			Home About us Contact

Unsaturated Polyester (unsaturated + polyester)

Distribution by Scientific Domains

Polymers and Materials Science	90%

Terms modified by Unsaturated Polyester

unsaturated polyester resin

Selected Abstracts

Nanocomposite systems based on unsaturated polyester and organo-clay

POLYMER ENGINEERING & SCIENCE, Issue 2 2005
I. Mironi-Harpaz
Unsaturated polyester (UP) systems give rise to numerous possible approaches in synthesizing nanocomposites. A simultaneous mixing method was used to synthesize UP-resin/organo-clay nanocomposites. The effects of various mixing processes, using several organically-modified clay types, were investigated. The incorporation of these organo-clays resulted in an intercalated structure, the extent of which depended mainly on the type of the clay organic treatment. Organo-clays that exhibited the highest intercalation levels were further studied using a sequential mixing method. The UP-alkyd (without styrene) was mixed with different organo-clays. Processing parameters such as mixing modes, applied shearing levels, clay contents, and mixing-temperatures were investigated. Prolonged high shear levels promoted the intercalation and exfoliation of the silicate layers, resulting in a better dispersion of clay particles. The high shear levels effects were achieved by vigorous mechanical mixing and were intensified by using large amounts of clay and optimized matrix viscosity. Rheological studies of the nanocomposites were found complementary and in correlation with morphological and thermal characterization. This methodological approach provides a basis for understanding the structuring processes involving the formation of the UP/clay nanocomposites and establishing materials-processing-structure interrelations. Polym. Eng. Sci. 45:174,186, 2005. © 2005 Society of Plastics Engineers. [source]

Processing, mechanical properties, and interfacial bonding of a thermoplastic core-foam/composite-skin sandwich panel,

ADVANCES IN POLYMER TECHNOLOGY, Issue 3 2010
S. Pappadà
Abstract In this work, a thermoplastic sandwich panel was designed, produced, and tested for use in insulating walls of containers for food transportation. A sandwich construction comprising a poly(ethylene terephthalate) core and polypropylene/glass fiber skins was evaluated as possible replacement of systems consisting of polyurethane foam in combination with unsaturated polyester glass-reinforced skins that are currently used for the manufacture of these structures. Factors were taken into account to satisfy the simultaneous need of thermal insulation and adequate mechanical properties that are required for the production of large flat panels 100-mm thick. The influences of different manufacturing processes and skin-core adhesion on the mechanical properties of this thermoplastic sandwich were investigated and are discussed in the text. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:137,145, 2010; View this article online at wileyonlinelibrary. DOI 10.1002/adv.20186 [source]

Dynamic mechanical analysis of pineapple leaf/glass hybrid fiber reinforced polyester composites

POLYMER COMPOSITES, Issue 6 2010
L. Uma Devi
The dynamic mechanical properties of randomly oriented intimately mixed hybrid composites based on pineapple leaf fibers (PALF) and glass fibers (GF) in unsaturated polyester (PER) matrix were investigated. The PALFs have high-specific strength and improve the mechanical properties of the PER matrix. In this study, the volume ratio of the two fibers was varied by incorporating small amounts of GF such as PALF/GF, 90/10, 80/20, 70/30, and 50/50, keeping the total fiber loading constant at 40 wt%. The dynamic modulus of the compositeswas found to increase on GF addition. The intimately mixed (IM) hybrid composites with PALF/GF, 80/20 (0.2 Vf GF) showed highest E, values and least damping. Interestingly, the impact strength of the composites was minimum at this volume ratio. The composites with 0.46 Vf GF or PALF/GF (50/50) showed maximum damping behavior and highest impact strength. The results were compared with hybrid composites of different layering patterns such as GPG (GF skin and PALF core) and PGP (PALF skin and GF core). IM and GPG hybrid composites are found more effective than PGP. The activation energy values for the relaxation processes in different composites were calculated. The overall results showed that hybridization with GF enhanced the performance properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source]

The influence of fiber surface modification on the mechanical properties of coir-polyester composites

POLYMER COMPOSITES, Issue 4 2001
J. Rout
Coir, an important lignocellulosic fiber, can be incorporated in polymers like unsaturated polyester in different ways for achieving desired properties and texture. But its high level of moisture absorption, poor wettability and insufficient adhesion between untreated fiber and the polymer matrix lead to debonding with age. In order to improve the above qualities, adequate surface modification is required. In our present work, fiber surface modification was effected through dewaxing, alkali (5%) treatment, aqueous graft copolymerization of methyl methacrylate (MMA) onto 5% alkali treated coir for different extents using CuSO4 , NaIO4 combination as an initiator system and cyanoexhylation with a view to improve the mechanical performance of coir-polyester composites. Mechanical properties like tensile strength (PS), flexural strength (ES) and impact strength (IS) of the composites as a function of fiber loading and fiber surface modification have been evaluated. Composites containing z5 wt% of fiber (untreated) improved tensile and flexural strength by 30% and 27% respectively in comparison to neat polyester. The work of fracture (impact strength) of the composite with 25 wt% fiber content was found to be 967 J/m. The elongation at break of the composites exhibits an increase with the introduction of fiber, All types of surface modification result In improved mechanical properties of the composites. Significant improvement in mechanical strength was also observed for composites prepared from 5% PMMA grafted fiber. [source]

Monitoring epoxy and unsaturated polyester reactions under pressure,Reaction rates and mechanical properties

POLYMER ENGINEERING & SCIENCE, Issue 11 2009
Javier C. Cruz
The effects of pressure on reaction rates and final mechanical properties were studied for an unsaturated polyester (UP) and epoxy resin. A pressure chamber where reactions can be monitored by use of Raman spectroscopy has been built for these purposes. The chamber allows for pressures up to 13.8 MPa at 200°C. An advanced temperature control system has been adapted to the vessel to precisely control and monitor sample temperature variations and overshoots. It is described how for an accelerated UP reaction increasing pressure will result in a competing effect on the reaction rate where the rate will initially lower, but with increased pressures it may accelerate due to acceleration of the reaction rate constants. The final mechanical properties exhibit a similar behavior slightly increasing with pressure but lowering as pressure is raised further. For epoxy, it was shown that the reaction kinetics were accelerated by pressure although no mechanical property differences could be noted for the pressure ranges tested. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers. [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]

Nanocomposite systems based on unsaturated polyester and organo-clay

New aspects of unsaturated polyester resin synthesis.

POLYMER INTERNATIONAL, Issue 5 2003
Part 2.
Abstract The distribution of unsaturations in the prepolymer of a typical unsaturated polyester (UP) resin (maleic anhydride, phthalic anhydride and 1,2-propylene glycol) has been shown to influence the kinetics of the cure process with styrene monomer. Segments containing double bonds in close proximity appear to lower the reactivity of the resin due to steric hindrance, as indicated by the fact that the rate of cure and the final degree of cure, measured by differential scanning calorimetry (DSC), increase as the average sequence length (SL) of maleic units decreases. This implies that the reactivity of UP resins may be improved by synthesis of prepolymers with certain reactant sequence-length distributions. The copolymer formed by the melt condensation process of maleic anhydride, phthalic anhydride and 1,2-propylene glycol in the absence of a transesterification catalyst has a non-random structure with a tendency towards blockiness. This was established using 1H NMR analysis in tandem with deterministic and Monte Carlo modelling techniques. Copyright © 2003 Society of Chemical Industry [source]

Synthesis and characterization of new unsaturated polyesters containing cyclopentapyrazoline moiety in the main chain

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
Ismail A. Alkskas
Abstract 3-p -Hydroxyphenyl-6- p -hydroxybenzylidene cyclopentapyrazoline (III) and 3-vanillyl-7-vanillylidene cyclopentapyrazoline (IV) were used as new starting materials for preparing new unsaturated polyesters. The polyesters were prepared by reacting (III) or (IV) with adipoyl, sebacoyl, isophthaloyl, and terephthaloyl dichlorides utilizing the interfacial polycondensation technique. The polyester samples have been characterized by elemental and spectral analyses. The polyesters have inherent viscosities of 0.55,0.97 dL/g. All the polyesters are semicrystalline and most of them are partially soluble in most common organic solvents but freely soluble in concentrated sulfuric acid. Their glass transition temperatures (Tg) range from 103.34 to 208.81°C, and the temperatures of 10% weight loss as high as 190 to 260°C in air, indicating that these aromatic polyesters have high Tg and excellent thermal stability. Doping with iodine dramatically raised the conductivity and produced dark brown colored semiconductive polymers with a maximum conductivity in the order of 3.1 × 10,7 ,,1 cm,1. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

New functionalized polyesters to achieve controlled architectures

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2004
Anna Finne
Abstract Following our continued interest in the production of bioerodible and biodegradable functional polymers for biomedical applications, we synthesized and characterized new unsaturated polyesters. The presence of functional groups in the polymer backbone provided sites for chemical modification, and through a variation in the structure, the physical properties, such as the hydrophilicity and solubility, could be affected. With 1,1-di- n -butyl-stanna-2,7-dioxacyclo-4-heptene as the initiator in the ring-opening polymerization of polyesters, a new set of functionalized polyesters was created. The polymerization of ,-caprolactone resulted in poly(,-caprolactone) with a double bond incorporated into the structure. The polymers were obtained in a controlled manner with low molecular dispersities. The double bond was previously incorporated into L -lactide polymers, and the two reactions were compared in this study. The conversion of ,-caprolactone, with a degree of polymerization of 50, was completed within 140 min, whereas for L -lactide, only a 45% conversion took place in the same period of time. The dispersities were somewhat higher with ,-caprolactone because of the higher reaction rate and, therefore, lower selectivity. The incorporated CC double bond in the polyesters provided a variety of opportunities for further modifications. In this case, the double bond of the L -lactide macromonomers was oxidized into epoxides. Epoxidation was carried out with m -chloroperoxybenzoic acid as a chemical reagent. The conversion of the double bonds into epoxides was completed, and the obtained yields were good (>95%). As a result of the mild reaction conditions, the epoxidation of the double bond was carried out quantitatively without any side reactions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 444,452, 2004 [source]