Showing papers in "Journal of Applied Polymer Science in 1977"
TL;DR: In this article, the supermolecular structure and viscoelastic and diffusion properties of a perfluorinated polymer containing sulfonic acid (Nafion) were investigated.
Abstract: The supermolecular structure and viscoelastic and diffusion properties of a perfluorinated polymer containing sulfonic acid (Nafion) were investigated. The breakdown of time–temperature super-position for the dry salt and and acid in the presence of 0.5 H2O/SO3H as well as the results of small-angle x-ray scattering suggest that the ions in this material are clustered. Above 180°C, the reestablishment of the time–temperature superposition in the salt suggests that ions in the clusters become mobile. Dynamic mechanical studies were performed over a temperature range from −190°C to above the glass transition temperatures Tg of the materials. The Tg of the salts is found at ca. 220°C, while in the acid it occurs at 110°C. A β peak in the acid is found at ca. 20°C, while in the salts it occurs between 140°C and 160°C. The β peak shifts to a lower temperature with the addition of water in both the acid and the salts, while the α and γ peaks are unaffected. The latter is located at ca. −110°C at 1 Hz. Dielectric behavior has also been studied as a function of water content for the acid sample and the potassium salt at frequencies of 100 Hz to 10 kHz. Two relaxations with different activation energies were observed. The position of both peaks shifts to a lower temperature as the water content increases. Finally, the diffusion of water in Nafion in the acid form has been determined. The diffusion coefficient can be represented by the equation
453 citations
TL;DR: In this article, the molecular weight between crosslinks Mc was calculated from swelling and from tensile experiments, and two values of Mc were calculated for each swelling experiment, allowing for observed variation in the polymer-solvent interaction parameter χ 1 with concentration, and fixing χ1 = 0.494 according to literature data.
Abstract: Transparent crosslinked PVA hydrogels were prepared by electron beam irradiation of aqueous solutions under nitrogen. These weak hydrogels, upon swelling at 30°C in water, showed low elastic moduli (up to 50 psi), low ultimate tensile strength (up to 4 psi), and low extensibility to break (not higher than 85%). Values of the molecular weight between crosslinks Mc were calculated from swelling and from tensile experiments. In fact, two values of Mc were calculated for each swelling experiment, (a) allowing for observed variation in the polymer–solvent interaction parameter χ1 with concentration, and (b) fixing χ1 = 0.494 according to literature data. The correlation of the Mc obtained from tensile data with the Mc obtained from swelling data, by (a) or (b), was approximately linear and gave the same per cent agreement.
341 citations
TL;DR: In this article, the formation of membranes from two systems has been studied and the mechanism for formation of the sponge-like structure proves to be a liquid-liquid phase separation with nucleation and growth of the diluted phase.
Abstract: The formation of membranes from two systems has been studied. In the system polyurethane-dimethylformamide-water, the mechanism for the formation of the sponge-like structure proves to be a liquid-liquid phase separation with nucleation and growth of the diluted phase. This mechanism has been confirmed for the system modified polystyrene-polyisoprene-polystyrene/o-dichlorobenzene/(methanol-water). Crystallization and gelation is discussed. The membranes prepared showed hyperfiltration activity. The mechanism proposed here is believed to be valid for other systems, too.
152 citations
TL;DR: In this paper, the morphology of porous polysulfone hollow fibers which were spun by the dry-wet spinning process is discussed and a relatively moderate quenching medium should be employed in the bore of the nascent fiber in order to produce an isotropic fiber free of macrovoids and intrusion cells.
Abstract: The morphology of porous polysulfone hollow fibers which were spun by the dry–wet spinning process is discussed. It was demonstrated that a relatively moderate quenching medium should be employed in the bore of the nascent fiber in order to produce an isotropic fiber free of macrovoids and intrusion cells. A rather delicate quantitative balance between the internal precipitant and the spinning solution has to be maintained, especially when low-viscosity polymeric solutions are employed. Scanning electron micrographs of fiber cross sections display highly porous, spongestructured walls which in some instances exhibit a rather dense interface skin. However, control of the extrusion/coagulation procedure allows the formation of skinned, porous skinned, and nonskinned fibers.
151 citations
TL;DR: In this article, the force required to propagate a 180° bend in an elastic-plastic strip has been calculated from elementary bending theory and measured forces for Mylar strips of various thicknesses, bent to various degrees, were in good agreement with these calculated values.
Abstract: The force required to propagate a 180° bend in an elastic-plastic strip has been calculated from elementary bending theory Measured forces for Mylar strips of various thicknesses, bent to various degrees, were in good agreement with these calculated values The corresponding additional stripping force in a peeling experiment will depend upon the thickness of the elastic-plastic adherend, becoming zero both for infinitesimally thin adherends and for those exceeding a critical thickness tc and passing through a maximum value at intermediate thicknesses Published data are in good agreement with these conclusions For a strongly adhering strip, higher peel strengths are found for a peel angle of 180°, compared to 90°, and the effect is greater than can be accounted for solely by plastic yielding of the adherend It is attributed in part to greater energy dissipation within the adhesive layer
137 citations
TL;DR: In this article, an extensive experimental study of structure development during the melt spinning of polypropylene and in as-spun polyethylene filaments was reported, and five polymers representing different molecular weights and polymerization methods were studied.
Abstract: Synopsis An extensive experimental study of structure development during the melt spinning of polypropylene and in as-spun polypropylene filaments is reported. Five polymers representing different molecular weights and polymerization methods were studied. WAXS, SAXS, and birefringence measurements were used to characterize the structure of the filaments. Spinning through air gives rise to monoclinic crystalline structures and spinning into cold water, the paracrystalline smectic form. Both crystalline and amorphous orientation factors were found to correlate with spinline stress for the different polymers studied, Mechanical properties of as-spun fibers such as modulus, yield strength, tensile strength, and elongation to break also correlate with spinline stress.
115 citations
100 citations
89 citations
TL;DR: The compatibility, morphology, and mechanical properties of poly-ϵ-caprolactone (PCL) blended with poly(vinyl chloride), nitrocellulose, and cellulose acetate butyrate are described in this article.
Abstract: The compatibility, morphology, and mechanical properties of poly-ϵ-caprolactone (PCL) blended with poly(vinyl chloride), nitrocellulose, and cellulose acetate butyrate are described in this study. Methods used in this investigation included differential scanning calorimetry, dynamic mechanical testing, small-angle light scattering, light microscopy and stress–strain testing. Blends of PCL with poly(vinyl chloride) (PVC) are shown to be compatible in all proportions. In the PCL concentration range 40–100%, the PCL crystallizes in the form of negative spherulites. The spherulites were found to be volume filling with as much as 35% PVC. The nitrocellulose blends with PCL exhibited the glass transition behavior of a compatible system over the composition range of 50–100% PCL. At lower PCL concentrations, phase separation was apparent. The PCL crystallinity was present only in the nitrocellulose blends with more than 50% PCL, and it was in the form of rod-like super-structures. Blends of PCL with cellulose acetate butyrate were shown to be phase separated, with one phase having nearly equal proportions of the two polymers. The PCL crystallinity was in the form of negative spherulites and was formed with PCL compositions as low as 50%. Stress–strain results show polycaprolactone to be an effective plasticizer for poly(vinyl chloride) and the cellulose derivatives studied.
89 citations
TL;DR: The concept of rotational isomerism of the O-(CH2)M-O part, which was fairly successful in poly(ethylene terephthalate) (C2T), was tried to apply to the polyesters other than C2T as discussed by the authors.
Abstract: Infrared spectra of some poly(methylene terephthalates) and some poly(methylene 2,6-naphthalates) were compared To interpret the spectral changes during drawing and heat treatment, the concept of rotational isomerism of the O-(CH2)M-O part, which was fairly successful in poly(ethylene terephthalate) (C2T), was tried to apply to the polyesters other than C2T Also, the bands originated from a benzene ring and from a naphthalene ring were distinguished Poly(ethylene 2,6-naphthalate) (C2N) has some bands behaving differently from those of other polyesters This would be due to the existence of certain intermolecular interactions arised from tight packing of the molecules in the crystal of C2N
87 citations
TL;DR: In this paper, castor oil was polymerized and crosslinked with sulfur or diisocyanates to form the vulcanized and urethane derivatives, respectively, and the resulting interpenetrating polymer networks were characterized using electron microscopy.
Abstract: Castor oil was polymerized and crosslinked with sulfur or diisocyanates to form the vulcanized and urethane derivatives, respectively. Both types were swollen with a plastic-forming monomer plus crosslinker, and a second polymerization was carried out in situ. Polyblends were also made by emulsion polymerization of styrene and methyl methacrylate employing hydrolyzed castor oil as the soap. In all three polymerizations, a wide range of compositions was obtained. The resulting interpenetrating polymer networks were characterized using electron microscopy, modulus–temperature measurements, and stress–strain analysis. The polystyrene phase size of the castor oil–urethane/polystyrene IPN was shown to decrease with increased crosslinking of the castor oil component and with increased polystyrene contents. The modulus–temperature study showed two distinct glass transitions in all cases, with evidence of significant mixing of the two components in many cases. The stress–strain results show that some of the IPN's behave as reinforced, highly extensible elastomers at low polystyrene levels, and a rubber-toughened plastics at high levels of polystyrene or crosslinking.
TL;DR: The kinetic parameters of the polymerization of diglycidyl ether of bisphenol A with hexahydrophthalic anhydride and benzyldimethylamine as catalyst were determined using differential scanning calorimetry as mentioned in this paper.
Abstract: The kinetic parameters of the polymerization of diglycidyl ether of bisphenol A with hexahydrophthalic anhydride and benzyldimethylamine as catalyst were determined using differential scanning calorimetry. The reaction was found to be first order with some variation with temperature, and the activation energy and natural log of the frequency factor were 25 kcal/mole and ∼25 sec−1, respectively. These results are discussed with respect to a steady-state mechanism of the polymerization and compared with results reported for other epoxide–anhydride reactions.
TL;DR: In this article, a limited number of tensile tests and tensile fatigue tests were performed on fiber B and PRD 49 to determine the fracture morphology of aramid fibers, and the results showed that both tensile and fatigue failure occurs by axial splitting with the fatigue splits being much longer.
Abstract: Samples of Fiber B and PRD 49 which were the forerunners of current Kevlar aramid fibers were subject to a limited number of tensile tests and tensile fatigue tests in order to determine their fracture morphology. The fibers were examined by optical and scanning electron microscopy. Both tensile and fatigue failure occurs by axial splitting, with the fatigue splits being much longer. Compressive effects in snap-back cause kink bands to form. The fatigue strength is only marginally less than the tensile strength.
TL;DR: In this article, the temperature dependence of the mutual diffusion coefficient at zero solvent concentration for a number of polystyrene-solvent systems is satisfactorily represented by an equation derived from a new version of the free-volume theory of molecular transport.
Abstract: The temperature dependence of the mutual diffusion coefficient at zero solvent concentration for a number of polystyrene–solvent systems is satisfactorily represented by an equation derived from a new version of the free-volume theory of molecular transport. The free-volume parameter which governs the temperature dependence of the diffusion rate is linearly related to the size of the solvent as estimated by its molar volume at OK. Data taken on various polystyrene–solvent systems are used to deduce information on the mechanism of solvent transfer in polymeric systems.
TL;DR: In this paper, the average pore sizes and effective porosity of microporous polysulfone hollow fibers were determined by the gas permeability method using scanning electron microscopy.
Abstract: Average pore sizes and effective porosity of microporous polysulfone hollow fibers were determined by the gas permeability method. Surface structure and porosity were determined by scanning electron microscopy. The values of effective porosity e/q2 (porosity/tortuosity factor) are approximately one order of magnitude lower than those reported previously for flat sheet porous membrane. These lower values are a direct outcome of a higher polymer concentration in the spinning dope. Correlations between the wall void volume, equivalent pore size, and hydraulic permeabilities of the hollow fibers have been determined. Rather low values of e/q2 have been calculated compared to those of the void volume; these effective porosity values indicate either a very high tortuosity factor or a large number of “dead end” pores. Exposure of the fibers to elevated temperature (110°C) for a short period of time drastically reduces the surface pore size and narrows the pore size distributions, whereas overall fiber dimensions are reduced only by 1%, and 85% of the fiber's hydraulic permeability is retained. The scanning electron microscopy study reveals the formation of a relatively dense skin in some spun fibers. For such “skinned” fibers, kinetic (permeability) evaluation of static structure such as mean pore size is not realistic and is further generalized to the term “equivalent pore size.”
TL;DR: In this paper, the effects of a long water immersion and the application of a silane-based primer have also been studied, and the results indicated that for dry joints fracture occurred near an epoxy resin/metal interface while with water-soaked unprimed joints, fracture occurred interfacially between the adhesive and iron oxide.
Abstract: The techniques of Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) have been used to study the locus of failure of epoxy resin joints. The effects of a long water immersion and the application of a silane-based primer have also been studied. Results indicated that for dry joints fracture occurred near an epoxy resin/metal interface while with water-soaked unprimed joints, fracture occurred interfacially between the adhesive and iron oxide. The application of the primer to the metal surface prior to bonding prevented the formation of a water-formed oxide although fracture was then found to occur through the primer.
TL;DR: In this article, straight polypropylenes (PP) with different melt flow index (MFI) and a glass fiber-reinforced polypropylene (FRPP) were injection molded at various molded at different temperatures into square plates with orientational anisotropy.
Abstract: By use of a mod with a film gate, two straight polypropylenes (PP) with different melt flow index (MFI) and a glass fiber-reinforced polypropylene (FRPP) were injection molded at various molded at various temperatures into square plates with orientational anisotropy. The anisotropies of tensile property, tensile impact strength, and flexural property were studied on the molded sample cut mainly in the machine direction (MD), 45°-direction (45°), and transverse direction (TD). Both the orders of the yield strength and tensile impact strength of the FRPP, and those of the necking stress and tensile impact strength of the straight PP, were MD >45° >TD, which are reasonable tendencies. The orders of the yield strength and flexural modulus of the straight PP were MD > TD > 45°, which suggests the presence of shear deformation between the lamellae in the skin layer. The variation of the flexural modulus with the angle to the MD fitted well to Hearmon's equation. Generally, for straight PP, the anisotropy of various properties increased as the MFI and cylinder temperature became lower, or as the skin layer became thicker. For the FRPP, the anisotropy increased as the cylinder temperature became higher, or as the degree of the orientation of glass fibers became higher.
TL;DR: In this paper, differential scanning calorimetry has been used to characterize moisture transitions in paper and cellulose, including free water incorporation point (0.05 g/g), total bound water, fiber saturation point, and fiber saturation points.
Abstract: The association of water with cellulose is of significant technological importance. It forms the basis for the manufacturability of paper and ultimately controls, either directly or indirectly, mechanical, electrical, thermal, and optical properties. Differential scanning calorimetry has been used to characterize moisture transitions in these materials. Total bound water contents have been determined. Specific transitions for the model system, cotton linters, have been identified including free water incorporation point (0.05 g/g), total bound water (0.18 g/g), and fiber saturation point (0.05 g/g). Results are compared to those found in a pulsed nuclear magnetic resonance study in which a moisture distribution model was generated; free water point (0.046 g/g) and total bound water (0.19 g/g). The differential scanning calorimetry technique can provide a more readily available, less expensive, and simpler technique for paper/cellulose characterization and study.
TL;DR: In this article, the fluorescence and phosphorescence excitation and emission spectra of commercial polypropylene have been examined using a fully compensated spectrofluorometer, which has made possible the comparison of the excitation spectra with model chromophores of those believed to be present in the polymer.
Abstract: The fluorescence and phosphorescence excitation and emission spectra of commercial polypropylene have been examined using a fully compensated spectrofluorometer. This has made possible the comparison of the excitation spectra of the polymer with model chromophores of those believed to be present in the polymer. The fluorescence emission is primarily associated with the presence of enone, and the phosphorescence with dienone chromophoric units. The behavior of the luminescent enones and dienones during irradiation under sunlight-simulated conditions has also been examined. Possible mechanisms for the participation of these chromophoric units in the photo-oxidation of polypropylene are discussed.
TL;DR: In this article, the structure of melt-spun nylon 6 filaments was studied using on-line x-ray diffraction and birefringence measurements, and it was shown that the filaments did crystalline gradually on the bobbin to a paracrystalline pseudohexagonal (γ) form.
Abstract: The structure of melt-spun nylon 6 filaments was studied using on-line x-ray diffraction and birefringence measurements. Measurements were also made on as-spun and treated filaments. On-line wide-angle x-ray scattering measurements indicated that crystallization did not occur on the nylon 6 spinline at spinning rates up to 1000 m/min when spinning was done into either ambient air of 60% relative humidity or into wet saturated air. The filaments did crystalline gradually on the bobbin to a paracrystalline pseudohexagonal (γ) form. The rate of crystallization was dependent on the molecular orientation developed in the spun filaments. Crystalline orientation factors based on hexagonal symmetry were computed as a function of take-up velocity for fibers which were conditioned 24 hr in air at 65% relative humidity. Annealing in air or treatment in water or 20% formic acid solution causes a transformation from the pseudohexagonal form to the α monoclinic form. The tangent modulus of elasticity and tensile strength of spun and conditioned filaments increase with increasing take-up velocity and spinline stress, while elongation to break decreases with these variables.
TL;DR: The morphology of chemically crosslinked urethane elastomer is correlated with its time-dependent mechanical properties, and the observed time dependence in modulus is believed to be caused by molecular relaxation resulting in densification of amorphous packing within the hard-segment domains.
Abstract: The morphology of a chemically crosslinked urethane elastomer is correlated with its time-dependent mechanical properties. Evaluation of this amorphous elastomer by electron microscopy and small-angle x-ray scattering reveals that incompatible chain segments cluster into separate microphases having a periodicity in electron density of about 90 A. This observed domain structure is similar to that seen previously in uncrosslinked, thermoplastic urethane elastomers. As in earlier studies on such linear systems, thermal pretreatment of the crosslinked elastomer causes a time-dependent change in its room temperature modulus. However, the magnitude of this modulus change (about 20%) is generally less than observed previously with the linear systems. Another contrast with previous findings is that this time-dependent phenomenon is apparently not caused by thermally activated changes in microphase segregation. Rather, the observed time dependence in modulus is believed to be caused by molecular relaxation resulting in densification of amorphous packing within the hard-segment domains. The validity of this proposed mechanism is supported by differential scanning calorimetry experiments showing evidence of enthalpy relaxation during room-temperature aging of the elastomer. This relaxation is qualitatively similar to that observed previously during sub-T/sub g/ annealing of single-phase glassy polymers.
TL;DR: In this paper, a semi-empirical derivation of equations which show quantitatively the dependence of the phase domain size of polymer II on the crosslinking density of polymer I, and also on the interfacial energy and the overall composition is presented.
Abstract: In previous papers, interpenetrating polymer networks were shown to display a cellular structure. The phase domain size of polymer II was shown to depend inversely on the crosslink density of polymer I. The present paper presents a semiempirical derivation of equations which show quantitatively the dependence of the phase domain size of polymer II on the crosslinking density of polymer I, and also on the interfacial energy and the overall composition. If polymer II is linear, the dependence on the molecular weight of polymer II is also included. The values of the phase domain sizes so estimated are compared with experimental results. While theory and experiment yield good agreement, the semiempirical nature of the equations must be borne in mind.
TL;DR: In this paper, the effect of center block compatible diluent can also be calculated, although the simple procedure used here tends to underestimate the plasticizer effect, particularly at high diluency concentration, and the calculation furnishes a useful criterion of compatibility of polydiene center blocks and low molecular weight resins used commonly as tackifiers in pressure sensitive adhesives.
Abstract: Styrene-diene (butadiene or isoprene) block copolymers of the SDS or (SD−)x type exhibit a plateau in the dynamic storage modulus located between the glass transitions of the polydiene and polystyrene domains. When the polydiene is the continuous phase, the height of this plateau can be estimated with good success from the entanglement spacing molecular weight of the polydiene and the filler effect of the polystyrene domains. The effect of introduction of a center block-compatible diluent can also be calculated, although the simple procedure used here tends to underestimate the plasticizer effect, particularly at high diluent concentration. Nevertheless, the calculation furnishes a useful criterion of compatibility of the polydiene center blocks and low molecular weight resins used commonly as tackifiers in pressure-sensitive adhesives. Center block compatibility is essential for the development of tack in these compositions.
TL;DR: In this article, a new method, called GPCV2, is proposed which uses the single broad molecular weight distribution (MWD) standard for calibration developed by those workers, but which also incorporates the chromatographic dispersion σ to make the method more accurate in general use.
Abstract: The method of Balke, Hamielec, LeClair, and Pearce for GPC calibration and molecular weight computation is reviewed and evaluated. A new method, called GPCV2, is proposed which uses the single broad molecular weight distribution (MWD) standard for calibration developed by those workers, but which also incorporates the chromatographic dispersion σ to make the method more accurate in general use. Equations are presented for computing the relationship between actual MW and retention volume VR under the chromatographically broadened curves. This relationship is then compared to those obtained by using the Balke et al. method and the peak position method.
TL;DR: In this article, the first successful attempts to graft copolymerize acrylonitrile, methyl methacrylate, and acrylamide to starch and starch derivatives are described using managanic pyrophosphate as initiator.
Abstract: Advantages in using the pyrophosphate complex of trivalent managanese over the sulfate complex as initiator for graft copolymerization onto starch are discussed. The first successful attempts to graft copolymerize acrylonitrile, methyl methacrylate, and acrylamide to starch and starch derivatives are described using managanic pyrophosphate as initiator. Selective solvent extraction of the reaction products and very low conversions of monomer to homopolymer in absence of starch substrates provide evidence for high grafting efficiencies obtained with acrylonitrile and methyl methacrylate. With acrylamide as monomer, however, low grafting efficiencies and considerable amounts of homopolymer are obtained under the experimental conditions investigated. Reaction mechanisms responsible for initiation of graft copolymerization are discussed. These are (a) glycol cleavage in the anhydroglucose units by Mn3+ ions leading to formation of a radical, and (b) enolization and further oxidation of oxidized starch by Mn3+ ions also leading to radical species. Mechanisms are also proposed for homopolymerization through Mn3+ oxidation of enols which probably are formed by “vinylogous” addition of water molecules to acrylamide and methyl methacrylate.
TL;DR: In this article, the engineering properties of polyurethane-poly(methyl methacrylate) simultaneous interpenetrating networks (SINs) were evaluated and the results indicated that the reinforcement in the ultimate tensile strength was not directly related to increased physical entanglement crosslinks but indirectly related by reducing the rigid phase domain sizes and increasing the adhesion between the two phases, thus enhancing the filler-reinforcing effect similar to that observed in a carbon black-filled rubber.
Abstract: The engineering properties of polyurethane–poly(methyl methacrylate) simultaneous interpenetrating networks (SIN's) were evaluated. The hardness behavior reflected the observed phase inversion in the electron-microscopic studies. The maximum ultimate tensile strength was observed at 85% polyurethane–15% poly(methyl methacrylate) IPN and was due to the filler-reinforcing effect of the rigid poly(methyl methacrylate) phase. The ultimate tensile strenght of the 75/25 polyurethane–poly(methyl methacrylate) IPN was higher than that of the corresponding pseudo-IPN's (only one network crosslinked) and the linear blend. The leathery and glassy compositions did not show any reinforcement in the ultimate tensile strength. This indicated that the reinforcement in the ultimate tensile strength was not directly related to interpenetration (by increased physical entanglement crosslinks), but indirectly related by reducing the rigid phase domain sizes and increasing the adhesion between the two phases, thus enhancing the filler-reinforcing effect similar to that observed in a carbon black-filled rubber. The tear strengths of the polyurethane-rich IPN's pseudo-IPN's, and linear blends were found to be higher than that of the pure polyurethane as a combined result of increased modulus and tensile strength. The weight retentions in the thermal decomposition of the IPN's, pseudo-IPN's, and linear blends were higher than the proportional average of the component networks. The results seemed to indicate that this enhancement was related to the presence of the unzipped methyl methacrylate monomer. It was suggested that the monomers acted as radical scavengers in the polyurethane degradation, thus delaying the further reaction of the polyurethane radicals into volatile amines, isocyanates, alcohols, olefins, and carbon dioxide.
TL;DR: In this article, a series of step reaction polymers have been prepared and studied as melt films or in solution in the overtone region and the combination region of the near-IR.
Abstract: A series of step reaction polymers have been prepared and studied as melt films or in solution in the overtone region and the combination region of the near-IR. Systems containing aryl rings show bands in the 2.13- to 2.16-μm region which are not observed in those systems not having aryl rings. Polyester, polyamide, and urea-formaldehyde polymers show carbonyl, hydroxyl, and NH overtones. Polyurethanes show only the intense band of NH, in the 2.0- to 2.1-μm region. Ureaformaldehyde and polyamides show this same band. Relative band intensities were compared to the first overtone of CH which appears at 1.67–1.72 μm. In this way, polymers can be compared in a quantitative manner, both with respect to reaction conditions and effect of heat curing.
TL;DR: In this paper, the dependence of the specific volume of poly(4-methylpentene-1) (Mitsui TPX, RT-20, abbr. PMP) on temperature (30°-320°C) and pressure (0-2000 kg/cm2) has been determined.
Abstract: The dependence of the specific volume of a commercial sample of poly(4-methylpentene-1) (Mitsui TPX, RT-20, abbr. PMP) on temperature (30°–320°C) and pressure (0–2000 kg/cm2) has been determined. Results are reported in tabular form and as approximate fits, making use of the Tait equation. The data show that the crystalline melting transition of this type of PMP is completed at 235°C under zero pressure and gives indication of a glass transition temperature Tg at about 20°C at p = 0. Its approximate pressure dependence is given by dTg/dp ≈ 0.015°C kg−1 cm2. The zero pressure results on the melting and glass transitions are in agreement with DTA results. The p-v-T data, quenching experiments, and a determination of the crystalline unit cell (tetragonal, a = b = 18.70 A, c = 13.54 A) confirm earlier work indicating that the room-temperature crystalline specific volume of PMP is greater than the amorphous specific volume. This unusual density behavior persists to a temperature of 50–60°C at p = 0 and to temperatures as high as 230–240°C under a pressure of 2000 kg/cm2.
TL;DR: In this paper, the relationship between the molecular weight of liquid hydroxyl-terminated polybutadiene (HTPB) and the physical properties of the elastomers were investigated.
Abstract: The relationship between the molecular weight of liquid hydroxyl-terminated polybutadiene (HTPB) and the physical properties of the elastomers were investigated. HTPB having various molecular weights were cured with 4,4′-diphenylmethane diisocyanate (MDI) by the one-shot method and the physical properties of these elastomers obtained were measured. The tensile strenght, modulus, tear resistance, and the hardness decreased with increase in the molecular weight of HTPB, and this phenomenon was remarkable in the low molecular weight HTPB (below about 3000). On the other hand, the ultimate elongation increased linearly with increase in the molecular weight of HTPB. The effects of incorporating a short-chain diol, N,N-bis(2-hydroxypropyl)aniline, on the physical properties on the elastomers are also discussed.