ABSTRACT:The mechanical properties and morphological changes of poly(lactic acid) (PLA), polycarbonate (PC), and poly(butylene adipate-co-terephthalate) (PBAT) polymer blends were investigated. Several types of blend samples were prepared by reactive processing (RP) with a twinscrew extruder using dicumyl peroxide (DCP) as a radical initiator. Dynamic mechanical analyses (DMA) of binary polymer blends of PC/PBAT indicated that each component was miscible over a wide range of PC/PBAT mixing ratios. DMA of PLA/PBAT/PC ternary blends revealed that PBAT is miscible with PC even in the case of ternary blend system and the miscibility of PLA and PBAT can also be modified through RP. As a result, the tensile strain and impact strength of the ternary blends was increased considerably through RP, especially for PLA/PBAT/PC ¼ 42/18/40 (wt/ wt/wt) with DCP (0.3 phr). Scanning electron microscopy (SEM) analysis of the PLA/PBAT/PC blends revealed many small spherical island phases with a domain size of approximately 0.05-1 lm for RP, whereas it was approximately 10 lm without RP.

The polymerization of -caprolactone (-CL) with a combination of tert-butyllithium (t-BuLi) and bis(2,6-di-t-butylphenoxy)methylaluminum [MeAl(ODBP) 2 ] in toluene at 0°C proceeded in a living manner to give polymers with narrow molecular weight distributions (MWD) within a few minutes, while the polymerization with t-BuLi alone gave a polymer with much broader MWD. The yield of the polymer did not reach 100 % at the Al/Li ratio of 5, because the excess MeAl(ODBP) 2 coordinates with -CL to protect it from the attack by the propagating species. The polymerization with t-BuLi/EtAl(ODBP) 2 gave polymers in quantitative yields regardless of Al/Li ratio, and also narrower MWD even for higher molecular weight polymers. IntroductionAnionic ring-opening polymerizations of -caprolactone (-CL) by alkali-metal alkyls or alkali-metal alkoxides are generally very fast, but are problematic in the control of polymer structure due to intra-and / or intermolecular transesterification reactions, that lead to the formation of macrocycles and to the broadening of molecular weight distribution (MWD). Decrease in the nucleophilicity of the initiator, through the modification of the counterion for example, has been found favorable to the propagation of linear chains compared to the macrocyclization process [1]. Thus, the living polymerizations of -CL have been attained by use of aluminum and zinc alkoxides such as Al(O i Pr) 3 [2], Zn[OAl(OR) 2 ] 2 [3], R x Al(OR) 3-x [4,5], and (tetraphenylporphyrinato)Al(OR) [6]. The polymerizations with lanthanide compounds such as yttrium alkoxides [7, 8, 9] and Cp * 2 SmMe(THF) (Cp * 2 = pentamethylcyclopentadienyl, THF = tetrahydrofuran) [10] and with bulky titanium bis(phenolate) [11] also give polymers with narrow MWD's.We have reported that combinations of tert-butyllithium (t-BuLi) and bulky aluminum bisphenoxides are efficient initiating systems for highly stereospecific living polymerization of methacrylates [12][13][14][15][16][17][18][19][20][21]. For example, polymerizations of primary alkyl methacrylates with t-BuLi/bis(2,6-di-tert-butylphenoxy)methylaluminum[MeAl(ODBP) 2 ] (Al/Li 2) in toluene at low temperature give highly heterotactic polymers with narrow MWD's. The existence of excess amounts of MeAl(ODBP) 2 over t-BuLi is essential for the heterotactic polymerization,

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In order to improve the brittleness of Poly (lactic acid) (PLA), the effect of blending several kinds of polyamide 12 (PA12) with PLA through Reactive Processing (RP) method was investigated. During RP, a maleic anhydridegrafted PLA (MAPLA) was synthesized as a pre-compatibilizer before blending PA12. From the result of static tensile test of PLA/PA12 with MAPLA, the elongation at break was increased and impact strength was increased as well. From the SEM observation results of PLA/PA12 with/without MAPLA, the diameter of PA12 phase in PLA with MAPLA was getting smaller than that of PA12 phase in PLA without MAPLA, which was good agreement with the mechanical properties of PLA/PA12 with/without MAPLA.

The crystallization behavior and rheological properties of PP in addition of polysilane which consists of Si-Si conjugation as a main chain were investigated. From the DSC measurement results, it was found that the crystallization temperature, melting point, and equilibrium melting point of PP decreased monotonically as the amount of PMPS added increased. On the SAXS measurement, the addition of PMPS reduces the long period and lamella thickness of PP crystals, while increasing the amorphous phase thickness and reducing the surface free energy. In the crystallization process, the temperature profile of the relative crystallization degree was shifted to the long-term side by adding PMPS to PP, and the crystallization was delayed. As a result of analyzing the compatibility between PP and PMPS with reference to the method of Nishi-Wang, it was deduced that these materials were compatible. From rheological measurements, it was found that PP in the molten state induces a decrease in viscosity due to the addition of PMPS, and the temperature dependence of the change also increased. Regarding the molecular motion in the solid state, it was found that the segment motion of PP near Tg was improved by the addition of PMPS. Finally, the uniaxial tensile test showed that the PP elastic modulus and yield stress decreased, but the elongation at break improved significantly.