Skip to main content
NCBI home page
ACS Omega logoLink to ACS Omega
. 2024 Nov 25;9(49):48149–48158. doi: 10.1021/acsomega.4c04940

Toward Sustainable Poly(lactic acid)/Poly(propylene carbonate) Blend Films with Balanced Mechanical Properties, High Optical Transmittance, and Gas Barrier Performance via Reactive Compatibilization and Biaxial Stretching

Xiaoying Ji †, Jia Guo †, Bingbing Zeng §, Xiaopeng Li †, Xue Liao †, Wanjiao Fang ‡, Juan Liu †, Yu Zheng §, Dongliang Li †,*, Jinshan Lei ‡,*
PMCID: PMC11635688  PMID: 39676996

Abstract

graphic file with name ao4c04940_0011.jpg

Sustainable poly(lactic acid) (PLA)/poly(propylene carbonate) (PPC) blends were compatibilized by the environmentally friendly epoxidized soybean oil (ESO) through the chemical reaction of epoxy functional groups on ESO with the terminated carboxyl and hydroxyl groups of PLA/PPC. The compatibilization effect of ESO was confirmed by Fourier transform infrared spectroscopy, rheological property testing, differential scanning calorimetry, and morphological observations. It was revealed that the molecular chain entanglement between PLA and PPC was significantly enhanced and the dispersed PPC phase size was decreased, which endowed the blend with high viscosity modulus, low tan δ, and great stretchability, especially for the blend containing 1.0 wt % ESO. The compatibilization effect dramatically reinforced the toughening modification of PPC on PLA, resulting in a great ductility with a fracture strain up to 187.3%, more than 20 times that of the pristine PLA, while maintaining a high strength of 44.5 MPa. Compared to the neat PLA and the PLA/PPC blend, the compatibilized blend showed a much larger draw ratio of up to 6.5 × 6.5 during biaxial stretching, producing a uniform film with balanced mechanical properties, high optical transparency, and good oxygen barrier performance. This work will be of vital importance for guiding the preparation of PLA-based films with superior comprehensive properties.

1. Introduction

Traditional polymer films, such as polyethylene (PE) and poly(butylene terephthalate) (PET) films, have been widely applied in the packaging field and agricultural industry. However, the intrinsic nondegradability of these petrochemical polymers led to numerous ecological issues. Therefore, lots of attention has been paid to promoting the development of degradable polymer films.1−3 Among them, the biodegradable poly(lactic acid) (PLA) film is regarded as the most promising candidate due to its excellent renewability, satisfactory strength, and excellent transparency.4,5 Nevertheless, the inherent brittleness is a significant limitation for the scale application of PLA films. Besides, its linear chain structure led to low viscoelasticity at processing temperature, which is unfavorable to realize good film-forming properties.6,7

Some recent studies have stated that biaxial stretching of PLA blends containing high viscoelastic and flexible polymer is a green and efficient film-forming route for achieving brittle-ductile transition and uniform film formation.8−11 For example, He et al.12 toughened the PLA film via reactive melt blending with high elastic poly(ethylene octene) (POE), and the interfacial intermolecular interaction and entanglement were tailored between the two phases, which finally realized the enhanced elongation at break and the relatively smooth surface after biaxial stretching. Moreover, Liu et al.13 conducted an investigation of biaxially stretched PLA/poly(butylene adipate-co-terephthalate) (PBAT) films. It was found that the stretched PLA/PBAT films presented reduced surface roughness and a 45% increase in tensile strength as compared with the unstretched films. However, the introduction of the above polymers and their analogues into PLA films inevitably induced the sacrifice of optical transparency due to the unmatched refractive index and poor compatibility. In addition, blending PLA film with nondegradable flexible polymers would exert negative effects on its environmental friendliness.

Sustainable and biodegradable poly(propylene carbonate) (PPC), originating from the synthesis of alternating copolymerization of propylene oxide and CO2, has many advantages, such as biodegradability, high viscoelasticity, oxygen barrier property, and high toughness.14−16 Meanwhile, PPC has a refractive index of 1.46 highly close with that of PLA (1.45).17,18 Given this, PPC was regarded as an outstanding partner of PLA in preparing biodegradable blend films by biaxial stretching. However, the poor compatibility and weak molecular entanglement between PLA and PPC is the major bottleneck to realizing each maximum contribution to satisfy the diversified needs of packaging products.19−22

In this work, epoxidized soybean oil (ESO) was used as a reactive compatibilizer to enhance the compatibility between PLA and PPC. PLA, PPC, and ESO were directly melt-blended at a certain mass ratio to prepare the blends. The compatibility effect of ESO on PLA/PPC blends was investigated by infrared spectroscopy, rheology, thermal behavior, phase morphology, and mechanical property. Besides, the compatibilized PLA/PPC blend films were fabricated by biaxial stretching. And the effect of compatibilization from ESO on the film formation, mechanical property, optical transparency, and barrier property of PLA/PPC blend films was systematically studied. This work provides a valuable guide for fabricating PLA-based films with superior comprehensive properties.

2. Experimental Section

2.1. Materials

The commercial PLA (trade name 4043D) with a density of 1.21 g/cm3 and 4% DLA was purchased from Nature Works Co., whose number-average molecular weight and polydispersity index were 7.04 × 104 g/mol and 1.6, respectively. The PPC with a density of 1.24 g/cm3 was kindly supplied by Jilin Yixian Technology Co. (China), whose number-average molecular weight was 17.3 × 104 g/mol. ESO with an average molecular weight of 975.4 was purchased from Shanghai Macklin Biochemical Technology Co. (China). Dicumyl peroxide (DCP) with an average molecular weight of 270.3 was purchased from Shanghai Aladdin Biochemical Technology Co. (China).

2.2. Sample Preparation

Before processing, the pristine PLA and PPC particles were vacuum-dried for 24 h at 80 and 40 °C, respectively. Then, the 70/30 wt % PLA/PPC with 0, 0.5, 1.0, 2.0, and 3.0 wt % ESO were directly melt-blended in the presence of fixed 0.15 wt % DCP initiator by a HAAKE internal mixer (Thermo Scientific) at 180 °C with a rotation rate of 40 rpm for 10 min. The produced blocks were manufactured into 0.5 mm films through hot-pressing at 180 °C for 5 min under 10 MPa. At last, the biaxial stretching of the films was carried out using a Brückner Karo IV laboratory stretcher with a deformation rate of 20%/s at 80 °C.

2.3. Fourier Transform Infrared Spectroscopy (FTIR)

FTIR spectrum was collected on a Nicolet iS10 FTIR spectrometer using the attenuated total reflectance mode, and the 32 scans from 600 to 4000 cm–1 at a resolution of 4 cm–1 were used.

2.4. Rheological Measurements

A rotational rheometer (AR1500EX, TA Instruments) was employed to measure the viscoelastic property of samples with a diameter of 25 mm, which was implemented at the frequency range of 100–0.01 Hz and the strain of 5%.

2.5. Differential Scanning Calorimetry (DSC)

Thermal properties of films were measured on a TA Instruments Q20 DSC under nitrogen flow. The sample with a weight of about 5 mg was heated from 0 to 200 °C with a heating rate of 10 °C/min. The crystallinity (Xc) of PLA in each sample was calculated by using the following equation:

2.5. 1

where ΔHm is the enthalpy of melting, ΔHcc is the enthalpy of cold crystallization and ΔHm0 is the melting enthalpy of 100% crystalline PLA (93.7 J/g), and W is the weight fraction of PLA in each sample.

2.6. Morphological Observation

The morphology of the samples was observed through a field-emission scanning electron microscope (SEM, JEOL JSM-5900LV) at an accelerating voltage of 5 kV. Before visualization, the samples were first cryofractured in liquid nitrogen and then coated with a golden layer.

2.7. Tensile Test

The Instron 4302 tension machine (Canton, MA) was used to test the mechanical properties at a crosshead speed of 50 mm/min in accordance with ASTM D638. At least five specimens for each sample were tested to obtain the average value.

2.8. Gas Barrier Measurements

The oxygen permeation test of samples was executed by the VAC-V1 permeability testing machine (Labthink Instruments, Jinan, China) with the 50 mm diameter disks at 25 °C and 50% relative humidity according to ISO2556:2001, and based on the differential pressure method.

2.9. Surface Morphology

The surface morphologies of biaxially stretched films were observed by an ultradepth three-dimensional (3D) microscope (VHX-1000C, Keyence) to synthesize stereoscopic three-dimensional graphics.

2.10. Optical Transparency

The optical transparency of samples was measured by an ultraviolet–visible (UV–vis) spectrophotometer (UV1750, Shimadzu, Japan), which was carried out with the wavelength range 400–800 nm, corresponding to an empty transmittance accessory.

3. Results and Discussion

3.1. Compatibilization Effect of ESO on PLA/PPC Blends

Figure 1a shows the FTIR spectra of PLA, PPC, and the blends. Thereinto, the unique epoxy functional groups in ESO were located at the two absorption peaks of 833 and 726 cm–1, as shown in Figure 1b. However, these two characteristic absorption peaks disappeared in the PLA/PPC/ESO blends, indicating that the epoxy groups on ESO reacted with PLA/PPC blend during melt processing. The peak intensity of the 3306 cm–1 band assigned to the terminated carboxyl groups of PLA and PPC is traced in Figure 1c. It could be observed that this absorption peak disappeared after blending with ESO, indicating the reaction between the epoxy and carboxyl groups. Besides, the 2750–3100 cm–1 band attributed to the −CH2– stretching vibration absorption is plotted in Figure 1d, and the corresponding intensity evolution of the four characteristic absorption peak is displayed in Figure 1e. By comparison, the PLA/PPC/ESO blends contain the −CH2– characteristic peaks of PLA, PPC, and ESO, and the absorbing intensity of the four characteristic absorption peaks was gradually enhanced as ESO content elevated. It could be concluded that DCP first initiated the grafting reaction of ESO on PLA or PPC and the degradation of PPC and PLA homopolymers, as displayed in Scheme 1a. Then, the chain extension reactions occurred among ESO, PLA-g-ESO, PPC-g-ESO, and degraded PPC/PLA homopolymers. Considering that the carboxyl group has higher reactivity with epoxy than the hydroxyl group, the structure of produced PLA/PPC copolymer is described in Scheme 1b, which could improve the compatibility of PLA/PPC blends (Scheme 1c).

Figure 1.

Figure 1

Open in a new tab

FTIR spectra of each sample: (a) Overall spectra from 600 to 4000 cm–1, (b) characteristic absorption peaks of epoxy at 841 and 723 cm–1, (c) intensity changes at 3306 cm–1, (d) −CH2– stretching vibration absorption peak at 2750 to 3100 cm–1; and (e) intensity changes at 2994, 2955, 2921, and 2850 cm–1 versus ESO content.

Scheme 1. (a) Reaction Route of the PLA/PPC Copolymer with DCP and ESO; (b) Molecular Structure of PLA, PPC, ESO, and the Produced Copolymer; (c) Schematic Diagram Involved in the Compatibilization Effect of ESO on PLA/PPC Blends.

Scheme 1

Open in a new tab

The rheological measurement was carried out to explore the enhanced molecular chain entanglement between PLA and PPC enabled by adding ESO. Figure 2a presents the storage modulus (G′) curves versus angular frequency of PLA, PPC, and their blends. With frequency increased, all of the curves showed a linear increasing trend and nearly overlapped as frequency reached 100 Hz. Nevertheless, in the low-frequency region, the G′ value of PLA was much lower than that of PPC, indicating a relatively poor molecular entanglement. Hence, blending with PPC elevated the G′ curve of PLA. After chemical connecting PLA and PPC with ESO, the formation of long-chain branches extended the relaxation time, further increasing the G′ value. Noticing that the G′ of the PLA/PPC/ESO blends was first increased and then decreased with ESO content enhanced, the sample with 1.0 wt % ESO possessed the maximum G′ value, meaning that such an ESO content was best for the molecular entanglement and phase compatibilization of PLA/PPC blends. Figure 2b shows the tan δ curves versus angular frequency, which were first downward and then upward as incorporated with more ESO. The linear PLA had the highest tan δ due to the strong chain slipping induced by its poor chain entanglement. In comparison, the blends showed a much lower tan δ, suggesting that the compatibilization effect of ESO accelerated the elastic response and decreased the viscous dissipation, especially for PLA/PPC/1.0ESO, which was believed to be beneficial for the film stretchability. In Figure 2c, the complex viscosity (η″) of each sample continuously decreased with increasing frequency, which is a typical representation of pseudoplastic fluid with a shear-thinning rheologic behavior. A higher η″ in the low-frequency region implied a stronger molecular chain entanglement. It can also be found that the PLA/PPC blend compatibilized with 1.0 wt % ESO showed a high η″, further supporting the view that this blend realized the best reactive compatibilization efficiency.

Figure 2.

Figure 2

Open in a new tab

Rheological curves versus angular frequency for each sample: (a) G′, (b) tan δ, and (c) η″.

DSC and DMA tests were conducted to further research the compatibilization effect of ESO on the PLA/PPC blends. The resultant DSC thermograms and DMA curves are shown in Figure 3a,3b, and the corresponding thermodynamic data is collected in Table 1. The DSC Tg and DMA Tg of pristine PLA were located at 57.4 and 64.2 °C, and the corresponding values of PPC were 26.6 and 28.3 °C. For the PLA/PPC blend without ESO, the two well-separated glass transitions respectively belonging to PLA and PPC moved slightly toward each other, indicating that a certain miscibility existed between PLA and PPC. And the cold crystallization of PLA shifted to a higher-temperature range, and the multiple melting of PLA disappeared to leave only one peak with a low melting point. However, due to the extremely poor crystallization ability of PLA, all of the samples exhibited a low Xc of ∼3.0%, as seen in the detailed values signed beside the DSC curves. With the introduction of ESO, ΔTg as the difference between the Tg of PLA and PPC was significantly reduced. When the 1 wt % ESO was added, the DSC ΔTg dropped to the lowest value of 20.3 °C, which was consistent with the DMA results, well demonstrating the great compatibilization effect of ESO on the PLA/PPC blends. Once the ESO content exceeded 1.0 wt %, the ΔTg started to increase and the PLA Tg became higher. It was speculated that the high content ESO led to the insertion of small ESO molecules between the PLA chains forming numerous cross-linking structures, thus restricting the chain mobility of PLA and lowering the compatibilization effect of ESO.23

Figure 3.

Figure 3

Open in a new tab

(a) DSC thermograms and (b) DMA curves of each sample.

Table 1. Summarizing the Thermodynamic Data of Each Sample.

  DSC
 DMA
Tg1(PPC) (°C) Tg2(PLA) (°C) ΔTg (°C) Tg1(PPC) (°C) Tg2(PLA) (°C) ΔTg (°C)
PLA   57.4     64.2  
PPC 26.6     28.3    
PLA/PPC 28.3 53.3 25.0 32.2 61.2 29.0
PLA/PPC/0.5ESO 28.9 52.0 23.1 32.4 58.7 26.3
PLA/PPC/1.0ESO 29.3 49.6 20.3 32.8 57.8 25.0
PLA/PPC/2.0ESO 29.1 49.8 20.7 32.5 58.4 25.9
PLA/PPC/3.0ESO 27.1 50.2 23.1 32.3 58.5 26.2
Open in a new tab

In addition, the compatibilization effect of ESO on PLA/PPC blends could be directly embodied by the SEM pictures. Figure 4a–e exhibits the SEM pictures of the cryofractured surface of the blends. For the PLA/PPC blend, the minor PPC phase existed in the form of dispersed spherical domains in the PLA matrix due to its much higher viscosity at the processing temperature of 180 °C compared to that of PLA. When the ESO was added, the interface between PLA and PPC became fuzzy and the phase size of PPC was continuously decreased from 2.5 to 1.4 um (Figure 4f) both of which further confirmed the excellent compatibilization effect of ESO on the PLA/PPC blends. Another attention needed to lie in the fact that the addition of ESO of more than 2 wt % gave rise to produce abundant cavities in the PLA/PPC blends, which was probably ascribed to some vaporization of the low-boiling ESO liquid during melting processing. This phenomenon exactly accounted for the reduction of the complex viscosity and G′ in Figure 2.

Figure 4.

Figure 4

Open in a new tab

SEM pictures of the PLA/PPC blends with different ESO contents: (a) 0.0, (b) 0.5, (c) 1.0, (d) 2.0, and (e) 3.0 wt %. (f) Phase size of the dispersed PPC domain.

3.2. Mechanical and Film-Forming Properties of PLA/PPC/ESO Blends

The strain–stress curves of each sample are displayed in Figure 5a, and the corresponding results are summarized in Figure 5b. The brittle PLA had a high tensile strength (σ) of 57.7 MPa but a poor elongation at break (ε) of 8.8%. The introduction of flexible PPC into PLA triggered the brittle-to-ductile transition, increasing the ε to 57.2% but decreasing the σ to 46.0 MPa. The compatibilization effect of ESO improved the compatibility of PLA and PPC and decreased the PPC domain size, thus enhancing the toughening modification of PPC on PLA. As a result, the σ was slightly declined with the addition of ESO. However, the ε was increased to 187.3% of the PLA/PPC/1.0ESO blend but then dropped to 94.0% of the PLA/PPC/3.0ESO blend. This is because the vaporization of high content ESO induced the formation of cavities, which would induce stress concentration, leading to the deterioration of ductility. By comparison, the PLA/PPC/1.0ESO blend showed the best mechanical performance with a σ of 44.5 MPa and a ε of 187.3%. It could be concluded that the interfacial molecular entanglement between PLA and PPC and the decreased PPC phase domain, enabled by the compatibilization effect from ESO, dramatically optimized the mechanical properties.

Figure 5.

Figure 5

Open in a new tab

Mechanical properties of each sample: (a) Strain–stress curves and (b) summarizing data of σ and ε.

Figure 6a demonstrates the captured images of the biaxial stretched films. Neat PLA had the maximum stretching ratio (MSR) of 5.0 × 5.0 (machine × transverse direction, MD × TD). The addition of flexible PPC improved the deformation capacity of PLA, resulting in a larger MSR of 5.5 × 5.5. For the PLA/PPC/ESO blends with long branched or cross-linked structure, the MSR was further enhanced to 6.5 × 6.5 for the sample with 1.0–2.0 wt % ESO, but then fallen back to 6.0 × 6.0 of PLA/PPC/3.0ESO. The deterioration in stretchability of the blend with high content ESO originated from the creation of massive cavities, as seen in the SEM images above. Subsequently, the ultradepth three-dimensional microscope was applied to reveal the surface 3D morphology of biaxial stretched films, as shown in Figure 6b. The surface of the PLA film was much rough, which became smoother after blending with PPC. Once the ESO was added, a greater film thickness uniformity was realized in the blends. Accordingly, the enhancement in molecular chain entanglement of PLA via incorporation with the more viscous PPC together with the compatibilization effect of ESO optimized the deformation capacity and the film surface roughness.

Figure 6.

Figure 6

Open in a new tab

(a) Captured images and (b) the surface 3D morphology of the biaxial stretched films.

3.3. Performance of the Biaxially Stretched Films

Figure 7 shows the mechanical properties of MD and TD for the biaxial stretched films. As can be seen, each sample showed a good isotropic mechanical performance. The PLA film obtained σ above 96.0 MPa and ε above 50.0% for MD/TD due to molecular orientation, changing from fragility to ductility. Although the flexible PPC was introduced, the PLA/PPC film could maintain the σ at ∼90.0 MPa but enhance ε because of its larger MSR inducing a stronger orientation. Moreover, adding ESO first increased and then decreased σ, with 1.0 wt % being the critical content of ESO. On the other hand, the film with ESO exhibited a relatively worse flexibility due to adequate stretching. And the significant decline of both σ and ε occurred as the ESO content became 2.0 wt %.

Figure 7.

Figure 7

Open in a new tab

Stress–strain curves of (a) MD and (b) TD, and the collected (c) σ and (d) ε of the biaxial stretched films.

Considering that the crystallization of PLA during biaxial stretching played a crucial role in mechanical properties, Xc of the stretched films was first researched by DSC testing. As shown in Figure 8a, the Xc of each sample was significantly increased after biaxial stretching, as compared to that of the unstretched ones. Besides, the Xc value was first enhanced as incorporated with ESO added and achieved the optimal value of 19.8% when the ESO content reached 1.0 wt %, but then declined after further adding ESO. The larger draw ratio of PLA/PPC/1.0ESO could induce a stronger chain orientation, which could be well maintained by its chain entanglement, thus contributing to the crystallization of PLA. However, more addition of ESO triggered the formation of some cross-linking PLA structures, which would restrict the arrangement of chains into crystals. Moreover, the 2D-WAXD patterns (Figure 8b) of unstretched and stretched films and the corresponding one-dimensional (1D)-WAXD intensity integration curves (Figure 8c,d) were obtained. Only an isotropic halo ring was visible for the unstretched films, indicating an amorphous structure. After biaxial stretching, two diffraction peaks assigned to the crystal planes (200)/(110) and (203) of α or α′ PLA crystalline forms appeared. It could be confirmed that the α′ crystals were created due to the presence of (110/200) α/α′ peak at 16.9° and (203) α/α′ peak at 19.2° but the absence of the (103) α peak at 12.7° and (211) α peak at 22.3° in the 1D-WXRD curves.24 But no obvious crystal orientation could be observed. In addition, the average crystal size was calculated, showing a first increasing but then decreasing trend as incorporated with ESO, Figure 8e. Consequently, the better mechanical properties of PLA/PPC/1.0ESO film were ascribed to its larger draw ratio, Xc value, and crystal size.

Figure 8.

Figure 8

Open in a new tab

(a) DSC heating curves, (b) two-dimensional WAXD patterns, (c, d) one-dimensional WAXD diffraction spectra, and (e) average crystal size of the biaxially stretched films.

The optical transmittance of films was characterized by UV–vis spectra, as compared in Figure 9a. The pristine PLA film presented great optical transparency with 93% light transmittance. Thanks to the much close refractive index of PLA and PPC, the addition of PPC into PLA just led to a slight decrease in the light transmittance to 90%. After compatibilization by ESO, the blend film achieved a larger MSR and a smooth surface. However, the light transmittance was only increased to 91.0%, which was ascribed to the fact that the dispersed spherical PPC domains in blend caused multiple light reflection and refractions in both backward and forward directions, in accordance with the Lorenz-Mie scattering theory.16 Furthermore, the oxygen permeability (OP) of the films was evaluated with consideration of its vital significance for practical application in the packaging field. From Figure 9b, the PLA film possessed the OP of 2.0 × 10–14 cm3·cm/(cm2·s·Pa), which was decreased to 6.9 × 10–15 cm3·cm/(cm2·s·Pa) after blending with the high barrier PPC. With an addition of 1 wt % ESO, the OP was further decreased to 3.2 × 10–15 cm3·cm/(cm2·s·Pa), indicating that the enhanced molecular entanglement via chemical reaction of PLA/PPC blend with ESO reduced the pathway of oxygen molecule. By contrast, further addition of ESO failed to continuously improve the gas barrier performance, suggesting that the cavities formed in the samples with more ESO facilitated the oxygen permeation.

Figure 9.

Figure 9

Open in a new tab

(a) Transmittance UV–vis spectra and (b) oxygen permeability of films.

4. Conclusions

In this work, ESO as a compatibilizer was introduced into the PLA/PPC blend via reactive processing to prepare various PLA/PPC/ESO blend films by biaxial stretching. The reaction between the epoxy functional group of ESO and the terminated carboxyl/hydroxyl groups of PLA/PPC improved the compatibility of PLA and PPC, leading to the enhancement in molecular entanglement and the reduction in dispersed PPC phase size. Compared to the pristine PLA, the PLA/PPC/ESO blend exhibited a higher viscosity modulus, lower tan δ, and better stretchability, especially for the blend containing 1.0 wt % ESO. And the compatibilization effect dramatically reinforced the toughening modification of PPC on PLA, resulting in a great ductility with a fracture strain up to 187.3%, more than 20 times that of the pristine PLA, while maintaining a high strength of 44.5 MPa. Moreover, the uniform PLA/PPC/ESO film with a stretching ratio up to 6.5 × 6.5 was fabricated by biaxial stretching, which showed balanced mechanical properties, high optical transmittance (91.0%), and good oxygen barrier performance (3.2 × 10–15 cm3·cm·cm–2·s–1·Pa–1). This work provided valuable guidance for the preparation of high-quality PLA-based films.

Acknowledgments

This work was supported by the Opening Project of Cigar Fermentation Technology Key Laboratory of China Tobacco (China Tobacco Sichuan Industrial Co., Ltd.) (No. 20202301BC530).

The authors declare no competing financial interest.

References

  1. Wu F.; Misra M.; Mohanty A. K. Challenges and new opportunities on barrier performance of biodegradable polymers for sustainable packaging. Prog. Polym. Sci. 2021, 117, 101395 10.1016/j.progpolymsci.2021.101395. [DOI] [Google Scholar]
  2. Hamad K.; Kaseem M.; Ayyoob M.; Joo J.; Deri F. Polylactic acid blends: The future of green, light and tough. Prog. Polym. Sci. 2018, 85, 83–127. 10.1016/j.progpolymsci.2018.07.001. [DOI] [Google Scholar]
  3. Tripathi N.; Misra M.; Mohanty A. K. Durable Polylactic Acid (PLA)-Based Sustainable Engineered Blends and Biocomposites: Recent Developments, Challenges, and Opportunities. ACS Eng. Au 2021, 1, 7–38. 10.1021/acsengineeringau.1c00011. [DOI] [Google Scholar]
  4. Rasal R. M.; Janorkar A. V.; Hirt D. E. Poly(lactic acid) modifications. Prog. Polym. Sci. 2010, 35, 338–356. 10.1016/j.progpolymsci.2009.12.003. [DOI] [Google Scholar]
  5. Lim L. T.; Auras R.; Rubino M. Processing technologies for poly(lactic acid). Prog. Polym. Sci. 2008, 33, 820–852. 10.1016/j.progpolymsci.2008.05.004. [DOI] [Google Scholar]
  6. Hou X.; Yao S.; Wang Z.; Fang C.; Li T. Enhancement of the mechanical properties of polylactic acid/basalt fiber composites via in-situ assembling silica nanospheres on the interface. J. Mater. Sci. Technol. 2021, 84, 182–190. 10.1016/j.jmst.2021.02.001. [DOI] [Google Scholar]
  7. Yang X.; Guo Y.; Han Y.; Li Y.; Ma T.; Chen M.; Kong J.; Zhu J.; Gu J. Significant improvement of thermal conductivities for BNNS/PVA composite films via electrospinning followed by hot-pressing technology. Composites, Part B 2019, 175, 107070 10.1016/j.compositesb.2019.107070. [DOI] [Google Scholar]
  8. Zhou L.; Xu P. P.; Ni S. H.; Xu L.; Lin H.; Zhong G. J.; Huang H. D.; Li Z. M. Superior Ductile and High-barrier Poly(lactic acid) Films by Constructing Oriented Nanocrystals as Efficient Reinforcement of Chain Entanglement Network and Promising Barrier Wall. Chin. J. Polym. Sci. 2022, 40, 1201–1212. 10.1007/s10118-022-2723-3. [DOI] [Google Scholar]
  9. Xu P. P.; Yang S.; Gao X. R.; Chen S. P.; Xu L.; Zhong G. J.; Huang H. D.; Li Z. M. Constructing robust chain entanglement network, well-defined nanosized crystals and highly aligned graphene oxide nanosheets: Towards strong, ductile and high barrier Poly(lactic acid) nanocomposite films for green packaging. Composites, Part B 2021, 222, 109048 10.1016/j.compositesb.2021.109048. [DOI] [Google Scholar]
  10. Jariyasakoolroj P.; Tashiro K.; Wang H.; Yamamoto H.; Chinsirikul W.; Kerddonfag N.; Chirachanchai S. Isotropically small crystalline lamellae induced by high biaxial-stretching rate as a key microstructure for super-tough polylactide film. Polymer 2015, 68, 234–245. 10.1016/j.polymer.2015.05.006. [DOI] [Google Scholar]
  11. Li W.; Srithep Y.; Shen J.; Pholharn D.; Sriprateep K.; Worajittiphon P.; Khoklang N. Preferential formation of the stereocomplex crystals of poly(L-lactide) and poly(D-lactide) blend by epoxidized soybean oil under nonisothermal crystallization. Polym. Adv. Technol. 2024, 35, e6278 10.1002/pat.6278. [DOI] [Google Scholar]
  12. He W.; Ye L.; Coates P.; Caton-Rose F.; Zhao X. Reactive processing of poly(lactic acid)/poly(ethylene octene) blend film with tailored interfacial intermolecular entanglement and toughening mechanism. J. Mater. Sci. Technol. 2022, 98, 186–196. 10.1016/j.jmst.2021.04.051. [DOI] [Google Scholar]
  13. Liu X.; Mo Z.; Cui L.; Yu C.; Zou Z.; Liu Y.; Zheng W.; Tan J. Effect of biaxial stretching on the microstructure evolution, optical, mechanical and oxygen barrier properties of biodegradable poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) films. Int. J. Biol. Macromol. 2023, 253, 126976 10.1016/j.ijbiomac.2023.126976. [DOI] [PubMed] [Google Scholar]
  14. Xu Y.; Lin L.; Xiao M.; Wang S.; Smith A. T.; Sun L.; Meng Y. Synthesis and properties of CO2-based plastics: Environmentally-friendly, energy-saving and biomedical polymeric materials. Prog. Polym. Sci. 2018, 80, 163–182. 10.1016/j.progpolymsci.2018.01.006. [DOI] [Google Scholar]
  15. Ren G. J.; Sheng X. F.; Qin Y. S.; Chen X. S.; Wang X. H.; Wang F. S. Toughening of poly(propylene carbonate) using rubbery non-isocyanate polyurethane: Transition from brittle to marginally tough. Polymer 2014, 55, 5460–5468. 10.1016/j.polymer.2014.08.052. [DOI] [Google Scholar]
  16. Chen L.; Qin Y.; Wang X.; Zhao X.; Wang F. Plasticizing while toughening and reinforcing poly(propylene carbonate) using low molecular weight urethane: Role of hydrogen-bonding interaction. Polymer 2011, 52, 4873–4880. 10.1016/j.polymer.2011.08.025. [DOI] [Google Scholar]
  17. Zeng B.; Yang L.; Qin J.; Zheng Y.; Guo S. Nacre-Inspired polymeric materials with body heat-responsive shape-memory effect, high optical transparence, and balanced mechanical properties. ACS Appl. Mater. Interfaces 2020, 12, 52008–52017. 10.1021/acsami.0c15871. [DOI] [PubMed] [Google Scholar]
  18. Xing C.; Wang H.; Hu Q.; Xu F.; Cao X.; You J.; Li Y. Mechanical and Thermal Properties of Eco-Friendly Poly(propylene carbonate)/Cellulose Acetate Butyrate Blends. Carbohydr. Polym. 2013, 92, 1921–1927. 10.1016/j.carbpol.2012.11.058. [DOI] [PubMed] [Google Scholar]
  19. Zhou Y.; Wang J.; Cai S. Y.; Wang Z. G.; Zhang N. W.; Ren J. Effect of POE-g-GMA on mechanical, rheological and thermal properties of poly(lactic acid)/poly(propylene carbonate) blends. Polym. Bull. 2018, 75, 5437–5454. 10.1007/s00289-018-2339-5. [DOI] [Google Scholar]
  20. Wang Z.; Zhang M.; Liu Z. Y.; Zhang S. Y.; Cao Z. Q.; Yang W.; Yang M. B. Compatibilization of the poly(lactic acid)/poly(propylene carbonate) blends through in situ formation of poly(lactic acid)-b-poly(propylene carbonate) copolymer. J. Appl. Polym. Sci. 2018, 135, 46009 10.1002/app.46009. [DOI] [Google Scholar]
  21. Wang Z.; Lai X. L.; Zhang M.; Yang W.; Yang M. B. Synthesis of an Efficient Processing Modifier Silica-g-poly(lactic acid)/poly(propylene carbonate) and Its Behavior for Poly(lactic acid)/Poly(propylene carbonate) Blends. Ind. Eng. Chem. Res. 2017, 56, 14704–14715. 10.1021/acs.iecr.7b03444. [DOI] [Google Scholar]
  22. Gao M.; Ren Z. J.; Yan S. K.; Sun J. R.; Chen X. S. An optical microscopy study on the phase structure of poly(L-lactide acid)/poly(propylene carbonate) blends. J. Phys. Chem. B 2012, 116, 9832–9837. 10.1021/jp3041378. [DOI] [PubMed] [Google Scholar]
  23. Han Y.; Shi J.; Mao L.; Wang Z.; Zhang L. Improvement of compatibility and mechanical performances of PLA/PBAT composites with epoxidized soybean oil as compatibilizer. Ind. Eng. Chem. Res. 2020, 59, 21779–21790. 10.1021/acs.iecr.0c04285. [DOI] [Google Scholar]
  24. Li C.; Jiang T.; Wang J.; Wu H.; Guo S.; Zhang X.; Li J.; Shen J.; Chen R.; Xiong Y. In Situ Formation of microfibrillar crystalline superstructure: Achieving high-performance polylactide. ACS Appl. Mater. Interfaces 2017, 9 (31), 25818–25829. 10.1021/acsami.7b06705. [DOI] [PubMed] [Google Scholar]

Articles from ACS Omega are provided here courtesy of American Chemical Society

RESOURCES