High⁃temperature Stretching Induced Multi⁃structural Deformation of PLA⁃based Composites

doi:10.19491/j.issn.1001-9278.2021.02.013

Abstract

Abstract:

The PLA/coiled carbon nanotube （HCNT） composites were prepared through melt blending with different mass fractions of PBAT. A series of rectangular samples based on these composites were prepared through hot pressing under different pressures and packing time by using an automatic vacuum hot?pressing machine. Their glass transition temperature and multi?structural deformation at a constant stretching rate were investigated by DSC， Linkam stage and wide?angle X?ray diffraction measurement. The results indicated that the molecular orientation and the rate of orientation evolution increased with an increase in macro?deformation. For two samples with lower and higher contents of PBAT， the rate of orientation evolution increased with the increase of packing time and pressure. However， in the cases of other samples， the dependence of the rate of orientation evolution on pressure and time was not evident. This phenomenon implied there was a synergetic effect on the molecular orientation from the dispersed PBAT， free volume and HCNT. A three?element viscoelastic model was used to analyze the experimental data. The fitting results indicated that the sample with a lower content of PBAT was more sensitive to packing time， but the sample with a higher content of PBAT was more sensitive to pressure.

Key words: poly（lactic acid）, helical carbon nanotube, molecular orientation, viscoelastic model, multi?structural deformation

CLC Number:

TQ321

LUO Fei, HAO Lingao, WANG Tengfei, LIU Hongpeng, DANG Xudan, WANG Yaming, LIU Chuntai, SONG Yan. High⁃temperature Stretching Induced Multi⁃structural Deformation of PLA⁃based Composites[J]. China Plastics, 2021, 35(2): 77-83.

Figures/Tables 10

样品编号	PBAT含量/%	保压压力/MPa	保压时间/min
1^#	10	1.11	3
2^#	10	1.11	5
3^#	10	1.11	7
10^#	10	1.66	7
11^#	10	2.22	7
4^#	20	1.11	3
5^#	20	1.11	5
6^#	20	1.11	7
12^#	20	1.66	7
13^#	20	2.22	7
7^#	30	1.11	3
8^#	30	1.11	5
9^#	30	1.11	7
14^#	30	1.66	7
15^#	30	2.22	7

Tab.1. The formula and hot press conditions of the samples

Fig.1. Assumption about the threshold structure of free volume and molecular orientation

Fig.2. DSC curves of the materials

Fig.3. The 2D?WAXD patterns of sample 15 during uni?axial drawing at a constant rate of 10 μm/s（the drawing direction is vertical）

Fig.4. The intensity?azimuthal angle curves of sample 15 during uni?axial drawing at a constant rate of 10 μm/s

Fig.5. The evolution of molecular orientation of different composite samples with time

Fig.6. The typical macro and micro deformation of 1# composites during stretch

Fig.7. Viscoelastic model for the tensile behavior

Fig.8. Fitting of the time dependent orientation of sample 1 using the tensile model

Fig.9. The slip viscosity of the composite samples with packing time and pressures

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