Preparation and characterization of phosphorylated graphene oxide grafted with poly(L‐lactide) and its effect on the crystallization, rheological behavior, and performance of poly (lactic acid)

Abstract

Phosphorylated graphene oxide (PGO) was prepared by using phosphoric acid as functional reagent, and PGO was grafted with poly(L‐lactide) (PGO‐PLLA) by ring‐opening polymerization of L‐lactide as monomer under nano‐ZnO catalyst. The results of the orthogonal analysis showed the optimum reaction conditions to be as follows: the reaction temperature of 170°C, reaction time of 14 hours, the mass ratio of PGO of 10 wt%, and the mass of nano‐ZnO of 1 wt%. PGO‐PLLA was characterized by fourier transform infrared spectroscopy, gel permeation chromatography, and X‐ray photoelectron spectroscopy, which demonstrated that the PLLA molecular chains were successfully grafted onto the surface of PGO. Poly (lactic acid)/PGO‐PLLA nanocomposites (PLA/PGO‐PLLA) were prepared by melt intercalation. Mechanical test and fracture scanning electron microscopy showed that PGO‐PLLA (0.3 wt%) improved impact strength of PLA by 52.19%, which resulted in ductile fractures surface of PLA/PGO‐PLLA. Microcalorimetry and thermal degradation kinetics proved that PGO‐PLLA improved the thermal stability of PLA. Polarized optical microscopy and differential scanning calorimetry confirmed that PGO‐PLLA increased crystallization rate and spherulite kernel density of PLA, and crystallinity of PLA/PGO‐PLLA reached to 22.05%. Rheological behavior proved that PGO‐PLLA increased the self‐lubricity of PLA. Enzymatic degradation results illustrated that PGO‐PLLA had some inhibition for the biodegradability of PLA based nanocomposites.

Preferential formation of the stereocomplex crystals of poly(L‐lactide) and poly(D‐lactide) blend by epoxidized soybean oil under nonisothermal crystallization

“…Unlike ESO, the T c of SO added to a PLLA/PDLA blend had no discernible trend; all T c values were lower than those for PLLA/PDLA. T onset − T c was used to estimate the total crystallization rate (Figure 4B)—smaller values indicated faster total crystallization rates 48 . When the ESO content was 3% (PLLA/PDLA/3ESO), T onset − T c stopped decreasing and continued to increase, indicating that the overall crystallization rate reached a maximum at 3% ESO content.…”

“…The relationship between crystallization temperature ( T ) and relative crystallinity ( X T ) can be expressed for nonisothermal crystallization as follows: $$$$ {\displaystyle \begin{array}{ccc}& & \\ {}& {X}_T& =\frac{\int_{T_0}^T\ \left({\mathrm{dH}}_c/\mathrm{d}T\right)\mathrm{d}T}{\int_{T_o}^{T\infty }\ \left({\mathrm{dH}}_c/\mathrm{d}T\right)\mathrm{d}T}\end{array}} $$$$ where T 0 and T ∞ are the beginning and ending points of the crystallization, respectively and d H c represents the exothermic enthalpy of crystallization within a temperature range dT 48 . Figure 10A–D shows the relationship between relative crystallinity, X T , and temperature, T .…”

“…where T 0 and T ∞ are the beginning and ending points of the crystallization, respectively and dH c represents the exothermic enthalpy of crystallization within a temperature range dT. 48 Figure 10A-D shows the relationship between relative crystallinity, X T , and temperature, T.…”

Toward Sustainable Elastomers from the Grafting-Through Polymerization of Lactone-Containing Polyester Macromonomers

“…In this last example, the microphase-separated graft copolymers with P­(γMCL)- b -PLA side chains, containing 20 wt % of rubbery poly­(γ-methyl-ε-caprolactone) (P­(γMCL)), showed delayed aging compared to pure PLA (which embrittled in less than 2 days), remaining ductile after 210 days at ambient conditions . Also, PLLA has been grafted onto different types of materials: graphene oxide, , lignin, chitosan, , chitin, cellulose nanofibers, and cellulose acetate. , Examples of graft polymers with PLLA as the backbone have also been studied . However, few examples of fully biobased synthetic copolymers with PLLA as the graft have been reported.…”

Synthesis of Graphene Oxide-Polystyrene Graft Polymer Based on Reversible Addition Fragmentation Chain Transfer and Its Effect on Properties, Crystallization, and Rheological Behavior of Poly (Lactic Acid)

“…Poly (lactic acid) (PLA) is one kind of biodegradable [4] and biocompatible thermoplastic that is fermented from renewable resources. PLA can be completely decomposed into environmentalfriendly CO 2 and H 2 O under the condition of composting, so its characteristics have attracted much attention in the research of polymer materials [5][6][7][8][9]. Since the lactic acid molecule has an asymmetric carbon atom, it has optical rotation.…”