Study Of Tensile Behavior And Blending Modification Poly (Butylene Succinate)

Based on brief overview of mechanism of deformation yield and fracture of polymers, research work on stress oscillation of some polymers during tensile process, and the relationship between the deformation behavior and microstructure of polymers, Stress oscillation phenomenon and the mechanisms of deformation and fracture during tensile process of Poly(butylene succinate) (PBS) were studied, it's known much more clearly about the relationship between the fracture mechanism and mechanical properties of PBS. In addition, aimed to application of PBS, blending modification of PBS was studied. PBS/PHBV (Poly(hydroxybutyrate-co-valerate)) blends,PBS/ wood fiber composite were prepared, Mechanical properties, phase morphologies, crystallization behavior and thermal behavior properties of the systems were studied, to obtain the excellent composites base on PBS.Periodic necking oscillation on stress-stain curves and transparent/opaque streaks on specimen during neck-propagation process were found, which was called stress oscillation phenomenon. According to the stress-stain curves at different tensile rates and temperature, corresponding morphology of drawn specimens, stress oscillation of PBS was found tensile rate during range from 10 mm/min to 200 mm/min, what's more, the tensile rate was larger, the amplitude for stress oscillation was lower; Stress oscillation was found during narrow temperature range (23-60 oC). Results of DSC and XRD about PBS undeformed specimens and drawn specimens, new crystal structure was not found, but crystallization heat during stress-induced crystallization during stretching was released, which made temperature of PBS specimens increased and lead the mechanism of"stick-slip", so the stress oscillation turned up and it induced the periodic changes of its appearance in form of transparent/opaque streaks on PBS specimens.AFM and FESEM photos showed the tensile process, with sequences of elastic deformation, localized orientation, plastic deformation, crazing, and fibril pulling during deformation. As semi-crystalline polymers, tensile process induced crystalline region re-stacking and amorphous region re-crystalline, and long period increased with increase of strain, such results made great sense for manufacture of PBS fiber; microviod turned up during crazing, FESEX and SAXS data proved existence and growth of microviods, then microviods evolved to cavitation. Fracture morphology of PBS indicated that cavitation led to fracture of specimens during tensile process.To widen the application of PBS and develop its good toughness, PBS/PHBV blends were prepared. With addition of PHBV, flexural properties and thermal resistance of blends were increased greatly. Excellent toughness of PBS made up for brittleness of PHBV. Phase morphology was gradually changed into a two-continuous structure from a sea-island phase structure, and finally a reverse sea-island phase structure. DSC results proved than incorporation of PHBV hindered the crystallization of PBS. With phase transformation and decrease of crystalline degree, formulation of PBS/PHBV (50/50) showed the lowest mechanical properties, so formulation of PBS/PHBV (70/30, 30/70) can be used for application.Wood fiber is a kind of natural product in abundance of cellulose. Wood fiber reinforced PBS composites have superior physical mechanical properties with low-cost, high modulus, and thermal resistance. PBS/Wood fiber composites were prepared by melt blending. Effect of content of wood fiber on mechanical, thermal, phase morphology and rheological properties of composite were studied. The results indicated addition of wood fiber increased the flexural properties but impact strength decreased a little. Based on rheological experiment, the storage modulus and complex viscosity increased greatly. With increase of content wood fiber, a solid-like behavior was observed in the low frequency zone. Morphology proved that the compatibility between PBS and wood fiber was poor with fiber pull-outs. The effect of four different silane coupling agents was investigated. The results showed that KH570 was more effective in improving the interface adhesion between wood fiber and PBS, tensile and flexural strengths increased with 4 MPa, impact strength increased a little. PBS-g-MAH was made to improve the interface adhesion, its efficiency is saturability. With addition of 10 phr PBS-g-MAH, properties of composites were the best, with impact strength and tensile strength increased 30% and 28% respectively.