In situ compatibilization of the toughening mechanism and properties in PPCU/PLA blends via DCP
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摘要: 聚乳酸(PLA)的脆性严重限制了其应用,使用弹性体共混增韧PLA是一种可行的策略,然而共混物两相相容性较差的问题仍亟待解决。本文采用过氧化二异苯丙(DCP)为反应增容剂与PLA、聚碳酸亚丙酯-热塑性聚氨酯弹性体(PPCU)熔融共混制备了PPCU/PLA共混物,研究了DCP添加量对共混物相形貌、流变性能、力学性能等的影响。结果表明:DCP引发了PLA与PPCU分子链间的支化交联反应,随着DCP添加量增加,PPCU/PLA共混物的复数黏度以及储能模量也随之增大,弹性行为逐渐增强,Cole-Cole图表明当DCP添加量大于0.3wt%后,共混物具有较高的同质性;随着DCP添加量增加,共混物相界面逐渐变得模糊,分散相尺寸明显减小,共混物相形貌得到改善。DCP的加入可显著提高共混物的断裂伸长率,添加量为0.2wt%的共混物断裂伸长率达到最大值224.37%,是未添加DCP共混物断裂伸长率的10.68倍;PPCU/PLA共混物的缺口冲击强度随着DCP添加量的增加而增大,添加量为0.5wt%的共混物其冲击强度达到了7.91 kJ/m2,是未添加DCP的共混物的2.94倍,PPCU/PLA共混物力学性能的提高主要归因于其两相相容性的改善。
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关键词:
- 聚乳酸 /
- 聚碳酸亚丙酯-热塑性聚氨酯弹性体 /
- 相容性 /
- 流变性能 /
- 力学性能
Abstract: The intrinsic brittleness of polylactic acid (PLA) greatly restricts broader application in multiple fields, while the blending with elastomer is considered a feasible strategy to improve the ductility of PLA materials. Unfortunately, the poor compatibility of two phases needs to be solved. In this work, using diisophenyl peroxide (DCP) as reactive compatibilizer, PLA and poly(propylene carbonate) polyurethane (PPCU) were melt blended to prepare PPCU/PLA blends. The effects of DCP content on the phase morphology, rheological properties and mechanical properties of PPCU/PLA blends were investigated. The results demonstrated that DCP initiated the branched crosslinking reaction between PLA and PPCU molecular chains. With the increase of DCP content, the complex viscosity and storage modulus of PPCU/PLA blends also enhanced, indicating the reinforcement of elastic behavior, and the Cole-Cole plot indicates that when the DCP addition exceeds 0.3wt%, the blend exhibits high homogeneity. As the DCP content increases, the phase interface of the blend gradually becomes blurred, the dispersed phase size significantly decreases, and the phase morphology of the blend is improved. Meanwhile, the addition of DCP significantly enhance the elongation at break of the blends. The elongation at break of 0.2wt% DCP in PPCU/PLA increased to 224.37%, which was 10.68 times as high as that of the blends without adding DCP. Additionally, notched impact strength of PPCU/PLA blends increases with DCP addition. When 0.5wt% DCP was added into the blends, the impact strength of the blends is increased to 7.91 kJ/m², which is more than 2.94 times than the pure PPCU/PLA blends. The proposed modification strategy may be responsible for the enhancement of mechanical properties of PPCU/PLA blends, exhibiting the improvement of compatibility between the two phases. -
图 5 PPCU/PLA共混物脆断面SEM图:(a) PPCU/PLA; (b) PPCU/PLA-0.1 D; (c) PPCU/PLA-0.2 D; (d) PPCU/PLA-0.3 D; (e) PPCU/PLA-0.4 D;(f) PPCU/PLA-0.5 D
Figure 5. SEM micrographs showing cvro-fractured surface morphology of PPCU/PLA blends: (a) PPCU/PLA; (b) PPCU/PLA-0.1 D; (c) PPCU/PLA-0.2 D; (d) PPCU/PLA-0.4 D; (e) PPCU/PLA-0.4 D; (f) PPCU/PLA-0.5 D
图 6 刻蚀后的PPCU/PLA共混物脆断面SEM图:(a') PPCU/PLA;(b') PPCU/PLA-0.1 D; (c') PPCU/PLA-0.2 D; (d') PPCU/PLA-0.3 D;(e') PPCU/PLA-0.4 D; (f ') PPCU/PLA-0.5 D
Figure 6. SEM micrographs showing cvro-fractured surface morphology of PPCU/PLA blends after etching: (a') PPCU/PLA; (b') PPCU/PLA-0.1 D; (c') PPCU/PLA-0.2 D; (d') PPCU/PLA-0.4 D; (e') PPCU/PLA-0.4 D; (f ') PPCU/PLA-0.5 D
图 11 PPCU/PLA共混物冲击断面SEM图:(a) PPCU/PLA;(b) PPCU/PLA-0.1 D;(c) PPCU/PLA-0.2 D;(d) PPCU/PLA-0.3 D;(e) PPCU/PLA-0.4 D;(f) PPCU/PLA-0.5 D
Figure 11. SEM micrographs of impact-fractured surfaces of PPCU/PLA blends: (a) PPCU/PLA;(b) PPCU/PLA-0.1 D; (c) PPCU/PLA-0.2 D;(d) PPCU/PLA-0.3 D;(e) PPCU/PLA-0.4 D;(f) PPCU/PLA-0.5 D
表 1 PPCU/PLA共混物原料配比
Table 1. Composition of PLA/PPCU blends
Sample PLA/wt% PPCU/wt% DCP/wt% PLA 100 0 0 PPCU/PLA 75 25 0 PPCU/PLA-0.1 D 75 25 0.1 PPCU/PLA-0.2 D 75 25 0.2 PPCU/PLA-0.3 D 75 25 0.3 PPCU/PLA-0.4 D 75 25 0.4 PPCU/PLA-0.5 D 75 25 0.5 Notes:PLA—poly(lactic acid); PPCU—poly(propylene cabonate) polyurethane; The xD in the table represents the amount of diisopropyl peroxide (DCP) added, for example 0.1 D means the amount of DCP added to the blend is 0.1 wt%. 表 2 刻蚀后脆断PPCU/PLA共混物中PPCU相以及空穴尺寸
Table 2. PPCU phase and hole size in cvro-fractured PPCU/PLA blends after etching
Sample PPCU/PLA PPCU/PLA-0.1 D PPCU/PLA-0.2 D PPCU/PLA-0.3 D PPCU/PLA-0.4 D PPCU/PLA-0.5 D PPCU particle size/nm — 178±72 161±32 175±37 111±19 106±20 Hole diameter/nm 525±159 463±69 414±140 387±114 352±154 273±55 表 3 PPCU/PLA共混物热失重参数
Table 3. Thermal weight loss parameters of PPCU/PLA blends
Sample T5%/℃ T50%/℃ Tmax/℃ PLA 342.3 366.7 369.8 PPCU 269.3 325.6 339.3 PPCU/PLA 285.4 323.5 325.1 PPCU/PLA-0.1 D 294.3 324.4 325.9 PPCU/PLA-0.2 D 305.0 335.5 330.1 PPCU/PLA-0.3 D 293.0 323.5 325.4 PPCU/PLA-0.4 D 294.7 332.3 325.7 PPCU/PLA-0.5 D 284.9 320.3 319.2 Notes:T5%, T50% and Tmax are the temperatures at which the weight loss of the sample is 5%, 50% and the weight loss rate is the highest, respectively. 表 4 PPCU/PLA共混物力学性能
Table 4. Mechanical properties of PPCU/PLA blends
Sample Tensile strength /MPa Elongation at break /% Notched impact strength
/(kJ·m2)PLA 68.61±0.74 7.06±0.63 2.25±0.18 PPCU/PLA 52.36±2.99 21.00±6.51 2.69±0.62 PPCU/PLA-0.1 D 44.84±1.32 122.12±13.53 3.20±0.60 PPCU/PLA-0.2 D 42.34±0.67 224.37±44.98 5.53±1.45 PPCU/PLA-0.3 D 43.19±1.63 173.80±20.37 6.33±0.94 PPCU/PLA-0.4 D 44.78±0.70 187.50±22.44 6.05±1.19 PPCU/PLA-0.5 D 43.78±0.57 22.69±3.82 7.91±2.19 -
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