Preparation of PTBA‐PAA‐PMMA Compatibilizer for PET‐PMMA Blends by Atom Transfer Radical Polymerization

The synthesis of diblock copolymer of tert butyl acrylate and methyl methacrylate (PTBA‐b‐PMMA) was prepared by Atom Transfer Radical Polymerization (ATRP). At the outset, macroinitiator of tert butyl acrylate (TBA) was prepared by using N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) ligand, Cuprous Bromide (CuBr) catalyst, and ethyl 2‐bromo isobutyrate (2‐EiBBr) initiator. Immediately after the intake of the utmost TBA in the macroinitiator, the second monomer, methyl methacrylate (MMA) was added to the reaction medium, for further polymerization. In these experiments the compositions of the monomers were varied, although the concentrations of ligand, catalyst and the initiator were kept constant. Subsequently, the diblock copolymers were hydrolyzed, under acidic conditions, using HCl catalyst, to obtain an amphiphilic copolymer. These block copolymers were characterized by NMR, IR, GPC, and DSC techniques. These copolymers will be used in, powder coatings, pigment dispersions, and as compatibilizers in polymer blends.     

POM／EVA共混物的研究

用力学测试、扫描电镜（ＳＥＭ）、热分析（ＤＳＣ）等手段研究了聚甲醛（ＰＯＭ）与乙烯－醋酸乙烯酯共聚物（ＥＶＡ）共混物（ＰＯＭ／ＥＶＡ）的力学性能及其微同形态；用聚甲醛与马来酸二丁酯（ＤＢＭ）的接枝物（ＰＯＭ－ｇ－ＤＢＭ）作相溶剂，能改变共的两相间的粘结力，从而提出了共混物的力学性能，ＳＥＭ观察表明接枝物的加入改变了ＰＯＭ／ＥＶＡ共混物的断裂方式，微观形态及结晶性能，对其热性能影响不大；通过改变ＰＯ     

Preparation, structure, and properties of styrene-ethylene-butylene-styrene block copolymer/clay nanocomposites: Part II fracture behaviors

Styrene-ethylene-butylene-styrene block copolymer (SEBS)/clay nanocomposites were prepared via a melt mixing technique. Various amounts of two types of maleated compatibilizers, styrene-ethylene-butylene-styrene block copolymer grafted maleic anhydride (SEBS-g-MA) and polypropylene grafted maleic anhydride (PP-g-MA), were incorporated to improve the dispersion of commercial organoclay (denoted as 20A), respectively. PP-g-MA compatibilized system conferred higher tensile strength and tear strength (initiation condition) than SEBS-g-MA compatibilized system. At a fixed content of compatibilizers, the above mechanical properties were improved with increasing clay content as well. By relating tensile strength to tear strength (arrest condition), the average depth of flaw was in the range of 33.8 ± 3.4 μm, which successfully confirmed the extension of Rivlin and Thomas’s theory for conventional elastomers to thermoplastic elastomer/clay nanocomposites for the first time. Cutting strength of SEBS/clay nanocomposites gave an intermediate value when compared with crystalline plastics and conventional amorphous elastomers, which further signified the importance of micro-yielding of styrene domains, crystalline yielding of compatibilizer, and filler reinforcement even in the nano-fracture zone of deformation.     

Highly toughened poly(lactic acid) (PLA) prepared through melt blending with ethylene-co-vinyl acetate (EVA) copolymer and simultaneous addition of hydrophilic silica nanoparticles and block copolymer compatibilizer

In this study, a highly toughened PLA was prepared through physical melt-blending with EVA at the presence of hydrophilic nanosilica and SEBS-g-MA block copolymer compatibilizer. The effect of nanosilica and compatibilizer on the morphology, mechanical properties, and linear rheology of the PLA/EVA blends was also investigated. According to TEM images, nanosilica was selectively located in the PLA matrix while some were placed on the interface between the two polymers as was also predicted by thermodynamic and kinetic analysis. Upon the addition of nanoparticles, the interfacial adhesion between the phases was enhanced and the average droplet size decreased. Interestingly, incorporation of SEBS-g-MA induced morphological changes as the spherical EVA droplets turned into a cylindrical shape. DSC results indicated that blending with EVA copolymer resulted in the reduction of crystallization of PLA matrix; however, the crystallinity increased at the presence of nanoparticles up to 5 wt%. The addition of compatibilizer considerably hindered the crystallization of the PLA phase. PLA/EVA blend containing optimum levels of nanosilica exhibited considerably enhanced tensile toughness, elongation at break, and impact strength. On the other hand, the simultaneous addition of nanoparticles and SEBS-g-MA led to synergistic toughening effects and the compatibilized blend containing nanosilica exhibited excellent impact toughness. For instance, the elongation at break of the compatibilized PLA/EVA blend containing the optimal content of nanosilica was increased from 7% to 121% (compared to neat sample). The notched Izod impact strength was also increased from 5.1 to 65 kJ/m². Finally, the microstructure of the blends was assessed by rheological measurements.     

COMPATIBILIZATION OF POLY(ETHYLENE OXIDE)/POLY(STYRENE) BLENDS: EFFECT OF THE MOLECULAR WEIGHT OF THE COMPATIBILIZER

The effect of the molecular weight and concentration of the compatibilizer maleic acid-alt-styrene copolymer (MAaS) on the compatibility behavior of incompatible poly(ethylene oxide)/poly(styrene) (PEO/PS) blends was studied by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). PEO with [Mbar] _w = 100,000 (PEO₁₀₀) and PS with [Mbar] _w = 225,000 (PS₂₂₅) were used for this study. DSC measurements showed two T _g values that were shifted relative to those of the pure components. This result should be indicative that MAaS acts as a compatibilizer for the blend. Diminishing of the spherulitic growth rate G was observed as the content and molecular weight of MAaS increased in the blend. This result was confirmed by morphological analysis, by which it was possible to observe that the amorphous component diminished its droplike domains. Contact angle measurements suggest that the wettability of PEO drops on a PS/MAaS surface are larger in the system containing MAaS as the compatibilizer.     

PVC／PE交联共混体系的动态力学研究

在ＰＶＣ／ＰＥ共混体系中加入交联剂和引发剂能产生ＰＶＣ－ＣＯ－ＰＥ共聚物，这种共聚物在共混物中可起到增容剂的作用。通过动态力学分析和扫描电镜研究了ＰＶＣ／ＰＥ交联共混体系的相容性。发现引发剂、交联剂、稳定剂和增塑剂等对共混物中的交联反应均有较大的影响。     

Dynamically vulcanized ethylene propylene diene terpolymer/nylon thermoplastic elastomers

A thermoplastic elastomer (TPE) of ethylene propylene diene terpolymer (EPDM) and nylon with excellent mechanical properties was prepared by dynamic vulcanization. The effects of the curing systems, compatibilizer, nylon content and reprocessing on the mechanical properties of EPDM/nylon TPEs were investigated in detail. Experimental results indicate that maleic anhydride (MAH) grafted EPR has a better performance in compatibilizing the EPDM/nylon blends compared with other compatibilizers containing acid group. Tensile strength and elongation at break go through a maximum value at a compatibilizer resin content (on total rubber dosage) of 20%. EPDM/nylon TPE using sulfur as curative has higher tensile strength and elongation than that of TPE using phenolic resin or peroxide as curatives. Tensile strength and elongation at break increase with increasing nylon content. Scanning electron microscopy results show that rubber particles distributed at an average size of 1 μm in dynamic vulcanized EPDM/MAH-g-EPR/nylon TPE.     

PP-EPR二嵌段共聚物作PP/EPT共混增容剂的探讨

对以实验室合成的PP-EPR二嵌段共聚物作为PP/EPT二元共混物的增容剂进行了探讨。共混物在增容前后的物理力学性能的变化说明PP-EPR对PP/EPT共混物具有优良的增容效果;同时又有克服通常因橡胶增韧塑料而强度下降的优点。形态结构的表征结果说明共混物为两相结构,阐明了PP-EPR的作用以及低温冲击强度大幅度提高和在增容后抗张强度损失减少的原因。     

Effect of poly(vinyl acetate) (PVAc) on thermal behavior and mechanical properties of poly(3-hydroxybutyrate)/poly(propylene carbonate) (PHB/PPC) blends

To assess the compatibility of blends of synthetic poly(propylene carbonate) (PPC), with a natural bacterial poly(3-hydroxybutyrate) (PHB), a simple casting procedure of blend was used. poly(3-hydroxybutyrate)/poly(propylene carbonate) blends are found to be incompatible according to DSC and DMA analysis. In order to improve the compatibility and mechanical properties of PHB/PPC blends, poly(vinyl acetate) (PVAc) was added as a compatibilizer. The effects of PVAc on the thermal behavior, morphology, and mechanical properties of 70PHB/30PPC blend were investigated. The results show that the melting point and the crystallization temperature of PHB in blends decrease with the increase of PVAc content in blends, the loss factor changes from two separate peaks of 70PHB/30PPC blend to one peak of 70PHB/30PPC/12PVAc blend. It is also found that adding PVAc into 70PHB/30PPC blend can decrease the size of dispersed phase from morphology analysis. The result of tensile properties shows that PVAc can increase the tensile strength and Young’s modulus of 70PHB/30PPC blend, and both the elongation at break and the tensile toughness increase significantly with PVAc added into 70PHB/30PPC.     

Reactive blending of polypropylene/polyamide-6 in the presence of tailor-made succinic anhydride-terminated oligopropene compatibilizers

Various anhydride-terminated isotactic and atactic oligopropenes of number average molecular weights ranging between 1,000 and 10,000 g/mole, prepared by maleinating vinylidene-terminated propene oligomers obtained with isospecific and nonstereospecific metallocene-based Ziegler–Natta catalysts, have been evaluated as blend compatibilizers of polypropylene/polyamide-6 (70 vol%/30 vol%) blends to study the role of blend compatibilizer molecular architecture. When added during processing, as shown by IR spectroscopic analysis, the anhydride-terminated oligopropenes react with the amine-terminated polyamide-6 to yield polypropylene-block-polyamide-6 in situ. Such block copolymers are efficient dispersing agents. While the polyamide dispersion in the polypropylene continuous phase is not affected by blend compatibilizer stereoregularities, both stiffness and yield stress as well as notched Charpy impact strength increase with increasing stereoregularities and molecular weights. With oligopropene molecular weights exceeding 1,150 g/mole, the average size of the dispersed polyamide microphases correlates with the volume fraction of the oligopropene-block-polyamide-6 blend compatibilizer and the dicarboxylic acid anhydride/amine molar ratio.