| The development of materials is tightly linked to the development of human society. Polymer was an important category in the field of materials, played an irreplaceable role in human life and offered a lot of convenient conditions. The use of polymer materials increased dramatically, that accompanied with the economic development. At the same time, waste plastic caused an influx of non-biodegradable rubbish. So, the conflict between economical development and ecological environment protection becomes very sharp-pointed. Thus, the interest for biodegradable polymers and plastic products as an alternative to traditional petroleum-based polymers and conventional plastic products has become a practical solution to the problem.As one of the most promising biodegradable polymers, poly(lactic acid)(PLA) has recently been discussed critically. But processing, toughness and heat resisting properties of PLA still needed improving.In this work, polyethylene glycol(PEG), dibutyl phthalate(DBP), dioctyl phthalate(DOP) and glyceryl triacetate(GT) were chosen as plasticizer to plastify PLA. The melt flow rate (MFR) of PLA increased dramatically after plastified with those plasticizers. Balancing torque of PLA plastified with different contents PEG-6000was about1.0-2.1N/m. And it avoided the uneven mixing of raw material using PEG-6000as the ultimate plasticizer. When contents of PEG-6000were higher than10wt%, the rising trend of MFR was much more obvious.Three kinds of modified starch(MS) that were two kinds of thermoplastic starch(MS-1, MS-2) and a kind of maleic anhydride grafted starch(MS-3) were prepared as the fillings of PLA. It can be known that the three kinds of MS were prepared successfully through the analysis of FTIR. The relevant properties of PLA/MS-3composites were better than those of PLA/MS-1and PLA/MS-2composites. When MS-3contents were20wt%, tensile-strength, flexural strength, notch impact strength, elongation at break of the composites can reach31.35Mpa,63.08MPa,6.37kJ/m2and51.42%, respectively. Three kinds of MS existed as dispersed phase in the PLA resin. Vicat softening temperature (VST) of PLA/MS composites decreased to43.2,40.2,45.88℃, respectively. And MFR of them decreased from17.74of PLA resin to12.21,13.27,14.73g/10min. It possessed the smallest quality transformation rate for PLA/MS-3compared with those of PLA/MS-1,2and PLA resin. The Tg of PLA/MS blends was found to be56.8,57.3and56.5℃respectively, which is about2℃lower than that of PLA. MFR and VST decreased with different degrees for PLA filled with acidification starch. PLA/MS blends were gradually degraded with time and the biodegradability rates of them were faster than that of PLA, which reached up to1.80,1.89,1.44g/day after60days, respectively.In this work, PLA/polybutylene succinate(PBS), PLA/polycaprolactone(PCL) and PLA/polycarbonate(PC) alloys were prepared respectively. For PLA/PBS alloys containing10-90wt%PBS, flexural strength and flexural modulus decreased gradually. Notch impact strength increased from5.16(containing10wt%PBS) to8.72kJ/m2(containing70wt%PBS). Tensile strength increased first, and then decreased with increasing of PBS contents. Elongation at breakcan reached up to211.37%for PLA/PBS alloy containing30wt%PBS. It turned from "seaisland structure" to "sea-sea structure" for alloy phases in the alloy. And thermal properties improved obviously after blending PLA with PBS compared with PLA resin:VST and MFR increased with the increasing of PBS contents. The quality transformation rate of alloys reduced evidently. At the same time, the final char conversion rate and thermal stability improved significantly.Compatilizer could change compatibility of PLA and PBS in the alloy and improve mechanical properties of it. The MFR of PLA/PBS alloy containing compatilizer increased compared with that(10.01g/lOmin) of PLA resin. And VST decreased by1.3-2.1℃. After adding compatilizer, notch impact strength reached up to6.50kJ/m2. Elongation at breakcan multiplied30-60times compared with PLA. At the mean time, notch impact strength increased. And flexural strength and flexural modulus decreased after adding ester exchange products of PLA/PBS into PLA resin.For PLA/PCL alloys, flexural strength and flexural modulus decreased with increasing of PCL contents in the alloys. When PCL contents in the alloys were10and40wt%, notch impact strength reached up to5.93kJ/m2and12.4kJ/m2respectively. When PCL contents in the alloys were10-50wt%, tensile-strength was38.49-70.37MPa respectively. When PCL contents in the alloys were40and50wt%, elongation at breakcan multiplied25and30compared with PLA(9.8%) respectively. It turned from "seaisland structure" to "sea-sea structure" for alloy phases. MFR and VST of PLA/PCL alloys increased and decreased with increasing of PCL contents in the alloy respectively. Thermal decomposition temperature and charing amount increased after blending PLA and PCL. And mass loss rate decreased compared with PLA resin. At the mean time, notch impact strength, flexural strength and flexural modulus decreased after adding ester exchange products of PLA/PCL into PLA resin. MFR and VST also decreased.For PLA/PC alloys, When PC contents in the alloys were10wt%, notch impact strength increased by1.27kJ/m2compared with PLA. But, tensile strength, flexural strength and flexural modulus decreased after adding PC into PLA resin. Fracture surface of PLA/PC alloy showed some convex edge with the increase of PC contents. But VST of them increased dramatically. Thermal decomposition and char forming improved after blending PLA and PC. Meanwhile, the largest quality loss rate decreased compared with PLA resin. |
PDF Full Text Request