PVC Specimens Research Articles

Photocatalyzed Degradation of Polymers in Aqueous Semiconductor Suspensions. 3. Photooxidation of a Solid Polymer: TiO2-Blended Poly(vinyl chloride) Film

The photooxidative degradation of a TiO2-blended poly(vinyl chloride) (PVC) film and other PVC specimens was carried out under UV light and under solar exposure to test the feasibility that such po...

Postbuckling strength design of open thin-walled cylindrical tanks under wind load

Open cylindrical steel tanks for the storage of liquids tend to be rather thin-walled because they are primarily designed for the circumferential tensile stresses from hydrostatic internal pressure. It is desirable to take advantage of the postbuckling strength of the thin cylindrical wall when designing the empty tank against wind load. The theoretical external pressure carrying behaviour of edge-stiffened thin-walled cantilever shells is discussed with regard to both bifurcation and postbuckling phenomena. For experimental verification, a series of postbuckling tests on cylindrical PVC and steel specimens with large radius/thickness ratio ( r/ t=2500) under internal underpressure and under a “wind-like” load arrangement has been carried out. Based on the numerical and experimental results, recommendations are put forward for an economic postbuckling strength design strategy. They are compared with existing design rules in tank codes.

New Structural and Mechanistic Chemistry in Polymerizations of Vinyl Chloride Initiated by Di-tert-alkylmagnesiums

The bulk polymerization of vinyl chloride initiated by di-tert-butyl- or tert-butyl-tert-pentylmagnesium etherate gives poly(vinyl chloride) (PVC) specimens containing considerable amounts of cyclopropyl, trans-2-tert-butylcyclopropyl, and -CHClCHCH2 chain ends. This result has no structural precedents among PVC samples that are made by conventional free-radical methods. Formation of the unusual end groups has been rationalized in terms of reactions of various polymeric intermediates having Mg−C bonds, and ethylene formed in situ has been shown to be involved in the process that produces the cyclopropyl chain end. Also observed is a trans-t-BuCHCHCH2− terminus, whose presence has not been explained. When the polymerization temperature is raised in stages from −20 to 40 °C, the unusual chain ends are gradually replaced by structures that are known to result from reactions of free macroradicals. The various end groups were characterized by high-field NMR techniques. These were applied to both original and Bu3SnH-reduced PVC specimens, as well as to synthesized end-group models that were used for reference purposes.

Plasticized PVC with low matter transfers in n-hexane by fixing a thin film of ethylene glycol on its surface

As plasticized PVC is widely used as packaging for various liquids, attempts to reduce the matter transfers are of interest. A new approach to obtaining a soft plasticized PVC with low matter transfers when in contact with a liquid such as n-hexane is explored. The method consists of creating a gradient of concentration for the plasticizer next to the PVC surface, by inserting a thin film of ethylene glycol on the PVC surface. The gradient of concentration of plasticizer is obtained by pre-immersing the plasticized PVC specimen in n-hexane for a short period and drying it in order to evaporate n-hexane at least next to the PVC surface. The presence of this gradient of concentration of plasticizer enables ethylene glycol to form a thin film on the surface. Very low matter transfers are found for these PVC specimens when they are put in contact with n-hexane. Ethylene glycol is selected for its poor solubility in the plasticizer (diethylhexyl phthalate) and in n-hexane.

Preparation of plasticized pvc packagings with low matter transfers in n-hexane by using a pre-immersion in methanol

Plasticized PVC is often used as packaging for blood and other liquids, and so is in contact with various liquids. Sometimes, two matter transfers are observed: the liquid enters the PVC and then enables the plasticizer to leave the solid. These two transfers are controlled by transient diffusion and are connected, their diffusivities depending on both the concentrations of the liquid and plasticizer. An attempt is made to reduce these transfers by using a two-step method: the PVC specimen is immersed in methanol for a short given time, and then the methanol is evaporated as far as possible. The final material exhibits low matter transfers when in contact with n-hexane, at least for some time. Methanol is selected as it is poorly soluble in n-hexane.

Loss of plasticizers from polymer films to liquid environments: counterdiffusion aspects versus immersion temperature and ultra-violet-induced surface crosslinking

Plasticized poly(vinyl chloride) (PVC) sheets were irradiated with ultra-violet light before immersion in petroleum oils to prevent plasticizer migration and counterdiffusion effects. The penetration of the liquid environment into the sheets was monitored as a function of immersion time at different irradiation levels and immersion temperatures. White spirit and kerosene penetration passes through a distinct maximum with increasing immersion time, suggesting a two-step phenomenon with liquid transfer into and out of the PVC specimens. Nevertheless, in agreement with previous experimental results on plasticizer migration behaviour, the ultra-violet treatment followed appears encouraging: the maximum penetration values do not vary significantly with irradiation time, but the equilibrium values eventually attained are positively influenced, presenting a decrease often close to 50%.

Effect of K‐value on the tensile yield properties of poly(vinyl chloride)

AbstractTensile measurements were made on milled compression molded test specimens of PVC of different K values from strain rates of 0.0001–0.1 s−1 and temperatures of −40 to 25°C. The dependence of yield stress on temperature and strain rate was treated in terms of the Ree–Eyring model as proposed by Roetling for poly(methyl methacrylate) and Bauwens‐Crowet et al. for poly(vinyl chloride). The data reduction was achieved using sophisticated and unbiased statistical techniques that not only provided parameter estimates but their confidence intervals. The yield stress parameters for the alpha and beta processes were found to be independent of K value and within experimental error the same as those reported by Bauwens‐Crowet et al. The activation energy for the beta process from these yield stress studies (15.1 ± 0.3 kcal) is within experimental error the same as that determined from viscoelastic measurements (14.1 ± 1.2 kcal) reported by the authors. This observation supports the contention that beta process in the viscoelastic and yield stress measurements are closely related mechanisms.

ポリ塩化ビニルの計装化シャルピ衝撃特性に及ぼす改質剤の影響

Two kinds of polyvinyl chloride specimens (Hi-PVC and PVC) with or without blending a reformer for impact resistance were prepared in order to compare their impact resistance properties. The effects of temperature and notch root radius on the specific absorbed energy, the impact strength and the fractographs were investigated by using the instrumented Charpy impact test apparatus.It was found that the impact resistance property of the PVC specimen depended on the temperature as well as on the notch root radius. It was also found that the Hi-PVC specimen showed a tendency similar to PVC at temperatures below 0°C, but improved its impact resistance property at temperatures above 20°C due to the reformer.

A comparison between instrumented charpy impact properties of reformed polyvinyl chloride and polycarbonate.

Polyvinyl chloride which is reformed for impact resistance (Hi-PVC) and polycarbonate (PC) which has excellent impact resistance properties are tested by using an instrumented Charpy impact tester. Effects of temperature and notch root radius on the specific absorbed energy, the maximum load and the fractographs are studied. It is found that the specific absorbed energy of the Hi-PVC specimen does not relate to the notch root radius below 0°C and the value is lower, but it increases rapidly at 20°C. The Hi-PVC specimen represents the brittle fracture similar to the PVC specimen below 0°C. The PC specimen initiates many microvoids at the notch surface as the notch root radius is larger above 0°C. Similarly, the Hi-PVC specimen initiates the trend which has many microvoids due to the rubber particles at the notch tip at 20°C.

ATR‐IR spectra of MBS impact modified and unmodified rigid PVC processed in different ways

AbstractThe surface IR absorption characteristics of MBS impact modified and unmodified PVC specimens prepared in various ways were determined by ATR‐FTIR techniques. These specimens include compression molded plaques and blow molded bottles. In addition and as a reference point, the IR spectrum of a solution cast film of unmodified PVC was obtained in the transmission mode. The IR spectra in the C‐Cl stretching region for unmodified plaques, i.e. 560 to 750 cm−1, were curve fitted to seven Lorenz functions centered at the literature frequencies, except for one band which was changed from 639 to 636.5 cm−1. Two additional bands (699 and 759 cm−1) were assumed to represent the modifier absorption in modified plaques and bottles. Only peak intensities and band widths were allowed to vary in the curve fitting process. Deconvoluted spectra of selected specimens support the number and location of the absorption peaks.Though these surface spectral changes can be represented in terms of surface configurational partitioning that occurred during processing, a more likely explanation is that conformational changes in the PVC polymer chain has occurred on the surface. Quantities representing the configuration of PVC polymer chains such as non‐syndiotacticity (NSS) or the fraction of PVC backbone carbon atoms that are found in the trans conformation (TRANS) were estimated from Lorenz parameters. NSS and TRANS were found to depend on processing conditions as well as the nature of the modifier.These results are discussed in terms of practical impact tests such as n‐Izod and falling bottle drop tests.

The effect of molecular orientation through uniaxial prestraining in poly(vinyl chloride) and polycarbonate on their friction and wear characteristics

The mechanical and tribological properties of polymers generally depend on the exact details of their molecular arrangements, i.e. both their crystalline morphology and their molecular orientation, these being intimately related. The objective of this paper is to investigate experimentally the effect of uniaxial prestraining of specimens of poly(vinyl chloride) (PVC) and polycarbonate (PC) on their friction and wear characteristics. For this purpose tensile sheet specimens of PVC and PC were uniaxially stretched to varying final extensions, thus obtaining various degrees of molecular orientation and mechanical anisotropy. Short pins were subsequently cut from these deformed sheets and tested at a sliding speed of 27.5 cm s −1 and a moderate normal load of 49 N in an instrumented pin-on-disc friction and wear testing machine with stainless steel as the rotating disc material. Results obtained on the friction coefficient and wear rates for various samples are presented and correlations are made with uniaxial prestrain, mechanical energy to fracture and loss modulus.

Multiple crazing at crack tips in PVC under plane strain conditions

AbstractThe nature of the yield zone at the crack tip of poly(vinyl chloride) (PVC) pipe materials has been investigated. Microscopy studies employing a plasma etching technique reveal the presence of multiple crazes ahead of the crack tip in the interior of specimens of pure PVC, CaCO3 filled PVC, and PVC pipe compound. The craze zone and the fracture toughness of blade‐notched specimens are compared with those of fatigue pre‐cracked specimens. Both types of specimens have similar fracture toughness values and form multiple crazes upon loading, suggesting that multiple crazing Is an intrinsic property of the material. The kinetics of craze initiation and the development of the multiple craze zones have also been explored.

Continuous fractionation and solution properties of PVC, 4. Pressure dependence of the solubility in a mixed solvent

AbstractUsing a self‐constructed light scattering apparatus, the pressure dependence of the demixing temperature of solutions of PVC 20 000, PVC 37 000 and PVC 70 000 in THE/water was determined up to 1 000 bar for different compositions of the mixed solvent. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) In contrast to the thetasolvents o‐xylene and phenetole, the solubility decreases with increasing pressure for all molecular weights and compositions under investigation typically by about 1 K/100 bar. The evaluation of the experimental findings demonstrates that the volume fraction of the nonsolvent in the mixed solvent, φ, is the variable that governs phase separation: For the present region of p and T, a given polymer solution demixes at a characteristic constant value of φ, no matter how it is reached. This fact allows the prediction of pressure influences from known pVT data of the pure components and measurements at atmospheric pressure. A qualitative theoretical understanding of the observed influences of p and T can be reached on the basis of the solubility parameter theory.

Continuous fractionation and solution properties of PVC, 6. Pressure dependence of the viscosity — influence of molecular weight and composition

AbstractViscosities were measured as a function of pressure and temperature with solutions of PVC 75 000 in cyclohexanone (CHO) and polymer contents ranging from 0,6 to 12 wt.‐%, by means of a Searle‐type (≥3 wt.‐%) and a rolling‐ball viscometer (<3 wt.‐%). Furthermore, the influence of molecular weight was determined with solutions of 8 wt.‐% of PVC 20 000, PVC 37 000 and PVC 100 000. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) For all concentrations and molecular weights, the viscosity increases in a more or less exponential manner with increasing pressure. The ratio f1000 of the viscosity of the solution at 1 000 and 1 bar can be varied by the change of the polymer content from 2,5 (the value of the pure solvent, index s) to 3,5 (12 wt.‐% PVC 75 000) at t = 25°C and from 2,23 to 2,94 at t = 80°C. An increase of the molecular weight of the polymer raises f1000 in a similar manner as the polymer concentration. Using the reduced variables V≠/V≠ (ratio of the volumes of activation of the solution and the pure solvent) and c̃ (product of the polymer concentration and the intrinsic viscosity), all results obtained by variation of T, c and Mw can be represented by a master curve. This means that it is possible to calculate the pressure dependence of a given polymer solution of arbitrary polymer concentration from a mere measurement of the intrinsic viscosity at normal pressure. Criteria are presented which allow a forecast concerning the occurrence of minima in the concentration dependence of the energy of activation of the viscous flow E≠ and V≠.

Continuous fractionation and solution properties of PVC, 3. Pressure dependence of the solubility in single solvents

AbstractFrom the break‐down in the viscosity and from the increase of the intensity of the scattered light, associated with the entrance into the two‐phase region, the pressure dependence of the demixing temperature of solutions of PVC 37 000, PVC 75 000 and PVC 100 000 in phenetole and PVC 75 000 in o‐xylene was measured up to 1 000 bar. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) The application of pressure increases the demixing temperatures of PVC in both solvents by about 1 K/100 bar. For a qualitative forecast of the pressure effects, the solubility parameter theory in combination with the corresponding states principle, and an empirical correlation to the relative distance of the critical demixing temperature to the melting point of the pure solvent were used. The results of both concepts are in accord with the experimental findings.

Condition of ductile and brittle fracture in tension on notched plate of rigid plastics.

The static tensile testing of notched flat bars of polycarbonate, polyvinylchloride and polymethyl methacylate has been carried out for a wide range of notch radii and notch depths. Sharply notched specimens of PC and PVC failed in brittle manner after the formation of a small crack at the tip of plastic zone. Bluntly notched specimens of PC and PVC failed in fully ductile manner with large shear bands. All specimens of PMMA failed in brittle manner. The predominant factor for determining the fracture mode of ductile to brittle transition is the notch root radius in the case of a constant thickness. Experimental results were discussed in terms of the maximum elastic stress at the notch root from the standpoint of linear notch mechanics. For specimens failed in brittle manner, it is shown that the maximum elastic stress is the one-to-one correspondence to the notch root radius, and is independent of notch depth and plate thickness. The fracture criterion of notched flat bars mentioned above holds commonly for PC, PVC and PMMA.

Effect of stabilizer type on the physicochemical properties of rigid PVC. III

AbstractThe crystallinity of rigid PVC specimens, stabilized by a tin mercaptide or a lead stabilizer, has been studied. It is found that the crystallinity of rigid PVC is greatly influenced by the type of stabilizer added, and that the response of the PVC toward subsequent UV exposure was also different. The effects of unstable structures and crystallinity, after UV irradiation, on the mechanical properties of rigid PVC have been investigated.

Determination of total migration from plastics-packaging materials into edible fats using a 14C-labelled fat simulant

In the future, total migration may prove to be of great importance in the assessment of the physiological acceptability of new packaging materials, provided a practicable. reliable and sensitive method of determination is available. A suitable radio-tracer method has been developed using a 14C-labelled standard triglyceride mixture, known as fat stimulant HB 307-[14C]. On the basis of the principle proposed by the Bureaux Internationaux Techniques des Matières Plastiques (BITMP), the sample of the packaging material is weighed before and after storage in fat simulant HB 307[14C]. The content of test fat remaining in and on the stored sample is determined by radio-analysis. The total migrate then equals the difference between (a) the weight of the sample before storage in the test fat and (b) the weight after storage less the weight of the fat absorbed by the sample during the storage.This method was tested with specimens of plasticized PVC, LD-polyethylene, polystyrene and polyvinylidene chloride. The coefficient of variation of the single results about the mean showed a marked dependence on the amount of total migrate, the coefficients associated with 1, 6 and 12 mg total migrate/dm 2 surface of packaging material being 9, 2 and 0·6% respectively.

Determination of total migration from plastics-packaging materials into edible fats using a 14C-labelled fat simulant

In the future, total migration may prove to be of great importance in the assessment of the physiological acceptability of new packaging materials, provided a practicable, reliable and sensitive method of determination is available. A suitable radio-tracer method has been developed using a 14C-labelled standard triglyceride mixture, known as fat simulant HB 307-[ 14C]. On the basis of the principle proposed by the Bureaux Internationaux Techniques des Matières Plastiques (BITMP). the sample of the packaging material is weighed before and after storage in fat simulant HB 307-[ 14C]. The content of test fat remaining in and on the stored sample is determined by radio-analysis. The total migrate then equals the difference between (a) the weight of the sample before storage in the test fat and (b) the weight after storage less the weight of the fat absorbed by the sample during that storage. This method was tested with specimens of plasticized PVC, LD-polyethylene, polystyrene and polyvinylidene chloride. The coefficient of variation of the single results about the mean showed a marked dependence on the amount of total migrate, the coefficients associated with 1, 6 and 12 mg total migrate/dm 2 surface of packaging material being 9, 2 and 0·6% respectively.

Failure of PVC specimens in impact compression

Failure of PVC specimens in impact compression