Poly(lactic acid)(PLA)is one of the most important bio-plastics,and chemical modification of the already-polymerized poly(lactic acid)chains may enable optimization of its material properties and expand its application areas.In this study,we demonstrated that poly(lactic acid)can be readily dissolved in acrylic acid at room temperature,and acrylic acid can be graft-polymerized onto poly(lactic acid)chains in solution with the help of photoinitiator benzophenone under 254 nm ultraviolet(UV)irradiation.Similar photo-grafting polymerization of acrylic acid(PAA)has only been studied before in the surface modification of polymer films.The graft ratio could be controlled by various reaction parameters,including irradiation time,benzophenone content,and monomer/polymer ratios.This photo-grafting reaction resulted in high graft ratio(graft ratio PAA/PLA up to 180%)without formation of homopolymers of acrylic acid.When the PAA/PLA graft ratio was higher than 100%,the resulting PLA-g-PAA polymer was found dispersible in water.The pros and cons of the photo-grafting reaction were also discussed. 相似文献
Biodegradable and bioabsorbable poly(lactic acid)s are one of the most important biomedical materials. However, it is difficult to introduce the functional groups into poly(lactic acid)s in order to improve their hydrophilicity and degradation rate. Here the authors describe the synthesis of functionalized cyclic lactide monomer 3,6‐bis(benzyloxymethyl)‐1,4‐dioxane‐2,5‐dione (BnLA) using an advanced synthetic route. Water‐soluble hydroxyl‐functionalized homopoly(lactic acid) (P(OH)LA) is synthesized via ring‐opening polymerization (ROP) of BnLA, followed by a hydrogenolytic deprotection reaction. Amphiphilic diblock poly(lactic acid) (P(OH)LA‐PLA) is synthesized via ROP of DL‐lactide using PBnLA as an initiator, followed by a hydrogenolytic deprotection reaction. P(OH)LA‐PLA is able to form polymeric micelles with the diameter of sub‐100 nm.
An aryl polyphenylphosphonate, poly(9-oxa-10-(2,5-dihydro-xyphenyl) phospha-phenanthrene-10-oxide) phenylphosphonate (WLA-3), was used to prepare a flame-retardant poly(lactic acid) (PLA) by direct melt compounding. The thermal behaviour, burning behaviour and mechanical properties of the flame-retardant PLA systems have been investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), vertical burning test (UL-94), limiting oxygen index (LOI), cone calorimeter test (CCT) and tensile test. The flame retardance mechanism has been studied via Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and P content analysis. The UL-94 ratings of PLA’s containing 7phr (W7P) and 10phr (W10P) of WLA-3 were enhanced to V-0 from no rating for neat PLA. However, the cone calorimetry of flame-retardant PLA (W7P) only showed a little decrease in heat release rate (HRR), peak of heat release rate (PHRR) and total heat release (THR) compared to neat PLA. TGA results showed that the PLA containing different amounts of WLA-3 presented more complicated thermal decomposition behaviours than neat PLA. Additionally, the results from DSC and tensile tests showed that the addition of WLA-3 into PLA had a slight impact on the crystallization behaviours and tensile properties. 相似文献
Poly(lactic acid), PLA, was chemically modified with maleic anhydride (MA) by reactive extrusion. The effect of this modification on molar mass (MM) and acidity was assessed by means of size-exclusion chromatography (SEC) and titration, respectively. PLA MM decreased in the presence of MA solely and of MA and peroxide. Reduction in MM was monitored by the increase in acidity. PLA blends containing poly(butylene adipate-co-terephthalate) (PBAT) were prepared through different mixing protocols, PLA/PBAT, PLA-g-MA/PBAT and PLA/PBAT/MA/peroxide (PLA/PBAT in situ). SEC results and rheological properties revealed reduction in MM and viscosity of the modified blends. PLA/PBAT presented increase in MM and bimodal MM distribution. The calculated interfacial tension was significantly lower for the modified blends, despite the lower average particle area of PLA/PBAT. Surprisingly, the modified blends presented higher yield strength than that predicted by the rule of mixtures, which might indicate interfacial reactions. 相似文献
The effect of phthalimide compound on the nonisothermal and isothermal crystallization behavior of poly(lactic acid) (PLA) was investigated by differential scanning calorimetry (DSC) and polarized optical microscopy. It was found that the incorporation of a small amount of phthalimide promoted the crystallization of PLA significantly. The Avrami model was applied to analyze the isothermal crystallization kinetics. It was found that the Avrami exponent was higher for PLA/phthalimide blends than for neat PLA, indicating a heterogeneous nucleation mechanism. These results indicate that phthalimide may act as an efficient nucleating agent to improve the crystallization of PLA and expand its applications. 相似文献