Failure mechanism of time‐temperature superposition for poly(vinyl chloride)/dioctylphthalate (100/70) system

The failure behavior and its mechanism of time‐temperature superposition (TTS) poly(vinyl chloride) (PVC)/dioctylphthalate (DOP) (100/70) system were studied from low to high temperatures with a step of 10°C. Arrhenius equation, WLF equation, mathematical nonlinear fitting, and manual shift were applied for TTS fitting. None of these methods could obtain the well‐superposed master curves with either single horizontal shift or two‐dimensional (horizontal and vertical) shift. The rheological data and differential scanning calorimeter (DSC) results were used to explain the failure mechanism of the TTS fitting. The curves of storage modulus versus frequency were well fitted to an empirical equation G^′ = G + Kωⁿ. The yield behavior was used to analyze the influence of test temperature on the dynamic rheological behavior for the PVC/DOP (100/70) system. A transition of rheological behavior from the solid‐like to the linear viscoelastic could be observed at 190°C because of the gradual melting of microcrystallites and the destruction of gel networks, which were confirmed by DSC analysis. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Characterization of PVC cable insulation materials and products obtained after removal of additives

Organic solvents cyclohexane, dichloromethane, hexane, and tetrahydrofuran were tested to separate the dioctylphthalate (DOP) as plasticizer from the poly(vinyl chloride) (PVC)‐based materials. It was found that the efficiency of ultrasound‐enhanced hexane extraction of the DOP from PVC is 70% and the efficiency of the separation of the DOP and other compounds from the PVC by dissolution in THF followed by subsequent precipitation was 98–99%. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to characterize the thermal behavior of PVC materials before and after extraction of plasticizers. It was found that during heating in the range 20–800°C the total mass loss measured for the nontreated, extracted, and precipitated PVC samples was 71.6, 66.6, and 97%, respectively. In the temperature range 200–340°C, the release of DOP, HCl, and CO₂ was observed by simultaneous thermogravimetry (TG)/FTIR. The effect of plasticizers on thermal behavior of PVC‐based insulation material was characterized by DSC in the range ?40–140°C. It was found that, concerning the PVC cable insulation material before treatment, the value of the glass transition temperature (T_g) was 1.4°C, whereas for the PVC sample extracted by hexane, the value of T_g was 39.5°C and for the PVC dissolved in THF and subsequently precipitated, the value of T_g was 80.4°C. Moreover, the PVC samples after extraction of plasticizers, fillers, and other agents were tested to characterize their thermal degradation. The TG and FTIR results of chemically nontreated, extracted, and precipitated samples were compared. The release of DOP, HCl, CO₂, and benzene was studied during thermal degradation of the samples by FTIR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 788–795, 2006     

Dynamic rheological behavior and mechanical properties of PVC/CPE/MAP–POSS nanocomposites

Poly(vinyl chloride)/chlorinated polyethylene (PVC/CPE)/methylacryloylpropyl‐containing polyhedral oligomeric silsesquioxane (MAP–POSS) nanocomposites are prepared. The plastic behavior and dynamic rheological behavior of PVC/CPE/MAP–POSS are investigated. The influences of composition on dynamic storage modulus G′, loss modulus G″, and complex viscosity η* of PVC/CPE/MAP–POSS melts are discussed. The dynamic mechanical properties, mechanical properties, and morphology are determined. The results show that both plastic time and balance torque of the nanocomposites decrease, but the G′, G″, and η* all increase with increasing MAP–POSS content. The maximum value of the dynamic mechanical loss tan δ decreases and elasticity increases when MAP–POSS is added. The impact strength of the nanocomposites increases with increasing MAP–POSS content and has the best value at 10% content of MAP–POSS, which is 5.38 kJ/m² higher than that of the blend without MAP–POSS. The MAP–POSS can be used as an efficient process aid and impact aid for the PVC/CPE blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Rheology and Mechanical Properties of PVC/Acrylonitrile–Chlorinated Polyethylene-Styrene/MAP-POSS Nanocomposites

The nanocomposite of the Poly(vinyl chloride)/acrylonitrile-chlorinated- polyethylene-styrene (ACS)/methylacryloylpropyl-contaning polyhedral oligomeric silsesquioxane (MAP-POSS) (PVC/ACS/MAP-POSS) was prepared. Plasticizing behavior, dynamic rheology behavior and mechanical properties of the nanocomposites were investigated. The results showed that the plastic time decreased with increasing MAP-POSS content. The dynamic storage modulus G ′, loss modulus G″ and complex viscosity η* of the nanocomposites all exhibit a monotonic change with increasing frequency, and all have maximum when MAP-POSS content is 4 wt%, at the same frequency. The MAP-POSS can be used as an efficient process aid and impact aid of PVC/ACS blend at appropriate content.     

Dielectric and mechanical properties of poly(vinyl chloride)–dioctylphthalate systems

The mechanical properties, tensile strength, and elongation were investigated for poly(vinyl chloride) (PVC) samples mixed with dioctylphthalate (DOP) at concentrations from 0 to 100 parts per hundred parts PVC at 23°C. It was found that the tensile strength decreased with the increase of concentration, and the elongation was increased until a concentration of 30 DOP content, and then decreased. This leads to the suggestion that intermolecular plasticization is dominant until 30 DOP content, while interstructural plasticization is prevailing for higher concentrations. The permittivity ε′ and the dielectric loss factor ε″ of the same samples have been measured in the frequency range 10²–10⁵ Hz at temperatures from 3 to 96°C. Results show that as the DOP content increases in PVC, the dielectric absorption becomes broader, and the glass transition temperature T_g is lowered. The magnitude of the loss peak decreases with an increase of DOP content to a minimum at concentrations from 40 to 60 DOP content. At higher concentrations the loss peak is increased and T_g is unaltered. Another absorption was observed at 100 Hz and at high temperatures, which was attributed to Maxwell–Wagner effect or direct current conductivity or both of them. It was found that the sample containing 40 parts DOP in 100 parts PVC possesses the best mechanical and electrical properties.     

Rheological properties of syndiotacticity-rich ultrahigh molecular weight poly(vinyl alcohol) dilute solution

Viscoelastic behavior of the dilute solution of ultrahigh molecular weight syndiotactic poly(vinyl alcohol) (UHMW s-PVA)/dimethyl sulfoxide (DMSO)/water was investigated through rheological response. Below a critical temperature, the dynamic storage modulus (G′) of the solution became greater than the dynamic loss modulus (G″) and the viscoelastic exponent for G′ became smaller than that for G″ before macroscopic gelation, which indicates the evolution of viscoelastic solid properties at the sol state. Also, the loss tangent (tan δ) of the solution below the critical temperature increased with increasing frequency. Consequently, the dilute solution of UHMW s-PVA/DMSO/water showed the rheological behaviors as can be observed in general chemical or physical gel systems below the critical temperature. These results suggest that solid-like heterogeneity prevailed in the solution before macroscopic gelation with decreasing temperature. Such heterogeneity was considered as phase-separated domains attributed to spinodal decomposition. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 569–576, 2001     

Rheological behavior of blends of poly(methyl methacrylate) (PMMA) and poly(acrylonitrile-stat-styrene)-graft-polybutadiene (ABS)

The rheological behavior of blends of poly(methyl methacrylate) (PMMA) and poly(acrylonitrile-stat-styrene)-graft-polybutadiene (ABS) was investigated using a cone-and-plate rheometer. The rheological properties measured were shear stress (σ₁₂), viscosity (η), and first normal stress difference (N₁) as functions of shear rate (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma$ \end{document}) in steady shearing flow, and storage modulus (G′) and loss modulus (G″) as functions of frequency (ω) in oscillatory shearing flow. It has been found that the rheological behavior of blends of ABS and PMMA was very similar to that of blends of poly(styrene-stat-acrylonitrile) (SAN) and PMMA, in that N₁ in logarithmic plots of N₁ versus σ₁₂, and G′ in logarithmic plots of G′ versus G″, vary regularly with blend composition. This has led us to conclude that the rubber particles that are grafted on an SAN resinous matrix in ABS resin plays only a minor role in influencing the compatibility of ABS/PMMA blends, and that the SAN chains attached to the surface of rubber particles, and the SAN matrix phase, play a major role in compatibilizing ABS resin with PMMA.     

Grafting of polyethylenes by reactive extrusion. II. Influence on rheological and thermal properties

In this article, the effects of the grafting degree and the processing conditions employed to prepare LLDPEs-g-DEM and HDPEs-g-DEM via reactive extrusion on their rheological and thermal properties were studied. The rheological properties of the virgin samples of LLDPEs, HDPEs, and their functionalized products were determined using capillary and dynamic rheometry. The thermal behavior of the virgin materials and their grafted products was examined by differential scanning calorimetry (DSC). It was found that the rheological properties are more sensitive than are the molecular structure characteristics to the changes produced by the grafting reactions with DEM, under the employed experimental conditions. There is an increase in the dynamic viscosity at low frequencies, in the storage modulus, and in the shear-thinning behavior when the grafting degree increases. The crossover between G″ and G′ moves to lower frequencies and the relaxation time spectrum functions are broader in the grafted materials. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2549–2567, 1999     

The rheological behavior and dynamic mechanical properties of syndiotactic 1,2‐polybutadiene

The rheological behavior and the dynamic mechanical properties of syndiotactic 1,2‐polybutadiene (sPB) were investigated by a rotational rheometer (MCR‐300) and a dynamic mechanical analyzer (DMA‐242C). Rheological behavior of sPB‐830, a sPB with crystalline degree of 20.1% and syndiotactic content of 65.1%, showed that storage modulus (G′) and loss modulus (G″) decreased, and the zero shear viscosity (η₀) decreased slightly with increasing temperature when measuring temperatures were lower than 160°C. However, G′ and G″ increased at the end region of relaxation curves with increasing temperature and η₀ increased with increasing temperature as the measuring temperatures were higher than 160°C. Furthermore, critical crosslinked reaction temperature was detected at about 160°C for sPB‐830. The crosslinked reaction was not detected when test temperature was lower than 150°C for measuring the dynamic mechanical properties of sample. The relationship between processing temperature and crosslinked reaction was proposed for the sPB‐830 sample. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synergistic Influence of pH and Temperature on Rheological Behavior of Adhesive Emulsions Stabilized with Micelle Dispersion of an Anionic Surfactant

The influence of emulsion pH and temperature on the rheological behavior of adhesive oil-in-water (o/w) emulsions stabilized with an anionic surfactant (sodium dodecyl benzene sulfonate, SDBS) was studied. The flow properties of emulsions as a complex fluid were investigated using steady and dynamic rheometry for characterization of non-Newtonian behavior. Emulsion pH was varied from 2 to 12 and temperature was varied from 20 to 50 °C, respectively. The influences of the above-mentioned variables on the rheology of o/w emulsion were studied using steady-shear and dynamic oscillatory experiments. Various viscosity models (2, 3, and 4 parameter rheological model) were used to predict the rheological parameters. An increase in the pH of the emulsion led to an increase in the emulsion stability, viscosity, and viscoelastic properties ( G′ , G″ , η* , and tan δ ), and a decrease in the mean droplet size of the emulsion. A decrease in the temperature yields higher values of steady-shear viscosity and viscoelastic properties upon a decrease in droplet size. Emulsions were characterized as flocculated structured liquid exhibiting a characteristic crossover frequency ( ω* ) within the range of angular frequency studied in oscillatory measurements. Overall, emulsions exhibited non-Newtonian shear-thinning behavior and the synergy of pH and temperature significantly influences the emulsion rheology.     

Rheological behavior of polymer blends

Steady and oscillatory shearing flow properties of compatible and incompatible polymer blend systems were measured, using a cone-and-plate rheometer. The compatible blend systems investigated are blends of two low-density polyethylenes (LDPE) having different values of molecular weight and blends of poly(methyl methacrylate) (PMMA) with poly(vinylidene fluoride) (PVDF). The incompatible blend system investigated is a blend of poly(methyl methacrylate) (PMMA) with polystyrene (PS). It was found that (1) plots of first normal stress difference (τ₁₁ – τ₂₂) vs. shear stress (τ₁₂) and plots of storage modulus (G′) vs. loss modulus (G″) for the LDPE blends become independent of temperature and blend composition; (2) plots of τ₁₁ – τ₂₂ vs. τ₁₂, and G′ vs. G″ for the PMMA/PVDF blends become independent of temperature but dependent upon blend composition. It was found further that, for the incompatible PMMA/PS blends, the dependence of τ₁₁ – τ₂₂ on blend composition, when plotted against τ₁₂, is different from the dependence of G′ on blend composition, when plotted against G″. However, in both compatible and incompatible blend systems, plots of τ₁₁ – τ₂₂ vs. τ₁₂ and plots of G′ versus G″ are independent of temperature. The seemingly complicated composition-dependent rheological behavior of the incompatible blend system is explained with the aid of photomicrographs describing the state of dispersion.     

Synthesis and evaluation of dialkyl furan-2,5-dicarboxylates as plasticizers for PVC

Di(2-ethylhexyl), di(2-octyl), dihexyl, and dibutyl furan-2,5-dicarboxylate were synthesized from furfural and characterized for their plasticizing abilities toward PVC by dynamic mechanical thermal analysis (DMTA) with di(2-ethylhexyl) phthalate (DOP) as the standard of reference. DMTA gave values for the depression of the glass transition temperature (T_g) per mass fraction of plasticizer, and it also yielded a set of parameters, relative to those for DOP, which describe the compatibility of the furan diesters with PVC. The efficiency in lowering T_g as exhibited by di(2-ethylhexyl) furan-2,5-dicarboxylate is similar to that of its benzenoid analog, DOP, and was determined at 2.41 and 2.45°C per mass % plasticizer, respectively. All four furan diesters were found to be more compatible toward PVC than toward DOP, with dibutyl furan-2,5-dicarboxylate the most highly compatible. © 1994 John Wiley & Sons, Inc.     

Thermomechanical behavior of poly(vinyl chloride) in the process of degradation

The thermomechanical behavior of poly(vinyl chloride) (PVC) was investigated during its thermal degradation by using torsional braid analysis. In thermomechanical behavior as a function of temperature, the relative rigidity G_r decreased initially with increasing temperature, then began to increase passing through a minimum at about 200°C, and finally decreased at 340°C. Increase in G_r from 200°C was caused by formation of a conjugated polyene chain accompanied by dehydrochlorination and by crosslinking reaction, and decrease in G_r at 340°C was related to scission reactions of the crosslinking network by oxidation. In the change in logarithmic decrement Δ, three peaks were observed: at 90°C, coinciding with the glass transition of the polymer; at about 200°C, due to the melting transition of crystallites, and at about 300°C, due to a loss of mechanical energy in the rheological transition of the polymer from a liquid state to a glassy state passing through a viscoelastic region. The thermomechanical properties of PVC with different molecular weights were also measured, and the effect of molecular weight G_r and Δ are discussed. In isothermal measurements of the relative rigidity in air, exponentially increasing curves were observed as a function of time. These curves were analyzed kinetically as a first-order reaction, and an activation energy of 22.7 kcal/mole was obtained.     

Alloying of poly(vinyl chloride) to reduce plasticizer migration

Concern over the migration of low molecular weight plasticizer from flexible poly(vinyl chloride) (PVC) used in toys and medical products has spearheaded the commercialization of a number of plasticizing polymers. In this study the plasticizing behavior of an ethylene/vinyl acetate/carbon monoxide terpolymer (Elvaloy® from DuPont) was investigated. Blends of PVC, Elvaloy 742, and dioctyl phthalate (DOP) were processed on a twin‐roll mill and compression molded into plaques. These materials were characterized in terms of their hardness, glass‐transition temperature (T_g), clarity, mechanical properties, and plasticizer migration behavior. The ratios of PVC/DOP/Elvaloy investigated were determined by experimental design. Using this approach it was possible to model the results and produce contour plots to map out the properties of a wide range of formulations. It was confirmed that Elvaloy 742 is compatible with PVC and has a plasticizing effect: this was demonstrated both in terms of a reduction in Shore A hardness and a reduction in T_g. Plasticizer migration was reduced in proportion to the amount of liquid plasticizer replaced. Plasticizing with Elvaloy gave an improvement in tear strength. However, at constant hardness there was no improvement in tensile strength from replacing DOP with Elvaloy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2022–2031, 2004     

Poly(diethylene glycol adipate): A Study of Its Behavior as a PVC Plasticizer

The compatibility of PVC with poly(diethylene glycol adipate) M _n = 1500 was evaluated by DSC, indicating a limit value of 15 phr. The behavior of the oligomer as a PVC plasticizer, alone or in combination with dioctylphthalate (DOP), was investigated by measurements such as hardness, glass transition temperature, heat stability, and solvent resistance. In spite of its limited compatibility the oligoester can act as a secondary plasticizer enhancing the overall performance of the compositions.     

Poly(vinyl chloride) plasticized with succinate esters: synthesis and characterization

Phthalates pose adverse health effects due to their propensity to leach and the most common, di(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DOP), are petroleum-based. Conversely, di-esters, succinates are biobased (produced from fermentation of biomass), biodegradable, and therefore potential sustainable replacements for phthalates. A series of succinates, di-octyl succinate (DOS), di-hexyl succinate (DHS), di-butyl succinate (DBS), and di-ethyl succinate (DES), were mixed with poly(vinyl chloride) (PVC). The interaction of the plasticizer ester carbonyl with PVC shows an average −5 cm⁻¹ shift of the carbonyl absorbance peak energy. The glass transition temperatures (T _g), were monitored by differential scanning calorimetry and dynamic mechanical analyses. The T _gs of DOS and DHS plasticized PVC were significantly lower than DOP plasticized PVC at a lower percent mass. On the other hand, PVC plasticized with either DBS or DES exhibited a similar trend in lowering the T _g as that of DOP plasticized PVC.     

Properties of Poly(vinylchloride) Blended with an Emulsion Copolymer of N-p-Tolylmaleimide,Methyl Methacrylate,and Acrylonitrile

Abstract

Copolymers of N-p-tolylmaleimide, methyl methacrylate, and acrylonitrile were synthesized by the semibatch emulsion polymerization method and used for blending with poly(vinylchloride) (PVC) to improve its heat resistance. The thermal properties of the blends with different terpolymer content were investigated by differential scanning calorimeter (DSC), thermogravimatric analysis (TGA), and Vicat softening point tester (T _Vicat). The results showed that the glass transition temperature (T _g ), Vicat softening point, and thermal decomposition temperature of the blends increased with increasing terpolymer content. The tensile strength increased with an increase in the copolymer content. The results of the rheological behavior showed that the apparent viscosity ? _α decreased with increasing shear rate and increased with the copolymer content.     

The rheological characterization of a series of thermotropic liquid crystalline polymers

Dynamic rheological experiments were performed on a series of two copolymers and a homopolymer based on units of terephthaloyl chloride and isophthaloyl chloride at 90/10 and 75/25 mole ratios combined with 1,10-bis(4-hydroxyphenyl)-decane. Optical microscopy and wide angle X-ray diffraction (WAXD) confirmed that all of the polyesters in the present series formed nematic liquid crystals with nematic-to-isotropic temperatures in the range of 270 to 320°C with increasing terephthaloyl unit content. Broad nematic-to-isotropic transitions observed by differential scanning calorimetry (DSC) were indicative of biphasic regions where the nematic and isotropic phases coexist. The rheological behavior of each polymer was more complex in the nematic phase than in the isotropic phase with shear thinning occurring in the former but Newtonian behavior in the latter. There were also some indications that nematic flow behavior could be induced in these polymers by dynamic oscillatory shear flow above the nematic-to-isotropic transition, T_i. A form of hysteresis was observed with the homopolymer in that measurements of the dynamic viscosity, η*, taken with ascending frequency sweeps were higher than those taken with descending frequency sweeps.     

Relationship between viscoelastic properties and gelation in thermosetting systems

A method is described for determining from dynamic viscoelastic data the gel time of thermosetting resins. Gelation of nine systems including epoxies, acetylene-terminated sulfone, and silicones was correlated with the crossover of the dynamic storage G′ and loss G″ moduli measured during isothermal curing. The effect of measurement frequency on gel time is discussed and related to the standard gel test. A lower temperature limit for the valid aplication of this technique was found to be at T > T_gg + 30°C, where T_gg is the glass transition of the system at the gel point.     

Conductive polymer composites: Electrical,thermal, and rheological study of injected isotactic poly(propylene)/long stainless‐steel fibers for electromagnetic interferences shielding

The influence of long stainless‐steel fibers (LSSF) on electrical, rheological, and calorimetric properties of conductive composites with poly(propylene) matrix was investigated as a function of filler content from ? = 0.15 to 3.6% v/v (1.3 to 23.5% w/w). The results show interesting features of the crystallization process: fibers act as nucleating agents and generate transcrystalline phases in quiescent conditions. LSSF also influences the flow properties and the dynamic rheological behavior, which is evidenced by evolution of G′ and G″ curves with filler content. Finally, SEM pictures of injected samples were used to determine the distribution and orientation of the fibers in the part thickness at different distances from the injection point. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3280–3287, 2006