Effect of thermal stabilizers composed of zinc barbiturate and calcium stearate for rigid poly(vinyl chloride)

Zinc barbiturate [Zn(H₂L)₂·2H₂O, abbreviated as ZnL₂] was synthesized by a precipitation method in aqueous solution, and investigated as a co-stabilizer with calcium stearate (CaSt₂) for rigid poly(vinyl chloride) (PVC) by the discoloration test and the dehydrochlorination test at 180 °C. ZnL₂ exhibits high stabilizing effect with excellent initial colour of PVC films. In comparison with the synergistic effect of CaSt₂/ZnSt₂ stabilizers, the CaSt₂/ZnL₂ stabilizers in mass ratios ranging from 0.3/1.2 to 0.6/0.9 exhibit better synergistic effect. Moreover, PVC films stabilized by CaSt₂/ZnL₂ show better initial colour with the addition of dibenzoyl methane as an auxiliary stabilizer. The mechanism of stabilizing action of ZnL₂ is also proposed. ZnL₂ may replace the labile chlorine atoms to interrupt the formation of conjugated double bonds in PVC chains, and act as the absorber of hydrogen chloride to restrain the self-catalytic dehydrochlorination.     

Hydroxylbenzylthioethers as novel organic thermal stabilizers for rigid PVC

An investigation was carried out on the performances of hydroxylbenzylthioethers employed as organic thermal stabilizers for rigid poly(vinyl chloride). The efficiency of these compounds as thermal stabilizers was evaluated by using Haake polydrive mixer and TGA. The stabilizing efficiency was compared with Ca-Zn soap and methyltin stabilizer. Hydroxylbenzylthioethers exhibit greater efficiency than both of these stabilizers. This is attributed to the ability of these compounds to prevent the formation of polyene sequences. The hydroxylbenzylthioethers-stabilized PVC showed a slightly lower glass transition temperature (T_g) in comparison with the original PVC. Hydroxylbenzylthioethers and epoxidized soybean oil (ESBO) exhibit synergistic effect on the stabilizing effect, when the mass ratios of ESBO to hydroxylbenzylthioethers are less than 0.5.     

Influence of lanthanum stearate as a co-stabilizer on stabilization efficiency of calcium/zinc stabilizers to polyvinyl chloride

Influence of lanthanum stearate (LaSt₃) as a co-stabilizer on stabilization efficiency of calcium stearate (Ca)/zinc glutarate (Zn) stabilizers to polyvinyl chloride (PVC) at 180 °C in air was investigated. The results showed that combination of LaSt₃ with Ca/Zn stabilizers presented an obvious improvement of stabilization efficiency to PVC compared with the Ca/Zn stabilizers. Moreover, addition of LaSt₃ to the Ca/Zn stabilizers could significantly enhance static stability time of PVC. Incorporation of 2 phr LaSt₃ co-stabilizer to PVC containing 3 phr Ca/Zn stabilizers resulted in marked increase of onset degradation temperature and reductions in average degradation rate as well as the dynamic storage modulus (G′) and loss modulus (G″) at 180 °C. Influence of Ca/Zn ratio on tensile strength of PVC in the absence or in the presence of LaSt₃ was discussed in detail. At low Ca/Zn ratios LaSt₃ had an obvious improvement in the tensile strength, while at high Ca/Zn ratios this effect became inconspicuous.     

Itaconamide derivatives as organic stabilizers for poly(vinyl chloride) against photodegradation

Itaconamide derivatives have been prepared and investigated as photo-stabilizers for rigid PVC. We investigated their stabilizing efficiencies by testing the weight loss (%) with the amount of formed gel. The results indicated a reasonable stabilizing efficiency of these derivatives compared with commercial UV absorber; phenyl salicylate. The extent of discoloration of the photodegraded polymer was also improved in the presence of the prepared compounds. Rheological properties were studied to investigate the flow behavior with providing a vision into the mechanical behavior for the tested materials. Employing the evaluated photostabilizers reflects the reduction in the extent of cross-linking of the polymer. This implies preserving the mechanical properties of PVC. A radical mechanism is proposed to account for the stabilizing action of the investigated materials. The prepared itaconamide derivatives provide appropriate photostability and mechanical properties for a durable poly(vinyl chloride).     

热稳定剂及与PVC混合物的热解反应研究

采用热分析方法对PVC加工成型中热稳定型的热解反应进行了研究，根据它们的热重曲线，分别求得热稳定剂及掺入热稳定剂后PVC混合物的热分解反应的各种特性参数，运用计算动力学参数的经验公式，求得热解活化能，定量地评价了热稳定剂及掺入热稳定剂后PVC混合物的热性能，并采用静态法测定了PVC混合物的热稳定时间。     

酯基硫醇锡PVC热稳定剂的合成

酯基硫醇锡ＰＶＣ热稳定剂的合成魏荣宝＊梁娅韩宝成卢世荣高铁男（天津理工学院化工系天津３００１９１）关键词酯基硫醇锡，制备，ＰＶＣ热稳定剂１９９６－０８－２０收稿，１９９６－１２－１２修回天津市自然科学基金资助项目酯基硫醇锡是７０年代末开发的一类ＰＶＣ...     

Vanillin–Schiff’s bases as organic thermal stabilizers and co-stabilizers for rigid poly(vinyl chloride)

Vanillin–Schiff’s bases (VSB) were examined as thermal stabilizers and co-stabilizers for rigid poly(vinyl chloride) (PVC) in air at 180 °C. Their high stabilizing efficiency were shown by their high thermal stability value (Ts), which is the time elapsed for the detection of HCl gas, if compared with dibasic lead carbonate and cadmium–zinc soap reference stabilizers used industrially, with better extent of discoloration. Blending these derivatives with reference stabilizers in different ratios greatly lengthens the thermal stability and the extent of discoloration of the PVC.Condensation products of Vanillin with amines are very active biologically, besides having good complexation ability with metal ions. The Ni²⁺ and Co²⁺ complexes of VSB derivatives gave better thermal stability and less discoloration than the parent organic stabilizer. Also, blending these complexes with either of the used reference stabilizers in different ratios gave better thermal stability and lower extent of discoloration. Thermogravimetric analysis confirmed the improved stability of PVC in the presence of the VSB derivatives, compared to blank PVC, PVC stabilized with reference stabilizers and PVC stabilized with binary mixture of VSB derivatives with reference stabilizer.The stabilizing efficiency of Vanillin–Schiff’s base (VSB) derivatives is attributed to the replacement of the labile chlorine atoms on the PVC chains by a relatively more stable moiety of the organic stabilizer.     

Influence of lanthanum stearate and calcium/zinc stabilizers on stabilization efficiency of dibutyltin dilaurate to polyvinyl chloride

<正>Influences of lanthanum stearate(LaSt_3) and calcium stearate/zinc stearate(Ca/Zn) stabilizers on stabilization efficiency of dibutyltin dilaurate(DBTDL) to polyvinyl chloride(PVC) in air were investigated.The results revealed that the stabilization effect of DBTDL could be achieved by the La/Sn stabilizers with a ratio of 8/2.Addition of DBTDL could enhance thermal property and reduce dynamic storage modulus(G′) at 180℃for PVC containing LaSt_3 or Ca/Zn stabilizers. On the other hand,incorporation of LaSt_3 did not influence the stabilization efficiency of DBTDL markedly;while addition of Ca/Zn stabilizers could significantly decrease thermal property for the DBTDL stabilized PVC.Furthermore,the effects of LaSt_3 and Ca/Zn stabilizers on the stabilization efficiency of DBTDL were explained in the framework of ionization potential.     

热稳定剂对PVC紫外光老化过程中微观结构及宏观性能演变的影响

通过UV-Vis、FTIR、DSC、以及色差、力学性能的测试表征,实时追踪分析了在紫外光老化过程中,含Pb、Sn以及Ca-Zn热稳定剂的PVC体系微观结构和宏观性能的演变过程.结果表明,在相同光老化条件下,PVC/Pb、PVC/Sn和PVC/Ca-Zn体系的微观结构变化规律基本一致,过程中主要的化学反应是,大分子吸收光能后,发生脱HCl生成共轭双键的反应、生成羰基的氧化反应、交联反应和降解反应;不同热稳定剂的作用,主要表现在对于微观结构变化的幅度和动力学过程的影响不同.相应地,3种体系的外观色差和力学性能的变化规律也相似,但色差的变化程度和速度以及老化后力学性能的保持率因所含热稳定剂的不同而不同,其中含Sn体系的颜色稳定性最好,含Pb体系的力学性能保持率最高。     

Effect of pentaerythritol and organic tin with calcium/zinc stearates on the stabilization of poly(vinyl chloride)

The stabilization effect of calcium and zinc stearates (CaSt₂/ZnSt₂) combined with pentaerythritol (PeE) and organic tin on poly(vinyl chloride) was investigated. The results show that the addition of calcium/zinc stearates combined with PeE and organic tin can improve thermal and colour stability of poly(vinyl chloride) in both static and dynamic tests. Mechanisms for improving stability of PVC are also discussed. The increase of stabilizing effectiveness of calcium/zinc stearates is ascribed to the synergistic effect between CaSt₂/ZnSt₂ and PeE and the interaction between organic tin and double bonds formed during the degradation of PVC. There is no synergistic action between organic tin and PeE or organic tin and calcium/zinc stearates.     

The effect of thermal processing on PVC—VII. Reactive antioxidants as thermal stabilizers

A benzyl thiol (BHBM) containing a hindered phenolic antioxidant group has been compared as a thermal stabilizer for PVC with a typical tin maleate stabilizer (DBTM). It has been shown that BHBM both adds to the developing double bond in PVC during processing and destroys hydroperoxides. It is thus an effective stabilizer but it is partially destroyed by side-reactions. In combination with DBTM, BHBM shows powerful synergistic effects which are optimal at a molar ratio of DBTM: BHBM ? 4:1. The reasons for the side-reactions and the synergism are rationalized on the basis of the known reactions of BHBM.     

新型有机高分子型PVC热稳定剂的合成

以经部分硝化和还原的低分子量聚苯乙烯为母链,利用其胺基和丙烯酰基异硫氰酸酯加成,合成了一种新型有机高分子型PVC热稳定剂——丙烯酰基硫脲接枝聚苯乙烯,其结构经IR和元素分析表征。     

Effect of stearate preheating on the thermal stability of plasticized PVC compounds

Effect of preheating of stearates on the processing and post-processing thermal stability of poly(vinyl chloride) compounds, plasticized with di(2-ethylhexyl) phthalate (DEHP) and epoxidized soybean oil (ESO), using several ratios of calcium/zinc stearates and DEHP/ESO is reported. The compounds were prepared as follows: (1) dry-blending the compound components, (2) pelletizing the dry-blend and (3) extruding the pellets to obtain a ribbon geometry. Processing stability was determined by: (a) mechanical characterization and (b) visual color comparison of extruded samples. Post-processing thermal stability was followed by: (a) measurement of HCl release from heated pellets and (b) color changes in heated ribbon samples. From a practical point of view, the preheating has a negligible effect on the initial color of formulations; except for the case of formulations without both ESO and CaSt₂. However, the effect of the preheating on the post-processing thermal stability is strongly determined by the composition formulation.     

Synergistic effect of maleimido phenyl urea derivatives mixed with some commercial stabilizers on the efficiency of thermal stabilization of PVC

Four novel antimicrobial maleimido phenyl urea stabilizers 1–4 were synthesized from N-[4-(chlorocarbonyl) phenyl] maleimide with phenyl urea and its derivatives (p-methyl, o-chloro and p-carboxy). The effect of mixing maleimido phenyl urea stabilizer 2 with each of the reference stabilizers, dibasic lead carbonate (DBLC), cadmium-barium-zinc stearate (Cd-Ba-Zn stearate) or n-octyltin mercaptide (n-OTM), on the stabilization efficiency in thermal degradation of rigid PVC at 180 °C in air, has been investigated. Mixing was effected in the range of 0–100 wt% of stabilizer 2 relative to each of the reference stabilizers. The stabilizing efficiency was evaluated by measuring the length of the thermal stability period (Ts), the period during which no detectable amount of hydrogen chloride gas could be observed, and also from the rate of dehydrochlorination as measured by continuous potentiometric determination, and by the extent of discoloration of the degraded polymer samples. The results show a true synergistic effect from the combination of stabilizer 2 with any of the reference stabilizers. Mixing of the stabilizers improves the Ts values, decreases the rate of dehydrochlorination and lowers the extent of discoloration of the polymer. The maximum synergism was attained when stabilizer 2 is mixed with either of the three reference stabilizers in equivalent weight ratio (50%/50%). The observed synergism may be attributed to the different mechanisms by which the investigated and the reference stabilizers work.     

Viscoelastic and thermal characterization of crosslinked PVC

Soft PVC is employed for the manufacturing of a wide range of products with different properties and a relatively low cost. The utilization of soft PVC is restricted by the poor thermal, chemical and mechanical resistance properties. Also, plasticizer migration can modify the properties or can make useless the materials for some applications because of toxicity or a general loss of properties. PVC crosslinking is the most effective way to improve mechanical and transport properties of rigid or flexible PVC at high temperatures, but at the same time the thermal stability of PVC may be significantly reduced. In this work, the crosslinking reaction of plasticized poly(vinyl chloride) (PVC) through difunctional amines was studied. The mechanisms involved in the crosslinking reaction were explained by Fourier transform infrared (FTIR) analysis. The thermal activated crosslinking reaction was studied by cone and plate rheometry, analyzing the evolution of viscoelastic properties of the suspension as a function of time and temperature. The effect of the addition of crosslinking agents on the thermal stability of the polymer was studied by thermogravimetric analysis (TGA), which revealed that crosslinking reactions promote thermal degradation phenomena in the polymer matrix. This is attributed to the formation of HCl and other species promoting polymer degradation during crosslinking, thus leading to higher weight loss during thermal treatment with respect to unmodified PVC plastisols. This was also confirmed by an evident yellowing after crosslinking, especially at higher temperatures.     

Comparing the effect of nanofillers as thermal stabilizers in low density polyethylene

A study of the thermal degradation under inert and oxidative conditions of LDPE and three 5-wt% nanocomposites has been performed. The bases of comparison were the geometries of the nanofillers (spherical, fibrous and laminar) and the sample thickness. Homogeneous and well-dispersed materials were obtained with the three nanoparticles, ensuring a relevant comparative analysis.The thermal degradation curves obtained from TGA under nitrogen flow did not show significant differences in behaviour within the nanocomposites and the reference LDPE. However, the results for the thermo-oxidation study showed a strong stabilization effect for both fibrous and laminar silicates, but not for the spherical silica nanoparticles. A kinetic study of the degradation under isothermal conditions showed that the nanocomposites made from fibrous and laminar silicates degraded following the mechanisms observed for thin films independent of the sample thickness. These results suggested the occurrence of a protective layer against thermo-oxidation on the film surface. Chemical analysis of the degraded surfaces by IR and EDX measurements gave data to explain these differences in behaviour.     

稀土PVC热稳定剂作用模式及协同效应研究

稀土化合物对ＰＶＣ良好的稳定作用，并存在广泛的协同效应。探索了一种计算机辅助研究稀土ＰＶＣ热稳定剂作用模式及效应的方法，可以预测稳定剂的稳定效能。结果表明，在稀土硬脂酸盐及同类稳定剂中，曲线回归方程参数有效地反映了热稳定剂类型的差别；引入协同效应函数，不仅提高了回归方程的可信度，而且能反映协同效应的形成规律。     

稀土PVC稳定剂的作用机制研究

稀土化合物可以作为聚氯乙烯稳定剂，硬脂酸稀土是稀土复合稳定剂的重要成分。本文通过研究PVC与硬脂酸镧及其它硬脂酸盐作用前后的红外光谱，探讨了硬脂酸盐对PVC的热稳定作用机制，发现了稀土化合物对PVC的特殊稳定机制，即改变PVC的构象和抑制脱氯化氢的作用，并对稀土稳定剂独特的协同作用做出了解释。     

脂溶性金属酞菁的合成及其作为PVC膜电极载体的研究

脂溶性金属酞菁的合成及其作为ＰＶＣ膜电极载体的研究李俊忠,庞新宇,陆素,高德,俞汝勤（湖南大学化学化工系,长沙,４１００８２）关键词脂溶性金属酞菁,载体,ＰＶＣ膜电极金属酞菁由于价廉、稳定及其所具有的氧化还原性、光导电和催化等独特的物理化学性质,已在...