Unsaturated Polyester Resins (unsaturated + polyester_resin)

Distribution by Scientific Domains


Selected Abstracts


Temperature dependence of electrical resistivity in carbon nanofiber/unsaturated polyester nanocomposites

POLYMER ENGINEERING & SCIENCE, Issue 7 2008
Toshiaki Natsuki
This article described the temperature dependence of electrical resistivity for carbon nanofiber (CNF)/unsaturated polyester resin (UPR) nanocomposites prepared by a solvent evaporation method. It was found that the CNF/UPR nanocomposites had quite low electrical percolation threshold due to CNFs having a large aspect ratio and being well dispersed into the UPR matrix. A sharp decrease in the electrical resistivity was observed at about 1 wt% CNF content. The influence of CNF content on the electrical resistivity was investigated as a function of temperature in detail. The nanocomposites showed a positive temperature coefficient effect for the resistivity, and had a strong temperature dependence near the percolation threshold. When the number of thermal cycles was increased, the electrical resistivity decreased and had a weak temperature dependence, especially in the case of melting temperature. Moreover, the size influences of CNFs on the electrical properties of nanocomposites were analyzed and discussed. POLYM. ENG. SCI., 2008. 2008 Society of Plastics Engineers [source]


Amine Modifiers with an s-Triazine Ring for Unsaturated Polyester Resins, 2,

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10-11 2007
Mono-, Multihydroxyalkyl Modifiers
Abstract The paper deals with the synthesis of amine modifiers for unsaturated polyester resins obtained from N -phenyl-2-amineethanol and 2,4-dichloro-6-methoxy-1,3,5-triazine (modifier A), 2-chloro-4,6-dimethoxy-1,3,5-triazine (modifier B) or with cyanuric chloride (modifier C). Properties of amine modifiers for unsaturated polyester resins are presented. The modifiers were incorporated into resins at the polycondensation stage. [source]


Composites from PMMA modified thermosets and chemically treated woodflour

POLYMER ENGINEERING & SCIENCE, Issue 5 2003
Betiana A. Acha
The mechanical behavior of composites made from woodflour and a modified thermoset unsaturated polyester resin has been examined. Polymethylmethacrylate (PMMA), a common low profile additive (LPA), was used as the matrix modifier. Woodflour, the reinforcing filler, was used ,as received' and was also modified with a commercial alkenyl succinic anhydride (ASA), in order to enhance the compatibility with the resin. The composites exhibited higher flexural and compressive modulus and compressive yield stress than the neat resin, while flexural strength and ultimate strain were reduced. The addition of PMMA to the unfilled thermoset led to a LPA morphology and decreased the flexural modulus, but produced an increment in flexural strain at break, impact energy and toughness of the UP resin. No enhancement in the mechanical behavior of the composites was found when treated woodflour instead of unmodified woodflour was used. [source]


Amine Modifiers with an s-Triazine Ring for Unsaturated Polyester Resins, 2,

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10-11 2007
Mono-, Multihydroxyalkyl Modifiers
Abstract The paper deals with the synthesis of amine modifiers for unsaturated polyester resins obtained from N -phenyl-2-amineethanol and 2,4-dichloro-6-methoxy-1,3,5-triazine (modifier A), 2-chloro-4,6-dimethoxy-1,3,5-triazine (modifier B) or with cyanuric chloride (modifier C). Properties of amine modifiers for unsaturated polyester resins are presented. The modifiers were incorporated into resins at the polycondensation stage. [source]


Radiation and postirradiation crosslinking and structure of two unsaturated polyester resins

POLYMER ENGINEERING & SCIENCE, Issue 9 2008
Irina Puci
Radiation and postirradiation crosslinking of two unsaturated polyester (UP) resins were monitored, and substantial differences in the reaction course and extents were observed. DSC thermograms of one of the resins showed double peaks and significantly lower residual reaction heats. Extraction revealed that gelation dose of the resin with double peak was twice the gelation dose of the other resin that had single peak in DSC thermograms. Although other components of the polyesters were identical, NMR spectra of the resin with a single peak revealed isophthalic units while in the polyester of the resin having double DSC peaks orthophthalic units were detected. Orthophthalate reduced the compatibility of polyester and styrene and caused the reaction-induced phase separation, influencing gel structure that was visible in scanning electron microscope micrographs. Previously, the double peaks in crosslinking thermograms of UP resins were usually attributed to initiator effects, but here no initiator was used, and, in the literature, we found that the double peaks are almost exclusively present in the thermograms of UP resins containing orthophthalates, whereas in resins with isophthalates double peaks almost never appear. Crosslinking extents were significantly higher in the resin-containing isophthalate and in both cases enhanced by postirradiation reaction that is often neglected. POLYM. ENG. SCI., 2008. 2008 Society of Plastics Engineers [source]


Thermal degradation of a brominated bisphenol a derivative

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2003
M. P. Luda
Abstract The thermal degradation of 2,6,2,,6,,tetrabromo-4,4,-isopropylidene-di phenol (tetrabromobisphenol A) (TBBPA) has been investigated and a mechanism for its thermal degradation is suggested. TBBPA is a comonomer widely used in epoxy and in unsaturated polyester resins to impart fire retardance. These resins find a common use in electric and electronic equipment. The presence of bromine atoms is the key factor in fire retardant activity, while on the other hand it represents an ecological problem when pyrolytic recycling is programmed at the end of the useful life of such items. However, pyrolysis is the more advantageous recycling system for thermosetting resins and thus efforts should be made to control the pyrolysis in order to avoid or minimize the development of toxics. Homolytic scission of the aromatic bromine and condensation of aromatic bromine with phenolic hydroxyl are the main processes occurring in the range 270,340C. A large amount of charred residue is left as a consequence of condensation reactions. HBr and brominated phenols and bisphenols are the main volatile products formed. Brominated dibenzodioxins structures are included in the charred residue and not evolved in the volatile phases. Copyright 2003 John Wiley & Sons, Ltd. [source]