改性淀粉/聚乳酸复合材料的制备与性能表征

采用接枝共聚-共混法制备了丙烯酸接枝淀粉/聚乳酸复合材料。通过拉伸强度测试、红外光谱、X射线衍射以及扫描电镜等对共混物进行分析,研究了复合材料的力学性能、结晶性、吸水性以及降解性能。结果表明,相对于未改性的淀粉/聚乳酸材料,经过接枝丙烯酸的淀粉/聚乳酸复合材料拉伸强度提高,结晶度减小,吸水性增加。SEM分析表明,经丙烯酸接枝改性后的淀粉与聚乳酸之间的相容性有较大提高,降解速率变缓。     

纳米二氧化硅/淀粉/聚乳酸三元复合材料力学性能研究

主要是对淀粉进行增韧改性,研究共混改性后对力学性能的影响。首先是制备不同含量的淀粉/聚乳酸共混材料,通过双螺杆挤出机进行挤出、造粒,在通过注塑机将共混材料注塑成样条,对注塑的样条进行力学性能测试,检测其拉伸强度、断裂伸长率。选出性能做好的一组材料,得到最佳的加工工艺。研究结果表明:在淀粉/聚乳酸共混体系中,随着偶联剂与纳米二氧化硅的增加,共混体系出现了曲线形的变化,随着聚乳酸含量的增加断裂伸长率升高再降低,由此得到了偶联剂、纳米二氧化硅的最佳配比,淀粉与甘油含量的最佳配比。由力学性能得到淀粉材料通过改性后的力学性能优于没有改性前,有明显的断裂伸长率,缓解了全淀粉断裂伸长率低的特点。     

生物降解材料制备及降解方法的研究进展

介绍了近年来淀粉基塑料、聚乳酸(PLA)基塑料的制备和降解方法。合适的改性剂、成型和降解方法,可以使淀粉和PLA成为力学性能和降解性能互补的共混体系。PLA/淀粉共混复合材料可作为以石油为原料的塑料的替代品。     

生物可降解高分子材料在食品包装中的应用

简述了能应用于食品包装中几种生物降解高分子材料,分为淀粉基改性的不完全降解高分子材料和可完全降解的聚乳酸和聚羟基脂肪酸酯高分子材料,阐明了降解机理、制备方法和相关的力学以及热力学性能。     

聚乙二醇改性淀粉/聚乳酸薄膜的结构与性质研究

将热塑性淀粉(TPS)与聚乙二醇(PEG)、聚乳酸(PLA)共混后,采用溶剂蒸发法制备出完全生物降解的聚乙二醇改性淀粉/聚乳酸薄膜(SPLA)。研究了SPLA膜的力学性能、耐水性,并对薄膜的结构进行了研究,结果表明聚乳酸可以明显改善淀粉基薄膜的耐水性与力学强度;当w(PLA)≤20%时,共混物各组分间有较好的相容性。SPLA膜的玻璃化转变温度低于淀粉和聚乳酸,XRD显示共混膜中淀粉和聚乳酸的颗粒结晶结构均受到破坏。     

氧化-双重醚化改性淀粉/PVA的复合膜性能及其黏合性的研究

为提高氧化木薯淀粉(OTS)的使用性能,在碱性条件下,以3-氯-2-羟丙基磺酸钠和3-氯-2-羟丙基三甲基氯化铵为醚化剂,与OTS反应制备了氧化-双重醚化改性木薯淀粉(ODES),使用傅里叶变换红外光谱(FTIR)对其进行了表征分析,并研究了共混比对其与聚乙烯醇(PVA)复合材料的薄膜、黏合等性能的影响规律。结果表明,PVA与ODES共混对复合膜的性能具有显著的影响,膜的断裂伸长率分别由PVA与ODES共混质量比0∶100的3. 37%提升到80∶20的134. 4%,断裂强度逐渐降低,表明复合膜具有良好的柔韧性;共混后对棉和聚乳酸粗纱的黏合性能得到了显著提升。     

聚乳酸基生物降解共混物的制备及应用

聚乳酸(PLA)是一种应用前景良好的生物基绿色高分子材料,具有良好的力学性能、生物相容性和生物可降解性,但PLA存在的韧性差、熔体强度低等性能缺陷很大程度上限制了其更广泛应用。通过与其他生物降解聚合物共混改性可以有效改善PLA的这些性能。文章综述了近年来国内外在聚乳酸与其他生物可降解物质共混改性材料的制备以及其在包装袋、生物降解地膜方面的应用,主要包括了聚乳酸/聚碳酸亚丙酯、聚乳酸/聚己二酸-对苯二甲酸丁二酯、聚乳酸/聚羟基脂肪酸酯、聚乳酸/淀粉等其混体系。     

GMA接枝聚乳酸对聚乳酸/淀粉共混物性能的影响

首先制备了聚乳酸与甲基丙烯酸缩水甘油酯(GMA)的接枝共聚物(PLA-g-GMA)和丁二酸酐功能化改性淀粉,并利用红外光谱和核磁共振谱对二者的结构进行了表征。进一步通过熔融共混法制备了聚乳酸(PLA)/改性淀粉/PLA-g-GMA三元共混物,并利用转矩流变仪、扫描电子显微镜、差示扫描量热仪和万能拉力试验机等手段研究了接枝物对共混物的流变性能、形貌结构、热性能以及力学性能的影响。结果表明,PLA-g-GMA的加入促进了淀粉在PLA基体中的分布,淀粉粒径最小在0.5μm以下;同时也抑制了PLA的热降解,提高材料的力学性能,尤其是断裂伸长率,最高达到260%;另外也抑制了PLA的结晶。     

聚乳酸生物复合材料降解性能的研究

研究了使用土埋法降解后,经聚乙二醇400改性前后的聚乳酸/热塑性淀粉复合材料其质量和力学性能的变化,进而分析聚乳酸生物复合材料的降解性能。结果表明:在改性前,样条的降解性能随着热塑性淀粉含量的增加而变得更好;经过PEG400改性后,样条的降解率随着PEG400含量的增加而增加,说明PEG400在一定程度上促进了复合材料的降解。     

淀粉含量对聚乳酸/淀粉共混物力学性能的影响

采用交联的方法对淀粉讲行改性,加入廿油作为增容剂,通过熔融共混的方法制备了聚乳酸/淀粉共混物。通过力学测试和扫描电子显微镜分析,研究了聚乳酸和淀粉在不同质量配比下,共混物力学性能,相容性的变化,研究了淀粉含量对共混物性能的影响。结果表明,随着淀粉含量的增加,共混物力学性能下降,但是随着淀粉交联度的提高,力学性能的下降减缓,交联剂用量为6份时,各项力学性能最佳。SEM分析表明,交联汾粉能够有效改善聚乳酸淀粉共混物的相容性。     

High-performance poly(lactic acid)/starch materials prepared via starch surface modification and its in situ enhancement

High-performance modified poly(lactic acid) (PLA)/starch (ST) blends were prepared by incorporating silane coupling agent. The coupling agent acted as a bridge between PLA and ST components, enhancing their interfacial compatibility during the melt blending. The addition of epoxy-functionalized silane coupling agent improved the interfacial adhesion between PLA and ST phases, as evidenced by the decreased number and spacing of gaps between the ST particles and PLA matrix. The coupling agent also filled the surface crack of the ST particles, improving their dispersion in PLA matrix. The tensile strength of the modified PLA/ST blend increased from 19.6 MPa for the neat PLA/ST blend to 53.4 MPa, exceeding that of neat PLA. The modified blend also showed improved hydrophobicity and thermal stability. This research presented an effective approach to reducing the cost of PLA-based materials and improving the performance of ST-filled PLA materials by enhancing the interfacial adhesion between ST and PLA through surface modification with silane coupling agent. It provided a simple and feasible strategy for the high-performance modification of polyester/ST materials.     

Effect of blending conditions on mechanical,thermal, and rheological properties of plasticized poly(lactic acid)/maleated thermoplastic starch blends

This research work has concerned a study on relationship between structure and properties of maleated thermoplastic starch (MTPS)/plasticized poly(lactic acid) (PLA) blend. The aim of this work is to investigate the effects of blending time, temperature, and blend ratio on mechanical, rheological, and thermal properties of the blend. The MTPS was prepared by mixing the cassava starch with glycerol and maleic anhydride (MA). Chemical structure of the modified starch was characterized by using a FTIR technique, whereas the degree of substitution was determined by using a titration technique. After that, the MTPS prepared by 2.5 pph of MA was further used for blending with triacetin‐plasticized PLA under various conditions. Mechanical, thermal, and rheological properties of the blends were evaluated by using a tensile test, dynamic mechanical thermal analysis, and melt flow index (MFI) test, respectively. It was found that tensile strength and modulus of the MTPS/PLA blend increased with the starch content, blending temperature, and time, at the expense of their toughness and elongation values. The MFI values also increased with the above factors, suggesting some chain scission of the polymers during blending. SEM images of the various blends, however, revealed that the blend became more homogeneous if the temperature was increased. The above effect was discussed in the light of trans‐esterification. Last, it was found that mechanical properties of the PLA/MTPS blend were more superior to those of the normal PLA/TPS blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

苹果酸对聚乳酸/热塑性淀粉共混物结构与性能的影响

将天然淀粉用甘油改性后制得了热塑性淀粉(TPS),再通过熔融共混法制备了聚乳酸(PLA)/TPS共混物。通过SEM、TG、DSC分析和拉伸性能、吸水性能、流变性能测试,研究了苹果酸对TPS和PLA/TPS共混物结构和性能的影响。结果表明:苹果酸能促进淀粉酸解,使TPS分散相尺寸减小,在PLA基体中的分布更加均匀;苹果酸能提高PLA/TPS共混物的拉伸性能;苹果酸对PLA/TPS共混物的玻璃化转变温度、熔融温度及冷结晶温度影响较小;少量的苹果酸可降低PLA/TPS共混物的吸水率。     

Mechanical properties of poly(lactic acid) and wheat starch blends with methylenediphenyl diisocyanate

Poly(lactic acid) (PLA) and wheat starch are biodegradable polymers derived from renewable sources. A previous study showed that thermally blending starch and PLA in the presence of methylenediphenyl diisocyanate (MDI) enhanced the mechanical properties of the blends. In this work, blends of PLA with various levels of wheat starch and MDI were hot mixed at 180°C then hot‐pressure molded at 175°C to form test specimens. The blends were characterized for mechanical properties, fracture microstructure, and water absorption. Pure PLA had a tensile strength of 62.7 MPa and elongation of 6.5%. The blend with 45% wheat starch and 0.5 wt % MDI gave the highest tensile strength of about 68 MPa with about 5.1% elongation. The blend with 20% starch and 0.5 wt % MDI had the lowest tensile strength of about 58 MPa with about 5.6% elongation. Dynamic mechanical analysis showed that storage modulus increased and tan δ decreased as starch level increased, but almost leveled off when starch level reached 45% or higher. Water absorption of the blends increased significantly with starch content. Yet the blend, if water proofed on its surface, has potential for short‐term disposable applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1257–1262, 2002; DOI 10.1002/app.10457     

Compatibility improvement of poly(lactic acid)/thermoplastic starch blown films using acetylated starch

The present research aims to improve the compatibility between relatively hydrophobic poly(lactic acid) (PLA) and hydrophilic thermoplastic starch (TPS) and the properties of the PLA/TPS blends by replacing TPS from native cassava starch (TPSN) with TPS from acetylated starch (TPSA). The effects of the degree of acetylation (DA) of acetylated starch, that is, 0.021, 0.031, and 0.074, on the morphological characteristics and properties of PLA/TPS blend are investigated. The melt blends of PLA and TPS with a weight proportion of PLA:TPS of 50:50 are fabricated and then blown into films. Scanning electron microscopy confirms the dispersion of TPS phase in the PLA matrix. Better dispersion and smaller size of the TPS phase are observed for the PLA/TPSA blend films with low DA of acetylated starch, resulting in improved tensile and barrier properties and increased storage modulus, thermal stability, and T_g, T_cc, and T_m of PLA. Elongation at break of the PLA/TPSA blend increases up to 57%, whereas its water vapor permeability and oxygen permeability decrease about 15%. The obtained PLA/TPSA blend films have the potential to be applied as biodegradable flexible packaging.     

Thermal,morphological, and mechanical properties of biobased and biodegradable blends of poly(lactic acid) and chemically modified thermoplastic starch

In this study, poly(lactic acid) (PLA) was blended with chemically modified thermoplastic starch (CMPS) in a twin‐screw extruder. The characteristic properties of PLA/CMPS blends were investigated by observing the morphology, thermal, and mechanical properties, and biodegradability. Differential scanning calorimetry showed that the PLA/CMPS were thermodynamically immiscible. However, scanning electron microscopy and Fourier transform infrared studies revealed that the interfacial adhesion was improved by the PLA‐g‐starch copolymers that were formed at the interface through a transesterification reaction between PLA and CMPS. The crystallinity of the PLA component in the blend was increased by the addition of the CMPS and was highly affected by the morphology of the blend. The tensile strength and elongation were found to decrease in a linear trend with increasing CMPS content. The biodegradability of the blends increased with increasing CMPS content, while initial time lag decreased. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Mechanical characteristics and thermal behaviours of polylactide blend films: influence of nucleating agent and poly(butylenes adipate-co-terephthalate)

Polylactide (PLA) blend films with poly(butylenes adipate-co-terephthalate) (PBAT) and a nucleating agent were prepared by the melt compounding technique. Thermal stability of the PLA decreased with added nucleating agent; in contrast, the decomposition temperature increased with the presence of PBAT. In addition, the differential scanning calorimetry thermograms demonstrated that the heterogeneous nucleation and cold crystallisation processes of the PLA blend films were accelerated.

The influence of the type and level of the nucleating agent and the presence of PBAT on the tensile properties, impact resistance, thermal stability and non-isothermal crystallisation behaviours of the PLA blend films were investigated. Both the PLA/nucleating agents and the PLA/PBAT/nucleating agent blends showed significant effects from the changes in the nucleation process on their tensile properties, impact toughness and thermal behaviour. Furthermore, the impact energy that the PLA blends absorbed during the entire impact tension test was obviously enhanced by the increased content of the nucleating agent.     

Thermal and mechanical properties of poly(lactic acid)/starch/methylenediphenyl diisocyanate blending with triethyl citrate

Triethyl citrate (TC) was added as a plasticizer to a blend of poly(lactic acid) (PLA) and starch in the presence of methylenediphenyl diisocyanate (MDI). As expected, TC improved the elongation at break and toughness and, at the same time, decreased the tensile strength and modulus. However, TC did not significantly affect the coupling effects of MDI on starch and PLA. The tensile strength of the blend with MDI was much greater than the tensile strength without MDI at the same TC level. The tensile properties of the blend changed dramatically as the TC concentration increased from 5 to 12.5%. At a TC concentration of 7.5%, the blend produced desirable elongation and toughness with fairly good tensile strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2947–2955, 2003     

Scaffolds based on hydroxypropyl starch: Processing,morphology, characterization,and biological behavior

In this study, a novel electrospun hybrid scaffold was developed, which consists of a blend of a modified natural substance, hydroxypropyl starch (HPS) with a synthetic one, poly(ethylene oxide) (PEO). Nanofibers with varying polysaccharide contents were fabricated using water as solvent and the electrospinning process conditions investigated as a function of the weight ratio of the blend. The fibers were characterized through mean diameter and morphology by scanning electron microscopy. Micrographs clearly showed the effect of HPS/PEO weight ratio of the blend on the nanofibers formation. Stability of the fibers was enhanced by coating with hydrophobic poly(methyl methacrylate) (PMMA). In vitro degradation analysis of the coated mats after 1 month of immersion showed porous formation, whereas the fibrous structure was retained. The biological response of the mats against human fibroblasts proved that cells were able to adhere to and proliferate on the fibrous materials. Thus, the feasibility of producing nanofibers of HPS/PEO blends with high proportion of starch and their biocompatibility after coating with PMMA was demonstrated, indicating that these materials have potential to be used as scaffolds in tissue engineering applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci., 2013