Layered double hydroxide/NaSb(OH)6–poly(vinyl chloride) nanocomposites: Preparation,characterization, and thermal stability

A novel layered double hydroxide/NaSb(OH)₆‐based nanocomposite (Sb‐LDH) has been prepared via intercalation of thio‐antimonite (SbS₃^3?) and reconstruction of LDH using Mg‐Al LDH as precursors. It is composed of LDH nanolayers with thickness of 25 nm and NaSb(OH)₆ nanoparticles with diameter of 3–25 nm. The presence of NaSb(OH)₆ will decrease the decomposition intensity and hinder the decomposition of Mg‐Al LDH because of the potential synergetic effect. When applied to poly(vinyl chloride) (PVC) composites, both Mg‐Al LDH and Sb‐LDH can enhance the thermal stability and increase the decomposition temperature of PVC. Compared with Mg‐Al LDH, Sb‐LDH results in higher decomposition temperatures and whiteness and higher initial and long‐term stabilities due to the presence of NaSb(OH)₆, which can react with HCl and coordinate with Cl in the PVC chains. Because Mg‐Al LDH will accelerate the dehydrochlorination of PVC driving by the Lewis acid such as AlCl₃, the thermal stability of PVC decreases with increasing nanofiller loading. When 1 wt % Sb‐LDH was added, the color change time and Congo red time of PVC composites are 140 min and 154 min, respectively. With enhanced thermal stabilization, this novel LDH nanocomposite could gain promising application in thermal stabilizer for PVC resins. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Reaction between HC1 and orthophthalates of lead in hot DOP without PVC,and stabilization in plasticized PVC

Reactions between hydrogen chloride, HCl, and either hydrocerussite, 2PbCO₃. Pb(OH)₂, or an orthophthalate of lead suspended in di(2-ethylhexyl)phthalate, DOP, at 180°C are discussed as models of what should happen during the stabilization of PVC if thermal dehydrochlorination were to yield HCl. There is a sharp contrast between the products of these model reactions and those actually found in plasticized PVC containing basic lead compounds. This is taken to show that basic lead stabilizing regimes inhibit PVC thermal dehydrochlorination, actually preventing the formation of HCl. It is proposed that these stabilizing regimes function by a free-radical mechanism which has been called “true stabilization” for ease of reference.     

Stabilization of poly(vinyl chloride). IV. Color changes on heating poly(vinyl chloride)–dye systems

The stabilization of poly(vinyl chloride) (PVC) involving complementary colors has been previously reported. Obliterating polyene color with various dyes containing complementary colors with the polyene color is studied on the basis of colorimetry. The changes in the color of heated PVC containing Thren Blue IRN, Ceres Blue GN, Oplas Violet 730, Macro-Lex Violet 3R, Macro-Lex Green 5B, or Macro-Lex Red 5B were investigated using a differential colorimeter. When the PVCs containing various dyes were heated, the discoloration from the color of each dye to the color mixture of each dye and polyene color was observed with increased heating times for all systems. In particular, an achromatic color has been observed, during the heat treatments, in PVC containing blue dyes such as Thren Blue IRN or Ceres Blue GN, which set up complementary color relationship with the polyene color. Thus the color of polyenes, which appears with advancing dehydrochlorination of PVC, is masked by the blue dyes. It is also apparent that the obliteration of polyene color does not depend on the chemical influences of the dyes added, but by color mixing of polyenes and the dyes. Cool-color dyes markedly slow down the appearance of polyene colors.     

Dehydrochlorination of poly(vinyl chloride)

PVC has been dehydrochlorinated with alcoholic alkali in soution at 7°C for different lengths of time. At early stages of dehydrochlorination the dominant reaction is intramolecular removal of HCl and this gives rise to two intense Raman bands at ～ 1126 (ν₁) and ～ 1518 cm^?1 (ν₂) and following UV irradiation, to a quadruplet ESR spectrum. Increasing polyene sequence length and intermolecular removal of HCl at later stages of reaction alters the quadruplet signal to a singlet, shifts ν₁ and ν₂ to lower frequencies and increases the molecular weight. The presence of polyene units stiffens the chain and increases the elastic modulus. The T_g is, however, lowered slightly due to the removal of bulky chlorine atoms which relieves steric hindrance and dipole interaction between neighboring chains. The β-transition is also rendered less distinct.     

Effect of zinc stearate and/or epoxidized soybean oil on gelation and thermal stability of PVC‐DOP plastigels

The effects of zinc stearate (ZnSt₂) and/or epoxidized soybean oil (ESO) on mechanical properties and on thermal stability of plastigels obtained from polyvinylchloride (PVC) and dioctylphthalate (DOP) plastisols were studied using calorimetric, spectroscopic, and tensile‐testing techniques. Plastigels having 2.5 or 5.0 part ZnSt₂ and/or 5 part ESO and 60 part DOP per 100 part PVC (phr) were gelled by heating at 140°C. The tensile strength of plastigels with no additive and having 5 phr ZnSt₂, ESO, and both ZnSt₂ and ESO were 0.79, 0.46, 0.98, and 0.58 kN/cm², respectively. The decrease of tensile strength of plastigels with ZnSt₂ could be explained by the existence of ZnSt₂ in the solid phase in plastigels, as shown by differential scanning calorimetry (DSC). ESO helped better fusion of the plastisols without any additive and with ZnSt₂. Higher tensile strengths of ESO containing plates indicated more complete gelation of the plastisols. The thermal stability of plastigels in terms of color and their yellowness index (YI) were higher for ZnSt₂ containing plastigels. Conjugated polyene concentrations were calculated from UV spectra of the films heated at 140°C. The reaction rate constant of the dehydrochlorination of PVC changed with the additives. Faster dehydrochlorination than control gels occurred in gels having ZnSt₂ at long heating times due to the autoaccelerating effect of ZnCl₂ formed by reaction of eliminated hydrogen chloride and ZnSt₂. Organic acid formation reaction between ZnSt₂ and HCl formed by dehydrochlorination is investigated from the IR band at 1540 cm⁻¹ and 3400 cm⁻¹ during heating of the plastigel films. A synergistic effect of ESO and ZnSt₂ was observed when the mechanical strength and heat stability were considered together. Although ESO increased tensile strength, ZnSt₂ increased thermal stability of the plastigels at early times when they were present simultaneously in plastisols. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2488–2498, 1999     

Synergistic effect of adipic acid pentaerythritol ester with calcium and zinc stearates on poly(vinyl chloride) thermal stability

Adipic acid pentaerythritol ester (AAPE) was synthesized in this study and confirmed by Fourier transform infrared spectroscopy (FTIR). The synergistic effect of AAPE with calcium and zinc stearates (CaSt₂/ZnSt₂) on poly(vinyl chloride) (PVC) thermal stability was evaluated by the conductivity test, thermal aging test, and thermogravimetric analysis (TGA). The results showed that the addition of CaSt₂/ZnSt₂ combined with AAPE could improve color stability and long‐term thermal stability of PVC. The results of UV‐visible spectroscopy showed that CaSt₂/ZnSt₂/AAPE could prevent the generation of conjugated double bonds. The possible mechanism is that AAPE can chelate ZnCl₂ to prevent the thermal degradation via dehydrochlorination. The contrast tests showed that the synergistic effect of AAPE and CaSt₂/ZnSt₂ is more obvious than that of polyethylene (PE) and CaSt₂/ZnSt₂, which may be attributed to the lower melting point of AAPE and the better compatibility with PVC. J. VINYL ADDIT. TECHNOL., 22:293–299, 2016. © 2014 Society of Plastics Engineers     

On the influence of HCl on the thermal degradation of poly(vinyl chloride)

The thermal degradation of PVC was studied at 190°C in pure nitrogen and nitrogen containing 10, 20, and 40% HCl (by volume). The rate of dehydrochlorination was determined by gravimetry. Degradations in nitrogen were followed with conductometry in addition. Changes in molecular weight distribution and degree of long-chain branching (LCB) were determined by gel permeation chromatography–viscometry and polyene sequence distribution by UV spectroscopy. The rate of dehydrochlorination increases with the HCI content of the atmosphere. The rate of molecular enlargement also increases but only as a result of the increased dehydrochlorination rate. The increase in M _w and LCB are thus related to the extent of conversion only. Changes in the UV spectra indicate that the increase in rate of dehydrochlorination is mainly due to increased propagation rate in atmospheres containing less than 10% HCI. At higher HCI contents an increase in initiation rate is noted. It is suggested that this, at least in part, is due to the fact that HCI, by forming a cyclic transition state, catalyzes the random elimination of HCI. This process, in turn, is promoted by the presence of polyene sequences.     

Stabilization of gamma-irradiated poly(vinyl chloride) by epoxy compounds. III. Conjugated double bonds and degree of unsaturation in gamma-irradiated PVC–stabilizer mixtures

The concentration of conjugated polyene sequences was studied in γ-irradiated PVC with 4% admixture of four epoxy stabilizers: diglycidyl ether of 2,2-bis(4-hydroxy-3-methylphenyl)propane (I), styrene oxide (1,2-epoxy ethyl benzene) (IV), epoxidized ricinus oil (VI), and epoxidized soybean oil (Drapex 6.8) (VII). As in the former investigations (Papers I and II), the process of the formation of the polyenes occurs in two stages. The concentration of polyene sequences with n double bonds, H_n the total amount of polyene sequences, ∑H_n, the average length of the polyene sequence, n , and the two extents of reaction x and p, were computed. The stabilizing effect of all compounds used agrees with the increasing content of epoxy groups. The addition of stabilizers diminishes the value of n . The decrease of the fraction of long sequences and the increase of short ones occurs. Apart from the binding of evolved HCl, the protective effect towards the macromolecules of PVC consists mainly in the inhibition of growth of chain dehydrochlorination by the epoxy groups.     

Kinetics and mechanism of the thermal degradation of poly(vinyl chloride)

The kinetics of the thermal degradation of solid powdered poly(vinyl chloride) (PVC) under nitrogen was studied by thermogravimetry, rate of hydrogen chloride evolution, and rate of polyene sequence formation. These results are accommodated by a chain mechanism involving initiation by random dehydrochlorination at normal monomer residues of PVC, and a series of intermediates, each leaking to a stable conjugated polyene sequence. Structural irregularities such as allylic and tertiary chlorine are responsible for a fast initiation process at the very beginning of the degradation. Mean rate constants and activation parameters for random initiation, propagation, and termination reactions of the PVC degradation chain were calculated by simulation. Activation enthalpy/entropy correlations for the experimental data available for dehydrochlorination of chloroalkanes and chloroalkenes in the gas and in the liquid phase or nonpolar solvents and elementary reactions of PVC degradation show that initiation is an HCl elimination through a transition state of four centers requiring a synperiplanar conformation of the >CH–CCl< group, whereas propagation is a dehydrochlorination through a transition state of six centers requiring a cis configuration of the double bond.     

Phosphate ester groups‐containing ricinoleic acid‐based Ca/Zn: Preparation and application as novel thermal stabilizer for PVC

Phosphate ester groups containing ricinoleic acid‐based Ca/Zn (LPPRA‐Ca and LPPRA‐Zn) stabilizer was successfully synthesized from ricinoleic acid (RA) and used as thermal stabilizers for poly(vinyl chloride) (PVC). These thermal stabilizers were characterized by Fourier transform infrared spectrometry, ¹H nuclear magnetic resonance, and inductively‐coupled plasma atomic emission spectroscopy. The effects of LPPRA‐Ca/LPPRA‐Zn, CaSt₂/ZnSt₂, and other stabilizers on the thermal stability of PVC were studied through Congo Red test, discoloration tests, thermogravimetric analysis (TGA), TGA–infrared, and TGA–mass spectrometry. The thermal stability tests show that LPPRA‐Ca/LPPRA‐Zn displays the best initial color stability and long‐term thermal stability for PVC. The superior performance is attributed to the synergistic effect of LPPRA‐Ca and LPPRA‐Zn. Moreover, a lower Zinc content of LPPRA‐Zn in PVC helps to decrease the “zipper dehydrochlorination” of the product, which contributes to a better initial thermal stability. Except for the better stabilization performance, LPPRA‐Ca/LPPRA‐Zn also displays better plasticization performance for PVC compared with other stabilizers. A possible stabilizing mechanism of PVC/LPPRA‐Ca/LPPRA‐Zn system was presented. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45940.     

Study on lanthanum‐pentaerythritol alkoxide as a thermal stabilizer for rigid polyvinyl chloride

Lanthanum‐pentaerythritol (La‐PE) alkoxide, a polyol‐based metal alkoxide, had been synthesized and used as a thermal stabilizer for polyvinylchloride (PVC) . Thermogravimetric (TG), differential thermal analysis (DTG), mass spectrum (MS), and Fourier transform infrared (FTIR) spectroscopy were used to confirm the synthesis reaction. The thermal stability of rigid PVC stabilized with La‐PE was tested by means of the Congo Red test, conductivity test, thermal aging test, thermal gravimetric analysis (TGA), and UV‐visible (UV‐vis) spectroscopy. The results showed that addition of La‐PE could significantly prolong static stability time of PVC and increase the apparent activation energy for degradation reaction. The oven aging test showed that La‐PE could improve the initial color of PVC. Moreover, addition of La‐PE could significantly reduce the concentrations of the conjugated double bonds of PVC and reduce weight loss . The possible thermal stability mechanism had also been discussed. Besides having good ability to neutralize hydrochloric acid (HCl), La‐PE could substitute or inactivate the labile chlorine atoms in the PVC chains. J. VINYL ADDIT. TECHNOL., 23:55–61, 2017. © 2015 Society of Plastics Engineers     

Structural changes of PVC in PVC/LDPE melt‐blends: Effects of LDPE content and number of extrusions

This paper investigates the structural changes of polyvinyl chloride (PVC) in melt‐blends of a low‐density polyethylene (LDPE) and polyvinyl chloride (PVC), and the effects of LDPE content and number of extrusion passes. These effects were examined in terms of changes in weight average molecular weight and number average molecular weight, polyene and carbonyl indices, color changes of the blend, and the variations in glass transition and decomposition temperatures. It was found that loading LDPE into PVC led to the formation of short‐chain LDPE grafted PVC (s‐LDPE‐g‐PVC) copolymers, via a macro‐radical cross‐recombination reaction, which had greater weight average molecular weight with unchanged number average molecular weight, increased decomposition temperature, lower glass transition temperature, as compared to the pure PVC sample. The dehydrochlorination reaction of PVC was suppressed by the macro‐radical cross‐recombination reaction with addition of LDPE, the effect being more pronounced at 13.0 wt% LDPE. For a given LDPE content, the macro‐radical cross‐recombination and dehydrochlorination reactions competed with one another, thus causing the increases in molecular weight average and molecular weight number up to the 4th extrusion pass. At the 5th extrusion pass, the dehydrochlorination reaction was predominant owing to a depletion of LDPE content to be grafted onto PVC molecular chains. The glass transition and decomposition temperature decreased with increasing number of extrusion passes. Polym. Eng. Sci. 44:487–495, 2004. © 2004 Society of Plastics Engineers.     

Zinc maleate and calcium stearate as a complex thermal stabilizer for poly(vinyl chloride)

Zinc maleate (ZnMA) and calcium maleate (CaMA) were synthesized by reaction of maleic acid with the corresponding metal oxides and were characterized by X‐ray diffraction, thermal analysis, and Fourier‐transform infrared (FTIR) spectroscopy. The thermal stabilizing effects of ZnMA and CaMA on poly(vinyl chloride) (PVC) were investigated at 180°C in air by a static stability test. The stabilization mechanism of ZnMA and the synergism of ZnMA/CaSt₂ (St = stearate) were also studied by UV‐visible and FTIR spectroscopies, as well as a thermal stability test. The PVC with the ZnMA stabilizer exhibited good thermal and color stability caused by the ability of ZnMA to replace the labile chlorine atoms in PVC chains, absorb hydrogen chloride, and react with the polyene intermediates via a Diels–Alder mechanism. The gel content of the PVC/ZnMA samples reached 31% after 2 min of heating and 44% after 10 min, thereby indicating that crosslinking could easily occur with ZnMA, probably owing to catalysis by Zn species. The static and dynamic stability results showed that the synergistic effect of the ZnMA/CaSt₂ stabilizer was greater than that of ZnSt₂/CaSt₂. J. VINYL ADDIT. TECHNOL., 20:1–9, 2014. © 2014 Society of Plastics Engineers     

CaSt_2和ZnSt_2对硬质PVC热稳定作用的热重分析研究

采用刚果红法和热烘箱法研究了CaSt2和ZnSt2及其按不同比例混合的混合物对PVC热稳定性能的影响,采用热重分析技术考察了PVC在180℃条件下恒温1 h的热损失变化情况和在20℃/min等速升温速率下30~500℃范围内的热损失情况。热稳定实验结果表明:CaSt2有利于延长PVC的长期热稳定时间,但不利于其初期着色性;ZnSt2有利于PVC的初期着色性,但不利于其长期热稳定性。热重分析结果表明:这种现象的出现是因为CaSt2有效降低了PVC脱HCl的速率,而ZnSt2加速了PVC脱HCl反应的发生。     

Effect of lanthanide (La(III))‐containing ionomer on thermal stabilization of poly(vinyl chloride)

A type of lanthanide (La(III))‐containing ionomer based on acrylate processing aid (ACR) for poly (vinyl chloride) (PVC) was synthesized, and influence of the ionomer on thermal stabilization of PVC was investigated with visual color comparison and Congo red methods. Results revealed that the ionomer with a suitable La(III) content behaved as a good costabilizer to PVC. It was able to extend static stabilization time of PVC and postpone “zinc burning.” The stabilizing efficiency of the ionomer to PVC depended on ion content, which was discussed in terms of Eisenberg–Hird–Moore model. Moreover, Fourier transform infrared test verified that this ionomer can react with zinc stearate (ZnSt₂) to form some new structures, which is responsible for postponing “zinc burning.” The ionomer and epoxidized soybean oil exhibited a synergistic effect on the stabilizing efficiency of calcium stearate (CaSt₂)/ZnSt₂ stabilizer to PVC compounds. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and application of an ultraviolet curable coating containing nanoscale α‐aluminum oxide

This study focuses on the preparation of an organic–inorganic ultraviolet (UV) curable coating containing the nanoscale α‐aluminum oxide (α‐Al₂O₃) powder and UV curable resin. This developed coating can form a protection film on the poly(vinyl chloride) (PVC) plastic tile surface. Thus, the abrasion resistance of the PVC plastic tile surface is improved. Besides, the adhesion between this UV cured film and the PVC plastic tile surface is well. After treatment with the UV curable coating that contains 6 wt % α‐Al₂O₃, the abrasion resistance of the PVC plastic tile surface can be improved up to 57%. From the result of a scanning electron microscopy (SEM) mapping photograph, it shows that the nanoscale α‐Al₂O₃ powder is well dispersed in the cured coating film. Under the wavelength of the visible light in the range of 400–800 nm, the degree of transparency for the coated film on poly(ethylene terephthalate) (PET) sheet is about 82–90%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5747–5752, 2006     

Chemical modification of rigid poly(vinyl chloride) by the substitution with nucleophiles

The reaction of rigid poly(vinyl chloride) (PVC) with iodide, hydroxide, azide, and thiocyanate as nucleophiles (Nu) in ethylene glycol (EG) resulted in the substitution of Cl by Nu additional to the elimination of HCl, leading to the dehydrochlorination of the rigid PVC. High substitution rates were observed for hydroxide, azide and thiocyanate, while the addition of iodide accelerated predominately the elimination of HCl. The substitution by thiocyanate resulted at 150°C in both thiocyanate and isothiocyanate structures, whereas at 190°C, only isothiocyanate was observed in the polymer. The dehydrochlorination yield increased with an increasing molar SCN/Cl ratio, resulting in a maximum substitution at high molar SCN/Cl ratios. When EG was replaced by diethylene glycol (DEG) as solvent, the dehydrochlorination was found to be accelerated. It was assumed that DEG has a higher compatibility with PVC, making it easier to penetrate the rigid PVC particle. For triethylene glycol (TEG), the rapid dehydrochlorination resulted probably in the coverage of the surface of the PVC particle by methyl methacrylate/butadiene/styrene (MBS), preventing the penetration by the solution. The substitution/dehydrochlorination ratio decreased in the order of EG > DEG > TEG because of the declining polarity of the solvent, stabilizing the activated S_N2 complex. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Insights into the use of zinc–mannitol alkoxide as a novel thermal stabilizer for rigid poly(vinyl chloride)

Zinc–mannitol alkoxide (Zn–Man) was synthesized through alcohol exchange reaction, and investigated by means of Fourier transform infrared spectroscopy and elemental analysis. The thermal stability of Zn–Man for rigid poly(vinyl chloride) (PVC) was evaluated by Congo red testing, conductivity measurements, thermal aging testing, thermogravimetric analysis (TGA), and ultraviolet–visible (UV–vis) spectroscopy test. The experimental results demonstrate that the addition of Zn–Man not only apparently prolonged the static thermal stability time to approximately 96.5 min but also evidently improved the initial color of PVC. More importantly, the color of the PVC sheets stabilized with Zn–Man did not change to black within 180 min; this showed that no zinc‐burning phenomenon occurred. In addition, the results of TGA reveal that Zn–Man raised the initial degradation temperature of PVC to about 273.4°C. UV–vis testing indicated that the presence of Zn–Man decreased the content and shortened the length of the conjugated double bonds of PVC. The possible thermal stability mechanism is discussed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42038.     

Visible light photocatalytic activity of TiO2/heat‐treated PVC film

BACKGROUND: Semiconductor TiO₂ has been investigated extensively due to its chemical stability, nontoxicity and inexpensiveness. However, the wide band gap of anatase TiO₂ (about 3.2 eV) only allows it to absorb UV light. TiO₂ nanoparticles modified by conditional conjugated polymers show excellent photocatalytic activity under visible light. However, these conjugated polymers are not only expensive, but also difficult to process. Polyvinyl chloride (PVC) was heat‐treated at high temperature to remove HCl and a C?C conjugated chain structure was obtained. When TiO₂ nanoparticles were dispersed into the conjugated polymer film derived from PVC, this composites film exhibited high visible light photocatalytic activity. RESULTS: The photocatalytic activity of TiO₂/heat‐treated PVC (HTPVC) film was investigated by degrading Rhodamine B (RhB) under visible light irradiation. The photodegradation of RhB follows apparent first‐order kinetics. The rate constants of RhB photodegradation in the presence of the TiO₂/HTPVC films with different mass content of TiO₂ are 16–56 and 4–14 times that obtained in the presence of the pure HTPVC and TiO₂/polymethyl methacrylate (PMMA) composite film, respectively. The TiO₂/HTPVC film showed excellent photocatalytic activity and stability after 10 cycles under visible light irradiation. CONCLUSION: TiO₂/HTPVC film exhibits high visible light photocatalytic activity and stability. Copyright © 2012 Society of Chemical Industry     

Thermal stabilization of PVC with khaya seed oil: Thermogravimetric studies

Thermal degradation of PVC stabilized with barium and cadmium soaps of Khaya senegalensis seed oil was studied by thermogravimetry up to 500°C using a constant heating rate of 10°C min⁻¹. At temperatures below 300°C, the extents of dehydrochlorination of both the unstabilized and stabilized PVC samples were low (less than 6% conversion). It was found from the values of weight loss that HCl was the only volatile product of degradation of PVC between 170 and 200°C. The rates of dehydrochlorination at about 200°C was of the order of 10⁻²% min⁻¹, about the same order of magnitude as the values obtained from kinetic studies. The temperatures at which maximum rates of degradation were attained, t_dmax, and the temperatures at which various extents of degradation were attained were used to assess the effectiveness of the metal soaps of Khaya seed oil in stabilizing PVC against thermal degradation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1432–1438, 2000