The Study On Modification Of Fully Biodegradable Poly(Butylenes Succinate)

Poly(butylenes succinate)(PBS), as a biodegradable material, is of great importance both to research and application. However, as a crystalline polymer, PBS has a limited use range due to its low molecular weight and viscosity but high MI, whose performance is closely linked by crystallinity, crystalline structure as well as crystalline morphology. The extended use of PBS is also blocked with the limitation of processing, e.g. casting and blow molding are not suitable for PBS, another deter to promote PBS is its high cost.Modifying methods were utilized to PBS to improve the limitations mentioned above; they were crystalline modifying, chain-extending and filler modification. In this research, analyzing methods such as DSC,POM and mechanical property testing, ect were used to study the effects of 4 nucleators to the crystalline action and mechanical property of PBS from the view of crystalline structure and macro-performance. Results showed that the existence of nucleator could thin the sperulite size of PBS, make sperulites regular and uniform, and induce the crystallizing temperature to move towards higher direction. For example, BenLa could make crystallizing temperature rise 9.16℃. Furthermore, nucleator modification could enhance the mechanical property of PBS.In order to improve the limitation of low molecular weight and viscosity but high MI of PBS, molecular design was used that we synthesized 2,2'-Bis(2-oxazoline) from diethyl oxalate, ethanolamine, thionyl chloride etc.. The effects of process conditions on the yield of BOZ were investigated. It was indicated that the maximum was reached when molar ratio of ethanolamine to diethyl oxalate was 3:1, thionyl chloride to N,N'-dihydroxyethyl-oxamide was 3:1, the concentration of alcoholic sodium hydroxide solution was 2 mol/L and the elimination reaction temperature was 80℃. What's more, the fact that BOZ belonged to clinorhombic system was confirmed by XRD and DSC testing proved that the melting point of PBS is 210℃.During the chain extending reaction, we considered the factors such as adding amount of BOZ, stabilizer and accelerant, reacting time and reacting temperature. Through orthogonal array, the best condition were got. It was showed that the higher the reacting temperature was, the sooner the viscosity of reacting system reached and the quicker the concentration of COOH went. But the decomposition of PBS could be caused at the over-high temperature, which led to decreasing of PBS'viscosity while the increasing concentration of COOH. On the other hand, it was not in favor of chain extension at lower temperature because of low activity of BOZ. In addition, the more BOZ was used, the better the chain extended effect was got. The prime amount was 1.2%wt to the polymer. Meanwhile, stabilizer could lower the rate of decomposition of PBS. To promise the viscosity not vary along with the prolonging reacting time. The concentration of COOH dropped compared to the non- stabilizer system. It was also indicated that adding of accelerant could accelerate the reaction, once fixed the temperature the chain-extended system with accelerant could get the maximum viscosity while the minimum concentration of COOH at shorter time than without. At the same time, the reacting rate increased as the amount of accelerant added.Through orthogonal array we got the best condition that the amount used was BOZ 1.2%, stabilizer 0.08%, accelerant 0.15%, reacting temperature 210℃and reacting time 4 min. GPC analyses showed the molecular weight of PBS increased, Mn rose from 111705 to 189528 and Mw from 270341 to 448683, which indicated BOZ functioned well in the chain extending reaction. Furthermore, the distribution of molecular weigh was consistent to non chain extended PBS, showing PBS's line degree after chain extending reaction, without branched structure or cross lined.With the purpose of reducing the cost, filler-modified research was done to discuss how components affected PBS. The out coming showed all mechanical property index slipped variously after filler modifying, with notch impact strength dropping from 29 to 21.77 kJ/m2, strength dropping from 32.79 to 26.82MPa, and the breaking extension from 186% to 138%. Further more, MI of modified PBS decreased, which meant it was good for processing. PBS film modified by starch and inorganic filler had a inferior macro mechanical properties than pure PBS film, while modified starch and CaCO3 didn't affect haze with a little drop of transmissivity.After doing the biodegradable estimate of PBS, facts were found that BOZ linked to COOH group so as to increase PBS's molecular weight and enhance its processing performances without changing the micro chain structure and the distribution of molecular weight. Not to vary the interior property of PBS as biodegradable polyester. Also filler modified PBS could enhance its processing application as well as lowing the cost. Both kinds of products presented well in degrading under the controlled composting, with a figure that degrading degree came near 100% after 95 days'composting.