Specific Volume Of Polymer Research Articles

Occupied and Accessible Volumes in Glassy Polymers and Their Relationship with Gas Permeation Parameters

AbstractIn order to relate the microstructure of polymer chains to the gas permeation properties, a novel method is proposed for the calculation of the van der Waals (Vw), occupied (Vocc), and accessible (Vacc) volumes of polymers, using polyimides as examples. In this approach,VoccandVaccvalues are obtained as characteristics of polymer–gas systems. Correlations betweenVoccand the gas permeability (P) and diffusion (D) coefficients are demonstrated. Accessible volume,Vacc, determined experimental densities, andVocccalculated using a Monte Carlo technique, as well as the fractional accessible volume (FAV) (Vacc/Vsp), whereVspis the specific volume of polymers, also correlate well with thePandDvalues. The slopes of these correlations increase with increasing molecular size of the diffusing molecules. In addition, the parameters of the equations forD(FAV) andP(FAV) strongly depend on conformation rigidity (Kuhn segment) of the polyimides. An interpretation of the results obtained is presented.Definition of occupied volume.imageDefinition of occupied volume.

A quantitative model for the specific volume of polymer–diluent mixtures in the glassy state

A quantitative model for the specific volume of polymer–diluent mixtures in the glassy state

Effect of Self Stress on Flexural Strength of Gypsum-Polymer Composites

Self stress generated in polymer impregnated gypsum (referred as GPC) when it is composed is estimated, and its influence on flexural strength is discussed. The estimation of the self stress is based on measured values of shrinkage caused by polymerization of impregnated monomer and elastic modulus of dried gypsum base just before impregnation. The effect of this self stress on flexural strength of GPC is investigated. It was found that the following equation is valid to predict flexural strength of GPC (б b ) in terms of the self stress as a variable: б b = б gb + V p (б p − б sp ), where б gb = flexural strength of gypsum base, V p = specific volume of polymer, б p = tensile strength of polymer, and б sp = self stress generated in polymer phase. If extremely low water-gypsum ratio is adopted to prepare gypsum base, cracking is observed just after polymerization preceding any flexural loading. For somewhat higher water-gypsum ratio, specimens are not cracked, but their flexural strength is decreased after polymer impregnation. The self stress corresponding to this case turns out to be higher than the tensile strength of polymethyl methacryrate used for the impregnation. Since prediction of б sp in the equation is based on tri-axial compressive strain of gypsum base that is within its elastic region, б sp in polymer phase should positively exist. Even for this condition, the validity of the equation seems to be maintained, although the value in the parenthesis of the equation becomes negative. Based on this fact, an unstable physical state where one phase of a composite material is stressed beyond its macroscopic strength as an individual material owing to the crack arresting effect of the other phase (gypsum in this case) has been postulated. This state is designated as a “superstressed” state, taking its resemblance with supercooling or supersaturation into consideration.

Description of a high-performance density cell. Application to new investigations in the field of polymers studies

A new density cell based on the vibrating tube principle is described. This cell provides an accuracy of density measurements of 2 × 10−6 g/cm3 and presents a great stability with respect to temperature and time variations. In two experiments—measurement of self-diffusion coefficient of heavy water through membrane and determination of partial specific volume of polymers in very dilute solutions—it is shown that such a precision leads to new types of investigations.

Temperature and pressure dependence of the specific volume of polymers—I. Polymethyl methacrylate

Temperature and pressure dependence of the specific volume of polymers—I. Polymethyl methacrylate

A study of the dependence of the specific volume of polymers on the temperature and pressure—II. Poly-(methyl methacrylate) plasticized with dibutyl phthalate

A study of the dependence of the specific volume of polymers on the temperature and pressure—II. Poly-(methyl methacrylate) plasticized with dibutyl phthalate

Specific volume of polymers as a function of temperature and pressure

The specific volume of pure and plasticized polyvinylchloride and of polymethylmethacrylate was studied with a dilatometer as function of temperature (−80 to +150 °C) and hydrostatic pressure (1 to 1000 at.). Beside the glass transition also two types of secondary transitions are observed with PVC and PMMA which correspond to dynamic secondary dispersion ranges. Below the glass transition the specific volumina depend on how they were reached. The transition temperatures of the samples were determined at elevated pressures with decreasing temperatures. Glass transition and secondary transitions cause stepwise increases of the thermal expansivities and the isothermal compressibilities. Above the glass transition the compressibilities are rising in proportion to the temperature. With PVC all transition temperatures are shifted by about 0,013 to 0,015 °C/at as the pressure is raised. With PMMA the transitions at −7 °C and at +62 °C are not affected by hydrostatic pressure while the glass transition is shifted by 0,018 °C/at. Addition of plasticizer to PVC shifts the glass transition to lower and the secondary transition to higher temperatures. There is no agreement between the measured shifting factorsdT g/dp and those calculated according toEhrenfest's lawΔβ/Δα=dT g/dp.