Synergistic effect of metal soaps and natural zeolite on poly(vinyl chloride) thermal stability

The synergistic effect of metal soaps (zinc stearate and calcium stearate) and/or natural zeolite (clinoptilolite) on PVC thermal stability was investigated. For this purpose, PVC plastisol was prepared by mixing poly(vinyl chloride) (PVC) and dioctyl phthalate (DOP) and stabilized with different amounts of metal soaps and zeolite. Kinetic studies of dehydrochlorination at 140 and 160°C were done for unstabilized and stabilized PVC plastigels using 763 PVC Thermomat equipment. The stabilizing effect of zeolite on the increase in the induction period of the sample was considered to result from the absorption of HCl, a property that was thought to reduce the autocatalytic effect of HCl evolved at the initial stages of dehydrochlorination. Since the induction time of the sample having 0.53% of zinc stearate and 0.53% of zeolite was higher than those of the PVC plastigels having only zinc stearate or zeolite, the synergistic effect on thermal stability was observed at low levels of these additives. J. VINYL. ADDIT. TECHNOL., 11:47–56, 2005. © 2005 Society of Plastics Engineers     

DEVELOPMENT OF SYNERGISTIC HEAT STABILIZERS FOR PVC FROM ZINC BORATE-ZINC PHOSPHATE

The importance of flame-retardant and smoke-suppressed poly(vinyl chloride) (PVC) compositions is increasing gradually in the polymer industry since PVC releases smoke and toxic gases (hydrogen chloride, HCl) during heating at temperatures above 140°C with the result of dehydrochlorination reaction. In this study, the synergistic effects of zinc borate (ZB)-zinc phosphate (ZP) on the thermal stability of PVC were investigated using thermal techniques. The induction and stability time values of PVC plastigels were obtained at 140° and 160°C. The results revealed that PVC plastigels having only ZP and ZB retarded dehydrochlorination of PVC compared with the unstabilized sample. However, the plastigels with both ZB and ZP had a superior synergistic effect on char formation of PVC. Since the induction periods of the samples having both ZB and ZP were higher than those of the unstabilized samples having only ZB or only ZP, the synergistic effect was observed.     

含氯废弃物燃烧过程中HCl排放特性

引　言生活垃圾中含有的有机氯主要以PVC塑料的形式存在 ,我国塑料制品中PVC占 30 %以上 ;无机氯通常以NaCl的形式存在于厨余中 ,单独焚烧厨余物 (主要含无机氯化物 )会导致大部分氯化物转化为HCl[1] .郭小汾等[2 ] 研究了PVC的燃烧特性和HCl的析出机理 ,认为PVC的燃烧过程分为     

Thermal stability and chemical durability of PVC‐based biomedical devices

Poly(vinyl chloride) (PVC)‐based blood circuits for extracorporeal hemodialysis were investigated for the assessment of their thermal stability as well as their chemical durability towards ionizing radiation sterilization and environmental conditions of storage and transportation. Thermal degradation was monitored by measuring the amount of hydrochloric acid (HCl) evolved as a function of different thermal stresses. HCl was extracted from the internal lumen of the blood circuits, and then quantitatively evaluated under the corresponding form of chloride ions by chromatographic technique (HPLC‐IC). Behavior of PVC heat stabilizers was evaluated as well, determining also the concentration of calcium and zinc released by the investigated materials, by flame atomic absorption spectroscopy (FAAS) technique. Electron beam irradiation revealed an impact on blood tubing higher than that of environmental storage conditions. Nevertheless, real operative cases of sterilization and storage conditions turned out to be quite safe, and all blood circuits displayed good performances in terms of thermal stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5378–5387, 2006     

Comparison of dynamic and static degradation of poly(vinyl chloride)

The thermal degradation of PVC was measured under dynamic and static conditions. The UV and IR spectra, as well as the molecular weight distribution of the PVC samples, taken after different time intervals were measured. It was established that during the dynamic PVC degradation, performed in a mixing chamber, two stages with different degradation rates can be distinguished both in extinction and torque vs. time curves. While oxygen does not, dissolved HCl does play an important role in the dynamic degradation: HCl steps into reaction with the formed polyenes and has a catalytic action. The chemical degradation, particularly the crosslinking, produces the changes in the rheological behavior of the material. Results were compared with those obtained under static conditions in argon, air, and HCl atmosphere.     

Thermal degradation behavior of poly(vinyl chloride) in presence of poly(N‐acryloyl‐N′‐cyanoacetohydrazide)

The thermal degradation behavior of poly (vinyl chloride), PVC, in presence of poly(N‐acryloyl‐N′‐cyanoacetohydrazide), PACAH, has been studied using continuous potentiometric determination of the evolved HCl gas from the degradation process from one hand and by measuring the extent of discoloration of the degraded samples from the other. The efficiency of blending PACAH with dibasic lead carbonate, DBLC, conventional thermal stabilizer has also been investigated. A probable radical mechanism for the effect of PACAH on the thermal stabilization of PVC has been proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Poly(ethylene glycol)–polyhedral oligomeric silsesquioxane as a novel plasticizer and thermal stabilizer for poly(vinyl chloride) nanocomposites

The plasticizing and thermostabilizing effect of poly(ethylene glycol)–polyhedral oligomeric silsesquioxane (PEG‐POSS) on poly(vinyl chloride) (PVC) is discussed thoroughly in this work. As PEG‐POSS content increases, PVC becomes more flexible and the decomposition temperature of PVC increases slightly. Meanwhile, the temperature of maximum HCl emission is elevated from 265.3 °C in neat PVC to 285.7 °C in PVC nanocomposites, with the peak intensity of HCl emission decreased by 30.8%, and a new lower intensity of HCl emission peak appearing at much higher temperature (around 370 °C), which is in accordance with the maximum degradation temperature of PEG‐POSS. Thereby, a possible dehydrochlorination mechanism is suggested according to the fact that the electron donor effect of ether groups would stabilize the C? Cl bonds by means of more electron cloud stacked in those bonds, which agrees with Fourier transform infrared and X‐ray photoelectron spectroscopy experiments in terms of hydrogen bonds. © 2016 Society of Chemical Industry     

Heat distortion temperature modification of rigid PVC and chlorinated PVC: A method to produce low smoke compositions

The use of a new low smoke, heat distortion temperature modifier for rigid PVC and chlorinated PVC is discussed. This material, CN-1427, is a tetrabromobisphenol A carbonate oligomer which is compatible with vinyl compositions. The carbonate oligomer can be compounded into PVC resin to improve heat distortion temperature of PVC and CPVC by 20–30°C. Unlike conventional HDT modifiers, brominated carbonate oligomers do not increase smoke evolution during flammability testing. Thus, using carbonate oligomer technology, it is possible to achieve low smoke, Class I (ASTM E-84) and V-O flammability (UL-94) performance. Vinyl compositions, modified with the carbonate oligomer described in this work, can be utilized as an alternative to expensive engineering thermoplastics. This paper reports recent studies on the use of carbonate oligomers as heat distortion temperature modifiers for low smoke vinyl applications. Formulation information addressing flammability and physical property performance is presented in detail.     

Update on smoke toxicity of vinyl compounds

All organic materials burn and give off toxic products. These always include water, carbon dioxide, and the single gas causing the greatest hazard in fires—carbon monoxide (CO). The intrinsic toxicity of the smoke of all combustible materials, including PVC, is very similar in terms of lethality, with very few exceptions. Toxicity of vinyl compounds is due to two major gases: CO and hydrogen chloride (HCI). Since natural combustible materials are not chlorinated, speculation has arisen about the toxicity of HCl and of PVC smoke. Recent studies have shown that it takes similar doses of HCl and CO to kill rats. Furthermore, rats and baboons will tolerate the same levels of HCl. However, mice are much more sensitive than either rats or baboons towards HCl. Baboons are a very good model for humans; therefore, mice will be killed by exposure to much lower HCl levels than those required to kill humans. HCl concentrations in real fires are quite low: HCl decays rapidly by reacting with wall materials such as gypsum, cement, or ceiling tile. It does not, however, react rapidly with plastic or glass walls, which is where toxicity tests are carried out. Therefore PVC smoke is less hazardous in reality than it appears to be from toxicity test results. Since most products have similar intrinsic toxicities, as regards lethality, the real toxicity in a fire is a consequence of the rate of generation of gases. PVC is a difficult polymer to ignite and burns very slowly, so that it will give off less toxic products per unit time than many other common materials and cause lower fire hazard.     

Silane‐modified PVC pervaporation membranes for bromoform/water separation

The transport properties of a unique family of silane‐modified poly(vinyl chloride) (PVC) pervaporation membranes for the separation of halogenated hydrocarbons from water were investigated. The PVC was modified by using a vinyl silane to improve its resistance to attack by halogenated hydrocarbons and to increase the flux. Two preparation routes were used: Route i included an initiator to promote the vinyl reaction before the hydrolysis and condensation of the methoxy silane group, whereas Route ni did not. The structures of the membranes were characterized and related to the transport properties, as derived from batch pervaporation experiments. The permeability of unmodified PVC membranes increases with exposure to haloorganics at low concentrations. Initially, the modified membranes exhibited a higher permeability than PVC and a lower selectivity. At long pervaporation times, the silane‐modified membranes exhibited a higher selectivity than PVC. The different preparation routes led to different morphologies, which affected the performance of the membranes; Route ni membranes exhibited higher permeabilities and selectivity than Route i membranes. Rubbery polydimethylsiloxane membranes were resistant to haloorganics but their high water permeability and low selectivity make them unsuitable for this pervaporative separation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1429–1438, 2001     

Chemically crosslinked poly(vinyl chloride)

The effect of mixing time, temperature, and thermal treatment on mechanical properties of crosslinked PVC is investigated. The tensile properties and gel content of crosslinked and uncrosslinked PVC molded samples are evaluated. The cured samples exhibited higher tensile strength and thermal stability than unmodified PVC.     

气相色谱-质谱法研究聚氯乙烯的热裂解行为

采用气相色谱-质谱法并结合热重分析法对聚氯乙烯(PVC)的热裂解行为进行了研究。首先对PVC的热失重行为进行考察,确定最佳裂解温度;然后分别在350℃和600℃下对PVC进行热裂解,并用气相色谱-质谱联用仪对裂解产物进行定性和半定量分析。结果表明:在350℃下,PVC裂解产物主要以HCl和苯等易挥发物质为主;在600℃下,裂解产物为多环芳烃,但未检测到HCl。根据裂解产物的种类及相对含量的变化,确定PVC的分段裂解回收工艺,从而提高了热裂解产物的回收率和热裂解效率。     

TG-FTIR分析技术在PVC热降解过程研究中的应用

利用热失重-红外光谱联机分析技术(TG-FTIR)研究了聚氯乙烯(PVC)共混物在氮气气氛下、30～900℃范围内的热降解行为。结果表明:PVC共混物的热降解过程可分为3个阶段,分别在200～380℃,380～570℃和570～758℃范围内。其中,第一阶段主要为PVC脱HCl反应阶段,热降解产物主要为HCl;第二阶段主要为共轭多烯结构的裂解和环化,产物为低烃类化合物、苯及其衍生物;第三阶段为碳酸钙的分解反应,产物为CO2。     

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     

Enhancement of Photostabilization of Poly(vinyl chloride) Doped with Sulfadiazine Tin Complexes

New sulfadiazine tin complexes were synthesized in 67–80% yields from the reaction of sulfadiazine, and different organotin(IV) chlorides and their structures were established. The synthesized complexes were used as additives at a low concentration (0.5% by weight) to enhance poly(vinyl chloride) (PVC) photostability. The PVC samples containing sulfadiazine tin complexes (thickness = 40 μm) were fabricated and irradiated with ultraviolet light at room temperature for 300 h. The changes that occurred within the PVC samples upon irradiation were investigated by inspecting the loss in weight, reduction in the average molecular weight, formation of small degradation fragments containing polyene, carbonyl, and hydroxyl moieties, and changes in the ultraviolet absorption intensity of polymeric materials. The surface morphology of irradiated PVC samples was investigated using optical, atomic force, and scanning electron microscopies. There were lesser changes within the PVC samples with sulfadiazine tin complexes compared to the blank PVC sample. The dimethyltin(IV) complex was found to be the most efficient additive in stabilizing PVC against irradiation. The role played by the complexes in reducing the photodegradation of PVC was investigated, and a mechanism was proposed. J. VINYL ADDIT. TECHNOL., 26:370–379, 2020. © 2019 Society of Plastics Engineers     

Über die Spaltung von PVC mit Alkali in Tetrahydrofuran

With the objective of scanning the molecular structure of PVC, its reaction with alkali in tetrahydrofurane which has been published previously was reexamined in detail. It was found that, stirring of a 1% solution of PVC in THF with KOH/MeOH at room temperature or 60°C for 90 min yields a product which has only two-thirds of the original K-value. If reacted at room temperature 16 molecules of HCl per 100 VC-units will be eliminated, obtaining at the same time 12 double bonds and the introduction of 2 oxygen atoms. If the splitting is performed at 60°C, 30 molecules of HCl per 100 VC-units will be eliminated obtaining 15 double bonds and the introduction of 10 oxygen atoms. Analysis by gelpermeation chromatography in combination with balance of materials indicates that parallel to chain splitting an increase in molecular weight takes place possibly by intermolecular elimination of HCl. As compared to reactions with low molecular weight compounds the possibility will be discussed that the splitting of the chain in THF could have proceeded at a head-to-head-addition site after HCl elimination followed by saponification (retroaldolreaction).     

环氧化天然橡胶/PVC共混物的热氧降解

采用热重－差示热重分析和差热分析了环氧化天然橡胶（ENR）／PVC共混物的热氧降解过程,结果表明,炭黑补强的ENR／PVC共混物的热氧降解过程分为3个阶段,第1阶段主要是PVC脱氯化氢,而氯化氢引起ENR发生催化氧化反应而放热,且该阶段明显受到ENR／PVC共混比的影响,随着PVC用量的增大,共混物的热氧稳定性下降。     

Lignin‐based carbon fibers: Accelerated stabilization of lignin fibers in the presence of hydrogen chloride

Organosolv switchgrass lignin (SGL) and hardwood lignin (HWL) polymers are used as precursors to prepare low cost carbon fibers (CFs). Lignin powder and fiber samples are stabilized and carbonized at different conditions to investigate the effect of HCl on thermal‐oxidative stabilization time, mass yield, fiber diameter, and mechanical properties. The results show that HCl can accelerate stabilization and reduce the stabilization time from many hours to 75 min for the SGL fibers, and to 35 min for the HWL fiber. The rate of rapid stabilization in HCl/air is at least four times faster than conventional stabilization in air. The CFs prepared with two different stabilization methods have almost the same strength and modulus, but higher carbon yield is obtained with the rapid stabilization due to a short time of oxidation. Pores and defects observed on the surface and the cross‐section of the CFs across all stabilization conditions contribute to low fiber strength. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45507.     

医疗废物典型组分在热解/焚烧过程中无机氯的析出特性

  为研究医疗废物典型组分热解/焚烧过程无机氯的析出特性,检测了不同热解温度、焚烧温度和气流量等工况下无机氯的释放,分析了多种典型组分对输液管无机氯析出特性的作用。结果表明,工况变化对医疗废物无机氯总析出的影响不大,对Cl-Cl₂和Cl-HCl转化率的影响相对明显。与单组分输液管相比,输液中加入纤维物质明显地促进Cl₂的生成,但对HCl的生成表现出一定的抑制作用;而橡胶的存在对HCl抑制作用最为显著,使Cl-HCl转化率有很大程度地降低。     

The roles of polyacrylate in poly(vinyl chloride)‐lignin composites

A novel method was adopted to improve the adhesion between lignin particles and poly(vinyl chloride) (PVC) matrix in PVC‐lignin composites. Lignin was treated with a polyacrylate, poly(ethyl acrylate‐co‐acrylic acid), and the composites was prepared with PVC and the treated lignin. The mechanical properties and morphology of the composites were investigated, and the roles of polyacrylate in the composites were discussed. The results show that both the tensile and impact strengths of the composites are improved when both the content of carboxyl in polyacrylate and its dosage are low, and the optimum is: yield strength, 24.17 MPa, higher than that of PVC control (21.88 MPa); breaking strength, 33.59 MPa, close to that of PVC control (35.62 MPa); and impact strength, 8.0 kJ m⁻², 31% higher than that of PVC control (6.1 kJ m⁻²). Microscopic morphology analysis suggests that polyacrylate improved the adhesion between lignin particles and PVC matrix. The roles of polyacrylate are as the following: polyacrylate is combined with lignin by hydrogen bond and ester bond, and most of its chains spread into PVC matrix due to its good compatibility with PVC, thereby lignin particles can be well bound with PVC matrix. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers