Unplasticized Polyvinyl Chloride Research Articles

A method of thermal analysis of polymers by measurement of electrical conductivity

Conventional methods of thermal analysis involve measuring either changes in mass or enthalpy of a substance, which is heated at a constant rate of rise of temperature in a controlled atmosphere. Work on a range of organic polymeric materials has now shown that, if the rate of change in electrical conductivity with temperature is plotted against temperature, then the curve obtained is characteristic of that particular substance. With the aid of information obtainable by a number of other techniques, it has proved possible to ascribe each of the peaks in the various curves to physical or chemical changes occurring in the heated polymer. The utility of this technique is illustrated by its application to a medium rank coal, both before and after chemical treatment, and to a sample of unplasticized polyvinyl chloride.

Recovery of Elongation of the Unplasticized Polyvinyl Chloride Stretched at High Temperature

The present investigation was undertaken in order to describe the recovery characteristic of elongation of unplasticized polyvinyl chloride stretched at temperatures above its glass transition point (Tg).The experimental procedure was as follows; after the specimens have been stretched up to elongation e1, at temperature T1(>Tg), they were cooled in cold water. They were then annealed at temperature T2(≤Tg) and the recovery of elongation was measured and its values are shown in Figs. 8 and 9.The data suggested that there was no particular recovery equilibrium in each curve but the strain might recover perfectly after sufficient duration time except at temperatures near the glass transition point or below. Approximate master recovery curves were drawn, as shown in Fig. 10, on the assumption that the method of reduced variables were valid to these experimental results. A simplified expression is also shown of the recovery characteristic derived from the results obtained at definite intervals.

On the Relation between Creep and Rupture of Unplasticized Polyvinyl Chloride

We have studied on a relation between minimum creep rate and time duration to rupture of unplasticized polyvinyl chloride.Although it has been shown by many reports on metals that they are reciprocally proportional to each other, we have recognized through our experiment that the relation is as follows;tr=M/(εmin)θ, where tr is time duration to rupture, εmin is minimum creep rate, M and θ are coefficients which change their values depending on testing temperatures, two ranges of εmin and conditions of heat treatment of specimens.Values of coefficient θ for normal specimens become larger than 1 in the lower range of minimum creep rate, though it is almost equal to 1 in the higher range in which time duration to rupture is approximately proportional to reciplocals of minimum creep rate. For the specimens kept at 60°C for 5 days, no range is recognized where the value of θ is almost equal to 1.A master rupture curve of normal specimens is drawn in the range of temperature -10 to 40°C, derived from the formula proposed by the authors in the preceding paper and from the above mentioned parameters.

On the Creep Rupture Behaviors of Unplasticized Polyvinylchloride under Various Chemical Reagents

Creep rupture tests of unplasticized PVC were carried out by having dipped the specimens in various chemical reagents. The authors called these tests as “Wet rupture tests.”Formerly, they studied the creep strength under air atmosphere (dry test) for unplasticized PVC which was previously dipped in chemical reagents at various temperatures, and confirmed that the creep strength was not markedly affected by the kind of chemical reagents used.But, the creep mechanism of these wet tests is very different from that in dry tests, for the action of chemical agents cooperated with the working stress.They classified the chemical reagents into three groups having regard to the behaviors in creep rupture and summarized in Table 1.

Influence of normal stress on creep in tension and compression of polyethylene and rigid polyvinyl chloride copolymer

AbstractNew apparatus suitable for compression creep tests of slender specimens is described. The apparatus is designed to prevent buckling and to introduce a minimum of friction. Results are reported for tension and compression creep of polyethylene and annealed, unplasticized polyvinyl chloride copolymer at 75 deg F and 50 per cent relative humidity. The stress, σ, strain ε, time t data from these tests were found to be describable with reasonable accuracy by the equation where εm′, m′, σε and σm are material constants.The results for polyethylene show that the creep in tension and compression were virtually the same. Creep in tension was similar but larger than in compression for polyvinyl chloride.

Influence of Normal Stress on Creep in Tension and Compression of Polyethylene and Rigid Polyvinyl Chloride Copolymer

New apparatus suitable for compression creep tests of slender specimens is described. The apparatus is designed to prevent buckling and to introduce a minimum of friction. Results are reported for tension and compression creep of polyethylene and annealed, unplasticized polyvinyl chloride copolymer at 75 deg F and 50 per cent relative humidity. The stress σ, strain ε, time t data from these tests were found to be describable with reasonable accuracy by the equation ε=ε0′sinhσ/σε+m′tnsinhσ/σm where ε0′, m′, n, σε, and σm are material constants. The results for polyethylene show that the creep in tension and compression were virtually the same. However, the creep in tension was similar but larger than in compression for polyvinyl chloride. These observations are interpreted in terms of the material structure and the influence of the normal stress on active shear planes.

硬質塩化ビニルのクリープ試験

Tensile creep tests of unplasticized polyvinyl chloride were carried out under constant load. Test pieces used in these tests were cut from the sheet of 1mm thickness.We see that the following expression may be applicable in primary period of creep obtained from these tests, e=mtnwhere e is creep strain, t is time duration for loading, and m, n are constants. Both these constants vary their values subjecting to applied stresses and testing temperatures.Next, creep in secondary period may be shown nearly as a straight line with tendency slightly concave upwards in the strain-time diagram as it may be regarded to be in the steady state.Relation between minimum creep rate emin, which is considered to be characteristics in secondary period, and conventional tensile stress σ at a constant temperatures is expressed byemin=c exp.(aσ), where c and a are constants.Minimum creep rates under constant stress at various absolute temperatures T are expressed byemin=A exp.(-B/RT), where A and B are constants and R is gas constant.The specimens kept at 60°C for 5 days show themselves to have smaller values of minimum creep rates than the normal, and become more brittle and considerably anisotropic.

RECENT APPLICATIONS IN CORROSIVE CONDITIONS OF: RIGID PVC PIPING

Of the thermoplastics group of materials, unplasticised polyvinyl chloride, commonly known as rigid PVC, appears to have made the slowest progress in the U.K. It was introduced here shortly after the war, but, as recently as 1958, the annual usage for industrial pipes was estimated at only 500 tons. In the same year, France, Holland and Italy processed approximately 4,000, 8,000 and 12,000 tons respectively. This article indicates the scope of the material in corrosive environments.

Color and radical formation in irradiated polyvinyl chloride

AbstractWhen polyvinyl chloride is irradiated with high energy radiation a visible color change varying through green‐yellow to deep red‐black is produced, depending upon the dose and temperature. Spectrophotometric and electron spin resonance techniques were used to investigate the formation of colored material by 2‐m.e.v. electron irradiation of unplasticized polyvinyl chloride moldings. The observed chemistry of the colored material is in agreement with the postulations of earlier workers that colored polyene structures are formed. Three radiation‐produced free radicals decaying at room temperature with half‐lives of 4.5, 63, and 1630 hr. were observed. The color in the 550 mμ region was found to be inversely proportional to the concentration of the long‐lived radical. The presence of absorption maxima in the 350–500 mμ region was observed in irradiated moldings and in tetrahydrofuran solutions of irradiated moldings.

The necking and cold-drawing of rigid plastics

The phenomena of necking and cold-drawing have been examined theoretically and experimentally with polythene mouldings and unplasticized polyvinyl chloride sheet. It has previously been thought that these phenomena are caused by adiabatic heating of the sample. As a consequence of these investigations, we now believe the following. 1.(1) The modulus of many polymers is much reduced by strain. The consequent downward bending of the stress-strain curve leads to mechanical instability and so causes a neck to form.2.(2) Cold-drawing is caused by this mechanical instability followed by a strain-hardening process, due to molecular orientation.3.(3) Cold-drawing is prevented by insufficient strain-hardening. This may be caused by high stretching rates, giving adiabatic heating, or by low molecular weight.

Topic of the Month—Erratic Performance of Type 1 Unplasticized Polyvinyl Chloride In 93 Percent Sulfuric Acid Pipelines

Topic of the Month—Erratic Performance of Type 1 Unplasticized Polyvinyl Chloride In 93 Percent Sulfuric Acid Pipelines

硬質塩化ビニールのクリープ破断性

Tensile creep-rupture tests of unplasticized polyvinylchloride were made on test pieces taken from pipes, up to 100 hours, under several temperatures below the second order transition temperature.It was found that the Larson-Miller method developed in the research of metals could be applied to that of this material. With the rupture time-temperature as parameter, T (50+logt), we obtained a considerably fair line, i.e., so called master rupture curve.A discussion was given on the fracture mechanism, especially on the deformation and fracture processes. We presented a significant temperature-stress diagram, having four characteristic regions divided by three straight lines started from 80°C. Each region indicates a different fracture mechanism. This diagram stands also for use in selecting the materials in design. It may be suggested that the similar relationship will be applied for other polymers.So far as the deformation process is concerned, this material flows perfectly in the shoulder of a neck, within certain stress-temperature regions. This region corresponds to a characteristic creep curve-at the end of the 3rd stage, the creep rate apts to decrease-and a fracture marking.The necking mechanism was studied by using X-ray diffraction pattern, electron microscope, density measurement and hardness test. Above all, electron micrographic studies by replica method revealed the fine direct evidence of a marked orientation of the material.The effect of residual stresses before and after a heat treatment, was also discussed.

硬質塩化ビニール板の機械的性質について

Mechanical properties of unplasticized polyvinylchloride under tension and compression were reported in this paper. The following results were obtained:(1) This material shows a distinct yield point and the strain corresponding to this point becomes larger as the testing temperature becomes low, and reaches the maximum value at about 0°-10°C.(2) The stress-strain curve up to the yield point is affected remarkably by the testing temperature and strain velocity which also greatly affect the total elongation at the breaking point.(3) Regarding the process of cross-necking, a peculiar type of deformation is observed as shown in Fig. 12.(4) A secondary test was made at a different temperature on a specimen stretched primarily at a certain temperature and the mechanical properties were examined.a) Properties of the specimen streched previously at a high temperature up to the yield point are in the second low temperature test not affected by the previous treatment.b) When the primary elongation at high temperature is greater than the breaking elongation at low temperature, the specimen shows no new necking deformation in the second test (low temperature test) and is fractured in a brittle manner.c) On the contrary, the specimen stretched previously at low temperature over the yield point, shows in the second stretching at high temperature no yield point and deforms according to its original stress-plastic deformation curve.