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Polymer-clay nanocomposites have been prepared by melt blending of commercial organoclay Cloisite 15A with blends of polyethylenes (PE) and maleic-anhydride-grafted PE (PE/PE-g-MA) with wide range of composition. Three types of PE/PE-g-MA blends with different molecular structure, namely blends of high-density PE (HD) with HD-g-MA (HDMA), blends of low-density PE (LD) with LD-g-MA (LDMA), and blends of linear low-density PE (LL) with LL-g-MA (LLMA) were used. The influence of the molecular structure of the PE matrixes and the compatibility between the blend components on the morphology of the nanocomposites was studied. The thermal properties, microhardness, and transparency of the nanocomposites were investigated. The influence of the degree of exfoliation/intercalation on the materials characteristics is discussed. [ABSTRACT FROM AUTHOR]

The article presents a study on the compatibility of clay nanocomposites with various clay concentrations. The research, which involved the structure, heat conductance, and microhardness of the nanocomposites ethylene-glycidyl methacrylate copolymer (EGMA)/clay and ethylene-acrylic ester-glycidyl methacrylate terpolymer (EAGMA)/clay and organoclays Cloisite 20A (C120A) and Cloisite 30B (C130B), revealed high compatibility between the nanocomposites and the organoclays.

Abstract: The calorimetric characteristics, the flammability, the thermal stability and the microhardness of polyethylene high density/clay nanocomposites (HDPE/clay) have been studied by differential scanning calorimetry, thermogravimetry, determination of limiting oxygen index and microhardness tests. The nanocomposites have been compatibilized by ethylene–acrylic acid copolymer (EAA), acrylic acid grafted HDPE (HDAA) and maleic anhydride grafted HDPE (HDMA). The clay was montmorillonite Cloisite 15A. The influence of the presence and the type of the compatibilizers on the properties of the nanocomposites has been evaluated. The results have shown that the thermal stability, the reduction of the flammability and the microhardness of HDPE/clay nanocomposites, compatibilized by HDAA and HDMA are higher than those for nanocomposite compatibilized by EAA. Moreover, the presence and the type of compatibilizer have negligible effect on the characteristics of the HDPE phase transitions. These results have been interpreted by the better clay dispersion and higher level of clay exfoliation in the presence of compatibilizers HDAA and HDMA, than those in the presence of EAA compatibilizer. [Copyright &y& Elsevier]

The nonisothermal crystallization kinetics and microhardness of nanocomposites consisting of a polypropylene matrix (PP) and carbon nanotube filler (CNT) have been investigated. Three types of PP matrixes have been used: two of them are nonfunctionalized PP that differ slightly in their melt flow index, whereas the third is grafted with maleic anhydride (MA). Ozawa formalism has been used to study the nonisothermal crystallization kinetics. The results show that the CNT filler has a nucleation role in the nonisothermal crystallization of PP. For all nanocomposites, the nonisothermal crystallization rate increases up to 4% CNT and then decreases slightly or remains almost constant at the higher filler content. This fact has been interpreted in terms of an aggregation of the particles at high filler concentration, which leads to a decrease of the nucleation ability of the filler because the number of heterogeneous nuclei decreases. The crystallization mechanism of the PP matrixes almost does not change in the presence of the CNT filler. The microhardness of the two nonfunctionalized PP increases when the filler content increases and then remains constant above a certain filler content. The experimental microhardness values of the composites based on the functionalized PP are lower than those of the corresponding calculated additive values. The decrease of the creep constant with the filler addition is not significant, as should be expected when inorganic filler is added to a polymer matrix. This is due to the very fine dispersion of the fillers into the polymer matrix at the nanoscale level. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents differential scanning calorimetry and electron microscopy of the fractionated crystallization and polydispersity of the dispersed PA6 phase in compatibilized LDPE/PA6 75/25 w/w blends. The compatibilizers used were (i) an acrylic acid functionalized polyethylene, Escor 5001 (EAA); (ii) an ethylene–glycidylmethacrylate copolymer, Lotader GMA AX8840 (EGMA); (iii) a polystyrene–poly(ethylene–butylene)–polystyrene triblock copolymer comprising 2wt.% maleic anhydride grafts, Kraton FG 1901X (SEBS-g-MA). The compatibilizer SEBS-g-MA has the strongest reduction effect upon the size of PA-6 droplets. Its implementation provides the best fractionated crystallization. The fractionated crystallization has not been observed for the blend compatibilized with EGMA. The results show that the degree of compatibilization could be evaluated qualitatively by the progress of the fractionated crystallization. So, the three compatibilizers could be rated according to their effectiveness as follows: SEBS-g-MA>EAA>EGMA. The self-nucleation experiments have demonstrated that the lack of active nuclei in the finely dispersed PA6 droplets is the determining factor for the fractionated crystallization at high supercooling, and not the considered absolute particle size. The measurement of the Vickers microhardness of the compatibilized blends confirms that the compatibilizing activity of SEBS-g-MA and EAA is stronger than that of EGMA. [Copyright &y& Elsevier]

The Vickers microhardness of PET-based liquid crystalline copolyesters has been investigated. The copolyesters have been synthesized by transesterification of PET with equimolar amounts of sebacic acid (S) and hydroquinone (Q) (or 4,4′-dihyroxybiphenyl (B)) and with varying amounts of 4-hydroxybenzoic acid (H). The variation of the Vickers microhardness of PET-S-Q-H and PET-S-B-H liquid crystalline polyesters with the composition have been interpreted by the microstructure of the materials. The increase in the concentration of 4-hydroxybenzoic acid (H) in both types of copolyesters leads to an increase in intermolecular distance and to enlargement of the domain size. This, on its, turn, leads to a decrease in the materials'' microhardness. The effect that the mixing time of the reactive blends of equimolar amounts of PET and poly(phenylene sebacate) (PQS) PET/PQS has upon the microhardness values has been also studied. The variation of the microhardness of PET/PQS blends prepared for different mixing times follows the same tendency as that of the melting enthalpy (i.e. the degree of crystallinity). Both parameters have lower values with the longer mixing time. The decreased crystallinity during the transreaction results into materials having higher creep rate under load. [Copyright &y& Elsevier]

Microhardness tests, water absorption and thermogravimetric measurements have been performed on blends of low density polyethylene (LDPE) with different molar mass and polyamide 6 (PA6) compatibilized with 2 pph poly(ethylene-co-acrylic acid) (Escor 5001 by Exxon). The negative deviation of Vickers microhardness from the additivity has been interpreted by changes in the crystallinity of the blend components. The hardness values of the compatibilized blends that are lower than those of the corresponding uncompatibilized blends have been explained by the decrease of the degree of crystallinity of PA6 phase in the presence of Escor. The molar mass of LDPE almost does not influence on the hardness values. The lower water absorption of the compatibilized blends, caused by the formation of a copolymer between PA6 and the compatibilizer leads to microhardness values of the wet compatibilized blends higher than those of the corresponding uncompatibilized blends. The thermogravimetric measurements demonstrate that the thermal stability of blends increases in the presence of 2 pph Escor 5001. The results confirm the compatibilizing efficiency of Escor 5001 towards LDPE/PA6 blends in a wide composition range. [Copyright &y& Elsevier]

Abstract: The flammability, microhardness and transparency of nanocomposites based on poly(ethylene-co-acrylic acid) copolymers having different concentration of acrylic acid and different molar mass, their Zn ionomer and ethylene-glycidylmethacrylate copolymer as matrixes and on organically modified montmorillonite as a nanofiller have been investigated. The presence and the increase in the content of the clay lead to the increase in the limiting oxygen index and to significant reduction of the burning rate of all materials. The results from the Vickers microhardness measurements have shown that the addition of the clay to matrixes of polar functionalized polyethylenes leads to a significant increase in the microhardness of the materials, while the creep constant does not decrease significantly. The UV spectra show that the light transmittance of the materials does not change significantly in the presence of the clay, i.e., the nanocomposite films preserve the polymer transparency. The results have been interpreted by the intercalated structures of the nanocomposites investigated. [Copyright &y& Elsevier]