4.3.1. Thermogravimetric Analysis (TGA)

The thermal properties of xanthan gum, titanium dioxide-based polyurethanes (XTPU) were analyzed by using the TGA technique. The TGA thermograms of XTPU 1 to 6 are shown in Figure 6. The thermograms of TGA of all XTPU samples showed thermal stability and thermal degradation behavior. In an inert atmosphere, the thermal analysis data revealed that all of the XTPU polymer samples are thermally stable up to 140–225 ◦C. All the polymer samples faced a 10% loss of weight in the range of 305–355 ◦C. These

samples faced a 20% loss of weight in the range of 372–410 ◦C. They also faced a 50% loss of weight in the range of 423–463 ◦C, and maximum decomposition observed in the samples occurred at 460–495 ◦C. The comparative results showed that the chain extender, i.e., BDO, and bioactive material, i.e., xanthan gum, play a vital role. The results illustrated that poly (ethylene glycol adipate)-based polyurethane [33] is thermally less stable compared to xanthan gum, TiO2-based polyurethanes with BDO as a chain extender. The values of temperature showed that pure polymers have lower degradation temperature, i.e., 460 ◦C, while, at the same time, the polymers having 1% XG, 5% of TiO2 have higher degradation temperature, i.e., 495 ◦C, showing degradation temperature variation about 35 ◦C. Results revealed that the percentage mole ratio of xanthan gum and TiO2 enhances the degradation temperature of polyurethane more than pure polyurethane, i.e., XTPU-1. The chain extender, i.e., BDO, and xanthan gum increase the decomposition temperature and thermal stability of XTPU, as shown in Table 2.

**Figure 6.** TGA thermogram of XTPUs at 500 ◦C.


Temperature at which 0%, 20%, 50%, and 80% weight losses obtained from TGA. Maximum decomposition temperature obtained from TGA.

#### 4.3.2. Differential Scanning Calorimetry (DSC) Study

The effect of chain extenders length, XG, and TiO2-based polyurethanes samples were also studied by DSC measurements. The XTPU thermograms are shown in Figure 7. In the XTPU 1 to 6 samples, it is clear by DSC analysis that thermal changes took place when temperature was increased from 0 to 500 ◦C. It is clear from the data of Table 3 and from DSC thermograms that polymer degradation started in the range of 140–225 ◦C, which is also in accordance with TGA thermograms. The polymers samples showed glass transition temperature (Tg) in between 178–193 ◦C, crystallization temperature in the range 368–373 ◦C, melting temperature (Tm) in the range of 430–450 ◦C, and decomposition/degradation temperature in the range of 460–495 ◦C [34]. Here, it has been observed that the melting transition was found to be high near the decomposition temperature. This causes an arrangment of the chains and facilitates a greater interaction between chains, increasing the miscibility between the rigid and soft segment, as seen in TM and Tc, for all materials. The glass transition temperature observed at these values is relative to the rigid segment. The value of the Tg of the polyurethane sometimes also depends on the type of nanofiller (TiO2) employed in the synthesis. This value is indicative of the soft and rigid segment mixing degee. The higher value of Tg usually represents the higher miscibilty or campatibity degree of rigid-flexible segments [35]. The results revealed that presence of a nanofiller, i.e., TiO2, and its bonding between xanthan gum and diisocyanate, i.e., IPDI, increases the stability and crystalline behavior of the synthesized polymer. So, the crystillinity may be observed because of nanofiller. The most probable reason for this behavior in the nanocomposite is reduction in mobility of chains of urethanes, which reduces the process of degradation, as reported in literature [36]. This can also be related to the formation of longer crosslinked microdomains of rigid segments or the structure with a greater degree of organization. This trend agrees with the results obtained in the literature.


**Table 3.** Thermal stability data of the XTPU samples based on DSC.

Tg is Glass transition temperature; Tc is Crystallization temperature; Tm is melting temperature; Td is degradation/decomposition temperature.

#### *4.4. X-ray Diffraction Study*

The crystalline behavior of XTPU samples was calculated by using the crystalline peak intensity of respective samples. The Debye-Scherer (powder) method, applying Bragg's relation, was used to estimate the d-spacing of various XTPUs [37].

In XTPU samples, relative contents, structure regularity, and thermodynamic incompatibility affect the phase separation of soft, as well as hard, segment. A well oriented crystallinity was perceived at 2θ = 20◦, as reported in literature [38]. The phase separation of the soft and hard segment in XTPUs is attributed to crystallinity of sample, and it was revealed by X-ray diffraction studies. So, crystalline behavior improved as % age of TiO2 in the final XTPU increased. Finally, in the current study, we can attribute the crystallinity to the soft segment, and increasing percentage of TiO2 did not show any appreciable change

in polymer structure. The chemical cross-linking of xanthan gum restricts the soft segment melting. So, it can be determined that only XTPU-6, having 1% xanthan gum and 5% TiO2, showed higher crystallinity, which has been associated with phase separation at 2θ = 20◦, as shown in Figure 8.

**Figure 7.** DSC curves of XTPU-1, 2, 3, 4, 5, and 6 at 500 ◦C.
