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Microstructure and Cold Deformation Shape Memory Effect of Poly(L-Lactide) and Its Copolymers
Author: TangWen
Tutor: CaiWei
School: Harbin Institute of Technology
Course: Materials Physics and Chemistry
Keywords: Polylactic acid A random copolymer Block copolymer The cold deformed shape memory effect
CLC: O631.2
Type: Master's thesis
Year: 2007
Downloads: 107
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Abstract
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Stannous octoate as initiator, the use of random copolymers and block copolymers of ring-opening polymerization to synthesize a series of poly lactic acid (PLLA) / poly ε-caprolactone (PCL), and the solvent evaporation method and the molten extrusion method polylactic acid copolymer sheet and wire. Analysis of the rheological characteristics, differential scanning calorimetry analysis, Raman spectroscopy, X-ray diffraction analysis, the spinnability of the tensile test and bending test of copolymer, microstructure, mechanical properties as well as the cold deformation of the shape memory effect, and explores the intrinsic link between the change of the polymer sheet and wire form structure and cold deformation shape memory effect. The study found that the PCLA random copolymer sheet yield a large strain occurs in the glassy stretching and having a high elastic deformation characteristics, showing good cold-deformed shape memory effect, wherein the crystalline PLLA phase as stationary phase PCLA Nil stereotypes as a softening phase. Random copolymer composition, the amount of deformation as well as the number of cycles of cold deformation of the shape memory effect have a significant impact, the shape retention rate of the copolymer is gradually decreased with the increase of the content of epsilon-CL, the shape recovery force is increased Save small, the maximum value of 9.3MPa, the 2 times of the restoring force generated by the thermal deformation of the shape memory effect; shape retention rate is gradually increased with the increase in the amount of deformation, the shape recovery rate is gradually reduced, the shape recovery force increases first reduce the restoring force reaches its maximum value, the shape becomes 100% shape recovery; With the increase of the cycle, the first decreases, and then stabilized. The annealing time for the cold deformation of shape retention rate of the random copolymer. As the annealing time is extended, the PLLA crystalline phase in the polymer content gradually increased shape retention rate of the polymer increases, the shape recovery rate decreased slightly. PCLA block copolymer sheet having a good cold deformation of the shape memory effect, wherein PLLA crystalline phase as the stationary phase, the the PCL chain segment as a softening phase. With PCL content increases, the shape-retaining rate decreases, the shape recovery when PCL content of 20%, the maximum rate reached 100%, the shape recovery force decreases first and then increases, the highest shape recovery force of 12.5MPa. Rheological properties of the the PCLA random copolymer having good spinnability, using the the PLLA crystalline phase exists only in the wire to melt extrusion method was its degree of crystallinity is higher than the sheet. With the increase of the content of epsilon-CL, the tensile strength of the wire material and shape retention rate is reduced, and the shape recovery ratio increases; shape restoring force gradually increases with the increase in the amount of deformation, but increases gradually amplitude becomes small. The wire the cold deformed shape retention and shape recovery ratio is higher than the sheet, but the restoring force is less than the sheet.
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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers > The physical properties of polymers
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