Improving Tear Strength Resistence Of Biodegradable Poly (Butylene Succinate) By Modification

Poly(butylene succinate) (PBS) is a kind of biodegradable material. It has the wide sources of the raw materials not only from the oil but also from plants. It could be degraded by the enzyme into carbon dioxide and water. It is well biocompatible and heat-resistant. PBS films are widely be used as packing bag, agricultural plastic bags, garbage bag and so on. These PBS products can be used stabilizedly in the air. PBS is of great importance in both research and application. However, as a crystalline polymer, PBS usage is limited due to its low tearing strength, which must be improved for more applications.The adapted modifications here include peroxide- and radiation-inducing crosslinking as well as blending with other polymer to raise tear-resistance. The prepared PBS in twin screw extruder was further blowed or pressed into films, which were partially crosslinked by heating and radiation. The effects of components and processing parameters were characterized by gel analysis, testing melt index and mechanical properties as well as DSC, IR, XRD, NMR and TEM.In peroxide-crosslinking modification, dicumyl peroxide (DCP) was mixed into PBS for modified PBS in extrusion at 170℃and 200r·min-1. The obtained material presented higher tear resistance and tensile strength compared with the pure PBS while reucing breakage elongation. The appropriated content of DCP was ca.0.5% resulting in incresements of 34% and 16% for tear resistance and tensile strength respectively. The gel crosslinkage was raised to a certain degree and then maintained constant while melt index reduced continously when more DCP was added. The gradual cooling was favorable for better crystallization corrsponding to relatively higher melting point.Itaconic acid (ITA) was mixed to PBS/DCP in extruder for grafting, hereafter facilatate the crosslinking efficiency resulting in higher tear resistance and tensile strength. The optimum contents of ITA and DCP were 2% and 0.2%-0.3% respectively. The latter content is higher than 0.5%-0.6% in DCP for ungrafted PBS/DCP. Thus, grafting is useful for both improving mechanical properties and reducing the quantity of DCP.The blown PBS film was radiated by 60Coγfor partial crosslinking reduced by different sensitizer. The effects were different for films with different thicknesses. The surfacial PBS molecule was opted for degradation when induced by oxygen in air. The ratio of un-oxygenized PBS molecules was greater for thicker film indicating higher crosslinking effect. The appropriate dose was different for different sentisizers, among which 10KGy was needed for triallyl isocyanurate. The modified PBS by 0.5wt% triallyl isocyanurate exhibited highest tear strength, which was 1.60 times of that of unmodified PBS. Characterizations showed that the main molecular structure remain stable while crystallity was reduced regardless of dropping the radiation dose. The gel content was expressed as one modified Charlesby-Pinner function of radiation dose.Poly(butylene terephthalate-1,4-butylene adipate) (PBAT) and poly lactic acid (PLA) were blended into PBS to improve the impact toughness. The tensile strength of PBS/PLA rose with the content of PLA almost linearly in contrast with the decrease of breakage elongation. It was up to 38.6Mpa for PBS/PLA=60/40.