含柔性链段聚右旋乳酸嵌段共聚物对聚左旋乳酸拉伸行为的影响
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摘要
采用聚右旋乳酸(PDLA)与聚乙二醇(PEG)的三嵌段共聚物(PDLA-b-PEG-b-PDLA)对聚左旋乳酸(PLLA)进行改性,系统研究熔融共混法制备的PLLA/PDLA-b-PEG-b-PDLA共混物的热性能和不同温度下的拉伸行为,并通过原位X射线散射(WAXS)技术探索不同含量的PDLA-b-PEG-b-PDLA对PLLA在拉伸过程中结晶行为的影响.结果表明,加入PDLA-b-PEG-b-PDLA对PLLA的热稳定性影响较小;PLLA/PDLA-b-PEG-b-PDLA共混物中由于立构晶的存在,能有效提高PLLA的α晶的结晶速率;室温(30°C)拉伸时,样品均呈现脆性断裂;拉伸温度提高至50°C,纯PLLA和PLLA/PDLA-b-PEG-b-PDLA(95/5)的共混物仍然呈现脆性断裂,但是随着PDLA-b-PEG-b-PDLA含量的增加,PLLA发生屈服,断裂伸长率由纯PLLA的10%左右提高至200%以上;80°C拉伸时,PDLA-b-PEG-b-PDLA的加入显著提高了PLLA在拉伸过程中的结晶速率,出现α晶的应变从纯PLLA的400%降低至50%以下,立构晶含量在拉伸过程中基本保持不变.上述结果显示含柔性链段的PDLA的嵌段共聚物可有效提高PLLA的结晶速率和延展性,拓宽PLLA的应用范围.
Poly(L-lactic acid)(PLLA) is a biodegradable and biocompatible material used in many fields, such as packaging, textile and drug delivery. The low crystallization rate and poor toughness are two major drawbacks for its processing and high-performance applications. In this study, poly(D-lactic acid)-polyethylene glycol(PEG)-poly(D-lactic acid) triblock copolymers(PDLA-b-PEG-b-PDLA) were used to modify the structure and property of PLLA. PLLA/PDLA-b-PEG-b-PDLA blends were prepared by melt blending, and their thermal and mechanical properties were systematically studied by thermal gravimetric analysis(TGA), differential scanning calorimetry(DSC) and temperature-variable tensile tests. To understand the structure evolution, the crystallization behavior of the blends during stretching was investigated by in situ wide angle X-ray scattering(WAXS). The results showed that the addition of PDLA-b-PEG-b-PDLA had no detrimental effect on the thermal stability of PLLA. By virtue of the nucleation capacity of the stereo-complex crystals formed between PLLA and PDLA chains, the crystallization rate of the α crystals of the PLLA matrix was improved remarkably compared with that of pure PLLA. When stretched at room temperature(30 °C), the modified PLLA samples displayed brittle fracture. With the stretching temperature increased to 50 °C, both PLLA and PLLA/PDLA-b-PEG-b-PDLA(95/5) exhibited brittle fracture. However, the blends showed clear yielding and ductile deformation with an elongation at break as high as 200% when the content of the triblock copolymer was above 5%. With the stretching temperature further increased to 80 °C, the crystallization of α crystals in the PLLA/PDLA-b-PEG-b-PDLA blends was significantly enhanced during the stretching process. The critical strain, where α crystals appeared in the blend, decreased from400% in pure PLLA to less than 50%. The stereo-complex crystallites had no change during the stretching process. The above results indicated that the triblock copolymer consisting of PDLA and PEG chains was an excellent candidate as PLLA modifier with dual effects of promoting crystallization and improving toughness.
Poly(L-lactic acid)(PLLA) is a biodegradable and biocompatible material used in many fields, such as packaging, textile and drug delivery. The low crystallization rate and poor toughness are two major drawbacks for its processing and high-performance applications. In this study, poly(D-lactic acid)-polyethylene glycol(PEG)-poly(D-lactic acid) triblock copolymers(PDLA-b-PEG-b-PDLA) were used to modify the structure and property of PLLA. PLLA/PDLA-b-PEG-b-PDLA blends were prepared by melt blending, and their thermal and mechanical properties were systematically studied by thermal gravimetric analysis(TGA), differential scanning calorimetry(DSC) and temperature-variable tensile tests. To understand the structure evolution, the crystallization behavior of the blends during stretching was investigated by in situ wide angle X-ray scattering(WAXS). The results showed that the addition of PDLA-b-PEG-b-PDLA had no detrimental effect on the thermal stability of PLLA. By virtue of the nucleation capacity of the stereo-complex crystals formed between PLLA and PDLA chains, the crystallization rate of the α crystals of the PLLA matrix was improved remarkably compared with that of pure PLLA. When stretched at room temperature(30 °C), the modified PLLA samples displayed brittle fracture. With the stretching temperature increased to 50 °C, both PLLA and PLLA/PDLA-b-PEG-b-PDLA(95/5) exhibited brittle fracture. However, the blends showed clear yielding and ductile deformation with an elongation at break as high as 200% when the content of the triblock copolymer was above 5%. With the stretching temperature further increased to 80 °C, the crystallization of α crystals in the PLLA/PDLA-b-PEG-b-PDLA blends was significantly enhanced during the stretching process. The critical strain, where α crystals appeared in the blend, decreased from400% in pure PLLA to less than 50%. The stereo-complex crystallites had no change during the stretching process. The above results indicated that the triblock copolymer consisting of PDLA and PEG chains was an excellent candidate as PLLA modifier with dual effects of promoting crystallization and improving toughness.
引文
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5 Weber C J,Haugaard V,Festersen R.Food Addit Contam,2001,19:172-177
6 Zhang Xiuqin(张秀芹),Xiong Zujiang(熊祖江),Liu Guoming(刘国明).Acta Polymerica Sinica(高分子学报),2014,(8):1048-1055
7 Rathi S,Chen X L,Coghlin E B.Polymer,2011,52:4184-4188
8 Han L L,Yu C T,Zhou J,Shan G R,Bao Y Z.Polymer,2016,103:376-386
9 Zhang X Q,Konrad Schneider,Liu G M.Polymer,2011,52:4141-4149
10 Zhan X J,Shi X T,Zhang G C.Polymer,2017,9(3):107
11 Stoclet G.Polymer,2016,(99):231-239
12 Shao J,Xiang S,Bian X C,Sun J R,Li G,Chen X S.Ind Eng Chem Res,2015,54(7):2246-2253
13 Tsuji H,Takai H,Fukada N,Takikawa H.Macromol Mater Eng,2006,291(4):325-335
14 Anderson K S,Hillmyer M A.Polymer,2006,47(6):2030-2035
15 Sawai D,Tsugane Y,Tamada M.J Polym Sci,Part B:Polym Phys,2007,45:2632-3629
16 Yin Y A,Song Y,Xiong Z J,Zhang X Q.J Appl Polym Sci,2016,133(10):43015
17 Wei X F,Bao R Y,Cao Z Q,Yang W,Xie B H,Yang M B.Macromolecules,2014,47:1439-1448
18Zhang J M,Wang S W,Zhao D Z.J Appl Polym Sci,2017,134(43):45193
19Chen Z M,Liu Y L.Mater Lett,2015,155:94-96
20Song Y,Wang D J.ACS Sustain Chem Eng,2015,3:1492-1500
2 Xiong Zujiang(熊祖江),Zhang Xiuqin(张秀芹),Liu Guoming(刘国明).Chem J Chinese U(高等学校化学学报),2013,(5):1288-1294
3 Rathi S R,Ng D,Coughlin E B.Macromol Chem Phys,2014,215(4):320-326
4 Saeidlou S,Huneault M A,Li H.Prog Polym Sci,2012,37(2):1657-1677
5 Weber C J,Haugaard V,Festersen R.Food Addit Contam,2001,19:172-177
6 Zhang Xiuqin(张秀芹),Xiong Zujiang(熊祖江),Liu Guoming(刘国明).Acta Polymerica Sinica(高分子学报),2014,(8):1048-1055
7 Rathi S,Chen X L,Coghlin E B.Polymer,2011,52:4184-4188
8 Han L L,Yu C T,Zhou J,Shan G R,Bao Y Z.Polymer,2016,103:376-386
9 Zhang X Q,Konrad Schneider,Liu G M.Polymer,2011,52:4141-4149
10 Zhan X J,Shi X T,Zhang G C.Polymer,2017,9(3):107
11 Stoclet G.Polymer,2016,(99):231-239
12 Shao J,Xiang S,Bian X C,Sun J R,Li G,Chen X S.Ind Eng Chem Res,2015,54(7):2246-2253
13 Tsuji H,Takai H,Fukada N,Takikawa H.Macromol Mater Eng,2006,291(4):325-335
14 Anderson K S,Hillmyer M A.Polymer,2006,47(6):2030-2035
15 Sawai D,Tsugane Y,Tamada M.J Polym Sci,Part B:Polym Phys,2007,45:2632-3629
16 Yin Y A,Song Y,Xiong Z J,Zhang X Q.J Appl Polym Sci,2016,133(10):43015
17 Wei X F,Bao R Y,Cao Z Q,Yang W,Xie B H,Yang M B.Macromolecules,2014,47:1439-1448
18Zhang J M,Wang S W,Zhao D Z.J Appl Polym Sci,2017,134(43):45193
19Chen Z M,Liu Y L.Mater Lett,2015,155:94-96
20Song Y,Wang D J.ACS Sustain Chem Eng,2015,3:1492-1500
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