Search results for "Thermal"
showing 10 items of 3576 documents
Thermomechanical properties and thermal degradation kinetics of poly(methyl methacrylate) (PMMA) and polycarbonate (PC) filled with cerium-doped yttr…
2016
This paper reports on the thermomechanical properties and thermal degradation kinetics of poly(methyl methacrylate) (PMMA) and polycarbonate (PC) composites filled with cerium-doped yttrium aluminium garnet (Ce:YAG) at different contents ranging between 0.1 and 5 wt%, and prepared by melt compounding. The interaction between PMMA and the filler was much stronger than that between PC and the filler, and this resulted in a significant improvement in the dynamic mechanical properties of the PMMA composites. The presence of filler did not significantly increase the thermal stability of the PC, while an observable increase in the thermal stability was only observed at higher filler loadings for …
Recycled Polycarbonate Based Nanocomposites
2013
Post-consumer polycarbonate (RPC) blends with various amounts (5, 10, 30 wt. %) of ethylene vinyl acetate copolymer (EVAc) are investigated as potential nanocomposite matrices. At EVAc weight content of 10 wt.% maximum tensile strength σM and impact strength AI increase is observed in comparison to neat RPC. Addition of EVAc, however, reduces resistance to creep as well as decrease thermal stability of the investigated compositions. Addition of montmorillonite nanoclay (MMT), however, allows increase modulus of elasticity E and yield strength σY of the investigated RPC blend with 10 wt. % of EVAc. Besides it creep resistance and thermal resistance of the investigated system is increased to …
Dynamic Model Metallo‐Supramolecular Dual‐Network Hydrogels with Independently Tunable Network Crosslinks
2020
Crystallization and melting of fractions of branched polyethylene
1983
Effects of the molecular weight on the crystallization behaviour of branched polyethylene become observable if isothermal crystallization is studied at temperatures near to the melting end. Crystallinities decrease with decreasing molecular weight. Thicknesses of lamellae grown during isothermal crystallization are independent of the molecular weight. They depend only on temperature. Compared to the effect of the branches polydispersity gives only a minor contribution to the broadening of the crystallization and melting range of low density polyethylene.
Crystallization kinetics of poly(ethylene oxide) from its melt and from mixtures with tetrahydronaphthalene and oligo(ethylene oxide-block-dimethylsi…
2004
The crystallization of poly(ethylene oxide) (PEO) from the pure state and from its mixtures with oligo(dimethyl siloxane-b-ethylene oxide) (COP) and tetrahy- dronaphthalene (THN) was investigated. The crystallization kinetics was studied iso- thermally and nonisothermally with an automated device that monitored the light passing through the corresponding liquids as functions of time and/or temperature. The rate was strongly influenced by the concentration of COP in the mixture. A substantial decrease in the induction time (the time required for the onset of crystallization) and a considerable shift in the crystallization temperature (the transition from a liquid state to a solid state) to h…
Hyperbranched PEG by Random Copolymerization of Ethylene Oxide and Glycidol
2010
The synthesis of hyperbranched poly(ethylene glycol) (hbPEG) in one step was realized by random copolymerization of ethylene oxide and glycidol, leading to a biocompatible, amorphous material with multiple hydroxyl functionalities. A series of copolymers with moderate polydispersity ($\overline {M} _{{\rm w}} /\overline {M} _{{\rm n}} $ < 1.8) was obtained with varying glycidol content (3-40 mol-%) and molecular weights up to 49 800 g mol(-1) . The randomly branched structure of the copolymers was confirmed by (1) H and (13) C NMR spectroscopy and thermal analysis (differential scanning calorimetry). MTS assay demonstrated low cell toxicity of the hyperbranched PEG, comparable to the highly…
ESTIMATION OF INJECTION PRESSURE DURING MOLD FILLING.
1982
Dimensionless diagrams for estimating the bulk temperature of the flow front and injection pressure in the limit of small viscous generation are obtained. Also, a criterion for neglecting viscous generation is identified, The diagrams, based on the Lord and Williams model, refer to rectangular geometry and amorphous materials. A satisfactory comparison is obtained with literature data taken on polystyrene. A reasonable estimate of polyethylene injection pressure was obtained by roughly accounting for latent heat of crystallization through modified thermal diffusivity.
Thermal stability and flammability of polyolefin/halloysite nanotubes composites
2015
Najnowsze badania w zakresie uniepalniania poliolefin są ukierunkowane na zastosowanie dodatku nanorurek haloizytowych (HNT) jako bezhalogenowego środka zmniejszającego palność, a jednocześnie zachowującego właściwości mechaniczne osnowy. Powstająca na powierzchni płonącego nanokompozytu, zawierającego HNT, warstwa tzw. zgorzeliny ogranicza przenikanie gazów oraz ciepła i zabezpiecza materiał przed dalszym paleniem. Unikatowa struktura HNT umożliwia dodatkowo pochłanianie produktów termicznego rozkładu poliolefinowej osnowy. Na podstawie dostępnej literatury dokonano oceny wpływu różnych czynników, m.in. modyfikacji nanorurek haloizytowych i/lub dodatku kompatybilizatora i/lub doboru odpowi…
Long-term ISO 23936-2 sweet oil ageing of HNBR
2021
Abstract A hydrogenated nitrile butadiene rubber (HNBR) compound is subjected to ageing in a simulated oil and gas environment in accordance with ISO 23936-2 standard at two elevated temperatures (130 °C and 150 °C) for a period of up to 9 months. Shore D hardness, thermal expansion, dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy, compression and compression set (CS) measurements are made before and after the chemical exposure. The hardness, modulus at short times, degree of relaxation and CS increases while the coefficient of thermal expansion in HNBR tends to decrease with ageing time and temperature. Temperature is shown to impose a greater effect on th…
Long-term thermomechanical degradation of molten polystyrene
1985
Abstract Rheological data on polystyrene samples processed for long periods under various mechanical stresses are presented. The data indicate that thermomechanical degradation occurs and that the rate of thermal degradation is increased by the applied stress. Moreover degradation does not reach a limiting value even at high processing times.