Showing papers on "Glass transition published in 1970"
TL;DR: The dielectric loss factor and permittivity of 8-16 mol% solutions of chlorobenzene, o−dichlorobenzenes, and 1-chloronaphthalene in cis-decalin were measured by DTA as mentioned in this paper.
Abstract: The dielectric loss factor and dielectric permittivity of 8–16 mol% solutions of chlorobenzene, o‐dichlorobenzene, and 1‐chloronaphthalene in cis‐decalin; 50–60 mol% mixtures of pyridine with chlorobenzene, bromobenzene, 1‐chloronaphthalene, and toluene; 50–60 mol% mixtures of tetrahydrofuran with bromobenzene and 1‐chloronaphthalene; the pure liquids cis‐decalin, o‐terphenyl, iso‐propylbenzene, propylene carbonate; and two fused salt systems, 45 mol% Ca(NO3)2–KNO3 mixture and Ca(NO3)2·4H2O have been measured from 50 Hz to 1 × 105 Hz from − 196° in the vitreous state to about 30° above their respective glass transition temperatures. The Tg's of the organic glasses have been measured by DTA. With the exception of propylene carbonate, all glasses show the presence of one secondary relaxation between − 196° and their respective Tg's either as a peak or shoulder in a tanδ–temperature plot at a single frequency, or in the dielectric loss spectrum. Arrhenius plots of the frequency of maximum loss against temper...
1,519 citations
01 Jan 1970
TL;DR: In this paper, the authors present a NMR study of the transition of a mixture of two Isomeric Cyano-Ester homologous series, showing that the phase transition of one of the two isomeric versions of this series is a transition of the other.
Abstract: Some Novel Ferroelectric Smectic Liquid Crystals.- Liquid Crystalline Esters of Phenylhydroquinone and 3-Phenyl 4-Hydroxybenzoic Acid.- The Synthesis and Characterization of Some Perylene and Anthraquinoic Dichroic Dyes for Liquid Crystal Display Applications.- Some New Thermotropic Discogens.- Syntheses and Properties of Liquid Crystalline Heterocycloalkanes.- Characterization of Two Isomeric Cyano-Ester Homologous Series -I.- Effects of Molecular Length on Nematic Mixtures - IV: Structure Effects on Viscosity of Ester Mixtures.- Orientational Disorder in Smectic Liquid Crystals: An Aspect of Structure that has to be Included.- Effect of Molecular Structure of Rigid - Flexible Polyesters on Their Thermotropic Liquid Crystalline Properties.- Relationships Between Molecular Structure and the Incidence of Crystal B and Hexatic B Phases.- Characterization of the Phases of Two Isomeric Cyano-Ester Homologous Series - II.- Unusual Glass Transition of Smectic Liquid Crystal in p-n-Hexyloxybenzylidene-p'-Butylaniline.- Some High Electric Field Effects in Nematic Liquid Crystals.- Application of Generalized Van Der Waals Theory of Homologous Nematogens - Part 1: Trans-4-Ethoxy-4'-N-Alkanoyloxyazobenzenes..- Application of Regular Solution Theory to Discotic Mesophases: Calculation of Phase Diagrams Exhibiting Minima.- Extension of McMillan's Model to Liquid Crystals of Disc-Like Molecules.- Thermotropic Liquid-Crystalline Polymers with Mesogenic Groups and Flexible Spacers in the Main Chain.- Effect of Mesogenic Unit and Spacer Structures on the Thermotropic Properties of Main Chain Liquid Crystal Polyesters.- The Role of Sequence Distribution on Liquid Crystalline Properties of Aromatic Copolyesters.- Diffusion of Rigid Polyamides Through Swollen Gel of Same.- The Molecular Weight Dependence of the Splay and Bend Elastic Constants of a Polymer Liquid Crystal.- DSC, Miscibility and X-ray Studies of the Thermotropic Liquid Crystalline Polyesters with Aromatic Moieties and Flexible Spacers in the Main Chain.- Influence of the Leprosy Drug, Dapsone, on the Phase Transitions of the Lyotropic, Dipalmitoy1 Phosphatidylcholine (DPPC).- Nonaqueous Lyotropic Liquid Crystals of Lecithin and Oligomers of Polyethylene Glycols.- The Diamagnetic Anisotropy of Lyotropic Nematic Mesophases.- Physical Models of Lipid Membranes in Latent Cancer Cells: Ordering Effects of Petroleum Hydrocarbons.- Adiabatic Compression: A New Method to Measure Latent Heats in Phospholipid Bilayers.- Anisotropy of the Electric Conductivity in Amphiphilic Liquid Crystals.- Phase Transition Properties of Bilayers of Mixed Lipids and Their Covalent Analogs.- On The Orientation of Liquid Crystals by Monolayers of Amphiphilic Molecules.- Refractive Index Measurements Using a Double Arm Converging Beam Interferometer.- A Pulsed NMR Study of Transient and Persistent Molecular Order in Nematic Liquid Crystals.- The Effect of Twist on Biaxial Ordering in the Cholesteric Phase.- Deuteron Magnetic Relaxation and Molecular Dynamics in Thermotropic Liquid Crystals.- An Effective Proton Hyperfine Tensor for Di-Tertbutylnitroxide.- Alkyl Chain Flexibility in Liquid Crystals.- Orientational Order in Binary Mixtures of Nematic Liquid Crystals.- The Effect of the Tricritical Region on the Smectic A - Smectic C Transition.- Spatial Correlations in Nematic Liquid Crystals.- Molecular Structure and Ordering in Liquid Crystals.- New Liquid Crystals, Polymeric and Monomeric, Derived From Binaphthyl.- Ioneneomeric Liquid Crystals.- Mesomorphic Properties of an Homologous Series of Alkyl-Terminated Enamine-Ketone Containing Liquid Crystals.- Liquid Crystalline Polymers with Amphiphilic and Non Amphiphilic Side Chains - Effect of the Main Chain on the Phase Behaviour.- The Fluid Mesophases of Polar Rods.- The Nematogeneity of Some Hydrocarbons.- Some Heterocyclic Analogues of Biphenyl Mesogens.- Alignment of Liquid Crystal Molecules on Various Surfaces: Myths, Theories, Facts.- Development of Dual-Frequency Addressable Liquid Crystals.- Dielectric Studies of Monoester and Diester Nematogens.- Intermolecular Guest-Host Interactions and the Optical Order Parameter of Pleochroic Dyes.- Liquid Crystal Alignment on Substrate Surfaces, A Collective Phenomenon.- Alignment of Liquid Crystals in the Vicinity of the SmA-N Transition.- Nematic-Substrate Interaction and the Boundary Layer Phase Transition.- Optical Properties of the Blue Phase of Cholesteric Liquid Crystals.- Lattice Parameters in Blue Phase Mixtures.- Blue Phase Structure Analysis by Optical Bragg Diffractions.- Mesomorphic Polymers as Three Component Systems.- Colloidal Crystals and Glasses.- Self Diffusion Constant and Viscosity of Charged Polystyrene Colloids.- Influence of Molecular Conformation on the Helical Twisting Power of Terpenes in Nematic Liquid Crystals.- Vibrational Spectra of Liquid Crystals XIII: Crystallization Kinetics Study of 4, Octyloxy, 4', Cyano Biphenyl by Rapid Raman Spectroscopy..- Nuclear Spin-Lattice Relaxation Due to Orientational Fluctuation in Smectic Liquid Crystals.- NMR Studies of Molecules Oriented in Mixed Thermotropic Liquid Crystals of Opposite Diamagnetic Anisotropies.- Discotic Mesophase: A Complementary Review.- Identification of the Structure of Mesomorphic Polymers by Means of their Miscibility.- Effect of Molecular Structure on Mesomorphism: Difluorinated Siamese Twin Mesogens.- Anisotropy Induced in a Semi-Flexible Polymer by a Liquid-Crystalline Solvent.- Electrooptical Behaviour of a Novel Strong-Weak Anchored Nematic Layer: First Measurements of MBBA Flexoelectric Coefficient of Splay elz.- On Thermotropic Disc-Like Mesogens.- On The Nature of the Smectic-C Phase.- Contributors.
1,036 citations
TL;DR: In this article, the curing reactions of epoxy resin with aliphatic diamines and the reaction of phenyl glycidyl ether with butylamine were investigated with a differential scanning calorimeter (DSC) operated isothermally.
Abstract: The curing reactions of epoxy resin with aliphatic diamines and the reaction of phenyl glycidyl ether with butylamine as a model for the curing reactions were investigated with a differential scanning calorimeter (DSC) operated isothermally. The heat of reaction of phenyl glycidyl ether with butylamine is equal to 24.5 ± 0.6 kcal/mole. The rate of reaction was followed over the whole range of conversion for both model and curing reactions. The reactions are accelerated by the hydrogen-bond donor produced in the system. The rate constants based on the third-order kinetics were determined and discussed for the model reaction and for the chemically controlled region of curing reactions. The activation energies for these rate constants are 13-14 kcal/mole. At a later stage of conversion, the curing reactions become controlled by diffusion of functional groups. The final extent of conversion is short of completion for most isothermally cured and even for postcured samples because of crosslinking. It was quantitatively indicated that the final conversion of isothermal cure corresponds to the transition of the system from a viscous liquid to a glass on the basis of the theory of glass transition temperature of crosslinked polymer systems.
436 citations
TL;DR: In this article, the composition regions of a large number of binary salt-water systems in which macroscopic samples can be obtained in the vitreous state have been determined, and the glass transition temperatures Tg within these regions have also been measured.
Abstract: As a first stage in a study of the low‐temperature‐region behavior of aqueous solutions, the composition regions of a large number of binary salt‐water systems in which macroscopic samples can be obtained in the vitreous state have been determined. The glass transition temperatures Tg within these regions have also been measured. Correlations of the magnitude of Tg at a given composition with the formal charge on the cation (for salts with a common anion) and with the viscosity “B” coefficient of the anion (for salts with a common cation) are presented. In addition, an important correlation is found with the basicity of the anion which is interpreted in terms of the bonding of anions to the protons of the water molecules in the cationic hydration sheath. Thermodynamic relations for the composition dependence of Tg are presented. From the breaks in the otherwise monotonic composition dependence of Tg in the chloride systems, the existence of low temperature liquid–liquid immiscibility regions is proposed and is utilized in discussion of “total” hydration numbers. The Tg for pure water, obtained by extrapolation of the data, is found to be in agreement with the value obtained for vapor‐deposited vitreous ice but to be incompatible with the value predicted from thermodynamic data; an interpretation in terms of different short‐range order possibilities for water molecules is offered.
315 citations
207 citations
TL;DR: In this article, a simple relationship between Vth and Tg was obtained: Vth ʗ exp (C. Tg), where Vth = threshold voltage for switching, and tg = glass transition temperature.
154 citations
TL;DR: In this article, a mixture of poly(2,6-dimethyl-1,4-phenylene ether) (PPO) and atactic polystyrene (PS) has been prepared by mechanically mixing powders of the two polymers and subjecting the mixtures to three different thermal treatments.
Abstract: Blends of poly(2,6-dimethyl-1,4-phenylene ether) (PPO) and atactic polystyrene (PS) have been prepared by mechanically mixing powders of the two polymers and subjecting the mixtures to three different thermal treatments. Three different compositions were studied by the dynamic mechanical and DSC techniques. The weight fractions of PPO in the mixtures were 0.25, 0.50 and 0.75. The dynamic mechanical measurements indicate that partial mixing took place but that two distinct phases, one rich in PS and the other in PPO, exist in all the mixtures studied. Each phase exhibits a characteristic relaxation peak associated with the glass transition of that phase. DSC measurements, on the other hand, reveal only a single glass transition apparently characteristic of the PS rich phase in each case. The results indicate that a given type of experiment will indicate compatibility or incompatibility depending upon the size of the molecular process it represents.
152 citations
TL;DR: In this article, a split-level cell model is proposed for ZnCl2, in which cells have discrete energies depending on the presence or absence of such Zn-Cl bonds.
Abstract: With a view to elucidating the structure of liquid ZnCl2 and deciding the extent of the analogy to SiO2 and BeF2 (liquid and vitreous) provided by ZnCl2 (liquid and vitreous), a variety of measurements on ZnCl2 have been performed. Density and expansivity measurements and probe ion electronic spectra are used to demonstrate the existence of an open tetrahedrally coordinated structure. Details supplied by x‐ray patterns, Raman spectra, and particularly, by far‐infrared spectral studies, are then used to establish a close similarity between the glass quasilattice and the network lattice of the α‐ZnCl2 crystal polymorph. Finally a new technique, impurity ion (CN−) vibrational spectroscopy, is introduced to show that the defects characteristic of the glass structure involve small numbers of singly and doubly broken anion bridges, no evidence for intermediate states being found. On the basis of these observations a split‐level cell model in which cells have discrete energies depending on the presence or absence of such Zn–Cl bonds, is constructed. The model proves capable of accounting for the volume data and for the characteristic changes in equilibrium thermodynamic properties which, it is known, must occur near (usually somewhat below) the glass transition temperature. The thermodynamic relations obtained for the simplest case are the same as those from the Macedo–Capps–Litovitz quasichemical two‐state model. The liquid is best regarded as a weakened version of this network in which the progressive disruption of the anion bridges is associated with a greatly reduced structural relaxation time for the quasilattice.
104 citations
TL;DR: For polyvinylchloride fractions having molecular weights between 500 and 105 using differential scanning calorimetry, the Gibbs-DiMarzio relation gave a more satisfactory fit with the data extending to lower molecular weights taking ϵ = 1·51 kcal/mole, V0 = 0·025.
79 citations
TL;DR: In this paper, the free ion levels of neodymium were completely split into J+½ Kramers doublets by the perturbation of the glass environment on the ion.
Abstract: Energy levels, linewidths, and oscillator strengths for trivalent neodymium ions in a commercial laser glass were determined from the fluorescence and absorption spectra. The spectra were composed of broad groups of overlapping lines and were deciphered from spectral variations produced by changes in glass temperature from 4° to 300°K. No thermal variation of the peak wavelengths and linewidths of the component lines was observed in this temperature range. The free ion levels of neodymium were completely split into J+½ Kramers doublets by the perturbation of the glass environment on the ion. The splitting patterns correlated closely with those determined from Nd2O3 crystals, indicating that the rare‐earth ion locates in an environment in glass much like the sesquioxide crystal environment.
79 citations
TL;DR: In this article, a study of the ratio of the glass temperature to the melting point of 132 polymers is described, and it is shown that there is no sharp division between the ratios observed for symmetrical and unsymmetrical polymers.
Abstract: A study of the ratio of the glass temperature to the melting point of 132 polymers is described. Contrary to some other workers' observations on smaller numbers of polymers there is no sharp division between the ratios observed for symmetrical and unsymmetrical polymers. The arithmetic mean of the ratio is 0·63 and 0·69 respectively, but the combined standard deviation is 0·11. There is no correlation between the ratios and the crystalline forms of polymers.
TL;DR: In this paper, the glass transition temperatures for 6 glasses were determined by DTA and X-ray diffraction data and the possibility that diphastic or microheterogeneous structures exist at both ends of the glass-forming region was indicated from the DTA data.
TL;DR: In this article, a method for predicting the glass transition temperature of polymers from the chemical structure was proposed, which uses increments for constitutional molecule groups and the found increments appear to correlate with the increments to the molar cohesion energy.
TL;DR: In this paper, the nuclear magnetic relaxation times for rubber, polybutene-1, polyethylene, polyvinyl chloride, polychlorotrifluoroethylene and polycarbonate were reported.
Abstract: Nuclear magnetic relaxation times T2, T1, and T1ρ are reported for natural rubber, polybutene-1, polyethylene, polyvinyl chloride, polychlorotrifluoroethylene, polyethylene terephthalate and polycarbonate. The measurements cover the temperature range form 77 K to above the melting or glass transition regions. All seven polymers exhibit glass transition effects. Methyl group reorientations are observed at low temperatures. An additional ethyl side group motion and a crystalline rotator phase (>50°) are observed in polybutene-1. Other mechanisms are discussed. Good agreement is found between mechanical, dielectric and n.m.r relaxation frequencies.
TL;DR: In this paper, the thermal expansion of a butadiene-styrene copolymer filled with carbon blacks differing tenfold in mean particle size (HAF and MT) was investigated.
Abstract: The thermal expansion of a butadiene–styrene copolymer filled with carbon blacks differing tenfold in mean particle size (HAF and MT) was investigated. The glass transition was unaffected by MT and was raised only 0.2°C for every 10 parts per hundred by weight of polymer of HAF black added. The coefficient of expansion of the polymer component of the composite in the rubbery region was substantially unaffected by either carbon black, but decreased markedly with increasing black loading in the glassy state. These results suggest that free volume is not altered appreciably by the presence of the filler in the rubbery state, but expands with decreasing temperature below Tg. The latter effect is explained by dilatation due to stresses set up around filler particles, arising from differences in the expansion coefficients of filler and polymer, which are not relieved in the glassy state. The near invariability of Tg and of the rubbery fected by adsorption of polymer segments on the carbon black surface. A conservative rough estimate indicates that restriction of segmental motion is confined to a 30 A layer around the particles in which Tg is elevated by only 10°C.
TL;DR: In this article, the results obtained from DTA and DSC on annealing a number of glassy polymers which have been rapidly cooled from above the glass temperature and on slowly cooled samples of the same polymers are discussed in the context of the calorimetric observations.
Abstract: It has previously been shown that glassy poly(ethylene terephthalate) gives rise to endothermal peaks in DTA when annealed at temperatures near to the glass temperature. The present work describes results obtained from DTA and DSC on annealing a number of glassy polymers which have been rapidly cooled from above the glass temperature and on slowly cooled samples of the same polymers. The polymers which have been studied are: poly(ethylene terephthalate), poly(methyl methacrylate), atactic and isotactic polystyrene, bisphenol-A polycarbonate, poly(ethyl methacrylate) and poly(vinyl acetate). In every case, evidence of structural reorganization is observed, and the rate at which this takes place is reported. Separate studies on poly(ethylene terephthalate) reflect density changes which also take place upon annealing. These results are discussed in the context of the calorimetric observations.
TL;DR: In this paper, a new quantitative thermal analysis technique was attempted on ABS and Noryl-type polyblends, where a particular component within a polyblend was identified by its glass transition temperature and the amount of the component was determined from the increase in specific heat at the transition temperature.
Abstract: A new quantitative thermal analysis technique was attempted on ABS and Noryl-type polyblends. A particular component within a polyblend was identified by its glass transition temperature and the amount of the component was determined from the increase in specific heat at the glass transition temperature.
Two commercial Noryl resins were determined to be blends of high impact polystyrene and polyphenylene oxide in 47-47 and 69-17 proportions by weight, respectively. Polystyrene appears to be cosoluble with polyphenylene oxide without the formation of any complex. The PS-PPO polyblends yield single sharp glass transitions which are a function of concentration.
Patent•
15 Sep 1970TL;DR: Toner as discussed by the authors is a block copolymer comprised of two polymers, which are incompatible with each other, prepared by dissolving the polymers in a common solvent, followed by vigorous agitation and removal of the solvent to provide an incompatible solid mixture of the polymer.
Abstract: Toner for use in the development of latent electrostatic images comprised of a resinous material and a colorant in which the resinous material is comprised of at least two polymers, the first of which has a glass transition temperature of at least 20°C., and the second of which has a glass transition temperature of at least 5°C. lower than the glass transition of the first. The polyblend is either a graft or block copolymer comprised of the aforesaid polymers, or a physical blend of such polymers which are incompatible with each other, prepared by dissolving the polymers in a common solvent in which the polymers are about equally soluble, followed by vigorous agitation and removal of the solvent to provide an incompatible solid mixture of the polymer.
TL;DR: In this article, the dynamic storage and loss moduli of SBR 1503 reinforced with 400 A˚ polystyrene particles were measured at 110 cps over a 200° temperature range.
Abstract: The dynamic storage and loss moduli of SBR 1503 reinforced with 400 A˚ polystyrene particles were measured at 110 cps over a 200° temperature range. The effect of the polystyrene filler on the rubber was to raise the storage modulus dramatically in the rubbery zone, but only slightly in the glassy region of viscoelastic response. As a result the transition zone appeared broadened and shifted toward higher temperature. Corresponding changes were observed in the loss maximum with a shift of 4° at the highest filler content (46%) investigated. The height of the loss maximum was nearly unaffected. The loss tangent of the filled and unfilled polymers showed no systematic shift with temperature and the dilatometric glass transition was raised only 2° C at the highest filler content. All the essential features of the dynamic behavior could be described in terms of the properties of the component polymers by the phenomenological equivalent mechanical model treatment of Takayanagi. It is concluded that th...
TL;DR: In this paper, a new class of high molecular weight polyarylsulfones is described, which are prepared by Friedel-Crafts type polycondensation of aromatic sulfonyl chlorides with aromatic hydrocarbons.
Abstract: A new class of high molecular weight polyarylsulfones is described. Polymer synthesis and structure–property relationships are discussed. The polymers are prepared by Friedel-Crafts type polycondensation of aromatic sulfonyl chlorides with aromatic hydrocarbons. A number of Lewis acids in small quantities are useful as catalysts for the polymerization. The polymerization reaction is carried out at elevated temperatures in the melt or in solution. Inert, nonbasic solvents which are compatible with the Lewis acid catalysts such as nitrobenzene and dimethyl sulfone are useful for conducting the polymerization. Many of the polyarylsulfones are amorphous, rigid thermoplastics with unusually high softening points, having glass transition temperatures in the range of 200–350°C. Outstanding resistance to air oxidation at high temperatures is derived from incorporation of the deactivating sulfone groups in the aromatic polymer backbone. Melt stability and solubility in selected solvents are emphasized as basis for processibility by conventional solution casting and molding techniques. The combination of properties, which in addition to thermal stability includes a high level of mechanical and electrical properties, chemical inertness, and hydrolysis resistance makes these new arylsulfone polymers useful over a wide temperature range and in severe and corrosive environments.
TL;DR: In this paper, the authors point out where the real thermodynamic low temperature limit on solution chemistry lies so as to discourage the tendency of researchers to avoid solutions below their thermodynamic crystallization temperatures.
Abstract: The purpose of this paper is to point out where the real thermodynamic low temperature limit on solution chemistry lies so as to discourage the tendency of researchers to avoid solutions below their thermodynamic crystallization temperatures.
TL;DR: The transition between the liquid or rubbery state and the glassy state is not sharp, but a glass temperature can be defined in terms of measurements of volume or heat capacity as mentioned in this paper.
Abstract: The transition between the liquid or rubbery state and the glassy state is not sharp, but a glass temperature can be defined in terms of measurements of volume or heat capacity. This temperature can be related to the relaxation regions in visco-elastic or dielectric behaviour. Theories of the glass transition relate this variously to molecular relaxations, to free volume and to excess enthalpy or entropy; these are not altogether mutually exclusive. Observed transition temperatures can be related qualitatively with molecular structure, but a quantitative treatment faces formidable difficulties. Properties of glassy polymers reflect the generally low cohesion and the frozen-in disorder and hole structure. Relaxation behaviour is observed in the vicinity of the glass temperature.
TL;DR: In this article, the free volume quantities proposed earlier by Boyer and Simha in connection with the glass transition are reformulated by taking into account the temperature dependence of the thermal expansivities α l and α g for the liquid and the glass, respectively.
Abstract: Free volume quantities proposed earlier by Boyer and Simha in connection with the glass transition are reformulated by taking into account the temperature dependence of the thermal expansivities α l and αg for the liquid and the glass, respectively. This necessitates an extrapolation of the liquid to temperatures below Tg which is performed by means of the reduced volume-temperature function established and given a theoretical foundation previously. For the glass, low temperature experimental data, encompassing all relaxations occuring below Tg, are required. Two polymer series are examined in detail, namely, poly(methacrylates) and poly(vinyl) alkyl ethers, where αg has been measured between at least 30°K and Tg. Results for poly(methylacrylate) and poly(styrene) are also given. The systematic decrease in the product (αl - αg) · T|T=Tg with increasing length of the side chain noted previously is considerably reduced but not eliminated when the appropriately corrected expression is substituted in...
TL;DR: In this article, the widths at half-value of high-resolution NMR spectra of bound water of cellulose were studied in relation to the temperature change, and it was shown that the bound water can be pointed out with higher accuracy the lower the temperature of the measurement.
Abstract: The widths at half-value of high-resolution NMR spectra of bound water of cellulose were studied in relation to the temperature change. Two points were made clear: First, the amount of bound water of the cellulose sample can be pointed out with higher accuracy the lower the temperature of the measurement. Second, it is possible to determine in a simple manner the boundary temperature Tc at which water molecules become bound by the cellulose. Tc is characteristic of the cellulose sample of a given water content and corresponds to the glass transition temperature of the water-containing sample. The measurements appear to be readily applicable to other hydrophilic polymers.
TL;DR: In this paper, a differential scanning calorimeter has been used to measure the heat capacity of both melt and solution crystallized samples of isotactic polypropylene from 200 to 500°K.
Abstract: A differential scanning calorimeter has been used to measure the heat capacity of both melt and solution crystallized samples of isotactic polypropylene from 200 to 500°K. An estimate has been made of heat capacity values below 200°K. Values of the heat capacity, entropy, enthalpy, and free energy have been estimated for 100% crystalline isotactic polypropylene and are listed at 10°K intervals. The glass transition occurs at about 265°K in both samples. A value of 207 ± 5 Jċg−1 is obtained for the heat of fusion of isotactic polypropylene.
TL;DR: In this article, the mean lifetime τ2 of ortho-positronium annihilating by pickoff depends upon the free volume of the atom and the number of atoms in the atom.
Abstract: In solid polymers the mean lifetime τ2 of ortho‐positronium annihilating by pickoff depends upon the free volume. τ2 has been measured for five samples of relatively monodisperse atactic polystyrene over a temperature range from room temperature to 120°C. The number average molecular weight of the samples ranged from 50 100 to 640 000. For each sample the variation of τ2 with temperature indicated a glass transition about 13 deg below that measured on a differential scanning colorimeter. An increase in the glass transition temperature with molecular weight was observed. The τ2 lifetime, which depends upon the overlap of the positron component of the ortho‐positronium atom with the lattice wavefunction, seems to be very sensitive to the cooperative motion about the chain axis which is associated with the glass transition.
TL;DR: In this paper, the authors investigated the temperature dependence of radiation-induced grafting on poly(ethylene terephthalate), polyamides, polyacrylonitrile, and polypropylene.
Abstract: The temperature dependence of radiation-induced grafting onto poly(ethylene terephthalate), polyamides, polyacrylonitrile, and polypropylene has been investigated for several monomers. In all cases a maximum grafting yield is obtained when the reaction is performed in the temperature range of the glass transition Tg of the polymer used. This maximum yield does not only appear with radiation-induced simultaneous grafting. It also appears when the graft polymerization is induced by pre-irradiation or even by thermal decomposition of organic peroxides. It is assumed that the pronounced maximum of the reactivity at Tg is obtained because in the glassy state below Tg the radicals formed cannot react due to a reduced diffusion of the monomer, whereas above Tg the number of radicals available for polymerization will be reduced with increasing temperature.
TL;DR: In this article, the densification of polymethyl methacrylate resulting from pressure and temperature treatment in a Bridgman anvil device has been studied at temperatures to 245°C and pressures to 50 kbar.
Abstract: The densification of polymethyl methacrylate resulting from pressure and temperature treatment in a Bridgman anvil device has been studied at temperatures to 245°C and pressures to 50 kbar. Treatment in the glass transition region at pressure produces samples 1.1%–1.5% more dense than the starting materials, depending on the length of treatment. Treatment in the glassy state produces samples up to 0.7% more dense than the starting material, depending on the temperature and the internal state of the sample immediately prior to the application of pressure. Samples held in the transition region under pressure and then vitrified by rapid application of a high pressure show densifications similar to but somewhat higher than those produced by treatment in the glassy state. The results are compared with thermodynamic theories of the glass transition and with similar data on other polymers and inorganic glasses.
TL;DR: The peel strength and tensile shear strength of polyester hot-melt adhesives on metals coated with epoxy resins are affected by four characteristics of the polyester: inherent viscosity, glass transition temperature (Tg), degree of crystallinity, and melting point as discussed by the authors.
Abstract: The peel strength and tensile shear strength of polyester hot-melt adhesives on metals coated with epoxy resins are affected by four characteristics of the polyester: (1) inherent viscosity, (2) glass transition temperature (Tg), (3) degree of crystallinity, and (4) melting point. The inherent viscosity affects the strength, toughness, and crystallinity of the adhesive. The Tg and degree of crystallinity affect the low-temperature adhesive properties; the peel strength is relatively low when the Tg is appreciably above the use temperature. The Tg, degree of crystallinity, and melting point affect the high-temperature adhesive properties. A hot-melt adhesive with high peel and tensile shear strengths from 0° to 120°C is the polyester of 1,4-butanediol and trans-1,4-cyclohexanedicarboxylic acid.