Effect of styrene-maleic anhydride on phase morphology and properties of PLA/PBAT blends
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摘要: 聚己二酸-对苯二甲酸丁二酯(PBAT)具有很好的延展性,但其强度较低,而聚乳酸(PLA)高模量可以解决PBAT的缺陷。以苯乙烯-马来酸酐共聚物(SMA)为增容剂,通过双螺杆挤出机制备了PLA/ PBAT共混物,研究了不同含量的SMA对PLA/PBAT共混物的结晶性能、热性能、流变行为及拉伸性能的影响。结果表明:SMA能显著降低分散相PLA的粒径大小,在SMA含量为1.5wt%时变化最明显,PLA的粒径从1.75 μm降低到0.60 μm;SMA能促进PBAT的结晶,随着SMA含量增加,PBAT的结晶度呈现先增大后降低的趋势,当SMA含量为2wt%时,PBAT的结晶度达到最大为9.22%;通过Han曲线发现,在SMA含量较低时,共混物更接近均质物,随着SMA含量提高,共混物的弹性行为增强;SMA能够提高PLA/PBAT共混物的拉伸性能,随着SMA含量增加,拉伸强度与断裂伸长率都呈现先增大后减小的趋势,但总体高于未加SMA时的拉伸强度与断裂伸长率,SMA含量为1.5wt%时,拉伸强度相对于未添加SMA时,从18.1 MPa增加到21.8 MPa,提高了21%,断裂伸长率在SMA含量为1wt%时达到最大,为433.7%,相对未添加SMA时提高了25%。Abstract: Poly(butylene adipate-terephthalate) (PBAT) has outstanding ductility, but its strength is low, then, high modulus of polylactic acid (PLA) can solve the defects of PBAT. The styrene-maleic anhydride (SMA) was used as compatibilizer to prepare poly(lactic acid)/poly(butylene adipate-co-butylene terephthalate) (PLA/PBAT) blends. The effect of the content of SMA on the crystallization performance, thermal performance, rheological behavior and tensile properties of the blends were investigated. The results show that the SMA can significantly reduce the particle size of PLA, and the size of the dispersed PLA phase decreases from 1.75 μm to 0.60 μm when the content of SMA is 1.5wt%. The SMA can increase the crystallinity of PBAT, and as the SMA is added up to 2wt%, the crystallinity reaches up to the maximum value of 9.22%. It is found by the Han curves that low content of the SMA can give rise to closely homogeneous blends, and the elasticity of PLA/PBAT melt increase gradually with the increase in amount of SMA content. Moreover, the SMA enhance the tensile properties of PLA/PBAT blends. As the addition of SMA, the tensile strength and elongation at break both increase first and then decrease. The tensile strength of the composite with 1.5wt% SMA is 21.8 MPa, which is 21% higher than that of the counterpart without SMA (18.1 MPa). The elongation at break reaches the maximum value of 433.7% when SMA content is 1wt%, which is 25% higher than that of the composite without SMA.
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图 3 PLA/PBAT共混物的脆断截面SEM图像及PLA的粒径分布直方图:(a) PLA/PBAT;(b) PLA/PBAT-0.5wt%SMA;(c) PLA/PBAT-1wt%SMA;(d) PLA/PBAT-1.5wt%SMA;(e) PLA/PBAT-2wt%SMA;(f) PLA/PBAT-3wt%SMA
Figure 3. SEM images showing fracture surface of PLA/PBAT blends and particle size distribution histogram: (a) PLA/PBAT; (b) PLA/PBAT-0.5wt%SMA; (c) PLA/PBAT-1wt%SMA; (d) PLA/PBAT-1.5wt%SMA; (e) PLA/PBAT-2wt%SMA; (f) PLA/PBAT-3wt%SMA
表 1 聚乳酸/聚己二酸-对苯二甲酸丁二酯(PLA/PBAT)共混物的原料配比
Table 1. Compositions of poly(lactic acid)/poly(butylene adipate-co-butylene terephthalate) (PLA/PBAT) blends
Sample PBAT/wt% PLA/wt% SMA/wt% PBAT 100.0 0 0.0 PLA 0.0 100 0.0 PLA/PBAT 75.0 25 0.0 PLA/PBAT-0.5wt%SMA 74.5 25 0.5 PLA/PBAT-1wt%SMA 74.0 25 1.0 PLA/PBAT-1.5wt%SMA 73.5 25 1.5 PLA/PBAT-2wt%SMA 73.0 25 2.0 PLA/PBAT-3wt%SMA 72.0 25 3.0 Note: SMA—Copolymer of styrene and maleic anhydride. 表 2 不同SMA含量的PLA/PBAT共混物中分散相PLA的平均粒径
Table 2. Mean diameter of PLA in PLA/PBAT blends with different SMA contents
Sample PLA/PBAT PLA/PBAT-0.5wt%SMA PLA/PBAT-1wt%SMA PLA/PBAT-1.5wt%SMA PLA/PBAT-2wt%SMA PLA/PBAT-3wt%SMA Mean diameter/μm 1.75 1.43 1.40 0.60 0.66 0.61 表 3 不同SMA含量的PLA/PBAT共混物的DSC热分析数据
Table 3. DSC thermal analysis data of PLA/PBAT blends with different SMA contents
Sample Tm/℃ Tc/℃ △Hm/(J·g−1) Xc/% PBAT PLA PBAT PLA PBAT PLA PBAT 122.98 — 58.58 15.62 — 13.70 — PLA — 152.46 — — 6.12 — 0.61 PLA/PBAT 125.41 151.72 77.83 5.41 2.72 6.32 11.68 PLA/PBAT-0.5wt%SMA 124.43 153.66 77.73 6.27 0.23 7.38 1.01 PLA/PBAT-1wt%SMA 125.69 153.12 77.70 6.53 0.25 7.74 1.06 PLA/PBAT-1.5wt%SMA 125.09 153.93 76.90 6.98 0.19 8.33 0.83 PLA/PBAT-2wt%SMA 124.54 — 73.45 7.68 — 9.22 — PLA/PBAT-3wt%SMA 124.38 — 71.68 7.12 — 8.68 — Notes: Tm and Tc—Melting peak temperature and the crystallization peak temperature; △Hm and Xc—Melting enthalpy and crystallinity. 表 4 不同PLA/PBAT共混物的热稳定性
Table 4. Thermal stability of different PLA/PBAT blends
Sample T5wt%/℃ T50wt%/℃ PBAT 372.3 413.9 PLA 336.7 365.4 PLA/PBAT 347.5 401.2 PLA/PBAT-0.5wt%SMA 349.3 402.1 PLA/PBAT-1wt%SMA 344.5 401.8 PLA/PBAT-1.5wt%SMA 347.1 401.5 PLA/PBAT-2wt%SMA 348.9 402.2 PLA/PBAT-3wt%SMA 348.7 402.0 Notes: T5wt% and T50wt%—Temperature when the mass loss of the samples is 5wt% and 50wt%, respectively. 表 5 不同SMA含量的PLA/PBAT共混物的非牛顿指数
${\boldsymbol{n}} $ Table 5. Non-Newtonian index
${\boldsymbol{n}} $ of PLA/PBAT blends with different SMA contentsSample n PLA/PBAT 0.627 PLA/PBAT-0.5wt%SMA 0.638 PLA/PBAT-1wt%SMA 0.611 PLA/PBAT-1.5wt%SMA 0.573 PLA/PBAT-2wt%SMA 0.595 PLA/PBAT-3wt%SMA 0.537 Note: Non-Newtonian index (n) was calculated from the linear fitting of the lnηa versus ln$ \dot{\gamma } $ curve at high shear rates. -
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