| Polylactic acid (PLA) is derived from biological base of renewable resources. It canbe completely composted into carbon dioxide and water after used and has no harm to theenvironment. PLA was considered to be the most application prospect biodegradableplastic. However, PLA has slow crystallization rate and low crystalline degree, lead to lowheat-resistance temperature, limit its application. Therefore, research on crystallizationkinetics and heat resistance performance of new nucleation agents has extremely scientificand application value.In this dissertation, Talc、TMC-328、NA1、ECO-13002and TMP-3000were selectedas nucleation agents. PLA/nucleation agent composites were prepared throughmelt-blending. The effect of nucleation agents on the isothermal crystallization kinetics,crystal morphology, thermal properties, mechanical properties, and heat resistance ofPLLA-ESO and its composites were studied.The effect of nucleation agents on the isothermal crystallization kinetics of PLA wereinvestigated by differential scanning calorimetry (DSC).The results showed that:The Avrami exponent n value of PLA/nucleation agent composites is in the range of2.32to4.67， the NA1was more efficient for PLA nucleation. It was found that thecrystallization rate of PLA/NA1composites was the fastest when isothermally crystallizedat110°C, the crystallization half-time values (t1/2) was19s. The composite nucleationagents (NA1and talc) could significantly increase the crystallization rate of PLA at130°C.With increasing of the content of nucleation agents the crystallization rate was speeding up.DSC non-isothermal test results showed that NA1and plasticizer were able to enhance thecrystallization peak temperature and relative crystallinity of PLA, and the two valuesincreased with plasticizer content. Crystallization peak temperature and relativecrystallinity achieve the highest at2%plasticizer content, were122.9°C and34.2%respectively.POM observed that all nucleation agents could effectively accelerate the nucleation ofPLA, increased the crystal density and decreased crystal size. The crystal morphology ofPLA and PLA/talc were spherulite, PLA/TMP-3000growed in acicular crystal, PLA/ECOand PLA/TMC-328growed in dendritic crystal. XRD results showed that all nucleationagents and plasticizer didn’t change the crystal structure of PLA, it was still the alphacrystal. DMA results indicated that adding nucleation agents and annealing processing couldincrease PLA’s storage modulus and whole flexibility. As the degree of crystallinity rise,the glass transition temperature increased. The Tgof pure PLA was60°C, while the TgofNA1/PLA composite reached72.9°C after annealing60s. Nucleaion agents couldsignificantly improve the HDT of PLA, especially after annealing. The HDT of all PLA/NAcomposites could exceed120°C after annealing60s. PLA/talc composite exhibited thebest heat resistance，its HDT value was about128.8°C.Mechanics performance results showed that the impact strength of PLA/NA compositewere reduced when compared with pure PLA. PLA/NA1composite possess the minimum,its value was about12.56KJ/m2. The impact strength and elongation of PLA compositeswere first decreased then increased with increased the plasticizer loading, the tensilestrength was the contrary. The tensile strength reached maximum while the impact strengthand elongation possess the minimum at1wt%plasticizer content, its value was about63.8MPa,8.15KJ/m2and0.98%respectively. |
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