Tensile Modulus (tensile + modulus)

Distribution by Scientific Domains

Selected Abstracts

Synthesis and properties of homopolyamide and copolyamides fibers based on 2,6-bis(p -aminophenyl)benzo[1,2-d;5,4- d,]bisoxazole

Xiangqun Chen
Abstract A novel aromatic homopolyamide with benzobisoxazole units in the main chain was synthesized with 2,6-bis(p -aminophenyl)benzo[1,2- d;5,4- d,]bisoxazole and terephthaloyl chloride by low temperature solution polycondensation, the inherent viscosity of which was 1.98 dL/g. The diamine and p -phenylendiamine with terephthaloyl chloride were used to synthesize the copolyamides. The structures of homopolyamide and copolyamides were characterized by IR spectra, elemental analysis, and wide-angle X-ray diffraction. Wide-angle X-ray diffraction measurements showed that homopolyamide and copolyamides were predominantly crystallinity. The results of thermal analysis indicated that the thermal stabilities of the copolymer increased with an increase of the molar fraction of benzobisoxazole in the copolymers. The thermal stability of the copolyamides with decomposition temperatures (at 10% weight loss) above 570C was better than that of poly(p -phenylene terephthalamide) (PPTA). Fibers of homopolyamide and copolyterephthalamides were spun from lyotropic liquid crystal dope in 100% H2SO4. When compared with PPTA fibers prepared under the same conditions, the tensile strengths of copolyamides fibers improved by 20,33% with tensile strengths of 1.81 GPa, tensile moduli of 76 GPa, and elongations at break of 3.8,4.1%, which indicated that copolyamides fibers had outstanding mechanical properties. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Polyimides based on 2,5-bis(4-aminophenoxy)biphenyl

Chin-Ping Yang
Abstract A diamine monomer II, 2,5-bis(4-aminophenoxy)biphenyl, was prepared through a nucleophilic substitution reaction of phenylhydroquinone and p -chloronitrobenzene in the presence of potassium carbonate in N,N -dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C. A series of all-aromatic, organosoluble polyimides bearing pendent phenyl groups were synthesized from the diamine with six kinds of commercial dianhydrides via a conventional two-stage process. For improving solubility of polypyromellitimide, copolypyromellitimides with arbitrary solubilities were prepared from II and a pair of dianhydrides, which were mixed at certain molar ratios. These polymers showed good solubilities in N -methyl-2-pyrrolidone and m -cresol. The softening temperatures of these polyimides were recorded between 206 and 269 C. Polymers had glass-transition temperatures at 230,286 C and 10% weight-loss temperatures above 521 C in air or nitrogen atmospheres. Their films had high tensile moduli and strengths. Excellent properties of these polyimides are attributed to the incorporation of the pendent phenyl group in diamine II. 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 429,438, 2002; DOI 10.1002/pola.10116 [source]

Orthotropic elastic constants for polyimide film

Seo Hyun Cho
The orthotropic constants of polyimide film have been characterized using the theory of elasticity of an anisotropic material. Experimental techniques coupled with the mechanics of orthotropic materials are used to determine all 9 independent orthotropic elastic constants (3 tensile moduli, 3 shear moduli, and 3 Poisson's ratios) and 3 coefficients of thermal expansion. Vibrational holographic interferom-etry is used to determine the orthotropic axes of symmetry. For this polyimide film, the two principal axes coincided with the machine and transverse directions. It is also used to evaluate the 2 in-plane Poisson's ratios by measuring residual stresses in 2-D and 1-D square membranes. Using other instruments such as a high pressure gas dilatometry apparatus, a tensile tester, a pressure-volume-temperature apparatus, a thermornechanical analyzer, and a torsion pendulum, the 7 other orthotropic constants and the 3 coefficients of thermal expansion are determined. [source]

Monotonic and cyclic modeling of interface between geotextile and gravelly soil

Ga Zhang
Abstract This paper describes a modified elasto-plasticity damage model to capture monotonic and cyclic behavior of the interface between a geotextile and gravelly soil. New damage variable and shear strength criterion are introduced on the basis of test observations. The formulations of the modified model are obtained by extending those of the original interface model. The model parameters with physical meaning are easily determined from a group of cyclic shear tests and a confining compression test. The model predictions are compared with the results of a series of direct shear tests and large-scale pullout tests. The comparison results demonstrate that the model accurately describes the monotonic and cyclic stress,strain relationship of the interface between a geotextile and gravelly soil while capturing new characteristics: (1) the strength that is nonlinearly dependent on the normal stress; (2) significant shear strain-softening; (3) the comprehensive volumetric strain response with dependency on the shear direction; and (4) the evolution of behavior associated with the changes in the physical state that includes the geotextile damage. This model is used in a finite element analysis of pullout tests, indicating that the tensile modulus of a geotextile has a significant effect on the response of the geotextile,gravel system. Copyright 2009 John Wiley & Sons, Ltd. [source]

Structure and properties of cross-linked polyurethane copolymers

S. Oprea
Abstract Polyurethane elastomers based on polyester diols and aromatic or aliphatic diisocyanates can be used as vibration dampers and isolation materials. Two series of cross-linked polyurethanes with various hard segment structures and different amounts were prepared and thermomechanical properties of these materials were studied. Cross-linked polyurethane copolymers composed of poly(ethylene adipate)diol as soft segment and 4,4,-methylenebis(phenylisocyanate), 1,6-hexamethylene diisocyanate, and diols glycerin, 1,4-butanediol, and 1,6-hexanediol as hard segments were synthesized by a two-step process. The networks have been prepared by end-linking a mixture of the bifunctional precursor chains with trifunctional cross-linkers at off-stoichiometric ratios. The results show that the cross-link and the polyurethane hard segment interaction play a special role in the interconnected chain density and its magnitude is revealed by the mechanical properties. Of most importance, maximum stress, tensile modulus, and elongation at break increased significantly at the 22 wt % composition of hard segment content. Interchain cross-linking improves thermal stability, which was measured by thermogravimetric analysis and differential scanning calorimetry. Cross-linked polyurethane behaves as an elastomer and is useful for shock, noise, and vibration control. 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:165,172, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20155 [source]

Mechanical and morphological properties for sandwich composites of wood/PVC and glass fiber/PVC layers

Narudol Mongkollapkit
Abstract This work manufactured sandwich composites from glass fiber/poly(vinyl chloride) (GF/PVC) and wood/PVC layers, and their mechanical and morphological properties of the composites in three GF orientation angles were assessed. The effects of K value (or viscosity index) of PVC and Dioctyl phthalate (DOP) loading were of our interests. The GF/PVC was used as core layer whereas wood/PVC was the cover layers. The experimental results indicated that PVC with low K value was recommended for the GF/PVC core layer for fabrication of GF/WPVC sandwich composites. The improvement of PVC diffusion at the interface between the GF and the PVC core layer was obtained when using PVC with K value of 58. This was because it could prevent de-lamination between composite layers which would lead to higher mechanical properties of the sandwich composites, except for the tensile modulus. The sandwich composites with 0 GF orientation possessed relatively much higher mechanical properties as compared with those with 45 and 90 GF orientations, especially for the impact strength. Low mechanical properties of the sandwich composites with 45 and 90 GF orientation angles could be overcome by incorporation of DOP plasticizer into the GF/PVC core layer with the recommended DOP loadings of 5,10 parts per hundred by weight of PVC components. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Mechanical and functional properties of composites based on graphite and carboxylated acrylonitrile butadiene rubber

Jian Yang
Abstract In this study, carboxylated acrylonitrile butadiene rubber (xNBR)/expanded graphite (EG) nanocomposites were prepared with a latex compounding technique by ultrasonic stirring. The dispersion of EG in the xNBR matrix was investigated with transmission electron microscopy, scanning electron microscopy, and X-ray diffraction analysis. EG could be exfoliated into lots of nanosheets dispersing in the xNBR matrix. More EG loading resulted in the presence of a few incompletely exfoliated agglomerates. The mechanical properties (hardness, tensile modulus, and tensile strength) of the xNBR/EG composites were determined. Dynamic mechanical thermal analysis was also performed, and it showed that the nanosheets of EG somewhat immobilized the motion of rubber macromolecular chains and led to the shifting and broadening of the tan , peak toward higher temperatures. Many other functional properties of EG-filled xNBR composites were studied, and it was established that the composites had excellent electrical conductivity as well as gas-barrier and wear properties. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Polypropylene nanocomposite film: A critical evaluation on the effect of nanoclay on the mechanical, thermal, and morphological behavior

S. K. Sharma
Abstract Polypropylene (PP)/clay nanocomposites prepared by melt blending technique using different percentages of clay with and without maleic anhydride grafted PP (MA-PP) were studied. The intercalated and exfoliated structure of nanocomposites was characterized by X-Ray Diffraction (XRD) and transmission electron microscopy (TEM). Because of the typical intercalated and exfoliated structure, the tensile modulus of the nanocomposites were improved significantly as compared to virgin PP. The viscoelastic behavior of the nanocomposites was studied by dynamical mechanical analysis (DMA) and the results showed that with the addition of treated clay to PP there was substantial improvement in storage modulus increases. The thermal stability and crystallization of the PP nanocomposites as studied by differential scanning calorimeter (DSC) and thermo gravimetric analysis (TGA) were also improved significantly compared to PP. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Mechanical and thermal properties of poly(butylene succinate)/plant fiber biodegradable composite

Zhichao Liang
Abstract Biodegradable polymeric composites were fabricated from poly(butylene succinate) (PBS) and kenaf fiber (KF) by melt mixing technique. The mechanical and dynamic mechanical properties, morphology and crystallization behavior were investigated for PBS/KF composites with different KF contents (0, 10, 20, and 30 wt %). The tensile modulus, storage modulus and the crystallization rate of PBS in the composites were all efficiently enhanced. With the incorporation of 30% KF, the tensile modulus and storage modulus (at 40C) of the PBS/KF composite were increased by 53 and 154%, respectively, the crystallization temperature in cooling process at 10C/min from the melt was increased from 76.3 to 87.7C, and the half-time of PBS/KF composite in isothermal crystallization at 96 and 100C were reduced to 10.8% and 14.3% of that of the neat PBS, respectively. SEM analysis indicates that the adhesion between PBS and KF needs further improvement. These results signify that KF is efficient in improving the tensile modulus, storage modulus and the crystallization rate of PBS. Hence, this study provides a good option for preparing economical biodegradable composite. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Mechanical properties and flammability of polycarbonate alloys containing nanosize additives

Zhiyi Zhang
Abstract Different organic,inorganic composite particles [montmorillonite/poly(butyl acrylate) (PBA)/poly(methyl methacrylate) (PMMA), SiO2/PBA/PMMA, and CaCO3/PBA/PMMA] were synthesized by emulsion polymerization. Furthermore, polycarbonate (PC) alloys were prepared via the doping of these composite particles into PC with a twin-screw extruder. The structure, mechanical properties, and flammability of the PC alloys were studied in detail. Although the tensile modulus of PC decreased a little, the flexibility and impact resistance were improved by the addition of these composite particles. This result was attributed to the fact that the composite particles were well dispersed in the PC matrix, with a cocontinuous phase formed between the particles and PC. In addition, the combustion behavior of the PC alloys, compared with that of the pure PC, resulted from a ceramic-like char that formed on the surface of the PC alloys during burning. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

The partial replacement of silica or calcium carbonate by halloysite nanotubes as fillers in ethylene propylene diene monomer composites

Pooria Pasbakhsh
Abstract The effect of partial replacement of silica or calcium carbonate (CaCO3) by halloysite nanotubes (HNTs) on the curing behavior, tensile properties, dynamic mechanical properties, and morphological characteristics of ethylene propylene diene monomer (EPDM) composites was studied. Five different compositions of EPDM/Silica/HNT and EPDM/CaCO3/HNT compounds (i.e. 100/30/0, 100/25/5, 100/15/15, 100/5/25, and 100/0/30 parts per hundred rubber (phr)) were prepared on a two-roll mill. The results indicated that the replacement of CaCO3 by HNTs increased the tensile strength, elongation at break (Eb), and tensile modulus of composites from 0 to 30 phr of HNTs whereas for silica, the maximum tensile strength and Eb occurred at 5 phr loading of HNTs with an enhanced stress at 300% elongation (M300). The curing results show that, with replacement of silica or CaCO3 by HNTs, the cure time (t90) and cure rate (CRI) were decreased and increased, respectively. Scanning electron microscopy investigation confirmed that co-incorporation of 5 phr of HNTs with silica would improve the dispersion of silica and enhanced the interactions between fillers and EPDM matrix. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

Effects of ultraviolet irradiation on the static and dynamic properties of neoprene rubbers

Hsoung-Wei Chou
Abstract Rubbers deteriorate when they are exposed to ultraviolet irradiation for long periods of time. By conducting a series of hardness measurements and simple tension tests, the static properties of neoprene rubbers before and after exposure to various durations of ultraviolet irradiation were first measured. It is found that the Shore A hardness and tensile modulus of neoprene rubbers after exposure to ultraviolet irradiation are increased but their elongation at break, tensile strength, and energy to break are significantly decreased. On the basis of a complex spring model of a vibration system, the dynamic shear properties of neoprene rubbers before and after exposure to different durations of ultraviolet irradiation were then determined from the experimental results of dynamic transmissibility tests. It is also found that the storage modulus, loss modulus, and loss factor of neoprene rubbers are drastically affected by the duration of ultraviolet irradiation they experienced. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Properties of styrene-methyl methacrylate grafted DPNR latex at different monomer concentrations

Siti Hajjar Che Man
Abstract The graft copolymerization of styrene and methyl methacrylate (MMA) on to deproteinized natural rubber (DPNR) latex was carried out. The effect of monomer concentrations on grafting efficiency, thermal and mechanical properties was studied. The synthesized graft copolymers were characterized by proton nuclear magnetic resonance (1H NMR) and the highest grafting efficiency was found at 20 wt % monomer concentration. At low monomer concentration (10 wt %) the grafting was not significant and at 30 wt %, the grafting efficiency was slightly decreased. The thermal properties of graft copolymers were analyzed using differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA). The degradation temperature (Tdeg) of the graft copolymer was increased with the increase in monomer concentration which indicates the improvement in thermal stability. The DSC result showed improvement in miscibility between the components as the monomer concentration increased. The mechanical properties of gum and filled modified NR were also investigated in terms of tensile strength, tensile modulus and elongation at break. The tensile strength and elongation at break decreased with an increase in monomer concentration while tensile modulus increased as the monomer concentration increased. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Properties of nanocomposites based on maleate-vinyl ether donor,acceptor UV-curable systems

Neena Ravindran
Abstract UV-curable nanocomposites based on donor,acceptor crosslinking chemistry were prepared containing organically modified montmorillonites. The coatings were characterized for thermal, mechanical, and morphological properties. X-ray diffraction and transmission electron microscopy showed that nanocomposites were formed in all samples. Results showed that an increase in the percentage of clay caused an increased modulus and glass-transition temperature. It was also seen that tensile modulus showed dramatic improvement when compared with the unmodified polyester sample. Real time IR kinetic data showed that higher conversions were obtained at higher clay loadings. Pendulum hardness values and tensile modulus values showed different trends in properties depending on the combination of polymer matrix and organomodification. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

Effect of dispersion state of organoclay on cellular foam structure and mechanical properties of ethylene vinyl acetate copolymer/ethylene-1-butenecopolymer/organoclay nanocomposite foams

Keun-Wan Park
Abstract In this study, our goal is to obtain lower density of ethylene-vinyl acetate copolymer (EVA)/ethylene-1-butene copolymer (EtBC) foams without sacrificing mechanical properties. For this purpose EVA/EtBC/organoclay (Cloisite 15A, Closite 30B) nanocomposite foams were prepared. To investigate the effect of compatibilizer on the dispersion state of organoclay in cellular foam structure and mechanical properties of the EVA/EtBC/organoclay foams composites were prepared with and without maleic anhydride grafted EtBC (EtBC-g-MAH). The dispersion of organoclay in EVA/EtBC/organocaly foams was investigated by X-ray diffraction and transmission electron microscopy. The EVA/EtBC nanocomposite foamswith the compatibilzer, especially EVA/EtBC/Cloisite 15A/EtBC-g-MAH foams displayed more uniform dispersion of organoclay than EVA/EtBC nanocomposite foams without the compatibilzer. As a result, EVA/EtBC/Cloisite 15A/EtBC-g-MAH foams have the smallest average cell size and highest 100% tensile modulus followed by EVA/EtBC/Cloisite 30B/EtBC-g-MAH foams. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3879,3885, 2007 [source]

Is the circumferential tensile modulus within a human medial meniscus affected by the test sample location and cross-sectional area?

Kate Lechner
Quantifying the material properties of the human menisci is paramount to understanding their biomechanical functions within the knee. One important intrinsic material property governing the biomechanical functions of the meniscus is the circumferential tensile modulus. The purpose of this study was to determine if the circumferential tensile modulus of the human medial meniscus depends on the location and thickness of the sample tested. The following three hypotheses were tested: (a) the circumferential location (anterior, central, and posterior) does not significantly affect the tensile modulus, (b) the radial location (inner to outer) significantly affects the tensile modulus, and (c) the thicknes (cross-sectional area) significantly affects the tensile modulus. Test samples, whose length was oriented in parallel with the circumferential collagen fibers, were collected from different circumferential and radial locations throughout 30 human medial menisci. Samples of three different thicknesses (0.5, 1.5, and 3.0 mm) were taken from three equal groups of 10 menisci (i.e., one thickness per group). The circumferential tensile modulus was measured under quasi-statc loading. Statistical analysis showed no significant effect of the circumferential or radial location of the sample on the circumferential tensile modulus. This indicates that an overall circumferential tensile modulus may be calculated for the human medial meniscus by averaging the values determined at the various locations. However, the thickness of the test sample had a significant effect on the measured circumferential tensile modulus: the modulus varied inversely with the thickness. Thus, moduli determined from test samples that are too small in cross-sectional area overestimate the effective modulus of the tissue on the whole, and the cross-sectional area of the sample must be considered when determining a representative circumferential tensile modulus for the medial meniscus in a human knee. [source]

Poly(ethylene terephthalate) terpolyesters containing isophthalic and 5- tert -butylisophthalic units

Darwin P. R. Kint
Abstract Poly(ethylene terephthalate- co -isophthalate- co -5- tert -butylisophthalate) (PETItBI) terpolymers were investigated with reference to poly(ethylene terephthalate) (PET) homopolymer and poly(ethylene terephthalate- co -isophthalate) (PETI) copolymers. Three series of PETItBI terpolyesters, characterized by terephthalate contents of 90, 80, and 60 mol %, respectively, with different isophthalate/5- tert -butylisophthalate molar ratios, were prepared from ethylene glycol and mixtures of dimethyl terephthalate, dimethyl isophthalate, and 5- tert -butylisophthalic acid. The composition of the terpolymers and the composition of the feed agreed. All terpolymers had a random microstructure and number-average molecular weights ranging from 10,000 to 20,000. The PETItBI terpolyesters displayed a higher glass-transition temperature and a lower melting temperature than the PETI copolymers having the same content of terephthalic units. Thermal stability appeared essentially unchanged upon the incorporation of the 5- tert -butylisophthalic units. The PETItBIs were crystalline for terephthalate contents higher than 80 mol %, and they crystallized at lower rates than PETI. The crystal structure of the crystalline terpolymers was the same as that of PET with the 1,3-phenylene units being excluded from the crystalline phase. Incorporation of isophthalate comonomers barely affected the tensile modulus and strength of PET, but the brittleness of the terpolymers decreased for higher contents in 5- tert -butylisophthalic units. 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 124,134, 2003 [source]

Poly(ethylene terephthalate) reinforced by N,N,-diphenyl biphenyl-3,3,,4,4,-tetracarboxydiimide moieties

Jun Xiao
Abstract Starting with 3,3,,4,4,-biphenyltetracarboxylic dianhydride and methyl aminobenzoate, we synthesized a novel rodlike imide-containing monomer, N,N,-bis[p -(methoxy carbonyl) phenyl]-biphenyl-3,3,,4,4,-tetracarboxydiimide (BMBI). The polycondensation of BMBI with dimethyl terephthalate and ethylene glycol yielded a series of copoly(ester imide)s based on the BMBI-modified poly(ethylene terephthalate) (PET) backbone. Compared with PET, these BMBI-modified polyesters had higher glass-transition temperatures and higher stiffness and strength. In particular, the poly(ethylene terephthalate imide) PETI-5, which contained 5 mol % of the imide moieties, had a glass-transition temperature of 89.9 C (11 C higher than the glass-transition temperature of PET), a tensile modulus of 869.4 MPa (20.2 % higher than that of PET), and a tensile strength of 80.8 MPa (38.8 % higher than that of PET). Therefore, a significant reinforcing effect was observed in these imide-modified polyesters, and a new approach to higher property polyesters was suggested. 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 852,863, 2002; DOI 10.1002/pola.10169 [source]

Correlation of morphology, rheology, and performance improvement in gasoline tubes based on PA-6 nanocomposites

Mehdi Moghri
PA-6/organo-modified layered silicate nanocompounds were prepared by the melt mixing of PA-6 with different nanoclay loadings in a corotating twin-screw extruder. Gasoline tubes based on these nanocompounds were produced at different silicate loadings. Thermal, mechanical, rheological, and barrier properties of the different samples were investigated and correlated to their morphology. Transmission electron microscopy, wide angle X-ray scattering, and linear melt state viscoelastic measurements were used to characterize the different aspects of nanoclay dispersion in the nanocomposite samples. While tensile modulus, softening point, heat distortion temperature, and gasoline barrier properties of the prepared tubes were improved considerably by increasing the clay content, performance improvement with respect to clay content (after a certain value) decreased with increasing clay loading. It could be attributed to the re-agglomeration of tactoids at higher concentrations. These findings were correlated with the rheological and morphological observations. J. VINYL ADDIT. TECHNOL., 2010. 2010 Society of Plastics Engineers [source]

Use of PP Grafted with Itaconic Acid as a New Compatibilizer for PP/Clay Nanocomposites

Edwin Moncada
Abstract Summary: Functionalized PP samples with different percentages of grafted IA, i.e., 0.7, 1 or 1.8 wt.-%, with similar molecular weights were used as compatibilizers in PP/clay nanocomposites. PP nanocomposites containing 1 wt.-% of organically modified clays, i.e., montmorillonite, natural hectorite and synthetic hectorite and 3 wt.-% of grafted PP with three different percentages of grafted IA as compatibilizers and two commercial PP samples of different molecular weights were prepared by melt blending. The nanocomposites were characterized by XRD, TEM and tensile mechanical measurements. It was found that the molecular weight of PP used as matrix as well as the percentage of grafted IA of the compatibilizer affected the degree of intercalation/exfoliation of the clay and consequently the mechanical properties of the nanocomposites. Values of 2,137 MPa for the modulus and 51 MPa for the tensile strength were obtained when natural hectorite was used and 2,117 and 40 MPa were obtained when montmorillonite was used. A comparative study was carried out, where PP grafted with maleic anhydride was used as the compatibilizer. Inferior mechanical properties were obtained for nanocomposites prepared by using this compatibilizer, where values of 1,607 MPa for the tensile modulus and 43 MPa for tensile strength were obtained. This result indicated that IA-grafted PP was far more efficient as compatibilizer for the formation of nanocomposites than commercially available maleic anhydride-grafted PP. Model showing interaction of the organically modified clay with grafted PP used as compatibilizer. [source]

Aging Effects on the Phase Composition and Chain Mobility of Isotactic Poly(propylene)

Cristian Hedesiu
Abstract Changes in phase composition and chain mobility in injection-molded isotactic poly(propylene), crystallized from the melt with slow cooling rate and subsequently quenched, associated with aging at temperature well above Tg for 150 and 1 000 h, are studied using time-domain 1H solid-state NMR and XRD. All sample exhibit physical aging when exposed to elevated temperatures, and the physical aging kinetics was observed to depend on the morphology of the homopolymer iPP and aging temperatures. The significant increase in the tensile modulus in time was observed for injection-molded iPP. The observed property changes induced by aging are attributed to microstructural changes within the semi-rigid and amorphous fractions. [source]

Chemically Extracted Cornhusk Fibers as Reinforcement in Light-Weight Poly(propylene) Composites

Shah Huda
Abstract Flexural, impact resistance, tensile, and sound absorption properties of composites from cornhusk fiber (CHF) and PP have been investigated. The effect of holding temperature, CHF length, CHF concentration, and enzyme treatment of CHF on mechanical properties and the effect of the latter two on sound absorption have been studied. Compared with jute/PP composites, CHF/PP composites have similar impact resistance, 33% higher flexural strength, 71% lower flexural modulus, 43% higher tensile strength, 54% lower tensile modulus, and slightly higher noise reduction coefficient. Enzyme treatment of CHF results in increased mechanical and sound absorption properties. [source]

A Solvent Free Graft Copolymerization of Maleic Anhydride onto Cellulose Acetate Butyrate Bioplastic by Reactive Extrusion

Arief C. Wibowo
Abstract Summary: Interfacial adhesion between fibers and matrix is a crucial factor for effective stress transfer from matrix to fiber; especially in short fiber reinforced composite systems. The use of a chemical compatibilizer is an efficient means to achieve such adhesion. Maleic anhydride-grafted-cellulose acetate butyrate (CAB-g-MA) is one such compatibilizer which can be used in biocomposite fabrication, and this has been synthesized in our laboratory by utilizing a twin-screw reactive extrusion process in the presence of a free radical initiator (2,5-dimethyl-2,5-di(tert -butylperoxy)hexane). The unique feature of this process is its solvent-free approach for grafting of maleic anhydride onto CAB, without hydroxyl group protection. CAB-g-MA was characterized using FTIR as well as by a non-aqueous titration method. The effects of initiator and monomer concentrations and various processing conditions on the graft content were also investigated. The preliminary results show that by adding approximately 10 wt.-% of CAB-g-MA into a plasticized cellulose acetate butyrate (TEB)-industrial hemp fiber biocomposites system, an improvement in tensile strength (20%) and in tensile modulus (45%) were obtained. These results are promising in that they pave the way for future studies involving the use of CAB-g-MA as a suitable compatibilizer for cellulose ester-natural fiber biocomposites. [source]

Polymer Nanocomposites Using Urchin-Shaped Carbon Nanotube-Silica Hybrids as Reinforcing Fillers

Wei-De Zhang
Abstract Summary: Carbon nanotubes (CNTs) have been grown on MCM-41 supported Fe nanoparticles and the as-prepared (no further purification) CNT-silica hybrid was directly incorporated into nylon-6 (PA6) by simple melt-compounding. The urchin-shaped CNT-silica hybrid filler was observed to be homogeneously dispersed throughout the matrix by scanning electron and transmission electron microscopy. Compared with neat PA6, the tensile modulus and strength of the composite are greatly improved by about 110%, with incorporation of only 1 wt.-% CNT-silica filler. SEM image and schematic representation showing polymer chains wrapping around the urchin-shaped CNT-silica hybrid filler. [source]

New organosoluble polyimides with low dielectric constants derived from bis[4-(2-trifluoromethyl-4-aminophenoxy)phenyl] diphenylmethylene

Der-Jang Liaw
Abstract A new kink diamine with trifluoromethyl group on either side, bis[4-(2-trifluoromethyl-4-aminophenoxy)phenyl]diphenylmethane(BTFAPDM), was reacted with various aromatic dianhydrides to prepare polyimides via poly (amic acid) precursors followed by thermal or chemical imidization. Polyimides were prepared using 3,3,, 4,4,-biphenyltetracarboxylic dianhydride(1), 4,4,-oxydiphthalic anhydride(2), 3,3,,4,4,-benzophenonetetracarboxylic dianhydride (3), 4,4,-sulfonyldiphthalic anhydride(4), and 4,4,-hexafluoroisopropylidene-diphathalic anhydride(5). The fluoro-polyimides exhibited low dielectric constants between 2.46 and 2.98, light color, and excellent high solubility. They exhibited glass transition temperatures between 227 and 253C, and possessed a coefficient of thermal expansion (CTE) of 60-88 ppm/C. Polymers PI-2, PI-3, PI-4, PI-5 showed excellent solubility in the organic solvents: N -methyl-2-pyrrolidinone (NMP), N,N -dimethylacetamide (DMAc), N,N -dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridkie and tetrahydrofuran (THF). Inherent viscosity of the polyimides were found to range between 0.58 and 0.72 dLg-1. Thermogravimetric analysis of the polyimides revealed a high thermal stability decomposition temperature in excess of 500C in nitrogen. Temperature at 10 % weight loss was found to be in the range 506-563C and 498-557C in nitrogen and air, respectively. The polyimide films had a tensile strength in the range 75-87 MPa; tensile modulus, 1.5-2.2 GPa; and elongation at break, 6-7%. [source]

Influence of yarn texture on the mechanical properties of textile composite castings

A. Zadhoush
In this research, mechanical properties of textile composite castings used for immobilizing a damaged limb have been studied. For this purpose, a fabric composite was made using a new knitted fabric and textured yarn for the first time. This composite possesses suitable mechanical properties. Mechanical and physical properties such as tensile, bending, and thickness of materials were studied. Results indicate that the use of textured yarns instead of flat yarns increases the amount of resin retainment in fabrics. Furthermore, it decreases tensile modulus and bending modulus of fabrics. Properties of the castings produced were compared with a valid commercial casting. Sample with textured warp and weft, with linear density of 1,500 den of weft, had the best physical and mechanical properties among produced samples. POLYM. COMPOS., 2010. 2009 Society of Plastics Engineers [source]

Characterization and properties of activated nanosilica/polypropylene composites with coupling agents

Ong Hui Lin
In this work, nanosilica/polypropylene composites containing 1 wt% of silica nanoparticles were prepared by melt mixing in a Thermo Haake internal mixer. Prior compounding, nanosilica was subjected to surface activation using sodium hydroxide (NaOH) solution. The effectiveness of the activation process was evaluated by measuring the amount of hydroxyl groups (OH) on the surface of nanosilica via titration method and supported by FTIR analysis. Two coupling agents namely 3-aminopropyl triethoxysilane (APTES) and neopentyl (diallyl)oxy, tri(dioctyl) phosphate titanate (Lica 12) were used for surface treatment after activation process. The mechanical properties of polypropylene matrix reinforced with silica nanoparticles were determined by tensile and impact test. Hydroxyl groups on the nanosilica surface played an important role in enhancing the treatment with silane coupling agents. To increase the amount of hydroxyl groups on the nanosilica surface, the optimum concentration of NaOH is 1 mol%. Tensile strength, tensile modulus, and impact strength of nanosilica/PP composites improved with activation process. As the coupling agent is concerned, APTES coupling agent is more pronounced in enhancing the mechanical properties of the composites when compared with Lica 12 coupling agent. POLYM. COMPOS., 2009. 2008 Society of Plastics Engineers [source]

Interfacial adhesion and molecular diffusion in melt lamination of wood sawdust/ebonite NR and EPDM

W. Yamsaengsung
Adhesion mechanisms and peel strengths of wood/ebonite NR-EPDM laminates were investigated. Three different chemical coupling agents: namely; N-(, aminoethyl)-,-aminopropyl-triethoxysilane (AAS), 3-methacryloxypropyl trimethoxysilane (ACS), and Bis-(3-triethoxylpropyl) tetrasulfan (Si69) were introduced into the wood/NR composites to enhance an interaction between wood sawdust (SD) particles and NR molecules, and to improve the adhesion strength between the SD/NR and EPDM layers. The quantitative evidences were given to explain the changes in the adhesion or peel strengths of the SD/NR-EPDM laminates through scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDS). The experimental results indicated that the suitable cure time and cure temperature for SD/NR-EPDM melt-laminates were the tc90 of SD/NR composites and 140C, respectively. The Si69 coupling agent was found to be the most effective coupling agent as compared with AAS and ACS coupling agents. The Si69 of 0.5 wt% was recommended for the optimizations of the tensile modulus of the SD/NR composites and the peel strength of the SD/NR-EPDM laminates. The diffusion level between the SD/NR and EPDM layers could be quantitatively substantiated by determining the sulfur content transfer from the SD/NR layer to the EPDM layer. The diffusion and entanglement of molecular chains from the SD/NR to the EPDM layer initiated the co-crosslinking reaction which played an important role on the changes in the interfacial strength in the SD/NR-EPDM melt-laminates. POLYM. COMPOS., 2009. 2008 Society of Plastics Engineers [source]

Mechanical properties of natural fibers/polyamides composites

Patricia Alvarez de Arcaya
The aim of this investigation has been to use high performance thermoplastic matrices such as polyamides instead of the commonly used polyolefins to develop natural fiber composites for substituting glass fibers without renouncing to their mechanical properties. For this purpose, different natural fibers such as flax, jute, pure cellulose, and wood pulps have been melt compounded with different polyamides to analyze the effect of fiber content on mechanical properties. Fibers have not been treated as polyamides are less hydrophobic than polyolefins. Thermal behavior of the different fibers was determined by thermogravimetry to know the boundary for processing at high temperatures, since the melting points of the polyamides are much higher than those of polyolefins and this could lead to a higher degradation of the natural fibers. Rheological parameters were deduced by measuring torque values during the mixing process. Flexural and tensile modulus and strength of composites were analyzed, finding an increase in the mechanical properties compared with the unreinforced matrix that turns natural fibers into a considerable reinforcement offering a wealth of possibilities for industrial applications. POLYM. COMPOS., 2009. 2008 Society of Plastics Engineers [source]

Tensile properties of carbon filled liquid crystal polymer composites,

Jason M. Keith
Electrically and thermally conductive resins can be produced by adding carbon fillers. Mechanical properties such as tensile modulus, ultimate tensile strength, and strain at ultimate tensile strength are vital to the composite performance in fuel cell bipolar plate applications. This research focused on performing compounding runs followed by injection molding and tensile testing of carbon filled Vectra A950RX liquid crystal polymer composites. The four carbon fillers investigated included an electrically conductive carbon black, thermocarb synthetic graphite particles, and two carbon fibers (Fortafil 243 and Panex 30). For each different filler type, resins were produced and tested that contained varying amounts of these single carbon fillers. The carbon fiber samples exhibited superior tensile properties, with a large increase in tensile modulus over the base polymer, and very low drop in the ultimate tensile strength as the filler volume fraction was increased. The strain at the ultimate tensile strength was least affected by the addition of the Panex carbon fiber but was significantly affected by the Fortafil carbon fiber. In general, composites containing synthetic graphite did not perform as well as carbon fiber composites. Carbon black composites exhibited poor tensile properties. POLYM. COMPOS., 29:15,21, 2008. 2007 Society of Plastics Engineers [source]