Showing papers in "Journal of Applied Polymer Science in 1985"
TL;DR: In this article, a technique is described which uses differential scanning calorimetry to estimate the glass transition of polymers containing a dissolved gas, and the effects of CO2 sorption at pressures up to 25 atm were examined.
Abstract: A technique is described which uses differential scanning calorimetry to estimate the glass transition of polymers containing a dissolved gas. The technique is simple and appears to give reliable results. The effects of CO2 sorption at pressures up to 25 atm were examined in detail for poly(methyl methacrylate) and its blends with poly(vinylidene fluoride). Less extensive results for polystyrene, polycarbonate, poly(vinyl chloride), and poly(ethylene terephthalate) are also given. Reductions in Tg of up to 50°C are observed. A theoretical relation by Chow predicts results in reasonable agreement with the experimental data. These findings are relevant to various applications such as membrane separation processes for gases.
364 citations
TL;DR: In this article, a new thermal conduction model is proposed to correctly predict thermal conductivity of a composite which contains various amounts of particles ranging from a small content, to the region in which conductive chains largely effect thermal conductivities of the composite.
Abstract: Thermal and electric conductivities of polyethylene and poly(vinyl chloride) filled with carbon materials over a wide range are measured in order to study the effect of formed conductive particle chains on thermal conductivities of the composites. With increase of content of carbon particles, the amount of formed conductive chains exponentially increases and the conductive chains tend largely to increase thermal conductivity of a composite. Some models proposed to predict thermal conductivity of a composite in a two-phase system could not be applied to the system with high volume content of particles. In this study, a new thermal conduction model is proposed to correctly predict thermal conductivity of a composite which contains various amounts of particles ranging from a small content, to the region in which conductive chains largely effect a thermal conductivity of a composite. Thermal conductivity of a polymer filled with high volume content of particles largely decreased with a rise in temperature. This phenomenon can be referred to as a PTC phenomenon in thermal resistance.
238 citations
TL;DR: In this article, an electron microscopy analysis of poly(methyl methacrylate)-polystyrene composite particle latexes was performed using batch, swelling-batch, and semibatch methods.
Abstract: Poly(methyl methacrylate)–polystyrene composite particle latexes were prepared by poly(methyl methacrylate)-seeded emulsion polymerization of styrene employing batch, swelling-batch, and semibatch methods. The changes in particle morphology taking place during the polymerization reaction were followed by electron microscopy. Anchoring effect exerted by ionic terminal groups introduced by ionic initiator was found to be the main factor in controlling the particle morphology. The polymer particles obtained by oil-soluble hydrophobic initiators such as azobisisobutyronitrile and 4,4′-azobis-(4-cyanovaleric acid) gave the inverted core-shell morphology. Water-soluble hydrophilic initiator, K2S2O8, also gave the inverted core-shell morphology. However, in this case the occurrence of the halfmoonlike, the sandwichlike, and the core-shell morphologies were also observed depending upon the polymerization conditions. The distribution of terminal SO groups on the surface area of polystyrene particles could be controlled by initiator concentration and polymerization temperature. Viscosity of polymerization loci dictated the movement of polymer molecules, thus causing the unevenness of particle shape and phase separation at high viscosity state. Viscosity was controlled by the styrene/poly(methyl methacrylate) ratio, the addition of a chain transfer agent or a solvent which is common to polystyrene and poly(methyl methacrylate).
218 citations
TL;DR: In this paper, the five crystalline Na-celluloses, previously shown to occur as intermediates during the mercerization of cellulose and exhibiting two types of crystallographic fiber repeats, further indicate that they fall into three classes based on their unit cells and NaOH contents.
Abstract: Continued study of the five crystalline Na–celluloses, previously shown to occur as intermediates during the mercerization of cellulose and exhibiting two types of crystallographic fiber repeats, further indicates that they fall into three classes based on their unit cells and NaOH contents. In one class are Na–celluloses I and III, both containing up to 34% NaOH; in the second class are Na–celluloses IIA and IIB, marked by ca.15 A fiber repeat and containing up to 65% NaOH; and in the third class is Na–cellulose IV which is likely to be a hydrated form of cellulose II. Na–cellulose I was found to be the common first alkali–cellulose structure produced in the NaOH treatment of both cellulose I and cellulose II. Further study of this conversion step suggested a mercerization mechanism in which the alkali begins the conversion of cellulose to Na–cellulose I in the amorphous parts of the fiber. The conversion of the parallel-chain cellulose I structure to an antiparallel one is likely to occur already in this first step.
213 citations
TL;DR: In this article, the deformation and fracture behavior of polypropylene (PP) and rubber-modified PP materials have been investigated, and the second phase morphology with smaller average rubber particle diameter D appears to be more efficient than that with larger D in toughening PP.
Abstract: To deformation and fracture behavior of several polypropylene (PP) and rubber-modified PP materials have been investigated. Plastic deformation mechanisms of these systems depend upon the test rate and temperature with high rates and low temperatures being in favor of crazing. The ductility and toughness of these materials are explained in light of the competition between crack formation and the degree of plastic deformation through crazing and shear yielding. The second phase morphology with smaller average rubber particle diameter D appears to be more efficient than that with larger D in toughening PP. Theoretical calculations indicate that the stresses imposed upon the rubber particles due to volume shrinkage of PP during crystallization are sufficient to compensate for the stresses due to differential thermal contraction in cooling from solidification temperature to end-use temperature. The difference between these two is small, and therefore they provide very little contribution to interfacial adhesion between rubber particle and PP matrix, the adhesion being insufficient for the rubber particles to be effective in controlling craze propagation. The rubber particles, in addition to promoting crazing and shear yielding, can also improve the fracture resistance of PP by varying the crystalline structure of PP (e.g., reducing the spherulite dimensions).
181 citations
TL;DR: The gas permeabilities of three polyacetylene films, prepared from poly[1-(trimethylsilyl)-1-propyne], poly(tert-butylacetylene), and poly(1-chloro-2-phenylacetane), were studied in this article.
Abstract: The gas permeabilities of three polyacetylene films, prepared from poly[1-(trimethylsilyl)-1-propyne], poly(tert-butylacetylene), and poly(1-chloro-2-phenylacetylene), were studied. Although depending on conditions of polymerization and membrane preparation, typical permeability coefficients P of the polymers to oxygen and nitrogen at 25°C were as follows: poly[1-(trimethylsilyl)-1-propyne], PO2 = 40 × 10−8, PNr2 = 20 × 10−8; poly(tert-butylacetylene), PO2 = 3.0 × 10−8, PN2 = 1.0 × 10−8; poly(1-chloro-2-phenylacetylene), PO2 = 9.4 × 10−10, PN2 = 2.0 × 10−10 cm3(STP) · cm/(cm2 · s · cm Hg). Thus PO2 of a poly[1-(trimethylsilyl)-1-propyne] film is the largest among those ever known, and the values of poly(tert-butylacetylene) and poly(1-chloro-2-phenylacetylene) films are also fairly large. Influences of polymer structure, measuring temperature, and so forth on the PO2 and PN2 of these polyacetylene films were studied. The possibility of applying these films to oxygen enrichment of air are being discussed.
166 citations
TL;DR: In this paper, effective chain extenders for linear polyesters were investigated among some bis-heterocycles, which were capable of coupling carboxyl terminals of the polyesters through addition reaction.
Abstract: Effective chain extenders for linear polyesters were investigated among some bis-heterocycles, which were capable of coupling carboxyl terminals of the polyesters through addition reaction. Consequently, 2,2′-bis(2-oxazoline), 2,2′-bis(5,6-dihydro-4H-1,3-oxazine) and N,N′-hexamethylenebis(carbamoyl-2- oxazoline) were found to be the most effective chain extenders. Starting from a poly(ethylene terephthalate) (PET) having intrinsic viscosity ([η]) of 0.66 and carboxyl content (CV) of 46 eq/106 g, one could obtain polyesters with [η] of above 1.0 and CV of below 5 eq/106 g in the presence of the chain extenders. Typical reaction condition for the coupling of PET was heating PET under atmospheric nitrogen above its melting temperature with 0.5 mol % of a chain extenders only for several minutes. Bis-2-thiazolines showed no effect under the condition investigated, while in case of bis-2-imidazolines definite degradation was observed. Bis-N-acylaziridines and bisiminocarbonates resulted in some gell formation, indicative of side reactions.
159 citations
TL;DR: In this article, the authors proposed a set of criteria for rheological compatibility of polyethylene blends, including plots of first normal stress difference (N1) against shear stress (σ12), and of storage modulus (G′) against loss modulus(G″).
Abstract: Criteria for rheological compatibility of polymer blends are suggested. The criteria suggested make use of plots of first normal stress difference (N1) against shear stress (σ12), and of storage modulus (G′) against loss modulus (G″). Compatible blend systems considered are (1) blends of two different grades of low-density polyethylene, (2) blends of poly(vinylidene fluoride) and poly(methyl methacrylate), (3) blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene, and (4) blends of poly(styrene-co-acrylonitrile) and poly(styrene-co-maleic anhyride). And incompatible blend systems considered are (1) blends of nylon 6 and poly(ethylene-co-vinyl acetate) and (2) blends of nylon 6 and an ethylene-based multifunctional polymer. It has been found that plots of N1 vs. σ12 and G′ vs. G″ give (a) temperature-independent correlations for both compatible and incompatible blend systems; (b) composition-independent correlations for compatible blends; (c) composition-dependent correlations for incompatible blends.
141 citations
TL;DR: In this article, it was shown that CO2 sorption of CO2 at relatively high pressures by glassy polymers reduces their glass transition temperatures and may convert the glass into a rubber under certain conditions.
Abstract: Previous work has shown that sorption of CO2 at relatively high pressures by glassy polymers reduces their glass transition temperatures and may convert the glass into a rubber under certain conditions. It is shown here that this plasticization by a gas can induce crystallization just as sorption of vapors or liquids is known to do. This point is extensively explored for miscible blends of poly(vinylidene fluoride) and poly(methyl methacrylate) and to a lesser extent for poly(ethylene terephthalate). In some cases, this secondary crystallization process results in small crystals whose melting endotherms are just above the glass transition and are very similar to peaks resulting from heat capacity overshoots, or enthalpic relaxation, caused by sub-Tg annealing; however, by appropriate techniques peaks arising from these two separate mechanisms can be distinguished. For oriented materials, evidence is shown which demonstrates that the additional crystals formed on CO2 sorption have the same preferential orientation as the original material.
122 citations
TL;DR: In this paper, the authors investigated the crystallization kinetics of polyphenylene sulfide by using differential scanning calorimetry and found that glass fibers have an accelerating influence on crystallization resulting in a 15-25% reduction in crystallization time.
Abstract: The crystallization kinetics of unfilled and glass-reinforced grades of polyphenylene sulfide has been investigated by using differential scanning calorimetry. The maximum rate of crystallization is observed at about 170°C. From the crystallization data, it is recommended that the molding parameters should be so specified that the polymer spends 10–15 s over the temperature range of 155–190°C during cooling, before demolding, in order to ensure stable morphology of the molded part. The glass fibers have an accelerating influence on crystallization resulting in a 15–25% reduction in crystallization time. The kinetic data have been interpreted by using Avrami analysis followed by a discussion of the possible crystallization mechanisms.
112 citations
TL;DR: In this article, the moisture transport characteristics of a difunctional epoxy resin cured with different amounts of metaphenylene diamine, using two cure cycles, were reported.
Abstract: The moisture transport characteristics of a difunctional epoxy resin cured with different amounts of metaphenylene diamine, using two cure cycles, are reported. Besides studying the kinetics of moisture sorption at 20, 50, 75, and 100°C, the investigations also included measurement of thermal expansion coefficients and dynamic mechanical transition of the dry and wet samples. The moisture sorption of the sample is shown to be related to its specific volume and hence to its fractional free volume. In the glassy state, the free volume is apparently in the form of frozen voids, and moisture sorption/desorption at this temperature is of the Langmuir type with little or no bond formation. At higher temperatures the free volume is generated predominantly through segmental motion of the α transition. The Henry's Law mode becomes operative, and the moisture can now form bonds. The possible effect of nonuniform crosslink density on moisture sorption is also considered.
TL;DR: In this paper, the effect of the soft segment in relation to chain length and weight contribution on the thermal and mechanical properties of the final networks was examined, and a significant sensitivity of glass transition temperature (Tg), of swelling in DMF, and of the mechanical properties to soft segment content was observed.
Abstract: Hydroxypropyl lignin-based thermosetting polyurethanes were synthesized with excess hexamethylene diisocyanate (HDI) and tolylene diisocyanate (TDI) by solution casting. Four polyethylene glycols (PEG) of molecular weight 400, 600, 1000, and 4000 were mixed with lignin polyol to incorporate different proportions of soft segment into the network prior to crosslinking. Neither thermal nor mechanical and limited small angle x-ray scattering (SAXS) analysis provided distinct evidence for phase separation and microstructure formation. The study examines the effect of the soft segment in relation to chain length and weight contribution on the thermal and mechanical properties of the final networks. A significant sensitivity of glass transition temperature (Tg), of swelling in DMF, and of the mechanical properties to soft segment content was observed. Some of this sensitivity must, however, be attributed to differences in crosslink density since the polyol to diisocyanate weight ratio was kept constant throughout the synthesis series. The magnitude of the change of the different properties was found to be influenced by both glycol content and glycol molecular weight. The Tg of the network decreased from 105°C to as low as 38°C (HDI), and from 158°C to 70°C (TDI), with incorporation of up to 17.8% glycol, and it was greater with lower molecular weight glycols than with higher ones at any weight fraction. Swelling in DMF increased as expected with soft segment content. Mechanical properties were affected most if HDI and lower molecular weight glycols were used. The uniformity in structure, reduction in brittleness, and considerable improvement in mechanical properties with inclusion of minor PEG contents indicates that lignin-based network polyurethanes can be synthesized with controllable performance characteristics.
TL;DR: In this paper, the reactions taking place during melt mixing of bisphenol-A polycarbonate (PC) with poly(ethylene terephthalate) (PET) were studied by selective degradation of PC sequences, solubility tests, and IR spectroscopy.
Abstract: In this work the reactions taking place during melt mixing of bisphenol-A polycarbonate (PC) with poly(ethylene terephthalate) (PET) were studied by selective degradation of PC sequences, solubility tests, and IR spectroscopy. It was found that exchange reactions between PC and PET took place, contrary to what has been previously suggested by other authors. Kinetic constants were evaluated from intrinsic viscosity measurements of PET blocks. The reaction rate was slow when only the Sb catalyst (residues of the PET polymerization) were present, but it was significantly accelerated by the addition of Ti(OBu)4. In the presence of the latter catalyst, other side reactions, leading to discoloration and gas evolution, took place.
TL;DR: In this paper, the elastic modulus and stress at break increase with contents of the hard polyimide segments, which is connected with greater phase separation of hard imide segments from the soft polyether or polyester-urethane matrix.
Abstract: Linear polyurethaneimide elastomers (PUI) were obtained from polyether- or polyester-diols, diphenylmethane diisocyanate or bitolylene diisocyanate and pyromellitic acid dianhydride. It was found that these polymers have considerably better mechanical properties than typical linear polyurethanes (PU). The elastic modulus and stress at break increase with contents of the hard polyimide segments. The softening temperatures and thermal stability of the PUI at 500°C were higher than the ones of PU with similar hard segment contents. Electric properties of PUI were close to the ones of conventional PU. It was shown that cellular PUI had considerably lower dielectric constant. Tg's of the soft segments PUI were less than Tg's corresponding to PU. It is connected with greater phase separation of the hard imide segments from the soft polyether– or polyester–urethane matrix.
TL;DR: In this article, a comparison of the effects of very low levels of long chain branching (less than 0.1 branch per 1000 CH2) on the rheological behavior of polyethylene for samples, in which the branching has been introduced by means of peroxide decomposition or thermal-mechanical degradation is made.
Abstract: A comparison is made of the effects of very low levels of long chain branching (less than 0.1 branch per 1000 CH2) on the rheological behavior of polyethylene for samples, in which the branching has been introduced by means of peroxide decomposition or thermal-mechanical degradation. Both the activation energy and viscosity at low rates are shown to increase considerably more rapidly with branching level for samples containing branching formed from peroxide decomposition than for samples containing branching formed as a result of thermal or mechanical degradation. A model, which is based on parameters obtained for highly branched low density polyethylene and experimental molecular structure measurements, is shown to adequately account for the flow curves of samples containing branching introduced by thermal or mechanical degradation. Poor agreement of the model with experimental flow curves for peroxide branched samples is obtained, presumably because of the inability of the low density polyethylene parameters to adequately describe the flow properties of these samples, which are thought to contain tetrafunctional branch points. The good agreement between theoretical models, predicting relationships between activation energy and branching level, and experimental data is taken as lending further credence to the idea that the large variations seen in the rheological behavior with branching concentration at low branching levels are due to changes in the relative proportion of discrete branched and linear species with branching level. In accord with experimental results, a maximum in low rate viscosity with branching level is predicted. The maximum is predicted at approximately 0.25 branches/1000 CH2.
TL;DR: In this article, the effect of pre-treatment by NaOH and/or gamma-preirradiation on the precondensation time of the impregnated fibrous press material, the resin-fiber ratio, and the pressing parameters have been studied.
Abstract: Thermosetting plastic composites have been prepared with phenol–formaldehyde resins as well as unsaturated polyesters as binders and coconut hair as fibrous reinforcement Using resole-type phenol–formaldehyde resins, the effect of coconut fiber pretreatment by NaOH, the precondensation time of the impregnated fibrous press material, the resin–fiber ratio, and pressing parameters have been studied Especially advantageous press-material has been obtained using 60–65 wt % linear novolac type phenol-formaldehyde resin as binder and 35–40 wt % of coconut hair Applying unsaturated polyester (UP) as binder, BMC (bulk molding compound)-type press material can be prepared using coconut fiber reinforcement instead of glass fibers To achieve better coupling between coconut fiber and UP matrix, coconut fiber was pretreated by NaOH and/or gamma-preirradiation It has been found that in glass-fiber-reinforced UP press materials a significant part of glass fiber could be changed for short-cut coconut fiber
TL;DR: In this article, the authors present a mathematical model for the free-radical chain polymerization of methyl methacrylate (MMA) and validate its predictions with experimental data over a range of conversions and product molecular weights.
Abstract: This paper reviews our current understanding of the kinetics and mechanisms of free-radical chain polymerization of methyl methacrylate. A mathematical model previously proposed to describe the bulk polymerization of MMA is here extended to cover solution polymerization. This extended model is validated by comparing its predictions with experimental data over a range of conversions and product molecular weights.
TL;DR: Differential scanning calorimetry was used on a range of synthesized phenol-formaldehyde resols to discover relationships between formulation parameters or physical properties of resols, and their thermal behavior during cure as mentioned in this paper.
Abstract: Differential scanning calorimetry was used on a range of synthesized phenol–formaldehyde (PF) resols to discover relationships between formulation parameters or physical properties of resols, and their thermal behavior during cure. The thermograms showed either one or two exothermic reactions. The lower exothermic peak temperature varied between 98 and 129°C with changes in the free formaldehyde content. This exotherm is caused by the addition of free formaldehyde to phenolic rings. The upper exothermic peak temperature varied from 139 to 151°C, with the higher temperatures occurring when the formaldehyde-to-phenol molar ratio was low or the total amount of sodium hydroxide relative to phenol was high. These two factors led to resins which contain a somewhat higher level of unreacted ortho or para aromatic ring positions and no free formaldehyde. Consequently, condensation is probably not solely by the faster self-condensation through hydroxymethyl groups, but also includes the slower condensation of hydroxymethyl groups with unreacted ring positions. Gel times show trends with changes of formulation parameters somewhat similar to trends of the upper exothermic peak temperatures.
TL;DR: In this article, the authors adapted the differential viscometry principle to the design of a viscosity detector for use in size-exclusion chromatography, which possesses excellent sensitivity and baseline stability.
Abstract: The new technique of differential viscometry measures directly the specific viscosity of a solution by subtracting the contribution of solvent in a balanced capillary bridge. The present work adapts the differential viscometry principle to the design of a viscosity detector for use in size-exclusion chromatography. It is shown that the resulting viscosity detector possesses excellent sensitivity and baseline stability with a minimum detectable specific viscosity of 2.7 × 10−5. The viscosity detector can be operated together with a refractive index detector to determine the intrinsic viscosity of polymer solute fractions as they elute from the SEC column. The bandspreading of the viscosity detector is compared to the refractive index detector by measuring the peak width of a compound having a single discrete molecular weight. The peak width at half-height was 0.29 mL for the viscosity detector and 0.25 mL for the refractive index detector.
TL;DR: In this article, the authors measured the viscoelastic properties of elastomers with a 1:l mixture of rubber and resins using a mechanical spectrometer, and found that the structure of the resins is very important in adjusting the visocelastic property of a rubber-resin blend to achieve pressure sensitive adhesive performance.
Abstract: Blends of elastomers with the proper concentration of appropriate low molecular weight resins exhibit performance as pressure sensitive adhesives. Viscoelastic properties, which may be related to adhesive performance, were measured on 1:l blends of rubber and resin using a mechanical spectrometer. Significant differences in viscoelastic properties were observed depending upon the resin structure. On plots of G′ and tan δ vs. temperature, the addition of a compatible resin produces a pronounced shift of the tan δ peak to a higher temperature and reduces the modulus in the rubbery plateau. An incompatible resin results in a minor shift in the tan δ peak of the elastomer along with the appearance of a second peak at higher temperature, attributed to a second phase which is predominantly resin. Also, the modulus is increased in the rubbery plateau. A polystyrene resin, Mw about 900, is shown to be incompatible with natural rubber but compatible with styrene–butadiene rubber. A cycloaliphatic poly(viny1 cyclohexane) resin, Mw about 650, prepared by hydrogenating the polystyrene resin, is compatible with natural rubber, but incompatible with styrene-butadiene rubber. An alkyl-aromatic poly(tert-butylstyrene) resin, Mw about 850, which is intermediate in aromaticity between the aromatic polystyrene resin and the cycloaliphatic poly(viny1 cyclohexane) resin, is compatible with both natural rubber and styrene-butadiene rubber. Therefore, the structure of the resin is very important in adjusting the viscoelastic properties of a rubber–resin blend to achieve pressure sensitive adhesive performance.
TL;DR: In this article, the tensile properties of composites prepared from treated and untreated cellulose fibers were studied before and after exposure to water and it was found that all types of fiber treatment decreased water absorption and the reduction of mechanical properties in wet conditions, but that the degradation at the fiber/matrix interface which occurs from immersion in water and drying could only be avoided through the development of covalent bonds between fiber and matrix.
Abstract: Cellulose fibers treated with different coupling agents based on trichloro-s-triazine have been evaluated in terms of their reinforcement effect on unsaturated polyesters. The treatment with coupling agents containing double bonds resulted in what we believe to be the formation of covalent bonds between fiber and matrix. This has been compared with a treatment, which can only lead to formation of close interfacial molecular contact by wetting. The tensile properties of composites prepared from treated and untreated fibers were studied before and after exposure to water. It was found that all types of fiber treatment decreased water absorption and the reduction of mechanical properties in wet conditions, but that the degradation at the fiber/matrix interface which occurs from immersion in water and drying could only be avoided through the development of covalent bonds between fiber and matrix. Scanning electron microscopy was used to study the adhesion between fiber and matrix. An explanation of the reduction of mechanical properties of cellulose-fiber reinforced polymers in wet conditions is proposed.
TL;DR: In this paper, the authors studied the dynamic moduli, E′ and E″, and tan δ for PET-CR, PET-EPDM, and PET-UR composites with unidirectional short fibers using a Rheovibron.
Abstract: The dynamic moduli, E′ and E″, and tan δ for PET–CR, PET–EPDM, and PET–UR composites with unidirectional short fibers were studied as a function of temperature by using a Rheovibron. The temperature dependence of tan δ showed three peaks for PET–elastomer composites. The peaks at the low temperature corresponded to the main dispersion of the respective matrixes and the peak at about 140°C to the α-dispersion of PET fiber. A small and broad peak observed at a temperature between 60 and 120°C may be caused by the relaxation of the interface region between fibers and matrix. The longitudinal storage modulus for the composite E was given by the parallel model as , where E and E are the storage moduli for fiber and matrix and Vf and Vm are the volume fraction of fiber and matrix, respectively. In the transverse direction of fibers, the composite modulus E was expressed by the logarithmic law of mixing as follows: . The peak values of tan δ from the main dispersion of the respective matrixes were given by the equation, (tan δ⊥max)c/(tan δmax)m 1 − β · Vf, where (tan δ⊥max)c and (tan δmax)m are the maximum values of the loss tangent for the composite and matrix, respectively, and β is coefficient depending on matrix's type. The β value of PET–CR composite is the largest one among those of the composites.
TL;DR: In this paper, an experimental study was conducted to investigate the rheological behavior of a heterogeneous polymer blend system consisting of nylon 6 and an ethylene-based multifunctional polymer (CXA 3101, DuPont Co.).
Abstract: An experimental study was conducted to investigate the rheological behavior of a heterogeneous polymer blend system consisting of nylon 6 and an ethylene-based multifunctional polymer (CXA 3101, DuPont Co.). For comparison purposes, we also investigated the rheological behavior of two additional blend systems, namely blends of nylon 6 with a chemically modified polyolefin (Plexar 3, Chemplex Co.) and blends of nylon 6 with ethylene–vinyl acetate copolymer (EVA). We have investigated the thermal and thermomechanical behavior of the blend systems, using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Also, we have attempted to identify the chemical structure of the functional groups present in the CXA 3101 and Plexar 3 resins, using infrared (IR) spectroscopy. This information has enabled us to interpret the observed rheological behavior. Furthermore, we have used both optical and scanning electron microscopies to investigate the state of dispersion of the constituent components in each of the blend systems. We have concluded that, during melt blending, chemical reactions have taken place between carboxyl or anhydride groups present in the CXA 3101 resin and the amino end groups of the nylon 6, forming a graft copolymer which then acted as an “interfacial agent.”
TL;DR: Etude par spectrometrie IR et DSC des oxydations photo et thermique de divers polycondensats tridimensionnels epoxyde-amine as mentioned in this paper.
Abstract: Etude par spectrometrie IR et DSC des oxydations photo et thermique de divers polycondensats tridimensionnels epoxyde-amine
TL;DR: In this article, the graft copolymers of guargum and polyacrylamide have been prepared and it has been shown that the purification and grafting enhance the drag reduction effectiveness and biodegradation resistance considerably in Guargum.
Abstract: Commercial guargum is known to be a shear stable drag reducing agent. However, the aqueous solutions of guargum start degrading within 8 hrs. of their preparation and after 65 hrs., they degrade completely. In the present investigation, the graft copolymers of guargum and polyacrylamide have been prepared. It has been shown that the purification and grafting enhance the drag reduction effectiveness and biodegradation resistance considerably in guargum.
TL;DR: The chemical composition of polymers plasma-polymerized was influenced by the X groups in (CH 3)3SiXSi(CH3)3, X = none, CH2, NH, O, and S atoms as mentioned in this paper.
Abstract: Plasma polymerizations in five silicon compounds having chemical formula of (CH3)3SiXSi(CH3)3, X = none, CH2, NH, O, and S atoms, were investigated by elemental analysis, infrared spectroscopy, and ESCA. The chemical composition of polymers plasma-polymerized was influenced by the X groups in (CH3)3SiXSi(CH3)3. Polymers, when X was S atoms, possessed no sulfur; and X was CH2 groups polymers rich in carbon and hydrogen atoms were formed. Details in chemical composition were discussed by IR and ESCA. Such differences in chemical composition reflected on gas permeability of the plasma films.
TL;DR: In this article, the dual-mode sorption isotherms and diffusion coefficients of water in a 0.3-mil Kapton polyimide film at 30, 45, and 60°C were reported.
Abstract: Sorption isotherms and diffusion coefficients of water in a 0.3-mil Kapton polyimide film at 30, 45, and 60°C are reported. The data are well described by the dual mode sorption and transport models at low activities. At high penetrant activities, clustering of water is suggested by a Zimm–Lundberg analysis of the sorption data and the fact that the diffusion coefficient for water decreases with increasing external vapor activity. The effect of temperature on the diffusion coefficients at infinite dilution and the dual mode sorption parameters kD, b, and C are presented and discussed. The magnitude of the activation energy of the diffusion coefficient at infinite dilution, 5.4 kcal/mol, is smaller than the corresponding activation energy in more flexible chain polymers, perhaps suggesting that rather small backbone motions are associated with diffusion of water through the Kapton matrix. The predictions for the isosteric enthalpy of sorption from the dual mode model are presented and compared with the values determined from graphical analysis of the sorption isotherms performed independently without reference to the dual mode sorption model.
TL;DR: In this paper, the effect of moisture absorption, desorption, and thermal spiking on the physical/mechanical properties of TGDDM/DDS epoxy resin was investigated and compared to the Gr/Ep composite.
Abstract: The effect of moisture absorption, desorption, and thermal spiking on the physical/mechanical properties of TGDDM/DDS epoxy resin was investigated and compared to the Gr/Ep composite The mechanism of moisture diffusion in the neat resin was described on the morphological level The diffusion rate of moisture in epoxy resin was found to depend on the mobility of molecular chains within an inhomogeneous epoxy network Two well-known concepts of plasticization of amorphous polymers, the lubricity theory and the gel theory, were invoked to describe the interactions between the absorbed moisture and the resin network Slight permanent changes in properties of the neat resin were observed after one absorption-desorption cycle In the thermal spiking experiment, only the spiking temperature above the glass transition of the moisture saturated epoxy resins changed their internal structure and produced very small (thin) microcracks By comparison with the neat epoxy resin, the Gr/Ep composites contain the reinforcement-matrix boundary region, characterized by the highest restrictions to molecular mobility The absorbed moisture during the static hygrothermal fatigue cannot effectively plasticize this region But during thermal spiking, the formation of microcracks is observed within the reinforcement-matrix boundary region as well as an increase in the moisture content
TL;DR: In this paper, a fibrous adsorbent for metal ions was synthesized by radiation-induced grafting of acrylonitrile followed by amidoximation of cyano groups with hydroxylamine.
Abstract: Amidoxime-group-containing fibrous adsorbents for metal ions were synthesized by radiation-induced grafting of acrylonitrile followed by amidoximation of cyano groups with hydroxylamine. The degree of amidoximation and the distribution of amidoxime groups in the fiber were follwed by means of electron probe X-ray microanalysis. The efficiency of adsorbing metal ions was increased by alkaline treatment of the adsorbent at high temperature for a short period before use. The order of adsorption for various bivalent metal ions was Hg > Cu > Ni > Co > Cd. From the distribution pattern of metal ions in the fibrous adsorbent, the adsorption was found to be controlled by the diffusion of the solution containing metal ions inside the adsorbent. It was found that confining amidoxime groups superficially and making short chain length of grafts were effective to obtain a high degree of adsorption.
TL;DR: In this paper, the formation of asymmetric pervaporation membranes is discussed in terms of the model proposed by the authors: formation of the top layer by gelation; formation of a porous sublayer by liquid-liquid phase separation followed by the gelation of the concentrated polymer phase.
Abstract: Pervaporation is carried out primarily with homogeneous membranes. An improvement in permeation rate can be achieved by using asymmetric or composite membranes. In order to maintain a high selectivity, very dense top layers are needed. The formation of asymmetric pervaporation membranes will be discussed in terms of the model proposed by our group: formation of the top layer by gelation; formation of the porous sublayer by liquid-liquid phase separation followed by gelation of the concentrated polymer phase. To obtain very dense top layers the following factors are important: the ratio of nonsolvent inflow and solvent outflow, polymer concentration, location of the liquid-liquid demixing gap, and location of the gel region. Asymmetric membranes have been prepared by varying these factors, and the obtained membranes have been tested on ethanol/water mixtures.