Crystallization, Structure and Significantly Improved Mechanical Properties of PLA/PPC Blends Compatibilized with PLA-PPC Copolymers Produced by Reactions Initiated with TBT or TDI

Abstract

Poly (lactic acid) (PLA)-Poly (propylene carbonate) (PPC) block copolymer compatibilizers are produced in incompatible 70wt%PLA/PPC blend by initiating transesterification with addition of 1% of tetra butyl titanate (TBT) or by chain extension with addition of 2% of 2,4-toluene diisocyanate (TDI). The above blends can have much better mechanical properties than the blend without TBT and TDI. The elongation at break is dramatically larger (114% with 2% of TDI and 60% with 1% of TBT) than the blend without TDI and TBT, with a slightly lower mechanical strength. A small fraction of the copolymer is likely formed in the PLA/PPC blend with addition of TBT, and a significant amount of the copolymer can be made with addition of TDI. The copolymer produced with TDI has PPC as a major content (~70 wt%) and forms a miscible interphase with its own Tg. The crystallinity of the blend with TDI is significantly lower than the blend without TDI, as the PLA blocks of the copolymer in the interphase is hardly to crystallize. The average molecular weight increases significantly with addition of TDI, likely compensating the lower mechanical strength due to lower crystallinity. Material degradation can occur with addition of TBT, but it is very limited with 1% of TBT. However, compared with the blends without TBT, the PLA crystallinity of the blend with 1%TBT increases sharply during the cooling process, which likely compensates the loss of mechanical strength due to the slightly material degradation. The added TDI does not have any significant impact on PLA lamellar packing, but the addition of TBT can make PLA lamellar packing much less ordered, presumably resulted from much smaller PPC domains formed in the blend due to better compatibility.

Determination of Residual Diisocyanates and Related Diamines in Biodegradable Mulch Films Using N-Ethoxycarbonylation Derivatization and GC-MS

“…HDA was only found in PBAT C. Other diisocyanates and related diamines were not detected. The aromatic diisocyanates (2, 6-TDI and 2, 4-TDI), precursors of 2, 6-TDA and 2, 4-TDA were widely applied biodegradable polymers as functions for chain extender and compatibilizer [ 39 ]. The added diisocyanates can provide improvement in mechanical properties, good interfacial adhesion with polymer blends and show a homogeneous distribution on the surface [ 40 ].…”

The Preparation of PLA/PBAT/PPC Ternary Blends and The Effect of Epoxidized Soybean Oil on the Physical and Mechanical properties of PLA/PBAT/PPC blends with the Reactive Compatibilization

“…Biodegradable polymers are good alternative to petroleum sourced plastics, and it decompose within months to years by microorganisms under the speci c composting conditions. There are various biopolymers such as bio-based/renewable resource based biodegradable polymer, poly (lactic acid) (PLA) [2][3][4][5][6][7][8][9][10][11][12][13], poly (hydroxy alkanoates) (PHAs) [14], starch and petroleum-based biodegradable polymers, polycaprolatone (PCL) [15], poly (butylene succinate) (PBS) [13,16,17], poly (butylene adipate-coterephthalate) (PBAT) [9,11,12,18,19], combined polymer of both renewable and petroleum-based biodegradable polymer, poly (propylene carbonate) (PPC) [4,6,7,9,10,[19][20][21][22][23]. PLA, an aliphatic polyester, is the most widely used biopolymer, and monomers are usually made from fermented plant starch such as corn, wheat, casava, sugarcane and beet pulp.…”

“…Adequate content of TBT and TDI improved mechanical properties over 70% PLA/30% PPC mixing by initiating transesteri cation of TBT and chain expansion of TDI. [7] The complementary polymer and suitable additives could enhance the properties of the polymer. Han et al used the epoxidized soybean oil(ESO) as compatibilizer to improve compatibility and the mechanical properties such as tensile strength, elongation at break, and notched impact strength of PLA/PBAT/ESO increased su ciently as compared to that of the PLA/PBAT composite.…”

Effect of Different Comonomers Added to Graft Copolymers on the Properties of PLA/PPC/PLA-g-GMA Blends

“…PPC is of particular interest as it is the only one of the above materials synthesized from the “greenhouse gases” carbon dioxide (CO 2 ) and propylene oxide (PO), which not only reduces the dependence on oil resources but also effectively alleviates the greenhouse effect [ 15 , 16 ]. PPC also possesses good properties such as toughness, biodegradability, and translucence [ 17 , 18 ], so PPC and PLA were complementary in performance [ 19 ]. However, while PPC and PLA have a degree of compatibility due to their similar chemical structures, many studies have revealed that this compatibility is low, and the properties of the blended materials cannot meet the actual use requirements.…”