PLLA-TAP _ GPC-FTIR-NMR-Crystallization kinetics data

PLLA-TAP _  GPC - FTIR - NMR - Crystallization kinetics data

1.1.Materials

A commercial PLLA grade, Luminy^® L-130, with l-isomer content ≥ 99% and melt-flow index of 23 g/10 min (210 °C/2.16 kg), was kindly provided by TotalEnergies Corbion (The Netherlands). Triallyl phosphate (TAP) was purchased from TCI America as GC-grade with purity of 96%. Dicumyl peroxide (P) was purchased from Sigma-Aldrich with a purity of 98%, acetone from Romil as HPLC grade solvent.

1.2. Synthesis of long-chain branched PLLA

Operators: Aniello Staiano, Valentina Marturano, IPCB-CNR.

Before processing, PLLA pellets were dried overnight under vacuum at 60°C. Preparation of branched PLLA began with a pre-batch, by mixing dicumyl peroxide, triallyl phosphate and dried PLLA pellets in acetone, in order to promote adsorption of the reagents on the pellets surface. After complete evaporation of acetone, the pre-preg polymer pellets were further dried at 60 °C under vacuum, to remove traces of residual acetone and humidity.

Reactive mixing was carried out using a Brabender Plastograph EC (Brabender GmBH & Co.KG, Germany), at 180°C and mixing rate of 100 rpm for 6 minutes. Plain PLLA pellets were also processed using the same protocol.

Seven formulations were prepared, by fixing peroxide content at 0.2 wt%, while varying TAP from 0.1 to 1 wt%, as detailed in Table 1, which also presents sample codes.

Table 1. Sample codes and compositions

1.3. Gel permeation chromatography

Operator: Giovanni Dal Poggetto, IPCB-CNR.

Gel permeation chromatography (GPC) analyses were performed with a Omisec Resolve&Reveal equipped with a multidetector array composed by with refractive index (RI), right angle laser light scattering (RALS), low angle laser light scattering (LALS) and intrinsic viscosity (IV) detectors. Samples were dissolved in CHCl₃ (Romil), filtered on 0.22µm PTFE membrane and eluted at flux of 0.8 ml min^-1, runtime 50 min with injection volume of 100 μl and a concentration of 5 mg ml^-1. Analyses were carried out using a column set composed of one pre-column and two Phenogel Phenomenex columns with exclusion limits 10⁶ and 10³ Da. Temperature of columns and detectors was set at 35°C. All samples were evaluated using triple point calibration, which provides absolute molecular weights, with polystyrene standard (M_n = 101.252 kDa and M_w = 104.959 kDa). All measurements were performed in duplicate.

1.4.Thermal analysis

Operators: Aniello Staiano, Valentina Marturano, Maria Laura Di Lorenzo, IPCB-CNR.

Thermal properties were investigated using a TA Instrument Q2000 Tzero DSC equipped with a RCS cooling accessory. Temperature and energy calibration were performed using a high-purity indium standard. For isothermal crystallization analysis, samples were melted at 200 °C for 2 min, then cooled to the selected crystallization temperature (T_c) at 30 K min^-1. For non-isothermal crystallization, the polymers were melted at 200 °C for 2 min, cooled to 170°C at 30 K min^-1 to limit thermal degradation, then cooled to room temperature at various rates, ranging from 1 to 20 K min^-1. Dry nitrogen was continuously fluxed as purge gas at a rate of 30 mL min^-1. All the experiments were repeated at least twice to ensure reproducibility.

The data report:

- the heat flow rate plots (exo up) as function of temperature, measured upon cooling at 5 °C/min;

- the onset (Ton) and peak (Tp) temperatures, measured upon cooling ate rates ranging from 1 to 20 °C-min;

- the half-time of crystallization of the samples detailed above, measured at T_c ranging from 135 to 160 °C;

- the ratio of the half-time of crystallization (τ_½) of the non-modified polymer and of branched PLLA, at T_c = 150 °C.

1.5. Nuclear Magnetic Resonance (NMR) spectroscopy

Operators: Huidi Sun, Minna Hakkarainen, KTH.

¹H and ¹³C nuclear magnetic resonance spectroscopy (NMR) measurements were performed on an Avance 400 spectrometer at 298 K and the chemical shifts were reported as δ values (ppm) with the residual CDCl₃ (7.26 and 77.16 ppm, respectively) taken as a reference. The proton frequency was 400.13 MHz and carbon frequency was 100.61 MHz, respectively.

The data report:

- ¹³C NMR spectra of PLLA and PLLA-TAP in CDCl₃;

- ¹H NMR spectra of PLLA and PLLA-TAP in CDCl₃.

1.6. Attenuated total reflectance Fourier transform infrared (FTIR) spectroscopy

Operator: Huidi Sun, KTH.

Fourier transform infrared spectroscopy was performed with a PerkinElmer 100 spectrometer equipped with an attenuated total reflection (ATR) setup. All spectra were recorded in the range of 600-4000 cm⁻¹, using 16 scans at a resolution of 8 cm⁻¹.

The data report FTIR (ATR) spectra of PLLA and PLLA-TAP, normalized to the carbonyl stretching band at 1748 cm^-1.