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首页> 外文期刊>Polymer: The International Journal for the Science and Technology of Polymers >Comparison of morphologies and mechanical properties of crosslinked epoxies modified by polystyrene and poly(methyl methacrylate)) or by the corresponding block copolymer polystyrene-b-poly(methyl methacrylate)
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Comparison of morphologies and mechanical properties of crosslinked epoxies modified by polystyrene and poly(methyl methacrylate)) or by the corresponding block copolymer polystyrene-b-poly(methyl methacrylate)

机译：聚苯乙烯和聚甲基丙烯酸甲酯或相应的嵌段共聚物聚苯乙烯-b-聚甲基丙烯酸甲酯改性的交联环氧树脂的形态和机械性能的比较

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Polystyrene (PS, M-n = 28,400, PI = 1.07), poly(methyl methacrylate) (PMMA, M-n = 88,600, PI = 1.03), and PS (50,000)-b-PMMA (54,000) (PI = 1.04), were used as modifiers of an epoxy formulation based on diglycidyl ether of bisphenol A (DGEBA) and m-xylylene diamine (MXDA). Both PS and PMMA were initially miscible in the stoichiometric mixture of DGEBA and MXDA at 80 C, but were phase separated in the course of polymerization. Solutions containing 5 wt% of each one of both linear polymers exhibited a double phase separation. A PS-rich phase was segregated at a conversion close to 0.02 and a PMMA rich phase was phase separated at a conversion close to 0.2. Final morphologies, observed by scanning electron microscopy (SEM), consisted on a separate dispersion of PS and PMMA domains. A completely different morphology was observed when employing 10 wt% of PS-b-PMMA as modifier. PS blocks with M = 50,000 were not soluble in the initial formulation. However, they were dispersed as micelles stabilized by the miscible PMMA blocks, leading to a transparent solution up to the conversion where PMMA blocks began to phase separate. A coalescence of the micellar structure into a continuous thermoplastic phase percolating the epoxy matrix was observed. The elastic modulus and yield stress of the cured blend modified by both PS and PMMA were 2.64 GPa and 97.2 MPa, respectively. For the blend modified by an equivalent amount of block copolymer these values were reduced to 2.14 GPa and 90.0 MPa. Therefore, using a block copolymer instead of the mixture of individual homopolymers and selecting an appropriate epoxy-amine formulation to provoke phase separation of the miscible block well before gelation, enables to transform a micellar structure into a bicontinuous thermoplastic/thermoset structure that exhibits the desired decrease in yield stress necessary for toughening purposes. (c) 2005 Elsevier Ltd. All rights reserved.
机译：使用了聚苯乙烯（PS，Mn = 28,400，PI = 1.07），聚（甲基丙烯酸甲酯）（PMMA，Mn = 88,600，PI = 1.03）和PS（50,000）-b-PMMA（54,000）（PI = 1.04）作为基于双酚A的二缩水甘油醚（DGEBA）和间二甲苯二胺（MXDA）的环氧配方的改性剂。 PS和PMMA最初在80°C下可混溶在DGEBA和MXDA的化学计量混合物中，但在聚合过程中会发生相分离。包含5重量％的两种线性聚合物中的每一种的溶液显示出双相分离。富PS相分离的转化率接近0.02，富PMMA相分离的转化率接近0.2。通过扫描电子显微镜（SEM）观察到的最终形态，是由PS和PMMA域的单独分散体组成。当使用10重量％的PS-b-PMMA作为改性剂时，观察到完全不同的形态。 M = 50,000的PS嵌段不溶于初始配方。然而，它们被可溶的PMMA嵌段稳定化为胶束而分散，导致透明溶液直至转化，PMMA嵌段开始发生相分离。观察到胶束结构聚结成渗入环氧基质的连续热塑性相。 PS和PMMA改性的固化共混物的弹性模量和屈服应力分别为2.64 GPa和97.2 MPa。对于用当量的嵌段共聚物改性的共混物，这些值降低到2.14 GPa和90.0 MPa。因此，使用嵌段共聚物代替单独的均聚物的混合物并选择合适的环氧-胺配方以在胶凝之前很好地引起可混溶嵌段的相分离，使得能够将胶束结构转变为展现出所需的双连续热塑性/热固性结构。降低增韧目的所需的屈服应力。 （c）2005 Elsevier Ltd.保留所有权利。

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