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Molecular Composites (molecular + composite)

Distribution by Scientific Domains
Polymers and Materials Science100%

Selected Abstracts

Structure, Morphology and Properties of a Novel Molecular Composite by In-Situ Blending of Anionic Polyamide 6 with a Polyamide Copolymer Containing Rigid Segments

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2007
Xiaochun Wang
Abstract Molten caprolactam, in which a polyamide copolymer (HPN) containing rigid segments was dissolved, was polymerized by means of anionic ROP to in produce polyamide (PA, nylon) 6 blends with HPN in situ. A novel molecular composite was achieved in which toughness and strength were simultaneously improved, as well as modulus, compared to virgin PA6. In view of the interchange reaction between PA6 and PA1212 (and PA66) in blends fabricated in the same way, it was deduced that a similar reaction between PA6 and HPN took place during the blending and led to copolymerization between the two components. The formation of copolymers was verified by their single glass transition and single melting peak, measured through DMA and DSC, respectively. DSC analysis also showed that the occurrence of the interchange reaction inhibited the crystallization and suppressed the melting point of PA6. Analysis by FT-IR spectroscopy indicated that the difference in the distance between the amide groups for PA6 and HPN induced a decrease in the amount and strength of hydrogen bonding. Moreover, characterization by POM and XRD revealed that the spherulite size of the PA6 crystals decreased dramatically and the amount of , crystal increased slightly with the majority of crystallites being , crystals. Furthermore, it was found through the observation of the morphology by SEM that no phase separation existed in the composites. On the basis of detailed analysis and a comparison between the in situ PA6/PA66 and PA6/HPN blends, it is believed that the combination of markedly decreasing spherulite size and similar segmental mobility resulted in the simultaneous improvement of mechanical properties for the in situ PA6/HPN blends. [source]

Molecular composites prepared by in situ direct synthesis of wholly aromatic rigid-rod polyamides via the phosphorylation reaction in a dissolved nylon-6 matrix

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2003
Satoshi Idemura
Abstract Wholly aromatic rigid-rod polyamides such as poly(p -phenyleneterephthalamide) (PPD-T) were synthesized in situ in a solution of nylon-6 via the phosphorylation polycondensation method to form nanocomposites or so-called "molecular composites." The incorporation of PPD-T into a nylon-6 matrix was achieved by this approach in a more compatibilized form than that obtained by the conventional coagulation method that entails precipitation of a blend of PPD-T and nylon-6 in a solvent, for example, concentrated sulfuric acid. Gelation occurred during the synthesis, presumably because of the formation of interpenetrating networks accompanied by some block-copolymer formation. The transparency and tensile properties of the resultant composite films from the rigid-rod aromatic polyamide/nylon-6 combination were improved over those of nylon-6 film alone. Rainbow-colored intense birefringence was observed for the composite films under crossed polarizers. These properties are discussed in context with the in situ synthesized rigid-rod polyamides uniformly incorporated in nylon-6. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1014,1026, 2003 [source]

Structure, Morphology and Properties of a Novel Molecular Composite by In-Situ Blending of Anionic Polyamide 6 with a Polyamide Copolymer Containing Rigid Segments

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2007
Xiaochun Wang
Abstract Molten caprolactam, in which a polyamide copolymer (HPN) containing rigid segments was dissolved, was polymerized by means of anionic ROP to in produce polyamide (PA, nylon) 6 blends with HPN in situ. A novel molecular composite was achieved in which toughness and strength were simultaneously improved, as well as modulus, compared to virgin PA6. In view of the interchange reaction between PA6 and PA1212 (and PA66) in blends fabricated in the same way, it was deduced that a similar reaction between PA6 and HPN took place during the blending and led to copolymerization between the two components. The formation of copolymers was verified by their single glass transition and single melting peak, measured through DMA and DSC, respectively. DSC analysis also showed that the occurrence of the interchange reaction inhibited the crystallization and suppressed the melting point of PA6. Analysis by FT-IR spectroscopy indicated that the difference in the distance between the amide groups for PA6 and HPN induced a decrease in the amount and strength of hydrogen bonding. Moreover, characterization by POM and XRD revealed that the spherulite size of the PA6 crystals decreased dramatically and the amount of , crystal increased slightly with the majority of crystallites being , crystals. Furthermore, it was found through the observation of the morphology by SEM that no phase separation existed in the composites. On the basis of detailed analysis and a comparison between the in situ PA6/PA66 and PA6/HPN blends, it is believed that the combination of markedly decreasing spherulite size and similar segmental mobility resulted in the simultaneous improvement of mechanical properties for the in situ PA6/HPN blends. [source]

Rigid-Rod Polymers: Synthesis, Processing, Simulation, Structure, and Properties

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 11 2003
Xiao-Dong Hu
Abstract Synthesis, structure, and properties of rigid-rod polymers with special emphasis on poly(p -phenylene benzobisoxazole) (PBO) and poly(p -phenylene benzobisthiazole) (PBZT) have been reviewed. Recent studies on chemical modifications and molecular simulations have also been given. After nearly 20 years of research and development, PBO fiber was commercialized in the late 1990s. However, due to processing difficulties, the concept of the so called molecular composites has not been successful. Development of the high compressive strength M5 and dihydroxy-PBI fibers clearly suggest that there is potential for further developing properties of this class of materials. Opto-electronic properties have also been reviewed. Synthesis of PBZT. [source]

Studies on Molecular Composites of Polyamide 6/Polyamide 66

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 19 2004
Yulin Li
Abstract Summary: A series of molecular composites of PA 6/PA 66 was synthesized via in situ polymerization. The impact resistance of PA 6 was improved dramatically by incorporating a minor amount of PA 66 (2,10 wt.-%), without decreasing the tensile strength. Inserting PA 66 macromolecules at a molecular level into a PA 6 matrix may interfere with the arrangement of the hydrogen bonds of PA 6, in turn changing the crystalline structure and impeding the crystallization of PA 6. SEM micrograph of the fractured surface of a PA 6/PA 66 composite containing 10 wt.-% PA 66. [source]

In situ generated diphenylsiloxane-polyimide adduct-based nanocomposites

POLYMER ENGINEERING & SCIENCE, Issue 1 2005
Manisha G. Goswami
Arylsiloxane was incorporated into polyimide (PI) via electronic interaction with polyamic acid (PAA)/PI, and a wide spectrum of properties were evaluated for different compositions. The samples prepared with relatively low concentrations (0.0001,0.1%) of oligomers showed unusual synergism, which is attributed to the generation of nanostructures dispersed in the continuous PI matrix. The incorporation of siloxane with bulky phenyl groups contributed to enhanced thermal stability as determined by thermogravimetric analysis. Water uptake and methanol absorption by these composites were evaluated and correlated with the underlying micro- and nanostructures. Fourier Transform Infrared (FTIR) spectroscopy was used to elucidate the probable reaction mechanism (including in situ polymerization of arylsilanol), and to study the synthetic aspects associated with the molecular composites and nanocomposites formation. POLYM. ENG. SCI., 45:142,152, 2005. © 2004 Society of Plastics Engineers [source]