Q20 differential scanning calorimeter

The ¹H-NMR spectrum of TLP was obtained by using a Bruker 400 MHz spectrometer (Bruker Corp., Karlsruhe, Germany) with D₂O as a solvent. The phase transition temperature of TLP was measured by using a Q20 differential scanning calorimeter (DSC, TA Instrument, Inc., New Castle, PA, USA) with a ramping rate of 10 °C/min from −80 to 50 °C in nitrogen atmosphere. TLP was first heated to 50 °C and then quickly cooled down to −80 °C. The second heating process was performed from −80 to 50 °C to determine the transition temperature of TLP. The inflection point (the maximum slope point) was determined as the transition temperature of TLP from its DSC curve. The thermal stability of TLP was investigated by using a Q50 thermogravimetric analysis (TGA, TA Instrument, Inc., New Castle, PA, USA) instrument with a heating rate of 10 °C/min in N₂ atmosphere. The temperature (T_5%) with the sample mass loss of 5% was determined to be the decomposition temperature of TLP. Three to five milligrams of TLP were used for DSC and TGA measurements, respectively. TLP was measured after heating at 70 °C under vacuum over 24 h to remove the water. Scanning electron microscopy (SEM) was used to observe the surface morphology of lithium metal by using a Hitachi S-4800 SEM, (Hitachi, Ltd., Tokyo, Japan).

Chemical interactions between the components of TA-loaded PCL implants were evaluated using Spectrum Two FTIR (Perkin Elmer, Waltham, MA) at room temperature. The IR spectra were recorded in the range of 4000–600 cm⁻¹ and analysed using Spectrum 10 software. The resolution and the number of scans to record IR spectra were 4 cm⁻¹ and 32, respectively.
The surface morphology of TA-loaded PCL implants was evaluated using scanning electron microscopy (SEM) (Hitachi TM3030; Tokyo, Japan). The observation condition was set to EDX mode. Implants were sectioned accordingly and mounted on HITACHI SEM Cylinder Specimen Mounts.
The thermal properties of the 3D-printed implants with and without TA were evaluated. For this purpose, thermogravimetric analysis (TGA) was performed to measure the weight loss of the 3D-printed ocular implants. TGA was performed using a Q50 Thermogravimetric analysis (TA instruments, Bellingham, WA, USA). Scans were run from 25 to 500 °C, at the heating rate of 20 °C/min under a nitrogen flow rate of 40 mL/min. Moreover, a Q20 differential scanning calorimeter (DSC) (TA instruments, Bellingham, USA) was used to establish if the TA was crystalline or amorphous within the performed 3D-printed ocular implants. Scans were run from 20 °C to 300 °C at 20 °C/min under a nitrogen flow rate of 50 mL/min.

DSC was conducted using a Q20 differential scanning calorimeter (TA Instruments, Newcastle, United States) to detect glass transition temperatures (T_g) and melting peaks for the different formulations. Raw materials, physical blends, granules and printed samples were characterised using a heat ramp with a temperature range of 0 °C to 200 °C at 10 °C/min with 1 min isothermal at 0 °C. Sample weights were 2–5 mg contained in an aluminium standard TA crimped pans and lids (TA Instruments, Newcastle, USA). All tests were done in triplicate.

The thermal properties of the neat and plasticized PLA samples were determined using a TA Instruments Q20 differential scanning calorimeter (New Castle, DE, USA) under a nitrogen atmosphere. The samples were firstly heated at a rate of 10 °C min⁻¹ from 25 °C to 200 °C, held for 2 min, and then cooled down to 25 °C with a cooling rate of 5 °C min⁻¹. This was followed by the second heating run from 25 °C to 200 °C at a heating rate of 10 °C min⁻¹. Nitrogen was used as a furnace purge gas. A sample mass of ~7 mg of each material was tested; triplicate samples were analyzed by DSC. Thermal parameters such as the glass transition temperature (Tg), melt temperature (Tm), cold crystallization temperature (Tcc), and enthalpy of melting (ΔH_m) were determined from DSC spectra.
The crystallinity of the studied materials was calculated by applying Equation (3) [39 (link)], where ΔH_m refers to the enthalpy of melting, ΔHcc is the enthalpy of cold crystallization, w_PLA is the weight percentage of PLA in the samples and $\mathsf{\Delta }{H}_{\mathrm{m}}^0$ is the enthalpy of melting for 100% crystalline PLA, with a value of 93.7 J/g [40 (link)].
$${\chi }_c=\frac{\mathsf{\Delta }{{\displaystyle H}}_{\mathrm{m}}-\mathsf{\Delta }{{\displaystyle H}}_{\mathrm{cc}}}{{{\displaystyle \mathsf{\Delta }H}}_{\mathrm{m}}^0\ast w_{\mathrm{PLA}}}\ast 100\%$$

The thermal behavior was characterized by modulated differential scanning calorimetry (MDSC), using a Q20 differential scanning calorimeter (TA Instruments, New Castle, DE, USA). The samples were placed in sealed aluminum pans and measured by heating from −40 to 200 °C, at a rate of 1.5 °C/min and with a modulation regime of 1.5 °C every 90 s. The glass transition temperature (Tg) and melting points were obtained with the Universal analysis 2000 software (v4.5A, TA Instruments, New Castle, DE, USA).