Showing papers in "International Journal of Polymeric Materials in 2000"
TL;DR: In this article, the response of wood flour reinforced polyethylene composites to 2 hours water boiling, five complete boiling and freezing cycles and fungal (Gloeophyllumm Traebum/Brown-rot fungus) exposure was investigated.
Abstract: The main purpose of this research work was to investigate the response of wood flour reinforced polyethylene composites to 2 hours water boiling, five complete boiling and freezing cycles and fungal (Gloeophyllumm Traebum/Brown-rot fungus) exposure. Five composite formulations were manufactured and analyzed (0, 50, 60, 70 and copper carbonate treated 60% wood flour/polyethylene composites). The results showed that wood flour loading decreased the resistance of the composites to moisture and fungal environment. The exposure of the composites to 2 hours water boiling and five complete boiling and freezing cycles caused serious damage to the interfacial adhesion between wood flour and polyethylene matrix due to contraction and swelling stresses developed during cyclic exposure. The addition of 1 percent copper carbonate salt during compounding of wood flour and polyethylene prevented the colonization and proliferation of fungus on the surface of the composites, but had a negative effect on the water...
36 citations
TL;DR: In this article, optical properties of polymer-dispersed liquid crystals (LCs) are analyzed from the point of view of the order created by the electric field, dynamic changes of the orientation parameter, and optical transmittivity.
Abstract: Electrooptical properties of polymer-dispersed liquid crystals (LCs) are analyzed from the point of view of the order created by the electric field, dynamic changes of the order (orientation) parameter, and optical transmittivity. Optical phase retardation causes an optical phase shift and is related to thermal effects. Nonlinear optical properties are investigated from the point of view of self-transparency, nonlinear gratings, threshold degenerate wave mixing, optical bistability and second harmonic generation.
30 citations
TL;DR: In this article, the suitability of the 3-phase microfibrillar model for high-tenacity Nylon 6 fibres was investigated and it was shown that the 3 phase model is not suitable for aliphatic polyamide fibers manufactured by the standard melt-spun process.
Abstract: The microfibrillar morphological structure of aliphatic polyamide fibers has been consistently presented by the three phase microfibrillar model proposed by Prevorsek and not by the two phase microfibrillar model proposed by Peterlin. A widely spread opinion is that the 3-phase or “Swiss-cheese” model is applicable in all cases, either in case of high-tenacity fibres or in case of standard Nylon 6 textile fibers. Although the 3-pbase X-ray analysis is now routinely performed, the basic issue of 2-phase vs. 3-phase model has not yet been resolved. We have investigated the suitability of both models and found out that the 3-phase model which is suitable for high-tenacity Nylon 6 fibres cannot be applied in case of aliphatic Nylon 6 fibres manufactured by standard melt spun process. The microfibrillar structure of these fibers resembles to the microfibrillar model of PE more than to the morphology of high-tenacity Nylon 6 fibres. The generally established opinion about applicability of the 3-phase m...
23 citations
TL;DR: In this article, flax fibers with different moisture content were used as reinforcement in polypropylene matrix with maleic anhydride grafted Polypropylene coupling agent, and three point bending and Izod impact strength were investigated as a function of moisture content of the fiber, and amount of applied coupling agent.
Abstract: Flax fibers with different moisture content were used as reinforcement in polypropylene matrix with maleic anhydride grafted polypropylene coupling agent. Mechanical properties-three point bending and Izod impact strength-were investigated as a function of moisture content of the fiber, and amount of applied coupling agent. By decreasing the moisture content of the fiber all the investigated properties can be improved. Using PPgMA as coupling agent the three point bending characteristics (flexural strength, flexural modulus, and ultimate bending stress) were better, while the impact strength decreased.
22 citations
TL;DR: In this article, Carboxymethylcellulose-g-Polyacrylamide was synthesized in ceric ion induced redox polymerization technique at 29 ± 1°C.
Abstract: Synthesis of Carboxymethylcellulose-g-Polyacrylamide was carried out in ceric ion induced redox polymerization technique at 29 ± 1°C. The graft copolymer was characterised by intrinsic viscosity measurement and IR spectroscopy. The flocculation performance of CMC-g-PAM and sodium alginate-g-PAM was tested in both 1 wt% coking and non-coking coal fine suspensions. The flocculation performance of CMC-g-PAM is better than that of SAG-g-PAM in both coking and non-coking coal suspension. CMC alone showed better performance than sodium alginate.
22 citations
TL;DR: In this paper, the electrical properties of mica-polystyrene composites were studied using the impedance measurements technique and the results fit approximately the reported empirical equations concerning the AC conductivity and dielectric behavior of polymer composites.
Abstract: The electrical properties of mica-polystyrene composites were studied using the impedance measurements technique. The study was carried out as a function of frequency and mica concentration. It was observed that the AC conductivity and the dielectric constant are increased with increasing of the mica content in the composite. The observed electrical results fit approximately the reported empirical equations concerning the AC conductivity and dielectric behavior of polymer composites. Relaxation processes were observed to take place for composites having high mica concentration. The observed relaxation and polarization effects of the composite are mainly attributed to the dielectric behavior of the mica filler. However, the results were explained on the basis of the interfacial (space-charge) polarization, dipolar polarization and decrease of the hindrance produced by the polymer matrix.
21 citations
TL;DR: In this article, the dyeing medium is not water but carbon dioxide in the supercritical state (temperatures above 31°C and pressures abov..., which is one of the most advanced dyeing technologies.
Abstract: Dyeing is supercritical CO2 is one of the most advanced dyeing technologies. The dyeing medium is not water but carbon dioxide in the supercritical state (temperatures above 31°C and pressures abov...
19 citations
TL;DR: In this article, the phase behavior and structures of thermotropic cholesteric PLCs are discussed, and optical properties of such materials are reported, including their textures, effects of composition variation on the helix twisting power and temperature dependence of the helike pitch.
Abstract: Synthesis of a number of cholesteric polymer liquid crystals (PLCs) is reported. Phase behavior and structures of thermotropic cholesteric PLCs are discussed. Optical properties of such materials are reported also, including their textures, effects of composition variation on the helix twisting power and temperature dependence of the helix pitch. Effects of molecular mass variation on the optical properties of PLCs are determined. Prospects of applications of these materials are pointed out.
14 citations
TL;DR: In this paper, the IR spectral analysis revealed that on heating interchain cross-linking occured between PU and EVA elastomers and degradation and weight loss were also retarded.
Abstract: Blends of polyurethane and EVA elastomers prepared by two different techniques, in different blend ratios, have been studied. Blend properties largely depended on the blend ratio and also blending techniques. Preheating technique offered better properties. IR spectral analysis revealed that on heating interchain crosslinking occured between PU and EVA. The degradation and weight loss were also retarded. Furthermore, preheating also restricted the extractibility of one phase by solvent extraction suggesting interchain crosslinking. Heat of vulcanization also confirmed the above view.
13 citations
TL;DR: In this paper, the effects of electric fields on monomer liquid crystals and polymer liquid crystals (PLCs) are analyzed, dealing separately with nematic and cholesteric PLCs.
Abstract: Effects of electric fields on monomer liquid crystals (MLCs) and polymer liquid crystals (PLCs) are analyzed, dealing separately with nematic and cholesteric PLCs. Electro-hydrodynamic instabilities affect the behavior of these systems. Thermooptical recording depends on the magnitude of the thermooptical effects. Information recording can be alternatively performed on the basis of photoorientation and the photoinduced birefringence. Capabilities and limitations of these techniques are pointed out.
13 citations
TL;DR: In this article, the viscosity of hydrophobically modified polyacrylamide copolymers was investigated as a function of polymer concentration in aqueous and in salt solutions.
Abstract: The viscosity of hydrophobically modified polyacrylamide was investigated as a function of polymer concentration in aqueous and in salt solutions, and also as a function of temperature. The graft copolymers were constituted of polyacrylamide backbone and different amount of hydrophobic polypropylene oxide) graft chains. Measurements of intrinsic viscosities have been performed by using a Contraves low-shear LS-40 rheometer. From these results, a dependence of the intrinsic viscosity of the polymer solution with the molecular weight was observed, where an increase of the latter resulted in higher intrinsic viscosity. In this case, the effect of the molecular weight was more emphasized than the effect caused by the slightly different degrees of hydrophobic incorporation. When enhancing the temperature, it was not verified a significant change on the reduced viscosities of the copolymer solutions and the graft chain length was also observed.
TL;DR: In this article, the structure particular to layer aluminumsilicates is discussed permitting the intercalation of polymers, which ultimately leads to nanocomposites that exhibit interesting properties.
Abstract: The structure particular to layer aluminumsilicates is discussed permitting the intercalation of polymers. This process ultimately leads to nanocomposites that exhibit interesting properties. It will be shown that many improvements of physical properties can be achieved by polymer-clay nanocomposites.
TL;DR: In this article, the results of construction on composite including up to 30% of the volume of foam polyethylene waste are discussed and the composition optimization to thermal conductivity value is carried out.
Abstract: The utilization of construction materials based on polymers is considerably limited by their low fire-safety and insignificant durability. In this paper the investigations results of construction on composite including up to 30% of the volume of foam polyethylene waste are discussed. Its destruction during the fire action and also utilization is limited by a cement concrete matrix which has a traditional composition. The composition optimization to thermal conductivity value is carried out The aggregate of amorphous structure in the form of ash-slag waste is used to decrease concrete thermal conductivity.
TL;DR: In this article, the effects of fullerenes C60 and C70 on the degradation of PMMA and PS under helium and oxygen by a DSC method were investigated.
Abstract: Investigation has been made on the effects of fullerenes C60 and C70 on the degradation of PMMA and PS under helium and oxygen by a DSC method. The dependences of the temperature of the onset of the thermal and thermo-oxidative degradation of the polymers on concentration of C60 and C70 have been obtained. The temperature limits of effective inhibition of the polymers by fullerenes have been determined. The temperature limit depends on the chemical structure of polymer, namely it is considerably greater in the degradation of more stable polymer. In the thermo-oxidative degradation of the polymers with addition of fullerenes, the temperature limit of inhibition of less stable PS is much less and of more stable PMMA is considerably greater than that in the presence of well-known antioxidants. It was concluded that fullerenes are more effective high temperature inhibitors of the thermo-oxidative degradation of PMMA than well-known antioxidants. The suggestion was made that the thermo-oxidative degra...
TL;DR: In this article, the influence of different woven geometry and ply effect on thermoplastic composite properties was investigated and the relationship between different geometry and weave characteristics was also noted, in general, the woven composite properties are influenced by many process variables such as type of towpreg, woven geometry, number of plies etc.
Abstract: Works on woven composite both thermoset and thermoplastic are numerous, however in most instances they involve the use of preimpregnated fabric. It is apparent that woven thermoplastic system has significant potential due to the combined properties such as better damage tolerence, recyclability, easy processing, storage, etc. Here work on woven thermoplastic composites based on Continuous Fiber Impregnated towpreg (COFIT) tape rather than conventional approach is reported. The influences of different woven geometry and ply effect were investigated. Correlations between different woven geometry and weave characteristics were also noted. In general, the woven composite properties are influenced by many process variables such as type of towpreg, woven geometry, number of plies etc.
TL;DR: Sago starch filled linear low density polyethylene (LLDPE) composites, have been prepared by melt mixing of the granular starch and LLDPE in a HAAKE internal mixer as mentioned in this paper.
Abstract: Sago starch filled linear low density polyethylene (LLDPE) composites, have been prepared by melt mixing of the granular starch and LLDPE in a HAAKE internal mixer. The tensile, water absorption and enzymatic degradation properties of the composites have been determined. Incorporation of sago starch into LLDPE led to decrease in tensile strength and elongation at break of the composites. Up to 15 wt.% of sago starch could be added to LLDPE without adverse effects on the tensile properties. The water uptake increased with immersion time and the rate of absorption is strongly controlled by the immersion temperatures. Dramatic reduction in tensile properties were observed in the composites that were immersed in water at 90[ddot]C. The recovery of the tensile strength and elongation at break upon redrying is about 37.5 and 1.6% respectively. The permanent damage to the composites was attributed to severe hydrolysis of the starch particles. The enzymatic degradation study using oc-amylase revealed tha...
TL;DR: In this article, the effects of magnetic fields on polymer liquid crystals (PLCs) are analyzed, dealing in turn with isotropic solutions, lyotropic LCs (including polypeptides, polyribonucleotides and DNA) and thermotropic PLCs, including polyesters and poly peptides.
Abstract: The effects of magnetic fields on polymer liquid crystals (PLCs) are analyzed, dealing in turn with isotropic solutions, lyotropic LCs (including polypeptides, polyribonucleotides and DNA) and thermotropic PLCs (including polyesters and polypeptides) Looking for a common denominator in LC behavior, living systems are also analyzed, including viruses, biological membranes, sperm nuclei, rhodopsin and fibrinogen Magnetropism is discussed, as are applications of PLC oriented in magnetic fields for the purpose of producing ultra-high modulus materials
TL;DR: In this paper, the area density of a plain knitted fabric according to product specification was reduced by optimizing the knitting and after-treatment process parameters and the elastic properties of knitted fabrics.
Abstract: The investigation objective was to reduce the area density of a cotton/Lycra plain knitted fabric according to the product specification. The knitting and after-treatment process parameters were optimized. Simultaneously, knitted fabric parameters were monitored and knitted fabric performance properties like shrinking and laundering and elastic properties: breaking extension, maximum extension at cyclic loading upto defined load/ extension and residual extension were assessed.
TL;DR: In this article, the infrared spectroscopy of precipitated lignin from waste black liquors of bagasse pulping with kraft sulfite pulping process was investigated.
Abstract: The infrared spectroscopy of precipitated lignin from waste black liquors of bagasse pulping with kraft sulfite pulping process was investigated. Also the effect of anthraquinon and methanol addition in the soda, kraft and kraft-sulfite pulping liquor on the infrared specra of the precipitated lignin was studied. The presence of methanol in the pulping liquor causes an increase in the degradation as well as increase in the carboxylic group in the precipitated lignin. Also, the phenolic hydroxyl group in case of kraft lignin is higher than soda lignin. Presence of sulfite in the kraft-sulfite pulping liquor produces lignin hydroxyl groups.
TL;DR: In this paper, the morphology of the segregated phases in the blends as well as the chemical architecture of the rubber phase have a definite influence on the mechanical and rheological properties of these materials.
Abstract: Blends of Polystyrene-(Styrene Butadiene) rubber copolymers were prepared in a twin screw extruder and then injected. The samples were characterized by various techniques and their properties compared to those of a sample with 0% rubber content. The results show that the morphology of the segregated phases in the blends as well as the chemical architecture of the rubber phase have a definite influence on the mechanical and rheological properties of these materials.
TL;DR: A series of polyamide 6 (PA 6) samples varying in their molecular weight (between 10000 and 50000) were annealed for 6 h in vacuum at various temperature (between 100 and 220°C) in order to create different morphological structures.
Abstract: A series of polyamide 6 (PA 6) samples varying in their molecular weight (between 10000 and 50000) were annealed for 6 h in vacuum at various temperature (between 100 and 220°C) in order to create different morphological structures. The samples have been characterized with respect of their density, melting and crystallinity (from DSC), thermal expansion coefficient, humidity, predomination α- or γ-crystalline modification (from IR), shear melt viscosity and their tribological behaviour (the specific wear rate Ws ). It is found that density increases with increasing annealing temperature Ta but decrease with the rise of molecular weight (m.w.). The thermal expansion coefficient is more sensitive to Ta than to m.w. Contrary, shear-viscosity increases from 35 MPa for PA 6 with a m.w. of 10000 to 7200 MPa for samples with a m.w. of 50000. Concerning wear behavior it is concluded that the observed tendency for a decrease of Ws with an increase of Ta , particularly for samples with low m.w. is attribut...
TL;DR: In this article, the phase structures of PP-LDPE blends in isotropic and oriented states were studied by the methods of DSC and polarization IR spectroscopy, and the composition intervals were established that correspond to the formation of interpenetrating network structures.
Abstract: The phase structures of PP-LDPE blends in isotropic and oriented states were studied by the methods of DSC and polarization IR spectroscopy. The composition intervals were established that correspond to the formation of interpenetrating network structures. The presence of LDPE increases the degree of PP orientation and the mechanical strength of the blends. This indicates that LDPE acts as a structure-modifying agent, while PP plays the role of strengthening (reinforcing) filler. A relationship between the deformation and strength properties of the oriented films of the PP-LDPE blend and the phase structure of the PP component is demonstrated. The stability of the blend to oxidation in the ozone-oxygen medium is determined by the structure of a less stable system component (PP). The oxidation rate reaches maximum in samples with an isotropic PP structure and is minimum in the blends with highly oriented PP component.
TL;DR: In this paper, a mixture of salt water glass, portland cement and dehydrated clay is used as binders for intumescent coatings, which can be used to maintain the durability of the composition due to their cohesive properties.
Abstract: The effectiveness of fireproof intumescent coatings based on water glass can be considerably increased if the coagulated sodium water glass is used as an intumescent component. When heated, the coagulated sodium water glass creates a steam-gas cloud above the protected surface which together with foam formation decreases the temperature of the protected surface. The mixture of sodium water glass, portland cement and dehydrated clay which, besides adhesion, maintain the durability of the composition are used as binders due to their cohesive properties.
TL;DR: A review of the different experimental techniques associated with the thermally stimulated discharge and depolarization current and their application to PLCs is provided in this paper, where experimental results for thermotropic longitudinal PLC are presented.
Abstract: Thermally stimulated discharge or thermally stimulated polarization and depolarization current is becoming a valuable technique in discerning transitions having a small relaxation strength. Polymer liquid crystals (PLCs) are a group of such materials. This article provides a review of the different experimental techniques associated with the technique and their application to PLCs. Experimental results for thermotropic longitudinal PLCs are presented.
TL;DR: In this article, two crude hemicellulosic fractions, obtained by extraction of steam-exploded birchwood with hot water, were treated with 8% NaOH at 20[ddot]C for 1 and 4h, and subsequently sub-fractionated into four lignin and four hemicello-sic fractions.
Abstract: Two crude hemicellulosic fractions, obtained by extraction of steam-exploded birchwood with hot water, were treated with 8% NaOH at 20[ddot]C for 1 and 4h, and subsequently sub-fractionated into four lignin and four hemicellulosic fractions. Acid hydrolysis, alkaline nitrobenzene oxidation, ultraviolet (UV), gel-permeation chromatography (GPC), Fourier transform infrared (FT-IR), and carbon-13 nuclear magnetic resonance (NMR) spectroscopies were used to investigate the chemical compositions and structural features of the fractionated hemicelluloses and lignins. The sugar analyses indicated that xylose was the predominant sugar component in the four hemicellulosic fractions. Due to the autohydrolysis at elevated temperature and lower in acidity during the steam treatment processes, all the four hemicellulosic fractions showed a low degree of polymerization (DP, 38–41), with molecular-average weights between 5620 and 6160. Assignments of all the signals in the NMR spectrum led to the conclusion tha...
TL;DR: In this paper, the dielectric properties and ion-selective conduction in polyvinylcfaioride/poiyethylene oxide (PVC/PEO) blended membrane of different composition immersed in electrolyte have been studied under the influence of frequency and temperature.
Abstract: The dielectric properties and ion-selective conduction in polyvinylcfaioride/poiyethylene oxide (PVC/PEO) blended membrane of different composition immersed in electrolyte have been studied under the influence of frequency and temperature. It was found that the dielectric constant of the prepared alloy increases with increasing the PEO concentration, the AC-conductivity increases with increasing the applied frequency, and the PEO content in the blended membrane. The thermal behavior was also investigated on a blend of 50wt.% PEO. It was observed that the temperature increases the dielectric constant at lower frequencies and enhances the AC-conductivity. Furthermore, it was found that the activation energy and the ionic conduction increase with temperature. The present study suggests the suitability of PVC/PEO blended membrane to be used as ion-selective electrode.
TL;DR: In this paper, the effects of polymerization temperature and initiator concentration on polymerization behavior and molecular structures of polyvinyl acetate (PVAc) and corresponding poly(vinyl alcohol) obtained by saponifying it with sodium hydroxide.
Abstract: Vinyl acetate (VAc) was bulk-polymerized at 30, 40 and 50°C using a low temperature initiator, 2,2′-azobis(2,4-dimethylvaleronitrile) (ADMVN), and effects of polymerization temperature and initiator concentration were investigated in terms of polymerization behavior and molecular structures of poly(vinyl acetate) (PVAc) and corresponding poly(vinyl alcohol) (PVA) obtained by saponifying it with sodium hydroxide. Low polymerization temperature and low conversion by adopting ADMVN proved to be successful in obtaining PVA of high molecular weight. PVAc having number-average degree of polymerization (Pn ) of 6,800–10,100 was obtained, whose degree of branching for acetyl group of 0.6–0.7 at 30°C, 0.8–1.1 at 40°C, and 1.0–1.9 at 50°C at conversion of below 40%. Saponifying so prepared PVAc yielded PVA having Pn of 3,100–6,200, and syndiotactic diad (S-diad) content of 51–53%. The whiteness, S-diad content, and crystal melting temperature were higher with PVA prepared from PVAc polymerized at lower tem...
TL;DR: In this paper, the effect of dichlorotin dioxine (DCTD) on the thermal degradation of polyvinyl chloride (PVC) was investigated using thermogravimetric techniques.
Abstract: Thermal degradation of polyvinyl chloride (PVC) and the effect of dichlorotin dioxine (DCTD) on this process have been investigated using dehydrochlorination (DHCl) and thermogravimetric techniques. A significant decrease in the rate of degradation was observed when PVC was mixed with a small amount which was maximum with 0.25 pph of DCTD and thermal decomposition temperature with DCTD was found to be higher than that of pure PVC. The value of apparent activation energy of the dehydrochlorination process has been calculated and a suitable mechanism for the stabilizing action of DCTD on PVC has been purposed.
TL;DR: Theoretical principles as well as experimental techniques are analyzed from the point of view of their capabilities in this paper for PET/xPHB, where PET = poly(ethylene terephthalate), PHB = p-bydroxybenzoic acid (the liquid crystalline component) and x is the mole fraction of PHB in the copolymers.
Abstract: Dielectric relaxation spectrometry is a useful tool to study molecular dynamics of macromolecular systems. Theoretical principles as well as experimental techniques are analyzed from the point of view of their capabilities. Results are reported for PET/xPHB, where PET = poly(ethylene terephthalate), PHB = p-bydroxybenzoic acid (the liquid crystalline component) and x is the mole fraction of PHB in the copolymers.
TL;DR: In this paper, the average angle of orientation of crystallites φ from the azimuthal record of the meridional reflection of the 1 05 diatropic plane for PET fibres is widely used.
Abstract: A method for the determination of the average angle of orientation of crystallites φ from the azimuthal record of the meridional reflection of the 1 05 diatropic plane for PET fibres is widely used. The 1 05 reflection is the closest to the meridian and the normal to this plane making an angle of approximately 10° with the c axis. The intensity distribution measured by this method reflects the distribution of the 105 plane normals and therefore it comprises: the distribution of the 1 05 plane normals relative to the c crystallographic axis, the distribution of the crystallites relative to the reference fibre axis and the tilted orientation; that is the molecular chain axis inclined by some degrees with respect to the fibre axis. By the studying of the diffraction intensity distribution from the 1 05 diatropic plane this particularly should be taken into account. The sub-meridional (1 05) reflection was scanned in two different geometries: omega and chi scan. Supercritical CO 2 fluid as an alternative dyeing medium changes the fibre structure to a certain extent in dependence on the treatment temperature and pressure used. Therefore the changes of crystalline orientation in poly(ethylene terephthalate) (PET) fibres as brought about under the influence of supercritical CO 2 fluid were investigated.