PVC Samples Research Articles

Polymerization of vinyl chloride catalyzed by a titanium complex with an anionic oxygen tripod ligand

Poly(vinyl chloride) (PVC) was prepared using a titanium complex with an anionic oxygen tripod ligand [CpCo{P(O)(OEt) 2} 3] − ( L OEt - ) as catalyst and methyl aluminoxane (MAO) as cocatalyst. The polymerization behavior was compared with that of pentamethyl cyclopentadienyl titanium trichloride (Me 5CpTiCl 3). It is observed that L OEtTiCl 3 can polymerize vinyl chloride with activity comparable to that of Me 5CpTiCl 3. The PVC samples prepared with L OEtTiCl 3/MAO exhibit bimodal molecular weight distribution and the fraction of high molecular weight peak decreases with polymerization temperature. The microstructure and thermal decomposition of the PVC obtained were studied. Five types of structural defect were detected by 1H-NMR. Only saturated structural defects are found at low polymerization temperature, but at high polymerization temperature unsaturated structural defects, possibly resulting from dehydrochlorination of the saturated structural defects, appear as well. No head-to-head structural defect is observed. 13C-NMR shows that the PVC prepared by L OEtTiCl 3 has an atactic stereostructure. Compared with the PVC from radical polymerization and anionic polymerization, the PVC samples prepared with L OEtTiCl 3 show improved thermal stability.

Flame Retardant Smoke Suppressant Protection for Poly Vinylchloride

Spread of fire along electrical cables may be alleviated by using flame-retardant smoke suppressant (FRSS) additives-based PVC compositions designed for use as insulation and sheathing. These compositions offer improved resistance to ignition, flame spread and smoke generation. FRSS protection may also be achieved by the application of intumescent coatings as fire-protective layers and barriers for electrical cables and cable installations. Metal-based organic (MBO) complexes were synthesized for use as flame retardant smoke suppressants in PVC formulations. Plasticized PVC compositions were prepared and evaluated for their fire performance. Excellent smoke suppression was observed when either of the two MBOs was used. The limiting oxygen index was also found to be fairly high, particularly when the PVC samples were plasticized with a phosphate plasticizer. Flame-retardant smoke-suppressant intumescent coatings were developed for PVC-sheathed electrical cables. The coatings were applied on cables, and their fire performance was evaluated by using national and international standard procedures. The coated cables did not show any surface spread of flame on exposure and their generation of smoke was found to be very low. The coatings were found to be quite effective in reducing the burning behaviour of power cables. Significant improvement in circuit failure time was noted for coated cable specimens.

Radiolytic degradation of poly(vinyl chloride) systems

We examined the gamma radiation effects on PVC plasticized with di(2-ethylhexyl)phthalate (DEHP), diisobutyl phthalate, trioctyl trimellitate and Viernol ®, as well as its effect on PVC plasticized with DEHP and stabilized with Tinuvin P ®. The PVC samples were analysed, before and after irradiation at different doses, by UV spectroscopy, viscometry and mechanical testing. A multivariate statistical analysis was carried out on five properties: tensile strength, percent elongation, number of scissions per chain, viscosity-average molecular weight and UV-visible absorbance. The scores from a principal component analysis (PCA) of the non-stabilized samples show that the PVC/DEHP samples were the most degraded by chain scission upon irradiation, especially at the 25 and 60 kGy dosages, while the 400 nm absorbance, associated with film yellowing, remained relatively unchanged for these samples. For the other three systems, degradation by chain scission is smaller, and the UV absorbance is more dependent on radiation dosage. For the PVC/DEHP samples, the addition of Tinuvin P ® significantly decreases the number of scissions per chain, especially at 25 and 60 kGy irradiation doses.

Some effects of the memory kernel singularity on wave propagation and inversion in viscoelastic media - II. Inversion

SUMMARY Viscoelastic inversion is developed for a realistic, simple, causal hereditary model with a power-law attenuation. In this class of models the energy travels with a delay behind the wave front because the effective speed of the seismic signal is lower than the infinite-frequency limit of the propagation speed which determines the wave front propagation. In inversion this discrepancy affects the correct positioning of scatterers and interfaces. Our inversion method is an extension of Ribodetti’s imaging method. Using a power-law model, propagation- and attenuation-related parameters are uncoupled for the acquisition geometries used in laboratory and in field seismic experiments. The method is applied to ultrasonic laboratory data where we have complete control of the acquisition parameters and the physical properties of the medium to be recovered are well known. An application to ultrasonic data for a wavefield scattered from a hollow PVC sample and a lava sample immersed in a water tank demonstrates that the proposed inversion method allows reliable parameter estimation in the power-law class of viscoacoustic models.

Effects of hydrothermal ageing on the thermal behaviour of poly(vinyl chloride) filled with wood flour

AbstractThe hydrothermal ageing of wood‐flour‐filled PVC produced by dry‐blending in a high‐speed mixer in the presence of a plasticizer and other processing additives was carried out to investigate its thermal behaviour, and the results obtained were compared with those for the unfilled material. The dry‐blended compounds were prepared as films by a calendering process. The accelerated hydrothermal ageing was carried out by immersing the samples in boiling water at 100 °C for 110 h. The thermal behaviour of the reference and the aged samples in water was characterized by differential scanning calorimetry (DSC) and determination of the weight changes. The study has shown that during hydrothermal ageing, the samples from the whole formulations absorbed water, for instance, for 30 wt% filled PVC (F30), 16 wt% of water absorption was obtained, while this was only 2.2 wt% for unfilled PVC (F0). It was also noticed that the formulations filled with wood flour up to 10 wt% exhibited similar water absorption kinetics, i.e. the water was mostly absorbed during the first 50 h and the amount absorbed was less than 5 wt%. On the other hand, the 30 wt% filled samples regularly absorbed water up to almost 16 wt% after 100 h of immersion. The DSC data showed that hydrothermal ageing significantly affected the onset temperature of decomposition (Td) of the unfilled samples by decreasing this temperature from 228 to 215 °C. For the 30 wt% filled samples, only additive migration was observed, while the Td remained almost unchanged. Furthermore, from the DSC data, processability of the 30 wt% filled PVC samples at elevated temperatures, i.e. 180 to 200 °C was shown. Copyright © 2004 Society of Chemical Industry

熱処理した非結晶性高分子材料の降伏過程

It has been shown that the yield process is very different between the annealed and quenched samples of amorphous polymers. Many slip lines appearing just before yielding cause a specimen necking near the peak stress in asreceived and annealed samples, while it occurs without visible formation of slip lines in quenched samples. To investigate this difference may promote the understanding on the yield mechanism of amorphous polymers. In this paper, the results mentioned previously were confirmed at tensile and shear tests and some mechanical properties related to the yielding were measured using as-received (AR) and quenched (Q) samples of amorphous polymers, PC, PVC, PMMA and PET. It was shown that (1) the values of tanδ are higher in Q than in AR samples, (2) the diffusion rate of methyl alcohol to PMMA is greater in Q than in AR samples, (3) the specific gravities of Q samples are smaller than those of AR ones and (4) the yield mechanism is very different between AR and Q samples under both tension and shearing.

Hydrothermic aging of plasticized poly(vinyl chloride): Its effect on the dielectric, thermal, and mechanical properties

Accelerated hydrolytic aging (according to the NFT 5166 method) was performed on samples of poly(vinyl chloride) (PVC) plasticized with dioctylphthalate (DOP) and dinonyladipate (DNA) at different concentration ratios. The aging test consisted of immersing the samples in boiling water at 100°C. The samples were removed from water regularly, that is, every 2 h, for mechanical, thermal, and dielectric characterizations. Thermograms of PVC plasticized with DOP revealed no migration of the plasticizer independent of the concentration used. Moreover, the thermal stability of the samples was not affected by the hydrothermal aging. However, for PVC samples plasticized with DNA, a small amount of the plasticizer migrated from the polymer matrix with a considerable effect on the thermal stability. In fact, the data indicated a decrease in the decomposition temperature from 275 to 225°C, particularly for samples containing 50% (w/w) DNA immersed up to 10 h. The mechanical results showed that for a plasticizer content greater than 30% (w/w), the strain at break obtained for samples plasticized with DNA was lower than that for samples plasticized with DOP because the DNA molecules were more likely to be removed by water on account of their polarity and dimension. Finally, the dielectric measurements showed that the permittivity of all the PVC samples plasticized with DOP and immersed in boiling water was higher than that of the virgin samples. On the contrary, the permittivity of the aged unplasticized PVC was less than that of the nonimmersed samples. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3447–3457, 2003

Studies on the effect of laser radiation on the thermal stability of stabilized poly(vinyl chloride)

Nonisothermal studies were carried out using thermogravimetry (TG) and differential thermogravimetry (DTG) to obtain the activation energy of the decomposition for poly(vinyl chloride) (PVC), stabilized by ethyl, N-phenylmaleimide, and 4-carboxylate (ENPMC). Thermal gravitational analysis (TGA) indicated that the ENPMC–PVC samples decompose in two main breakdown stages. The effect of the addition of a stabilizer (ENPMC), with different concentrations, to PVC was studied. The results indicate that the addition of ENPMC with 0.01 g/1 g PVC enhances the thermal stability of pure PVC. Samples from 0.01 g ENPMC/1 g PVC were exposed to infrared laser radiation with energy fluency at levels between 0.95 and 8.53 J/cm2. The results of the thermal experiments indicate that the onset temperature of decomposition T0 and thermal activation energy of decomposition Ea are affected by the laser energy fluency owing to the simultaneous processes of degradation and crosslinking. The variation of transition temperatures with either the stabilizer concentration or the laser energy fluence was determined using differential thermal analysis (DTA). The results indicate that the irradiation with a laser to 7.11 J/cm2 decreases the melting temperature of the pure PVC and this is most suitable for applications requiring the molding of this polymer at lower temperatures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2249–2255, 2003

Identification and fragmentation study of plasticizers with post-source decay matrix-assisted laser desorption/ionization mass spectrometry.

A detailed investigation of the most commonly used plasticizers, such as phthalate, adipate and trimellitate esters, using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and post-source decay (PSD) MALDI-TOFMS/MS is described. It is shown that PSD MALDI-TOFMS/MS is capable of unambiguous determination of the different types of plasticizers. The determination of the types of plasticizers from different PVC samples by PSD MALDI-TOFMS/MS, without the need for solvent extraction, is also demonstrated. The fragmentation mechanisms of these plasticizers cationized with protons and sodium ions are also reported.

Dose rate effects in radiation degradation of polymer-based cable materials

Cable ageing under the nuclear power plant (NPP) conditions must be effectively managed to ensure that the required plant safety and reliability are maintained throughout the plant service life. Ionizing radiation is one of the main stressors causing age-related degradation of polymer-based cable materials in air. For a given absorbed dose, radiation-induced damage to a polymer in air environment usually depends on the dose rate of the exposure. In this work, the effect of dose rate on the degradation rate has been studied. Three types of NPP cables (with jacket/insulation combinations PVC/PVC, PVC/PE, XPE/XPE) were irradiated at room temperature using 60Co gamma ray source at average dose rates of 7, 30 and 100 Gy/h with the doses up to 590 kGy. The irradiated samples have been tested for their mechanical properties, thermo-oxidative stability (using differential scanning calorimetry, DSC), and density. In the case of PVC and PE samples, the tested properties have shown evident dose rate effects, while the XPE material has shown no noticeable ones. The values of elongation at break and the thermo-oxidative stability decrease with the advanced degradation, density tends to increase with the absorbed dose. For XPE samples this effect can be partially explained by the increase of crystallinity. It was tested by the DSC determination of the crystalline phase amount.

Discrimination of Poly(vinyl chloride) Samples with Different Plasticizers and Prediction of Plasticizer Contents in Poly(vinyl chloride) Using Near-infrared Spectroscopy and Neural-network Analysis

In the recycling of poly(vinyl chloride) (PVC), it is required to discriminate every plasticizer for quality control. For this purpose, the near-infrared spectra were measured for 41 kinds of PVC samples with different plasticizers (DINP, DOP, DOA, TOTM and Polyester) and different plasticizer contents (0-49%). A neural-network analysis was applied to the near-infrared spectra pretreated by second-derivative processing. They were discriminated from one another. The neural-network analysis also allowed us to propose a calibration model which predicts the contents of plasticizers in PVC. The correlation coefficient (R) and the root-mean-square error of prediction (RMSEP) for the DINP calibration model were found to be 0.999 and 0.41 wt%, respectively. In comparison, a partial least-squares regression analysis was carried out. The R and RMSEP of the DINP calibration model were calculated to be 0.993 and 1.27 wt%, respectively. It is found that a near-infrared spectra measurement combined with a neural-network analysis is useful for plastic recycling.

Artificial accelerated weathering of poly(vinyl chloride) for outdoor applications: the evolution of the mechanical and molecular properties

We have performed artificial accelerated ageing in xenon light and a natural exposure in Lisbon (hot, Mediterranean climate), using four different types of TiO 2 pigmented PVC formulations, containing various other additives. The experimental results obtained permit us to compare the performance of the additives present in the different formulations and give us information about the sensitivity of each analytical technique used to evaluate the effects of degradation in the PVC samples, originated by the weathering from light, referred to previously.

Cone calorimetric study of copper-promoted smoke suppression and fire retardance of poly(vinyl chloride)

Copper-based smoke suppression additives for poly(vinyl chloride) (PVC) were tested for crosslinking capability in pyrolysis studies and for smoke suppression and fire retardance by the use of cone calorimetry. Crosslinking of PVC at 190 °C was promoted by most of the additives without an obvious dependence on additive copper content or copper oxidation state. The copper additives (at 10 parts by weight per hundred parts of resin) proved to inhibit both smoke and heat evolution in burning PVC samples (both rigid and plasticized) in cone calorimetric studies. Mixed-metal oxides of copper were especially effective in this regard. Synergism in smoke suppression was noted for combinations of Cu 3(MoO 4) 2(OH) 2 and CuSnO 3 in plasticized PVC. A 2:1 (w/w) mixture of Cu 3(MoO 4) 2(OH) 2 and CuSnO 3 yielded a reduction in specific extinction area (a measure of smoke obscuration) of 64% and a reduction in total smoke release of 79% vs. the control sample.

Crystallization and Relaxation Behavior of Partially Disentangled Poly(vinyl chloride) Prepared from Large Molecule Solvent Dioctyl Phthalate

Poly(vinyl chloride) (PVC) samples for the conformation and structural relaxation studies were prepared by freeze-extracting the solutions in various solvents and with varying concentrations. The partially disentangled PVC samples could be obtained by freeze-extracting very dilute PVC/tetrahydrofuran (THF) and PVC/dimethyl phthalate (DMP) solution (0.05 wt %), while the PVC sample remains in an entangled state after freeze-extracting the concentrated solutions in THF and in DMP. Surprisingly, the extent of interpenetration of PVC chain decreases, even in concentrated solution in dioctyl phthalate (DOP) (5 wt %), which is contrary to accepted theories. DSC and infrared spectroscopic studies showed that a higher ordered conformation could be achieved for the disentangled specimens recovered from concentrated solution in DOP than for the entangled samples prepared from THF and DMP. DSC heating curves showed strong and sharp endothermal peaks for the disentangled polymer after sub-Tg annealing. The structural relaxation behavior of the disentangled PVC freeze-extracted from DOP solutions is more predominant, which is in good agreement with the modeling predictions.

Utilization of some oligomers based on poly(ethylene terephthalate) wastes as modifiers for polyvinyl chloride

AbstractTwo glycolyzed products, PET‐TEG and PET‐BD, were prepared by depolymerization of PET wastes using 30 wt % triethylene glycol (TEG) and 40 wt % 1,4‐butanediol (BD). In this work we investigated how the mechanical and electrical properties of PVC and PVC/EPDM blend were affected by mixing them with different concentrations of the two obtained glycolyzed products. Dynamic mechanical, DSC, and dielectric behaviors of PVC containing various amounts of the two modifiers were studied. The present data confirm that the α‐relaxation dynamic of PVC at constant frequency shifts to a lower temperature with increasing modifier content. PVC samples containing 5 phr of the two modifiers show the highest impact strength at −30°C. It was noted that addition of PET‐TEG to PVC or PVC/EPDM blend led to end products with enhanced insulating properties, which makes them suitable for industrial applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2501–2509, 2002

The Gas Transport Properties of PVC Functionalized with Mercapto Pyridine Groups

The diffusivity, permeability, and solubility coefficients of O2, N2, CO2, and CH4 have been measured in PVC and in four samples of PVC functionalized with mercapto pyridine groups up to 6.8, 11, 21, and 46 mol %. It has been found that the permeability of all four gases progressively increases by a factor of more than 4 because of a similar increase in the diffusion coefficients. In addition, permeability selectivity augments significantly for the gas pair O2/N2 and only slightly for the pair CO2/CH4. The structural changes in the modified samples have been monitored by means of density and Tg determinations and FFV calculations, which are a measure of interchain spacing and chain stiffness. An interpretation of the changes seen in the gas transport properties of modified PVC samples has been proposed in terms of the structural changes introduced by the progressive functionalization of the PVC chains.

Photostabilization of poly(vinyl chloride) by protective coatings

AbstractThe light stability of poly(vinyl chloride) plates has been substantially increased by protecting their surface with a UV‐cured acrylic clearcoat containing both a UV absorber and a HALS radical scavenger. To ensure a long‐lasting adhesion, the coating was photochemically grafted onto the PVC substrate. The coated PVC sample remained transparent, non‐colored, and glossy upon accelerated QUV‐B weathering for up to 3000 hours. An additional advantage of this method of photostabilization is to improve some of the surface properties of the coated polymer, such as its resistance to solvents, abrasion, and scratching. The method was also successfully used to recover highly photodegraded PVC and make it even more weathering‐resistant than the original polymer.

On the coupling in molecular motions: A novel molecular micro-structure approach to the physical meaning of the Ngai's coupling parameter

The dielectric behaviour through DETA system has been studied for six PVC samples of distinct molecular microstructure in terms of content and associated surroundings and conformation of the local configurations mmr termini of isotactic sequences. Both the dielectric studies and the microstructure of the samples, as obtained by stereospecific substitution reaction of an additive-free commercial PVC are to be published in detail separately. For purposes of clarity some of the results are mentioned in Experimental section. The phenomenological correlation between the β parameter as defined by Ngai's theory and the microstructure of the samples, quantities both issued from the above quoted work, is considered in the present paper with the objective of providing some novel ideas on the physical meaning, at molecular level, of the Ngai's coupling parameter, in the light of mobility constraints and local free volume associated with mmr structure at its likely conformations.

Studies on photoconductivity of C60 and C60-doped poly(vinylchloride)

Abstract Single crystals of buckminsterfullerene (C 60 ) were grown by low-temperature solution growth technique. Using the same technique, poly(vinylchloride) was doped with 1% of C 60 by mass. FTIR spectra were recorded for pure C 60 , pure poly(vinylchloride) and C 60 -doped poly(vinylchloride) by Bruker IFS 66V FTIR spectrometer. From the nature of the FTIR spectrum of the C 60 -doped material, it is found that the material is polycrystalline and the presence of C 60 has been confirmed. The absorption spectra for C 60 and C 60 -doped PVC samples were recorded using SL159 UV–vis spectrophotometer. Photoconductivity studies were also made for these materials. It was interesting to observe that the C 60 -PVC exhibited negative photoconductivity. Stockmann model has been successfully applied to explain this behaviour of the doped sample.

Study of fusion percolation thresholds of rigid PVC compounds

AbstractRigid poly(vinyl chloride) (PVC), PVC/chlorinated polyethylene (CPE), and PVC/CPE/oxidized polyethylene (OPE) compounds were prepared in a Haake torque rheometer. The fusion percolation thresholds (FPTs) of these compounds were defined and compared. Moreover, the fusion curves of these compounds were illustrated and compared. A higher processing temperature resulted in a shorter fusion time and a lower FPT. For PVC/CPE compounds, a higher concentration of CPE could decrease the FPT and promote PVC particles to fuse together easily. Meanwhile, in the beginning of the fusion process, the interaction between a higher concentration of OPE and calcium stearate in PVC/OPE compounds could also promote an easy fusion of the PVC particles. For PVC/CPE/OPE compounds, the synergistic interaction among CPE, OPE, and calcium stearate resulted in the shortest fusion time and the lowest FPT. The FPTs of rigid PVC samples were strongly dependent on not only the processing conditions but also the formulations of the samples. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3022–3029, 2001