| As a kind smart material with stimuli-responsive property,triple-shape memory polyneric materials(TSMP)can realize more complex recovery motions,providing fundamental strategies,methods and insights into multi-shape memory effects,bridging the gap from traditional dual-shape memory effect(DSME)to multi-shape memory effect(MSME).This thesis was intended to have different semi-crystalline resins with biodegradability blended and electron-beam(E-B)irradiated.The two Tc/Tm switches related to the shape fixity and recovery were treated as the basie mechanisms for this kind of TSMP.And the large deformability,well-separated shape transitions and high shape stability was our target.This thesis was therefore arranged as follows:1.The semicrystalline blends poly(butylene succinate)/?-polycaprolactone(PBS/PCL)was given as an example,influence of E-B irradiation on the mechanical properties of the immiscible semi-crystalline blends were investigated.It was verified that crosslinking induced by E-B irradiation was typical of in situ crosslinking,cold crosslinking and post crosslinking features,and it was a kind of free radical crosslinking induced by the physical maimer in the quasi-liquid system.So the E-B irradiation can only improve the miscibility of the phase separated blends by certain degree.And the large deformability for TSME can't be realized in this kind of blends via E-B irradiation.Combined with the knowledge from material mechanics and micromechanics,to get excellent TSME via E-B irradiation of polymer blends,measures should be adopted to reduce the mechanical mismatch of the components or to improve the thickness,density and strength of the interfacial tie molecule.2.Based on the poly(butylene succinate adipate)/polyethylene oxide(PBSA/PEO)and its thermal miscibility,the dependence of E-B irradiation effect on the molecular structure was particularly emphasized.Though the density and thickness of interfacial tie molecule was enough due to the thermal miscibility of this system,the mechanical property of irradiated sample was deteriorated by radiolysis of PEO.The large deformability for excellent TSME was therefore can't be realized.3.Radiation effect on poly(butylene adipate-co-terephthalate)/caprolactone(PBAT/PCL)was studied in view of the structural dependence of E-B irradiation effect.Results showed that the blends was selectively crosslinked upon E-B irradiation and the crosslinking rule obeyed Charlesby-pinner formula;The irradiated sample exhibited excellent interfacial strength and no interfacial slip was observed before eventual fracture,the elongation at break can be as high as 900%;PCL55 exhibited the best TSME with both fixity ratios and recovery ratios above 90%;4.This part investigated the shape stability and discrete of shapes during continuous but slow recovery for the first time via selectively crosslinked PBAT/PCL/bentonite.The results showed that the weak interactions that can be broken down during shape progranuning made up an important part within the irradiated blends;The irradiation dose had higher influence on the shape stability of middle temporary shape and separated recovery ratio;For the selectively crosslinked sample exposed to 41.4 kGy,the amount of deformation for first shaping and the second shaping mainly influenced the staged recovery ratios and shape stability of middle temporary shape separately;The mechanical coupling effects among the components improved the shape stability at both high and low temperature. |
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