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Interchange Reaction (interchange + reaction)
Selected AbstractsThermal properties and phase morphology of melt-mixed poly(trimethylene terephthalate)/poly(hexamethylene isophthalamide) blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Fang-Chyou Chiu Abstract This work examines the thermal properties and phase morphology of melt-mixed poly(trimethylene terephthalate) (PTT)/poly(hexamethylene isophthalamide) (PA 6I) blends. Two temperatures, i.e., 250 and 260°C, are used to prepare the blends, respectively. Differential scanning calorimetry results indicate the immiscible feature of the blends. It is thus concluded that the ester-amide interchange reaction hardly occurred in the PTT/PA 6I blends. Depending on the composition and mixing temperature, the crystallization ability of PTT in the blends is either enhanced or hindered. Basically, a lower PA 6I content shifts the PTT melt crystallization to a higher temperature, whereas a higher PA 6I content causes an opposing outcome. The original complex melting behavior of neat PTT becomes more regular after the incorporation of 60 wt % or 80 wt % of PA 6I. Thermogravimetry analyses (TGA) show that the thermal stability of the blends improves as the PA 6I content increases. The two-phased morphology of the blends is examined by scanning electron microscopy (SEM). Polarized light microscopy (PLM) results reveal that the PTT spherulites become coarser with the inclusion of PA 6I; only smaller/dispersed crystallites are observed in the blend with 20 wt % of PTT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Preparation and Characterization of Hybrid Nanocomposites Coated on LDPEMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 22 2006Laura Mazzocchetti Abstract Summary: Hybrid organic-inorganic nanocomposites containing hyperbranched structures were prepared through a dual-curing process, which involves photopolymerization and condensation alkoxysilane groups. In particular, an oligomer containing PEO units and ,,, -methacrylate groups was used together with a HBP bearing acrylic groups as the organic phase precursors. MEMO, as the organic-inorganic linker, and TEOS, as inorganic phase precursor, were also employed. The kinetics of both photopolymerization and condensation reactions were investigated by double bond conversion analysis (via FT-IR) and weight loss determination, respectively. The mobility of the organic phase was studied by means of DSC and DMTA and correlated with hybrid composition. TEM analyses performed on microtomed film slices indicated the formation of nanoscale silica domains. Hybrids were coated onto an LDPE film previously subjected to a plasma treatment, and substrate-coating interfacial adhesion was investigated through stress-strain and DMTA experiments. Reaction scheme showing the insertion of furanic units in copolyester chains by ester interchange reaction. [source] Structure, Morphology and Properties of a Novel Molecular Composite by In-Situ Blending of Anionic Polyamide 6 with a Polyamide Copolymer Containing Rigid SegmentsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2007Xiaochun 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] HALS in polyamide 6 polymerizationMACROMOLECULAR SYMPOSIA, Issue 1 2003Roberto Filippini Fantoni Abstract The use of Hindered Amine Light Stabilizers (HALS) directly in polyamide 6 polymerization can cause some problems. The following two problems were the focus of our project: 1) We investigated, from a theoretical point of view, the results of introducing directly one of the precursors of HALS into polyamide 6 polymerization. For the investigation, 4 amino-2,2,6,6-tetramethylpiperidine (triaceton-diamine or TAD) was chosen. We considered the TAD chain-ending effects and their influence on the total amount of amino chain-endings that can be titrated, a parameter of primary importance in the fibre field. 2) We examined the amide interchange reaction in the case of an HALS containing two amide groups, using a product available on the market, N,N,-bis(tetramethyl-4-piperidyl)isophtalamide. In this case we were able to generate a couple of equations that allows one to calculate the quantity of amide interchanged HALS. This was done by comparing the results (molecular weight and chain-endings analysis) of polymerization with and without HALS. [source] On the Interrelationship of Transreactions with Thermal Properties and Dynamic Mechanical Analysis of PTT/PEN BlendsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2009Seyed-Hassan Jafari Abstract An attempt was made to explore the effects of interchange reactions on the crystallization, melting, and dynamic mechanical behavior of binary blends based on poly(trimethylene terephthalate) (PTT)/poly(ethylene 2,6-naphthalate) (PEN). 1H NMR spectroscopy is used to verify the occurrence of interchange reactions at the interface, which are increased upon an increase in the melt processing time and temperature. The crystallinity of PTT was reduced while that of PEN was increased on blending. In addition, the crystallization temperatures of both phases showed depression. A single composition-dependent glass transition temperature (Tg) was detected in the second and subsequent heating thermograms of the blends, which is indicative of miscibility. The cold crystallization of the PTT phase was observed to increase while that of PEN was suppressed on blending. Each phase crystallized individually and a melting point depression was evident, which suggests a certain level of miscibility. Dynamic mechanical thermal analysis corroborated differential scanning calorimetry results. A constructive synergism was observed in the glassy state storage moduli of the blends, which is suggestive of a reduced specific volume of the system because of enhanced interactions and crystallinity. [source] | ||||||||||