New insights into the degradation mechanism of poly(vinyl chloride), based on the action of novel costabilizers. I.

Recent legislation introduced to limit the use of heavy metal stabilizers (cadmium based) in poly(vinyl chloride) (PVC) has necessitated the use of organic costabilizers as adjuncts to alternative main stabilizer systems (barium/zinc or calcium/zinc). It has been suggested in the literature that costabilizers substitute allylic chlorine by a C‐alkylation reaction; costabilizers act as reverse catalysts for the initiation of degradation by complexing the π‐electron sites that would otherwise have an activating affect on labile chlorines; and costabilisers destroy carbonylallyl active sites by proton donation. To rationalize this debate, the focus of this paper is to elucidate the type of interactions that occur between a model compound for PVC and the novel costabiliser N‐phenyl‐3‐acetylpyrrolidin‐2,4‐dione (P24D). The model compound chosen was 4‐chloro‐2‐hexene (4C2H), which simulates the in‐chain allylic chlorine impurities present in PVC and are considered the most labile defects present in the polymer. Results suggested that stabilisation involves concerted reactions involving metal complexes rather than a series of stepwise reactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2731–2743, 2004     

环保型钙/锌PVC热稳定剂的发展现状

环保型热稳定剂是世界PVC热稳定剂发展的重要方向。分析了国内外PVC热稳定剂的发展趋势,讨论了当今环保型热稳定剂的主要优缺点,介绍了内外环保型钙/锌PVC热稳定剂的技术进展,并对国内环保型钙/锌PVC热稳定剂发展方向进行了预测。     

新型β-二酮辅助热稳定剂DBM-S和SBM-S的应用

将新型β-二酮类辅助热稳定剂DBM-S和SBM-S分别与传统的β-二酮辅助热稳定剂DBM和SBM应用效果进行对比,结果表明,在粉状钙锌复合热稳定剂中,用新型辅助热稳定剂代替传统的辅助热稳定剂,热稳定效能基本不变,但添加新型辅助热稳定剂的复合热稳定剂及其所稳定的PVC制品的存放变色情况明显减轻,同时能显著提高PVC制品的耐候性。     

Design of green zinc‐based thermal stabilizers derived from tung oil fatty acid and study of thermal stabilization for PVC

In this study, a new type of mixed calcium (Ca) and zinc (Zn) thermal stabilizers was prepared and evaluated for poly(vinyl chloride) (PVC) thermal stabilization. The mixed stabilizers were based on the Ca and Zn salts of polycarboxylic acid derived from eleostearic acid—the dominant fatty acid of tung oil fatty acids. Eleostearic acid was converted to a 21‐carbon diacid (C21DA) and a 22‐carbon triacid (C22TA), respectively, which were subsequently turned into calcium (Ca) and zinc (Zn) salts. Thermal stability of PVC compounds was examined by thermogravimetric analysis (TGA), discoloration test, Congo red test, and thermal decomposition kinetics. In comparison, commercial mixed Ca/Zn thermal stabilizers composed of stearate salts (CaSt₂/ZnSt₂), were employed as controls. Because the salts of C21DA, C22TA and stearate have different metal contents, thermal stabilization effects were compared on the basis of both equal salt weight and equal metal ion content. It was noted that under both cases the long‐term thermal stability of the PVC samples followed the order of C21DA‐Ca/C21DA‐Zn > C22TA‐Ca/C22TA‐Zn > CaSt₂/ZnSt₂. The results suggest that the mixed Ca/Zn salts based on tung oil‐derived polycarboxylic acids have higher metal ion contents and cycloaliphatic structures and can effectively improve the thermal stability of PVC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44679.     

Properties and reactions of metal terephthalates

Divalent metal terephthalates such as the zinc, calcium, barium, and cadmium salts appear, from their properties, to be polymeric. As a result, exceptionally high decomposition temperatures and unusually low solubilities are found. Although not in themselves vinyl heat stabilizers, in concert with typical mixed metal stabilizers, divalent metal terephthalates function as boosters and secondary stabilizers. In such capacity, they are characterized by little or no contribution to lubrication, odor, volatility, or moisture absorption.     

钙/锌稳定剂对硬质PVC制品耐候性能的影响

介绍了影响PVC硬制品耐候性能的因素,研究了钙/锌稳定剂对PVC硬制品耐候性能的影响。     

新型PVC用液体钙锌复合热稳定剂的合成与应用

对环氧油酸钙、锌皂的合成工艺,以及聚氯乙烯(PVC)用钙锌复合液体热稳定剂的配方进行研究,并探究了复合热稳定剂的协同效应。通过刚果红法、热老化烘箱法等,考察了钙/锌比、金属皂含量、亚磷酸酯、β-二酮、抗氧剂等对复合热稳定剂热稳定性能的影响,确定了这种液体复合热稳定剂配方。目前两种液体钙锌复合热稳定剂已经中试。     

环氧油酸钙(锌)的合成及在PVC中的应用

以油酸、甲酸和双氧水为原料合成了环氧油酸,经复分解反应制得了环氧油酸钙(锌)盐,将其作为热稳定剂应用于PVC中,通过电导率、热老化以及热失重测试来考察环氧油酸钙(锌)的热稳定特性。研究结果表明:环氧油酸钙具有长期热稳定性,环氧油酸锌具有初期热稳定性,当环氧油酸锌/环氧油酸钙的比例为1∶3时,PVC的热稳定效果最好。     

不同钙锌稳定剂的性能对比

采用刚果红法和转矩流变仪法分析了不同厂家生产的不同型号钙锌稳定剂的热稳定性能和流变性能.结果 表明:不同厂家生产的不同型号钙锌稳定剂的热稳定性能和流变性能各不相同,具有专有性强、通用性低的特点.使用钙锌稳定剂生产PVC制品时,应根据不同钙锌稳定剂的具体性能特点,合理确定配方和工艺参数,确保生产的正常进行.     

无毒钙-锌稳定剂的合成与性能研究进展

钙锌类稳定剂具有高效、廉价、无毒的特点,有很好的发展前景.综述了近十年来钙锌类热稳定剂的合成与性能研究的进展情况.目前,钙锌热稳定剂的研究方向包括研究开发新型钙锌热稳定荆,如设计引入多(二)元羧酸钙锌盐或一些基团(环氧基等),以提高热稳定性、增加相容性;研究新型吸收HCl气体的无机和有机化合物与钙锌体系协同并用,以开发钙锌复合体系产品.     

Removal of zinc from dilute aqueous solutions by galvanochemical treatment

The possibility of zinc removal, a common toxic metal, from simulated liquid effluents by the application of a novel treatment method, termed galvanochemical, was investigated. The galvanochemical process is considered as a simple, economic, friendly to the environment, method, which does not create harmful end‐products. Synthetic wastewaters were examined, these contained concentrations of zinc commonly found in real wastewaters from small‐to‐medium size industrial units, such as metal‐plating or metal‐treatment plants. These liquid wastes pose an important environmental problem, due to the content of heavy metals. The optimization of the main operating parameters was the objective of the study. The galvanic pair scrap ratio iron:coke was used for these investigations. It was found that the use of the galvanic pair mixture of 80 g dm^?3 (weight per solution volume ratio), agitated at 160 rpm for 5 h, removed more than 90% of zinc from the initial solution, containing initially 50 mg dm^?3 of zinc. The scanning electron microscopy/energy disperse spectrometry (SEM/EDS) analysis performed on the products showed that zinc was adsorbed onto the coke to a small extent and that the zinc removal was mainly based on the adsorption of zinc onto the surface of active iron oxides formed as a result of galvanochemical reactions. Copyright © 2005 Society of Chemical Industry     

不同脂肪酸钙和脂肪酸锌热稳定作用机制研究

将硬脂酸钙/硬脂酸锌、月桂酸钙/月桂酸锌、癸二酸钙/癸二酸锌、亚磷酸-苯二异辛酯(PDOP)、季戊四醇(PER)作为稳定剂应用于聚氯乙烯(PVC)中,通过热老化法、电导法和紫外光谱分析法对比了上述不同脂肪酸钙和脂肪酸锌稳定剂的热稳定特性,并进一步研究了单独脂肪酸钙和脂肪酸锌的热稳定机理.结果表明:单独硬脂酸钙的热稳定性相对较好;硬脂酸钙/脂肪酸锌的协同效应相对较好;月桂酸钙/月桂酸锌/PDOP的协同效应最为明显;月桂酸钙/月桂酸锌/PER能有效抑制PVC降解形成共轭长链烯烃,硬脂酸钙/硬脂酸锌/PER能有效抑制PVC降解形成共轭短链烯烃;硬脂酸钙能吸收PVC降解所产生氯化氢,硬脂酸锌能置换PVC中的不稳定氯原子.     

不同配比钙／锌复合稳定剂对PVC—U性能的影响

采用转矩流变仪和白度颜色测定仪等设备,研究了钙／锌复合稳定剂中钙／锌比以及不同锌盐和硬脂酸钙的复配对PVC—U制品动态热稳定性能和加工流变性能的影响。结果表明：当m（Ca）：m（Zn）：5：4、加工温度为180℃时,PVC—U体系的动态热稳定时问为767S,具有良好的协同稳定作用;4种锌盐对PVC—U动态热稳定性能的影响顺序为：硬脂酸锌〉月桂酸锌〉硼酸锌〉乙酸锌,4种锌盐对PVC—U的加工流变性能影响相当。     

Environmentally friendly copolymeric beads of Chlorella vulgaris and poly(methacrylamide) grafted aliginic acid di‐block copolymers for biosorption of zinc ions

The synthesis of biodegradable environmentally friendly copolymeric beads for water treatment biosorption processes is demonstrated. The synthesized poly(methacrylamide) grafted aliginic acid copolymers were characterized using ¹H NMR, Fourier transform infrared spectroscopy, TGA and SEM. The di‐block copolymers showed a morphological change from two‐dimensional layer‐by‐layer structures to three‐dimensional well‐compacted wrinkles as grafting efficiency increased. The copolymeric beads were formed from the di‐block copolymer and algae crosslinked with 5% calcium ions (w/w). These copolymeric beads were then subjected to biosorption investigations for zinc ions as a model heavy metal ion at different pH values and stirring time periods. Batch adsorption experiments showed that the copolymeric beads were effective in zinc ion removal from aqueous solutions with maximum uptake exceeding 89.0 mg g^–1 using higher grafting efficiency copolymeric beads at pH 5.5. Equilibrium pH studies revealed that zinc biosorption was pH dependent and maximum uptake was obtained at pH 5.5. Dynamics studies showed that the biosorption of zinc was rapid with equilibrium attained within 40 min and the data followed pseudo‐second‐order kinetics. The equilibrium biosorption of zinc ions on the copolymeric beads exhibited a Freundlich isotherm fit. © 2012 Society of Chemical Industry     

Electrokinetic remediation of lead‐, zinc‐ and cadmium‐contaminated soil

Electrokinetic remediation of lead‐, zinc‐ and cadmium‐contaminated sand and clayey soils has been investigated under laboratory‐scale conditions. Soil extracts of heavy metals (by 1 M HCl solution) were analysed by optical emission spectrometry. The efficiency of electrochemical remediation was partially dependent on the pH of the soil media. With pH increase, the migration of heavy metal ions toward the cathode was limited. When acetic acid was added to the sandy soil, almost complete remediation was achieved. A clay layer inserted in the cathode area did enhance the remediation rate. The most effective clean‐up was achieved for zinc and cadmium, with less effective clean‐up being achieved for lead. The effectiveness of the electrokinetic remediation of heavy metal‐contaminated clayey soil was low. The appropriate acidity was not achieved using acetic acid because of the high buffering capacity of clay, and metal ion migration was impeded by its sorption onto some clay components. The conclusion was made that clays could be used as immobilizing media for heavy metal ions by electrokinetic remediation of various soils. © 2001 Society of Chemical Industry     

Influence of processing conditions on the leaching of thermal stabilizers from plasticized polyvinyl chloride in the presence of water

Plasticized PVC formulations for pharmaceutical packaging contain calcium and zinc stearates, which are PVC heat stabilizers. It was found in the literature that these additives can migrate to some aqueous solutions, especially when the pH is alkaline, the best example being sodium bicarbonate solutions. So, the aim of this work was to demonstrate the correlation between the lubricant ability of these stearates and their further migration in fluids. For this purpose, we studied the migration of calcium and zinc stearates during an extrusion step, focusing essentially on slip phenomenon. We have demonstrated here that slip phenomenon occurs in the case of plasticized PVC heat stabilized by calcium and zinc stearates. The slip phenomenon amplitude increases with the total amount of stearates in the formulation and also when the extrusion temperature decreases. The analysis of a die insert through scanning electron microscopy coupled with an X-ray energy dispersive technique could allow us to see that the additive mainly responsible for the slip is calcium stearate. The analysis of the leachable components of the formulations migrating after steam sterilization in sodium bicarbonate solutions leads to conclude that zinc stearate also migrates to the metal surface of the die during extrusion, but in a lower extent than calcium stearate. So, a good correlation exists between the processing conditions, including essentially the stearate concentration and the extrusion temperature, and the migration of these additives from the extruded sample to aqueous solutions. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2391–2400, 1998     

Effects of MgAlCe‐CO3 layered double hydroxides on the thermal stability of PVC resin

MgAlCe‐CO₃ layered double hydroxides (LDHs) with different Ce/Al molar ratios were prepared by the constant pH coprecipitation method. The synthesized materials were characterized by XRD and FTIR, and the results showed that the hydrotalcite‐like materials have a layered structure. Different LDHs as stabilizers were mixed with PVC resin. The tests of thermal aging and Congo red for the PVC composites were carried out at 180 ± 1°C, respectively. The results showed when MgAlCe‐CO₃‐LDHs were added into PVC as single thermal stabilizers, 3 phr (parts per hundred PVC resin) MgAlCe‐CO₃‐LDH with Ce/Al (molar ratio) = 0.075 has a better stabilizing effect on PVC than others. Compared with single thermal stabilizers (LDHs or Ca/Zn systems), the composite thermal stabilizers including 0.3 g calcium stearate (Cast₂), 1 g zinc stearate (Znst₂), and 3 g MgAlCe‐CO₃‐LDH have significantly enhanced the thermal stability of PVC sample, and the thermal stable time was over 190 min. The main reason could be concluded to the special structure of Ce element and the synergistic reaction among MgAlCe‐CO₃‐LDHs, Cast₂, and Znst₂. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A study of the processing characteristics and mechanical properties of multiple recycled rigid PVC

This study focuses on the ability of U‐PVC to be processed a number of times. Three different types of U‐PVC were investigated: virgin lead‐stabilized material; virgin calcium/zinc‐stabilized material; and reground, 20‐year‐old, post‐consumer windows. Each material was extruded four times, without any addition of any stabilizers. Samples were taken at each stage for rheological and mechanical analysis. J. Vinyl Addit. Technol. 10:174–178, 2004. © 2004 Society of Plastics Engineers.     

PVC热稳定剂的发展趋势

综述了聚氯乙烯(PVC)热稳定剂的发展历程、种类、特点、性能,提出了各类热稳定剂在目前的国内外法律法规要求下的发展方向。最具发展前景的热稳定剂为具有无毒、环保等特点的钙/锌类、水滑石类、稀土类、聚合物类以及他们的复配物;而开发高效的有机化合物类PVC热稳定剂也是发展的一个趋势。     

以氧化镁和氧化锌为主稳定剂的PVC的热稳定性和力学性能

用HAAKE流变仪研究了氧化镁／氧化锌稳定体系对聚氯乙烯的动态热稳定性能。结果发现，在氧化镁／氧化锌质量比为2／3的条件下，配合环氧大豆油、硬脂酸钙、无毒亚磷酸酯和有机稳定剂作为辅助稳定剂，其初期着色和热稳定效果都超过了市售钙锌稳定体系，流变性能和动态热稳定特性接近铅盐稳定体系。用这种稳定体系稳定的PVC的力学性能与市售钙锌稳定体系稳定的相当。