{"title":"Poly(lactic acid)/saponite grafted polystyrene composites films: ultraviolet aging, enzymatic degradation behavior, and molecular dynamics simulation analysis","authors":"Zhe Wang, Tengfei Shao, Yikelamu Jilili, Yumiao Ma, Weijun Zhen","doi":"10.1007/s13726-025-01470-6","DOIUrl":null,"url":null,"abstract":"<div><p>The aim of this study was to compare the UV aging and enzymatic degradation behavior of pure PLA film (PLA0) and modified saponite composite (PLA3) film at 0.5% (by wt). Polarized microscopy tests showed that the addition of a modified saponite (SAP-<i>g</i>-PS) significantly increased the crystallization rate of the PLA films. The growth rate of spherical crystals of PLA3 composites film was 1.52 μm/min, which was much lower than that of PLA0 films. The elongation-at-break and tensile strength of the PLA3 composite films decreased from 94.03% and 33.24 MPa to 50.59% and 20.38 MPa during UV aging. However, the elongation-at-break and tensile strength of PLA0 film was decreased to 12.53% and 25.12 MPa. The carbonyl index results showed that PLA0 film was reduced from 1.86 to 1.51, and PLA3 was reduced from 2.56 to 2.29, which proved that SAP-<i>g</i>-PS effectively alleviated the UV aging of PLA films. The enzymatic degradation experiments showed that the mass loss results of PLA0 film reached 40.82% at the temperature of 50℃ and the degradation time of 10 h, while the mass loss rate of PLA3 was 35.40% after degradation by proteinase K. Thermogravimetric analysis showed that even after 10 h of enzymatic degradation, the <i>T</i><sub>5%</sub>, <i>T</i><sub>50%</sub>, and <i>T</i><sub>end</sub> of PLA3 film were still 0.48 °C, 6.08 °C, and 8.62 °C higher than those of PLA0 film, which further indicated that SAP-<i>g</i>-PS was beneficial to the inhibition of the enzymatic degradation process of PLA films. The FTIR analysis results showed that the C–O–C and C=O intensities of PLA0 were lower than those of PLA3, which proved that the enzymatic degradation of PLA3 was lower than that of PLA0. Finally, molecular dynamics simulations revealed that the interaction force of the PLA-based film was increased from 355.89 to −72.32 kcal/mol, and the MSD curves showed that there was a strong force between SAP-<i>g</i>-PS and PLA, and also indicated that the mobility was lower.</p><h3>Graphical Abstract</h3>\n<div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":601,"journal":{"name":"Iranian Polymer Journal","volume":"34 10","pages":"1677 - 1691"},"PeriodicalIF":2.8000,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Iranian Polymer Journal","FirstCategoryId":"92","ListUrlMain":"https://link.springer.com/article/10.1007/s13726-025-01470-6","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"POLYMER SCIENCE","Score":null,"Total":0}
引用次数: 0
Abstract
The aim of this study was to compare the UV aging and enzymatic degradation behavior of pure PLA film (PLA0) and modified saponite composite (PLA3) film at 0.5% (by wt). Polarized microscopy tests showed that the addition of a modified saponite (SAP-g-PS) significantly increased the crystallization rate of the PLA films. The growth rate of spherical crystals of PLA3 composites film was 1.52 μm/min, which was much lower than that of PLA0 films. The elongation-at-break and tensile strength of the PLA3 composite films decreased from 94.03% and 33.24 MPa to 50.59% and 20.38 MPa during UV aging. However, the elongation-at-break and tensile strength of PLA0 film was decreased to 12.53% and 25.12 MPa. The carbonyl index results showed that PLA0 film was reduced from 1.86 to 1.51, and PLA3 was reduced from 2.56 to 2.29, which proved that SAP-g-PS effectively alleviated the UV aging of PLA films. The enzymatic degradation experiments showed that the mass loss results of PLA0 film reached 40.82% at the temperature of 50℃ and the degradation time of 10 h, while the mass loss rate of PLA3 was 35.40% after degradation by proteinase K. Thermogravimetric analysis showed that even after 10 h of enzymatic degradation, the T5%, T50%, and Tend of PLA3 film were still 0.48 °C, 6.08 °C, and 8.62 °C higher than those of PLA0 film, which further indicated that SAP-g-PS was beneficial to the inhibition of the enzymatic degradation process of PLA films. The FTIR analysis results showed that the C–O–C and C=O intensities of PLA0 were lower than those of PLA3, which proved that the enzymatic degradation of PLA3 was lower than that of PLA0. Finally, molecular dynamics simulations revealed that the interaction force of the PLA-based film was increased from 355.89 to −72.32 kcal/mol, and the MSD curves showed that there was a strong force between SAP-g-PS and PLA, and also indicated that the mobility was lower.
期刊介绍：
Iranian Polymer Journal, a monthly peer-reviewed international journal, provides a continuous forum for the dissemination of the original research and latest advances made in science and technology of polymers, covering diverse areas of polymer synthesis, characterization, polymer physics, rubber, plastics and composites, processing and engineering, biopolymers, drug delivery systems and natural polymers to meet specific applications. Also contributions from nano-related fields are regarded especially important for its versatility in modern scientific development.
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