Influence of polyesterurethane plasticizer on the kinetics of poly(vinyl chloride) decomposition process

Poly(vinyl chloride) (PVC), plasticized by di(2-ethylhexyl) phthalate (DEHP), medium molecular mass polyesterurethane (PU) or by both plasticizers, was thermally degraded under dynamic thermogravimetric conditions and the kinetics of decomposition was studied by isoconversional methods and by non-linear regression. It has been found that the initial decomposition temperature is higher for PVC plasticized with PU, as compared with PVC plasticized with di(2-ethylhexyl) phthalate (DEHP) or plasticized with PU/DEHP, and thermal degradation shows features of a multi-step complex process. Application of polymeric plasticizer leads to the increase and a 'smoothing' effect in the course of energy of activation and pre-exponential factor at the initial stage of decomposition indicating thus the hindered migration of medium molecular mass compound from PVC matrix (in comparison with PVC containing monomeric DEHP) due to steric hindrances as well as due to specific interactions between C=O and Cl groups along the macrochains. Kinetic model function of the decomposition process of PVC/DEHP and PVC/DEHP/PU blends was found to be a two-stage autocatalyzed reaction of n^th order; autocatalytic effect is associated most likely with the role of HCl formed during PVC decomposition. For PVC/PU blend best fit was found by non-linear regression for a two-stage scheme in which first stage was Prout-Tompkins model and the second was autocatalytical model of n^th order - the first one involves particle disintegration, which was promoted by product generation at branching PVC 'pseudo-crystals' nuclei, thus exposing more surface on which decomposition reaction proceeds.     

Fluoride-selective sensors based on polyurethane membranes doped with Zr(IV)-porphyrins

The feasibility of using Tecoflex polyurethane as a polymeric matrix for fluoride-selective membranes doped with Zr(IV)-octaethyl-(OEP) or Zr(IV)-tetraphenylporphyrins (TPP) is examined. Membranes containing cationic or anionic additives were prepared, with ionophore working according to neutral or charged carrier mechanism, respectively. Results are compared to those found previously using conventional poly(vinyl chloride) (PVC) as the membrane matrix. It was found that this polymer does not affect significantly the properties of these porphyrins, compared to poly(vinyl chloride) matrix. A dimer-monomer equilibrium determined recently to occur for Zr(IV)-porphyrins in PVC/o-NPOE membranes containing lipophilic anionic additives is also observed to occur (via UV-vis spectrophotometry) in the PU matrix. However, the equilibrium constants for dimer-monomer reactions appear to be lower in PU membranes compared to PVC films, as determined from the degree of super-Nernstian responses towards fluoride as well as the anion concentration ranges required to break the dimer as determined spectroscopically. Due to reduced dimerization of Zr(IV)[OEP]Cl₂ it was possible to obtain electrodes with PU/o-NPOE/KTFPB membranes exhibiting only slightly super-Nernstian (−64.6 mV/dec) response towards fluoride and response time (t₉₅ < 120 s) faster than observed for PVC-based membranes. Good working parameters were also obtained for this metalloporphyrin in PU membrane that forces neutral carrier mechanism (PU/DOS/TDMACl): F⁻ calibration slope −58.3 mV/dec and response time t₉₅ < 12 s. Tested membranes were subsequently applied for construction of miniaturized silicon-based sensors. Better fluoride selectivity was observed for sensors with Zr(IV)[OEP]Cl₂/PU/o-NPOE/KTFPB membranes (: ClO₄⁻ 0.7; Br⁻ −1.9; NO₃⁻ −1.9; Cl⁻ −3.1), compared to Zr(IV)[OEP]Cl₂/PU/DOS/TDMACl matrix (: ClO₄⁻ −0.8; Br⁻ −1.3; NO₃⁻ −1.5; Cl⁻ −2.1). However, latter composition was chosen to be better for flow measurement mode, as dimer formation can be totally prevented within this membrane. Sensors with Zr(IV)[OEP]Cl₂/PU/DOS/TDMACl maintained their characteristics at least for 2 months.     

Analysis of the carcinogen 4,4′-methylenedianiline (MDA) in gamma-ray and in autoclave-sterilized polyurethane

Summary A carcinogen, 4,4-methylenedianiline (MDA, p,p-diaminodiphenylmethane), was determined in gammaray- and in autoclave-sterilized thermoplastic polyurethane (PU). The determination of MDA in aqueous extracts of PU has been reported, however recovery of MDA and its determination using a complete dissolution of PU by organic solvents have not. In addition, we report the MDA determination in methanol extract of PU. No MDA was detected in gamma-ray sterilized thermoplastic PU, but in autoclavesterilized thermoplastic PU, MDA was detected (possibly formed by hydrolysis). The amount of MDA formed was inversely related to the molecular weight of PU by a second order equation. No change in the weight average molecular weight was observed as a result of autoclave sterilization. Essentially the same amounts of MDA were extracted from PU with serum as with methanol.

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Analyse des Carcinogens 4,4-Methylendianilin (MDA) in -Strahlen- und Autoklav-sterilisiertem Polyurethan

     

用DSC研究线形多嵌段聚氨酯与聚氯乙烯、氯化聚氯乙烯共混相容性

用示差扫描量热法（DSC）研究了线形多嵌段聚氨酯（PU）与聚氯乙烯（PVC）、氯化聚氯乙烯（CPVC）共混相容性，说明了PU／VC、PU／CPVC的相容是由于共混物中形成了新的氢键的缘故．聚酯型聚氨酯与PVC、CPVC的相容性要好子聚酸型聚氨酯，CPVC与PU的相容性又要好于PVC．聚氨酯中硬段的引入不利于PU／PVC、PU／CPVC的相容性．     

用FTIR研究线形多嵌段聚氨酯与聚氯乙烯、氯化聚氯乙烯共混相容性

用溶液法得到线形多嵌段聚氨酯（PU）与聚氯乙烯（PV）、氯化聚氯乙烯（CPVC）的共混物。用FTIR研究PU/PVC、PU／CPVC共混物的相容性，发现PVC、CPVC的加入破坏了PU中原来的氢键，并且PU中的炭基（C=0）与PVC、CPVC中的α－H形成了新的氢键，因而说明了PU／PVC、PU／CPVC共混物具有良好的相容性。     

The spin-allowed and spin-forbidden 5s 2 1 S 0-5s5p 1 P 1,3 P 1 transitions in strontium isoelectronic sequence

Relativistic multiconfiguration Dirac-Fock (MCDF) transition energies and oscillator strengths are determined for both the spin-allowed 5s ^{2 1} S ₀-5s5p ¹ P ₁ and the spin-forbidden 5s ^{2 1} S ₀-5s5p ³ P ₁ transitions in the strontium isoelectronic sequence. The modest relativistic configuration mixing to represent intravalence correlation is combined with a polarization model to account for valence-core electron correlations. The multiconfiguration Dirac-Fock calculations are performed in an average level scheme; however for neutral strontium and singly ionized yttrium a thorough comparison of the average and the optimal level schemes is presented. The average level scheme, though less accurate for the neutral end of the sequence, avoids the convergence problems encountered for highly ionized systems, where the 5s 5p ³ P ₁,¹ P ₁ states are raised owing to the collapse of the 4d _{3/2, 5/2} spin-orbitals in the isoelectronic sequence and, thus, allows us to extend our study to multiple charged ions (throughW ³⁶⁺). Since for such systems there is practically no difference between the results of the average and the optimal level versions of MCDF calculations, we believe that our average level predictions of ionization energies and oscillator strengths for states with total angular numberJ=0 andJ=1 are of comparable quality to those that could be obtained with an optimal level scheme.This study was supported by the Pedagogical Academy of Kraków Statutory Activity Grant No BS-29/91     

Fourier transform infrared study of segmental orientation in polymer blends

The effect of the macromolecular plasticizer poly(-methyl--n-propyl--propiolactone), PMPPL, on the orientation of poly(vinyl chloride), PVC, has been studied by FTIR spectroscopy. The addition of PMPPL to PVC does not change significantly the degree of orientation of PVC segments. In blends, PMPPL chains are more oriented when the matrix is richer in PVC but the PMPPL orientation function always remains smaller than that of PVC segments.     

Dynamic mechanical properties of irradiated polyvinyl chloride

Summary Effects of gamma radiation on the dynamic mechanical properties of polyvinyl chloride (PVC) have been studied at audio frequencies from 80 K to 450 K for doses up to 1400 megarads. Two damping peaks were observed between 80 K and 400 K. The onset of main relaxation near 350 K shifted to lower temperatures at low doses, and then shifted to higher temperatures at a dose of 1400 megarads. Only slight changes are discernible in the damping peak near 250 K upon irradiation, but definite variations are noted in the modulus curves. Upon irradiation to 270 megarads an additional damping peak appeared near 150 K accompanied by an increase in modulus at lower temperatures. The height of this peak increased with increasing radiation dose.Crosslinking was confirmed from rubber elastic behavior, swelling, and solvent extraction studies. Some tentative explanations for the changes occurring in the dynamic mechanical properties of irradiated PVC are given in terms of crosslinking, loss of crystallinity, and dehydrochlorination followed by the formation of conjugated series of double bonds.

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Zusammenfassung Es wurde die Wirkung von-Strahlung auf die dynamisch-mechanischen Eigenschaften von Polyvinylchlorid (PVC) bei Hörfrequenzen von 80 K bis 450 K für Dosen bis zu 1400 Megarad untersucht. Zwei Dämpfungspiks zeigen sich zwischen 80 und 400 K. Das Einsetzen der Hauptrelaxation nahe 350 K verlagert sich zu tieferen Temperaturen bei kleineren Dosen, um dann zu höheren Temperaturen bei einer Dosis von 1400 Megarad hinaufzugehen. Nur leichte änderungen sind im Dämpfungspik nahe 250 K durch die Strahlung zu beobachten; aber in der Modulkurve werden definierte Variationen erkennbar. Nach Bestrahlung mit 270 Megarad erscheint ein zusätzlicher Dämpfungspik nahe 150 K, begleitet durch ein Anwachsen des Moduls zu tieferen Temperaturen. Die Höhe dieses Piks wächst mit wachsender Strahlungsdosis.Die Vernetzung wurde aus dem gummielastischen Verhalten, der Quellung und aus Lösungsmittel-Extraktionen bestimmt. Die im dynamisch-mechanischen Verhalten durch die Strahlung des PVC auftretenden änderungen werden auf Grund der Vernetzung, der Abnahme an Kristallinität, der Dehydrochlorierung — gefolgt durch die Bildung von Serien konjugierter Doppelbildungen — erklärt.

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This work was supported in part by the National Science Foundation and the National Aeronautics and Space Administration.     

Radiation dosimetry using clear PMMA and PVC in the range of 5–45 kGy

Some plastic sheets manufactured or commercially available in Pakistan have been tested as radiation dosimeters for cobalt-60 -rays. Radiation induced colouration in the plastics have been measured spectrophotometrically. The results show that 2 mm thick clear poly(methyl methacrylate) (PMMA) can be used as radiation dosimeter up to 45 kGy when absorption measurements are made at 305 nm and 314 nm; whereas 1 mm thick clear poly(vinylchloride) (PVC) is useful up to 30 kGy when measured at 396 nm. The response of PMMA dosimeter is stable for at least 15 days and that for PVC for 30 days, when stored under ambient conditions after irradiation. Post-irradiation stability at various temperatures (–10 to 55°C) has also been studied.     

Nondestructive Quantification of Local Plasticizer Concentration in PVC by 1H NMR Relaxometry

The properties of plasticized poly(vinyl chloride) (PVC) , one of the most important polymers today, are strongly dictated by the concentration of plasticizer. Yet, it has been impossible to quantify this concentration at different positions inside a PVC product without its destruction because of a lack of suitable analytical methods. Thus, this paper introduces a simple, fast, and efficient way to determine truly nondestructively the concentration of plasticizer in PVC by single‐sided nuclear magnetic resonance (NMR). With the help of correlation curves between the concentration of plasticizer inside nonaged PVC samples and the corresponding volume‐averaged NMR parameters, single‐sided NMR allows the quantification of the local concentration of plasticizer in aged PVC plates at different depths by spatially resolved relaxation measurements. The presented approach represents a fundamental step toward in situ characterization of plasticized PVC.

     

Bis-substituted benzo-15-crown-5 ethers as ion carriers in potassium ion-selective electrodes

Lipophilic bis-substituted ester and ether derivatives of benzo-15-crown-5 have been synthesised. The correlation between the structure and potentiometric ion-selectivity has been studied in PVC membrane ion-selective electrodes. An ion-selective potassium sensitive electrode based on 4,5-bis (biphenyloxymethyl)benzo-15-crown-5 exhibited the best electrode properties. The detection limit was loga _K = -5.4; logK _K,Na ^ppot = -3.5. The effect of the lipophilicity of neutral carriers upon electrode performance has been also discussed.     

Exciton Chirality. (A) Origins of and (B) Applications from Strongly Fluorescent Dipyrrinone Chromophores

(A) The origin of exciton interaction and examples of its application to organic stereochemistry are presented. (B) N,N-Carbonyl-bridged dipyrrinones constitute a new class of highly fluorescent chromophores suitable for investigations of stereochemistry and absolute configuration. N,N-Carbonylxanthobilirubic acid esters are strongly fluorescent, with a fluorescence quantum yield (_F) 0.8, but produce only weak exciton CD from the trans-1,2-cyclohexanediol template. The ester of an analog with benzoic acid replacing propionic, N,N-carbonyl-8-(4-carboxyphenyl)-3-ethyl-2,7,9-trimethyl-(10H)-dipyrrin-1-one, exhibits strong fluorescence (_F=0.68, _em=493nm, _ex=422nm in CHCl₃) and UV-Vis absorption (21000 at 424nm) in organic solvents. Its diester with (1S,2S)-cyclohexanediol is fluorescent and exhibits exciton circular dichroism (=+15dm³·mol^–1·cm^–1, =432nm; =–4dm³·mol^–1cm^–1, =380nm) that correlates with the Exciton Chirality Rule.     

On the role of TiO<Subscript>2</Subscript> nanoparticles on thermal behavior of flexible polyurethane foam sandwich panels

A series of flexible polyurethane foam (FPUF) and monolithic polyurethane (PU) sandwich panels reinforced with different contents of TiO₂ nanoparticles (0, 0.5 and 1 mass%) have been successfully prepared by compression molding process at room temperature. The influence of TiO₂ nanoparticles on the thermal properties of PU matrix has been investigated by thermogravimetric and dynamic mechanical thermal analysis (DMTA). The morphology of porous structure of FPUF sandwich panels has been characterized by scanning electron microscopy. The presence of TiO₂ nanoparticles as reinforcement has improved the thermal properties of the FPUF and PU sandwich panel samples. It has been observed that FPUF and PU sandwich panel reinforced with 1 mass% of TiO₂ nanoparticles possessed the highest enhancement in thermal properties in all accomplished thermal tests. The DMTA results for the FPUF and PU sandwich panel reinforced with 1 mass% of TiO₂ nanoparticles indicated that the storage modulus and loss modulus have increased about 1.22 and 1.25 times, 1.5 and 1.55 times, respectively, compared to pure samples. Furthermore, the glass transition (T _g) obtained from the damping factor (tanδ) curves has increased 2 and 1 °C for FPUF and PU sandwich panels, respectively.     

Study on the Mechanism of the Radiation-Induced Chain Oxidation of N,N,N,N-Tetramethyl-4,4′-diaminodiphenylmethane by Tetrabromomethane in Poly(vinyl chloride) Films

Kinetics and mechanism of the radiation-induced chain oxidation of N,N,N,N-tetramethyl-4,4-diaminodiphenylmethane (Am) by tetrabromomethane in poly(vinyl chloride) (PVC) films were studied by ESR and optical spectroscopy. The quantitative analysis of the ESR spectra of PVC films containing Am and CBr₄ irradiated with -rays at 77 K was performed. The nature of radical species involved in the chain process was established. It was shown that the heating of the films after their irradiation at 77 K resulted in the formation of free radicals Am^·, which initiated the chain oxidation of amine with a chain length of 100. The kinetic features of the chain oxidation–reduction reactions occurring in vacuum and in the presence of oxygen were compared.     

Poly(vinyl chloride) composite emulsion resins modified by polyurethane

An ionomer-type of polyurethane (PU) emulsion was prepared from toluene diisocyanate (TDI), polypropylene glycol (PPG) and dimethylol propionic acid (DMPA) following a self-emulsification process. The modified poly(vinyl chloride) (PVC) emulsion resin was obtained by in situ emulsion copolymerization using the PU as seeds in an autoclave. The effects of PU molecular weight on the mechanical properties and thermal stability of the PU/PVC materials were investigated. The composite latex particles and composite materials were determined and characterized using a laser particle size analyzer, transmission electron microscopy or scanning electron microscopy. The study results showed that the PU/PVC hybrid emulsion particles possess a core/shell structure. When the general mechanical properties of the composite materials increase, the thermal stabilities decrease a little. The tough fractures on the surface of the PU/PVC composite sample following impact are quite obvious. __________ Translated from Journal of Hebei Normal University (Natural Science Edition), 2007, 31(2): 228–232 [译自: 河北师范大学学报(自然科学版)]     

Surface-modified carbon nanotubes and the effect of their addition on the tribological behavior of a polyurethane coating

The toluene-2,4-diisocyanate (TDI) treatment was used to bind isocyanate functional groups (OCN-) on the surface of multi-walled carbon nanotubes (MWCNTs), after which the TDI modified MWCNTs and unmodified MWCNTs were added to the polyurethane (PU) to produce composite coatings with improved wear properties. When the modified MWCNTs were added to the PU binder, the grafting TDI can take part in the curing of the PU binder so that chemical bonding was established between the MWCNTs and the matrix. Friction and wear tests indicated that modified MWCNT reinforced PU composite coating has the highest coefficient of friction and the highest wear resistance of the examined composite coating. Furthermore, the effects of sliding speed and applied load on the friction and wear behavior of the PU coating filled with MWCNTs or MWCNTs-TDI were also studied. The results showed that the coefficient of friction decreased with increasing sliding speed and applied load, and the anti-wear behavior of the PU coating filled with MWCNTs-TDI was the best under 320 N at a speed of 3.0 m s⁻¹.     

Studies on the relationship of structure and properties of the polyesterurethanes adhesives

Three series of linear segment polyurethanes (PHAU, PBAU, PEAU) based on three polyesters (PHA, PBA, PEA), MDI and butanediol were synthesized by solution polymerization. The crystallinity of these polyesters and polyurethanes and the compatibility of Blends of polyurethane (PU) with poly(vinyl chloride) (PVC) were studied by means of X-ray diffraction, DSC, DMA and phase contrast microscopy respectively. The influence of polyester type and molecular weight, the hard-segment content in PU on the crystallinity of PU and the influence of compatibility on adhesion are discussed. The results showed that, on condition that the hard-segment content was not high (< 25%), the crystallinity in PU was mainly caused by the polyester, soft-segment, which was in the order of PHA PBA PEA, and that, PBAU/PVC, PHAU/PVC were compatible systems, but PEAU/PVC was incompatible. The adhesive strength of the three adhesives was quite different from one another, with the order of PBAU PHAU PEAU. An interpretation of adhesion for the PU-PVC system by the diffusion theory is proposed.     

Preparation of Silica-Silk Fibroin-Polyurethane Composite Films via a Sol-Gel Route

A tetraethoxysilane (TEOS)-derived sol aged for 0 h–6 h at room temperature was mixed with a polyurethane (PU) matrix. A composite of silk fibroin (SF) powders and acrylamide (AAm) was dispersed in the sol-PU mixture and dried isothermally at temperatures between 25°C and 120°C to obtain composite films. Three competitive reactions take place, i.e., those between silica-silica, SF-PU and silica-organic phases, during formation of the composite films. These reactions determine the properties such as morphology and homogeneity of the composite films. IR absorption bands for amide groups (–CONH–), C=O (amide I, 1730 cm^–1) and N–H (amide II, 1530 cm^–1) become larger with decreasing aging time of TEOS-derived sol, or increasing drying temperature. DTA exothermic peak due to the thermal decomposition of SF-AAm composite, on the composite films prepared from the 0 h-aged sol or dried at more than 50°C, shifts toward higher temperature by 44 K or more than 63 K respectively, as compared to the SF-AAm composite. Shorter aging time of TEOS-derived sol and higher drying temperature increased the extent of dispersibility, among SF-AAm composite, PU and silica, to bring a composite film more homogeneous.     

Network structure and mechanical properties of allophanate-cured polyurethane rubber

An allophanate-cured polyurethane (PU) has been prepared. The relationship between trifunctional network structure and mechanical properties is discussed. Mooney-Rivlin constants C₁ and C₂ are determined from stress-strain isotherms. C₂ is approximately constant. The average value of structure factor A₃ in the limit at large deformation is 0.432, in fair agreement with the theoretical prediction of 1/3. The structure factor A′₃ of all PU samples becomes roughly unity in the limit at small deformation. The experimental results are interpreted by the recent Flory theory (a fluctuation-constraint model of junctions). The κ parameter decreases with increasing crosslink density; the ξ parameter is small and approaches zero. Increasing crosslink density tends to cause phantom deformation for extended PU networks. However, the absolute value of the reduced stress in the limit at large deformation (or for the equivalent phantom network) [f] is believed to be overestimated for PU networks with high crosslink density. The origin of this behavior is discussed in detail.     

Crystallization of Poly(ε‐caprolactone)/Poly(vinyl chloride) Miscible Blends Under Strain: The Role of Molecular Weight

Summary: The effect of poly(ε‐caprolactone) (PCL) molecular weight on the orientation of crystalline PCL in miscible poly(ε‐caprolactone)/poly(vinyl chloride) (PCL/PVC) blends, melt crystallized under strain, has been studied by a combination of wide angle X‐ray diffraction (WAXD) and small angle X‐ray scattering (SAXS) studies. An unusual crystal orientation with the b‐axis parallel to the stretching direction was observed in miscible PCL/PVC blends with PCL of high molecular weight (>21 000). SAXS showed the presence of nanosize confined PCL in the PCL/PVC blends, which could be preserved at temperatures higher than the T_m of PCL but lower than the T_g of PVC. A mechanism based on the confinement of PCL crystal growth was proposed, which can explain the formation of b‐axis orientation in PCL/PVC blends crystallized under strain.

SAXS pattern of stretched PCL/PVC blend after annealing at 90 °C for 5 min.