Dielectric properties of poly(α-methyl α-n-propyl-β-propiolactone)/poly(vinyl chloride) blends

The dielectric properties of miscible blends of poly(vinyl chloride) (PVC) and poly(α-methyl-α-n-propy-β-propiolae-tone) (PMPPL) have been investigated at different temperatures above and below T_g. The results were analyzed using the Cole-Cole representation and lead to the conclusion that this mixture does not exhibit micro-scale heterogeneities. Dielectric constant and dielectric loss master curves were constructed using the stress relaxation shift factors determined previously; the same shift factors could be used for the homopolymers and their blends. Similarities between the dielectric master curves and the stress relaxation master curves of PVC, PMPPL, and their blends, are also discussed.     

Dielectric relaxation analysis of biopolymer poly(3‐hydroxybutyrate)

Poly(3‐hydroxybutyrate), PHB, is a widely distributed carbon storage polymer among prokaryotes including Rhizobium. Capacities of Rhizobium etli R13 to produce the bioplastic during growth on media with different carbon sources appeared to be specific carbon‐source. In fed batch fermentation, R. etli R13 resulted in cell dry weight 6.2 g/L and PHB 51.4%. Gas chromatography‐mass spectrometry and gel permeation chromatography analysis revealed that PHB produced from R. etli R13 was solely composed of 3‐hydroxybutyric acid and the molecular mass of the purified PHB was 3.4 × 10⁵ Da with polydispersity 1.47. Dielectric relaxation of PHB has been studied in the temperature and frequency ranges 300–440 K and 10 kHz–4 MHz, respectively. A clear dielectric α and ρ‐relaxation processes are observed in these studied ranges of temperature and frequency. The first process is due to the dipole relaxation in the crystalline phase of PHB. The second one is due to the space‐charge formation or Maxwell‐Wagner‐polarization. The α‐relaxation process has been investigated by semiempirical Havriliak‐Negami relaxation function. The activation energy (E_a) and the relaxation time (τ₀) are calculated using the Arrhenius equation. The dielectric relaxation strength (Δε) is strongly temperature dependent. The calculated values of E_a for ac conductivity, ln(σ), of PHB provide information about the presence of electronic conduction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Inhibition of the thermal degradation of rigid poly(vinyl chloride) using poly(N‐[4‐(N′‐phenyl amino carbonyl)phenyl]maleimide)

Poly(N‐[4‐(N′‐phenyl amino carbonyl)phenyl]maleimide), poly(PhPM), has been investigated for the inhibition of the thermal degradation of rigid poly(vinyl chloride) (PVC) in air, at 180°C. Its stabilizing efficiency was evaluated by measuring the length of the induction period, the period during which no detectable amounts of hydrogen chloride gas could be observed, and also from the rate of dehydrochlorination as measured by continuous potentiometric determination, and the extent of discoloration of the degraded polymer. The results have proved the greater stabilizing efficiency of poly(PhPM) relative to that of the DBLC commercial stabilizer. This is well demonstrated by the longer induction period values and by the lower rates both of dehydrochlorination and discoloration of the polymer during degradation relative to those of the DBLC reference stabilizer. The greater stabilizing efficiency of the poly(PhPM) is most probably attributed not only to its possession of various centers of reactivity that can act as traps for radical species resulting during the degradation process, and replacement of labile chlorine atoms on PVC chains by relatively more thermally stable poly(PhPM) moieties, but also due to the ability of its fragmentation products to react with the evolved hydrogen chloride gas. A radical mechanism is suggested to account for the stabilizing action of this polymeric stabilizer. A synergistic effect is achieved when the poly(PhPM) was blended in various weight ratios with DBLC. This synergism attains its maximum when poly(PhPM) and DBLC are taken at 3 : 1 weight ratio. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Chlorinated poly(vinyl chloride) and plasticized chlorinated poly(vinyl chloride)—thermal decomposition studies

The thermal decomposition of chlorinated poly(vinyl chloride) and three plasticized chlorinated poly(vinyl chloride) systems has been investigated. The routes of decomposition of these systems have been elucidated by investigating char formation and by using a combination of thermogravimetric analysis (TGA) and prolysis/gas chromatography/mass spectroscopy methods (Py/GC/MS). The effects of the charforming/smoke‐suppressing iron(III) compound FeOOH in these polymer systems has also been investigated. The structure of both CPVC polymer and plasticzer determine the path of thermal decomposition and also the quantity and nature of the decomposition compunds formed. Changes in oxygen index and the formation of smoke during burning in these systems have been related to the char that is formed and also to the chemical nature of the decomposition products.     

NMR analysis of chlorinated poly(vinyl chloride)

The chlorination of poly(vinyl chloride) takes place preferentially at the methylenic carbon, leading to 1,2-dichloroethylenic units, and to a lower extent at the methynic, leading to 1,1-dichloroethylenic units. The ratio between 1,2- and 1,1-dichloroethylenic units tends to decrease with increasing degree of chlorination, and it seems to depend also on the chlorination conditions. The number-average sequence length of 1,2-dichloroethylenic units does not differ significantly from 1 during a great part of the process, substantially in agreement with a random distribution of these units along the chain. The 1,1-dichloroethylenic units can be found either between two unchlorinated units or at one end of a sequence of chlorinated units. Since among the unchlorinated units more racemic units are present than expected for a completely random chlorination, it can be suggested either that chlorination is affected by stereoregularity or that it does not take place in the crystalline regions of the polymer.     

Dielectric analysis of chlorinated polyvinyl chloride stabilized with di‐n‐octyltin maleate

Dielectric relaxation of chlorinated polyvinyl chloride stabilized with di‐n‐octyltin maleate has been studied in the frequency range 1 kHz–1 MHz at various temperatures between 300 and 450 K. A clear dielectric relaxation band (α‐type) associated with dipolar polarization has been observed in the studied range. The stabilizer molecules increase the segmental mobility of the polymer, and specific interaction occurs between both the C? Cl and C?O polar groups. The temperature dependence of the relaxation process was analyzed by combining the critical free volume expression by Cohen and Turnbull with the Williams‐Landel‐Ferry (WLF) model of the thermal expansion of free and occupied volumes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal degradation of ternary blends of poly(ε‐caprolactone)/poly(vinyl acetate)/poly(vinyl chloride)

The thermal degradation of ternary blends of poly(ε‐caprolactone) (PCL), poly(vinyl acetate) (PVAC), and poly(vinyl chloride) (PVC) was studied using a thermogravimetry analyzer under dynamic heating in flowing nitrogen atmosphere. PCL degraded in a single stage, whereas the PVAC and PVC degraded in two stages during which acid is released in the first stage followed by backbone breakage in the second stage. The addition of PVC to either PCL or PVAC affected the thermal stability of the blend, whereas the addition of PVAC to PCL did not alter the thermal stability of the blend. In ternary blends, the addition of PVC affected the degradation of PVAC but did not influence the degradation of PCL in the range investigated. The increased addition of PCL to the binary blends of PVC/PVAC decreased the extent of thermal instability of PVAC because of the addition of PVC. The addition of even 10% PVAC to the PCL/PVC blend removed the thermal instability of PCL resulting from the addition of PVC and can be attributed to the ease of chlorine or hydrogen chloride capture of PVAC over PCL. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1378–1383, 2004     

Toughening modification of poly(vinyl chloride)/ α‐methylstyrene‐acrylonitrile‐butadiene‐styrene copolymer blends via adding chlorinated polyethylene

In this study, poly (vinyl chloride) (PVC)/α‐methylstyrene‐acrylonitrile‐butadiene‐styrene copolymer (AMS‐ABS) (70/30)/chlorinated polyethylene (CPE) ternary blends was prepared. With the addition of CPE, it did not exert a negative influence in both the glass transition temperature and heat distortion temperature. Thermogravimetric analysis showed that addition of CPE did not play a negative role in the thermal stability. With regard to mechanical properties, high toughness was observed combined with the decrease in tensile strength and flexural strength. With the addition of 15 phr CPE, the impact strength increased by about 21.0 times and 8.5 times in comparison with pure PVC and PVC/AMS‐ABS (70/30) blends, respectively. The morphology correlated well with the impact strength. It was also suggested from the morphology that shear yielding was the major toughening mechanisms for the ternary blends. And there existed a change in the fibril structures that are observed in scanning electron microphotographs. Our present study shows that combination of AMS‐ABS and CPE improves the toughness without sacrificing the heat resistance, and the value of notched impact strength can be enhanced to the same level of super‐tough nylon. POLYM. ENG. SCI., 54:378–385, 2014. © 2013 Society of Plastics Engineers     

Photosensitivities and rates of photocrosslinking of poly(vinyl α-cyanocinnamate) and poly(vinyl α-cyanocinnamoxy acetate)

The photosensitivities and the rates of photocrosslinking of poly(vinyl α-cyanocinamate) and poly(vinyl α-cyanocinnamoxyacetate) were investigated. The photocrosslinkings of these polymers proceeded mainly through radical addition, and these polymers showed higher photosensitivities than poly(vinyl cinnamate) and poly(vinyl cinnamoxyacetate), in spite of lower rates of photocrosslinking of the former polymers.     

Miscibility in poly(vinyl chloride)/chlorinated poly(vinyl chloride) blends,and blends of different chlorinated poly(vinyl chlorides)

Blends of poly(vinyl chloride) with chlorinated poly(vinyl chloride) (PVC), and blends of different chlorinated poly(vinyl chlorides) (CPVC) provide an opportunity to examine systematically the effect that small changes in chemical structure have on polymer-polymer miscibility. Phase diagrams of PVC/CPVC blends have been determined for CPVC's containing 62 to 38 percent chlorine. The characteristics of binary blends of CPVC's of different chlorine contents have also been examined using differential calorimetry (DSC) and transmission electron microscopy. Their mutual solubility has been found to be very sensitive to their differences in mole percent CCl₂ groups and degree of chlorination. In metastable binary blends of CPVC's possessing single glass transition temperatures (T_g) the rate of phase separation, as followed by DSC, was found to be relatively slow at temperatures 45 to 65° above the T_g of the blend.     

Study of poly(vinyl chloride) blends with solid‐state chlorinated polyethylene

The influence of solid‐state chlorinated polyethylene of various chlorine content and residual crystallinity on the mechanical properties of rigid poly(vinyl chloride) has been studied. The impact strength of poly(vinyl chloride) was found to increase significantly as 10–20 mass% chlorinated polyethylene, containing from 10.2 to 27.3% chlorine content (preferably 21.8% Cl) were added. This dependence corresponded to the higher elasticity and impact strength of the solid‐state chlorinated polyethylene with chlorine content below 30% as well as the microstructure of its chlorinated block fragments. Multicomponent system of high impact strength and good flowability, consisting of poly(vinyl chloride), chlorinated polyethylene, hydroxyl‐terminated polybutadiene, and ethylene–propylene–ethylidenenorbornene terpolymer was also obtained. Regardless of the incompatibility between the polymer components of this blend, the similarity in the chemical nature of poly(vinyl chloride) and chlorinated polyethylene blocks on one hand, and the methylene sequences in the chlorinated polyethylene and elastomers on the other, resulted in the formation of an efficient interfacial layer. The changes in the structure of the blends were established by both calorimetric and microscopic studies. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2602–2613, 2006     

Study of dynamic mechanical properties of poly(vinyl chloride)–ethylene vinyl acetate copolymer and poly(vinyl chloride)–chlorinated ethylene vinyl acetate copolymer mixtures

The compatibility of the mixtures poly(vinyl chloride)—ethylene vinyl acetate copolymer and poly(vinyl chloride)—chlorinated ethylene vinyl acetate copolymer was studied by the method of dynamic mechanical testing. The character of G′ and G″ was confronted with the Takayanagi model. In all cases a limited compatibility of the components was observed.     

Dielectric studies of poly(vinyl chloride)

Measurements of the dielectric constant and loss factor of polyvinyl chloride (PVC) have been made over a wide range of temperature and frequency. Maxima in dielectric loss were observed at a temperature corresponding to the α or glass transition temperature and secondary β transition temperature. The sensitivity of these maxima to both frequency and thermal pretreatment was investigated. It was found that the position of the β peak on the temperature axis changed markedly with frequency, while the glass transition or α peak showed only small variations. Neither the α nor the β peak were very sensitive to thermal pretreatment, but interesting changes in the minimum between these peaks were observed. In quenched samples a distinct shoulder peak at T_β < T_s < T_α was observed; it was possible to eliminate it by a slow cooling of the samples. The effect of plasticizer content was also studied.     

Properties and morphology of poly(vinyl chloride) blends with solid‐state‐chlorinated polyethylene

Correlations of the stress‐strain behavior and impact strength of poly(vinyl chloride) (PVC) blends with different amounts and chlorine contents of solid‐state‐chlorinated polyethylene (CPE) were studied. The relationships between the morphology and properties of the PVC/CPE blends also were investigated. The results of dynamic mechanical analysis and transmission electron microscopy showed that PVC/CPE blends are partially compatible systems and that a certain interaction exists between the two phases. When the amount of CPE (chlorine content, 36–42%) was 7–15 phr (parts by weight per hundred parts of resin), an essentially perfect CPE network was formed, and the blends showed better impact resistance. A Brabender Plasticorder study revealed that CPE can promote the plasticity of PVC and improve its processability. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Synthesis of poly(vinyl alcohol)‐graft‐poly(ε‐caprolactone) and poly(vinyl alcohol)‐graft‐poly(lactide) in melt with magnesium hydride as catalyst

Grafting of poly(ε‐caprolactone) (PCL) and poly(lactide) (PLA) chains on poly(vinyl alcohol) backbone (PVA degree of hydrolysis 99%) was investigated using MgH₂ environmental catalyst and melt‐grown ring‐opening polymerization (ROP) of ε‐caprolactone (CL) and L ‐lactide (LA), that avoiding undesirable toxic catalyst and solvent. The ability of MgH₂ as catalyst as well as yield of reaction were discussed according to various PVA/CL/MgH₂ and PVA/LA/MgH₂ ratio. PVA‐g‐PCL and PVA‐g‐PLA were characterized by ¹H‐ and ¹³C‐NMR, DSC, SEC, IR. For graft copolymers easily soluble in tetrahydrofuran (THF) or chloroform, wettability and surface energy of cast film varied in relation with the length and number of hydrophobic chains. Aqueous solution of micelle‐like particles was realized by dissolution in THF then addition of water. Critical micelle concentration (CMC) decreased with hydrophobic chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of chlorinated poly(vinyl chloride)‐g‐poly(N‐vinyl‐2‐pyrrolidinone) membranes and their water permeation properties

Chlorinated poly(vinyl chloride) (CPVC) membranes for microfiltration processes were prepared with the combined process of a solvent evaporation technique and the water‐vapor induced‐phase‐inversion method. CPVC membranes with a mean pore size of 0.7 μm were very hydrophobic. These membranes were subjected to surface modification by ultraviolet (UV)‐assisted graft polymerization with N‐vinyl‐2‐pyrrolidinone (NVP) to increase their surface wettability and decrease their adsorptive fouling. The grafting yields of the modified membranes were controlled by alteration of UV irradiation time and NVP monomer concentration. The changes in chemical structure between the CPVC membrane and the CPVC‐g‐poly(N‐vinyl‐2‐pyrrolidinone) membrane and the variation of the topologies of the modified PVC membranes were characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, and field emission scanning electron microscopy. According to the results, the graft yield of the modified CPVC membrane reached a maximum at 5 min of UV exposure time and 20 vol % NVP concentration. The filtration behavior of these membranes was investigated with deionized water by a crossflow filtration measurement. The surface hydrophilicity and roughness were easily changed by the grafting of NVP on the surface of the CPVC membrane through a simultaneous irradiation grafting method by UV irradiation. To confirm the effect of grafting for filtration, we compared the unmodified and modified CPVC membranes with respect to their deionized water permeation by using crossflow filtration methods. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3188–3195, 2003     

Synergistic combination of metal stearates and β‐diketones with hydrotalcites in poly(vinyl chloride) stabilization

A synergistic effect of synthetic hydrotalcites as long term stabilizer with metal soaps (the mixture of calcium and zinc stearate) and metal acetylacetonates on dehydrochlorination of PVC has been studied. A proper balance between color stabilization and HCl scavenging capacity has been obtained. Hydrotalcite was prepared by hydrothermal treatment and characterized by EDX, XRD, FTIR, TGA, and SEM techniques. The material is reasonably crystalline and suggests a relatively well ordered sheet arrangement with crystallite size 24.87 nm. The interlayer water content was calculated from the TGA curves and the suggested formula is Mg_0.76 Al_0.24(OH)₂(CO₃)_0.12·0.5H₂O. Synergism in PVC stabilization has been studied by measuring the HCl evolution during the processing at 180°C. Oven aging method was used to study the color stabilization at higher temperature. PVC sheet with different formulation was prepared using Labcoater and subjected to oven for different time interval. The color development (polyene formation) on oven ageing was recorded using UV–visible spectroscopy. UV–visible studies shows that an average sized polyene gives pale yellow color, whereas red or brown color was developed due to long range polyene (n = 10–14) sequences. Hence, the HCl evolution depends on the rate of dehydrochlorination but color depends on the kind of polyene formed. Mechanism of stabilization suggests that adsorption and ion exchange, both phenomenon, are responsible for hydrotalcites as long term stabilizers. The acetylacetonate complex too substitute allylic chlorides and inhibit formation of long polyene responsible for darkening. A clear effect of synergism has been observed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Translucent blends of chlorinated polyethylene with poly(vinyl chloride)

Some experimental chlorinated polyethylene (CPE) resins that produced translucent blends with PVC were used to study the effects of CPE chlorine content and chlorine distribution on the morphology, optical clarity, and toughness of blends with PVC. The CPE resins were characterized in terms of the glass transition temperature, residual crystallinity, density, and refractive index. Increasing residual crystallinity and increasing chlorine content both increased the refractive index closer to that of PVC. A linear relationship was observed between the fourth power of the refractive index and the CPE glass transition temperature. With a phase-separated blend morphology in all cases, improved transparency was achieved in this system by reducing the refractive index difference between CPE and PVC. Both haze and transparency showed the predicted linear dependence on the square of the refractive index difference. To a first approximation, modifications of the experimental CPE resins that improved optical transparency of the blends also tended to reduce the toughness enhancement.     

Controlled radical alternating copolymerization of N‐phenyl maleimide with ethyl α‐ethylacrylate by reversible addition fragmentation chain‐transfer process

The alternating copolymerization of N‐phenyl maleimide (NPMI) with ethyl α‐ethylacrylate (EEA) by the reversible addition fragmentation chain‐transfer process was investigated. The monomer reactivity ratios were measured and r₁ = 0.19 ± 0.03 for NPMI and r₂ = 0.20 ± 0.04 for EEA. It was found that before about 45% of the comonomer conversion, the molecular weight of the copolymer increased with the conversion, the molecular weight distribution was rather narrow, and the molecular weight of the copolymer approached a constant value, irrespective of the length of the polymerization time. Electronic spin resonance determined that the radical signal disappeared quickly after the conversion of comonomer exceeded 45%, which may be attributed to the coupling termination of the propagating polymer chains with the EEA end with the intermediate radicals when the concentration of comonomers decreased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2376–2382, 2004     

Development of novel conducting composites of nanostructured poly(1‐naphthylamine) with poly(vinyl chloride)

Investigations on the synthesis of nanoconducting polymers have gained much popularity during the past few decades. The processibility of the nanostructured conducting polymers is poor, which hinders their commercial application. Considering the drawbacks of nanostructured conducting polymers, this article reports for the first time the synthesis of processible composites of nanostructured poly(1‐naphthylamine) (PNA), a polyaniline derivative with poly(vinyl chloride) (PVC). The composites were prepared by loading different weight ratios of PNA (2–10 wt%) in PVC. The composites were characterized by spectral, thermal, morphological, and conductivity studies. The particle size of PNA/PVC composites was confirmed by transmission electron microscopy and was found to be in the range of 5–20 nm. The highest conductivity of 2.5 × 10⁻² S/cm was obtained in the composite with 4 wt% loading of PNA. The high conductivity of the composites was correlated to the agglomerate‐free uniform dispersion of self‐assembled nanofibrillar network of PNA particles in the PVC matrix. The PNA/PVC composites exhibited good mechanical properties, which holds potential for use in semiconductor nanodevices. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers