纳米纤维素/聚乳酸全绿色纳米复合材料的制备及性能

doi:10.7503/cjcu20170513

摘要/Abstract

摘要：

制备得到纳米纤维素(NC), 其为横向尺寸20~40 nm、长度400~2000 nm的纳米丝. 对NC进行醋酸酯化疏水改性得到醋酸酯化纳米纤维素(ANC). 分别将NC和ANC与聚乳酸(PLA)复合制备纳米复合材料, 研究了NC添加量、疏水改性及与PLA的复合方式对PLA力学性能和结晶性能的影响规律. 结果表明, 采用溶液浇铸法制备纳米复合膜时, ANC在PLA基体中的分散性优于NC, 但是对于复合膜拉伸性能的改善不明显. DSC等温结晶结果表明, ANC可以提高PLA的结晶度和结晶速率; 采用熔融复合法制备的NC/PLA纳米复合材料, 不仅保持了PLA的高强度、高模量和较高的热稳定性, 而且显著改善了其韧性, 当NC添加量为3.5%(质量分数)时, 断裂伸长率比纯PLA提高了12.1倍.

关键词: 纳米纤维素, 聚乳酸, 熔融复合法, 纳米复合材料

Abstract:

A novel approach for mass production of filamentous nanocellulose(NC) with a transverse size of 20—40 nm and a length of 400—2000 nm was developed. The NC was modified with acetic anhydride, and obtained hydrophobic acetylated nanocellulose(ANC). NC and ANC were respectively blended with polylactide(PLA) to prepare nanocomposites by a solution-casting process. The effect of filler content, chemical modification and blending methods on the mechanical and crystallization properties of nanocomposites were investigated. The results showed that ANC displayed better dispersibility than NC in PLA matrix. However, the improvement for mechanical properties of nanocomposites was not obvious. Moreover, differential scanning calorimetry(DSC) isothermal crystallization test showed that ANC increased crystallization rate and crystallinity degree of PLA simultaneously. The NC/PLA nanocomposites prepared by melt compounding not only maintained high modulus, high yield strength, but also exhibited better thermal stability and remarkably improved toughness. For instance, when the addition of NC was 3.5%(mass fraction), the elongation at break of the nanocomposites increased by 12.1 folds in comparison with that of neat PLA matrix.

Key words: Nanocellulose, Polylactide, Melt compounding, Nanocomposites

中图分类号:

O636.9

刘星, 王文俊, 邵自强, 李磊. 纳米纤维素/聚乳酸全绿色纳米复合材料的制备及性能[J]. 高等学校化学学报, 2018, 39(2): 373-381.

LIU Xing, WANG Wenjun, SHAO Ziqiang, LI Lei. Preparation and Characterization of Nanocellulose/Polylactide Fully Green Nanocomposites[J]. Chemical Journal of Chinese Universities, 2018, 39(2): 373-381.

图/表 18

Fig.1 FTIR spectra of M30(a), NC(b) and ANC(c)

Fig.2 Dispersibility of NC and ANCa. NC in water; b. NC in acetone; c. ANC in acetone.

Fig.3 TEM images of NC(A) and ANC(B)

Fig.4 XRD patterns of M30(a), NC(b) and ANC(c)

Fig.5 Photographs of NC/PLA(A) and ANC/PLA(B) films(A) a.PLA-a; b. PLA-NC1.0; c. PLA-NC3.5.(B) a. PLA-b; b. PLA-ANC1.0; c. PLA-ANC3.5.

Fig.6 Typical stress-strain curves of NC/PLA(A) and ANC/PLA(B)(A) a. PLA-a; b. PLA-NC1.0; c. PLA-NC3.5. (B) a. PLA-b; b. PLA-ANC1.0; c. PLA-ANC3.5.

Table 1 Mechanical properties of the neat PLA and nanocomposite films

Sample	σ_y/MPa	ε_b(%)	Sample	σ_y/MPa)	ε_b(%)
PLA-a	50.1±0.9	2.7±0.2	PLA-b	36.5 ±0.3	75.0±0.9
PLA-NC1.0	46.2±0.7	3.2±0.5	PLA-ANC1.0	38.0±0.5	40.4±0.4
PLA-NC3.5	39.6±1.3	6.1±0.5	PLA-ANC3.5	43.1±0.8	37.1±0.3

Fig.7 DSC curves of neat PLA and NC/PLA nanocomposite films(A) The first heating process; (B) the second heating process. a. PLA-a; b. PLA-NC1.0; c. PLA-NC3.5.

Table 2 Thermal properties of the neat PLA and NC/PLA nanocomposites

Sample	T_g/℃	T_m/℃	X_c(%)
PLA-a	50.2	152.3	33.4
PLA-NC1.0	43.4	153.4	32.3
PLA-NC3.5	42.0	153.3	29.3

Fig.8 DSC isothermal curves of neat PLA and ANC/PLA nanocomposite films(A) The first heating process; (B) the second heating process(after 1 h in 110 ℃); (C) heat preservation process in 110 ℃.a. PLA-b; b. PLA-ANC1.0; c. PLA-ANC3.5.

Table 3 Thermal properties of ANC/PLA nanocomposites

Sample	T_g/℃	T_m/℃	T_c/℃	X_c(%)
Sample	T_g/℃	T_m/℃	T_c/℃	Before insulation treatment	After nsulation treatment
PLA-b	41.8	149.5	114.3	13.0	37.8
PLA-ANC1.0	45.1	151.5	118.3	16.3	38.3
PLA-ANC3.5	45.1	152.0	113.8	21.2	39.4

Fig.9 Dynamic mechanical properties of NC/PLA nanocomposites(A) Storage modulus vs. temperature; (B) tanδ vs. temperature. a. PLA-a; b. PLA-NC1.0; c. PLA-NC3.5.

Fig.10 Typical stress-strain curves of NC/PLA-z nanocomposites a. PLA-z; b. PLA-NC1.0-z; c. PLA-NC3.5-z.

Table 4 Mechanical properties of NC/PLA-z nanocomposites

Sample	σ_y/MPa	ε_b(%)
PLA-z	64.2±1.2	7.3±0.2
PLA-NC1.0-z	52.0±0.7	70.8±0.4
PLA-NC3.5-z	57.0±0.2	95.4±1.0

Fig.11 SEM images of cross-section NC/PLA-z nanocomposites (A) PLA-z; (B) PLA-NC1.0-z; (C) PLA-NC3.5-z.

Fig.12 DSC curves of NC/PLA-z nanocompositesa. PLA-z; b. PLA-NC1.0-z; c. PLA-NC3.5-z.

Table 5 Thermal properties of NC/PLA-z nanocomposites

Sample	T_g/℃	T_c/℃	T_m/℃	X_c(%)
PLA-z	61.5	128.7	155.6	42.3
PLA-NC1.0-z	56.3	114.2	156.6	38.3
PLA-NC3.5-z	53.2	109.8	156.8	38.2

Fig.13 TG curves of neat PLA and PLA nanocompositesa. PLA-z; b. PLA-ANC1.0-z; c. PLA-ANC3.5-z;d. PLA-NC3.5-z; e. PLA-NC1.0-z.

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