Basic principles of thermal degradation and thermal stabilization of poly(vinyl chloride). Synergism of stabilizer action

Changes in the quantities of active stabilizing components during thermal aging of plasticized poly(vinyl chloride) containing a mixture of calcium and zinc stearates were analyzed. A mathematical model of the stabilization process by using the stabilizer mixture and a computer program for analyzing the process of PVC thermal degradation after the beginning of HCl evolution are given.     

Epoxidized Mesua ferrea L. seed oil‐plasticized thermostable PVC and PVC‐clay nanocomposites

The use of vegetable‐oil‐based polymeric plasticizers with nanotechnology can create new applications for plasticized poly(vinyl chloride) (PVC). Epoxidized Mesua ferrea L. (Ceylon Ironwood) seed oil was used as a plasticizer for PVC. Further, nanocomposites were prepared through an ex‐situ technique using epoxidized‐oil‐swelled organically modified montmorillonite (5 wt%) and PVC. Notable improvement in thermal and processing characteristics of the nanocomposites was observed over those of the virgin polymer (in both unplasticized and plasticized PVC), as studied by TGA. The prepared nanocomposites were characterized by FTIR, SEM, TEM, and XRD techniques. A dramatic decrease in viscosity (7‐fold) was observed in THF for a 10% solution of epoxidized‐oil‐modified PVC compared to unplasticized PVC in THF, as measured by Brookfield viscometer. Isothermal analysis at three different temperatures (100, 150, and 200°C) reveals sufficient stability of the epoxidized oil modified PVC nanocomposites, as confirmed by gravimetric and FTIR analysis. Augmentation of thermostability and good retention of mechanical properties of the (Mesua ferrea L.)‐plasticized‐PVC/clay nanocomposites with respect to rigid PVC vouch for the utility of the former as advanced industrial materials. J. VINYL ADDIT. TECHNOL., 18:168–177, 2012. © 2012 Society of Plastics Engineers     

Diamide derivatives as photostabilizers for plasticized poly(vinyl chloride)

Some diamide derivatives have been prepared, characterized, and investigated as photostabilizers for plasticized poly(vinyl chloride) (PVC), containing dioctyl phthalate and dibutyl phthalate in a concentration of 30% by weight of the polymer. The stabilizing efficiency of the prepared diamides was evaluated by determining the weight loss percentage that resulted from HCl evolution during the photodegradation process. Moreover, the efficiency was evaluated by determining the amount of gel formed as well as the intrinsic viscosity of the soluble fractions of the photodegraded polymer. The extent of discoloration of the photodegraded stabilized and plasticized PVC was also investigated. The stabilization mechanism and the effect of plasticizers on the photostability of PVC are discussed. J. Vinyl Addit. Technol., 2008. © 2008 Society of Plastics Engineers     

Silane cross-linking of PVC. II. Influence of silane type and conditions on cross-linking by water

The cross-linking of plasticized and unplasticized poly(vinyl chloride) (PVC) grafted with amino- and mercaptoalkyltrialkoxysilanes has been studied in water and in air at 20–140°C. In both media, the cross-linking occurs faster for plasticized PVC grafted with aminosilanes; however, at temperatures above 100°C, the effect of degradation cross-linking is apparent. For mercaptosilanes, a marked dependence of the cross-linking rate on the silane structure was found; plasticized PVC with grafted 3-mercaptopropyltrimethoxysilane was cross-linked in water at 100°C after 6 h, whereas this process took 12 h for 5-mercaptopentyltriethoxysilane. Practically no cross-linking occurred in unplasticized PVC below T_g, whereas the rate at 100°C was comparable with that for plasticized PVC. The cross-linking rate is affected by the chain mobility, water content, and diffusion of water into the material; a very slight dependence on the thickness of the material was found for plasticized PVC. © 1993 John Wiley & Sons, Inc.     

自制环保稳定剂在增塑PVC制品中应用性能的评价

通过刚果红热稳定性实验、热老化实验、流变、力学性能以及黄色指数测定等实验,对比研究了自制钙/锌稳定剂与国外知名钙/锌稳定剂对增塑PVC热稳定性能、加工性能、热老化性能和力学性能的影响。研究发现:自制钙/锌稳定剂在增塑PVC制品方面各种性能几乎与该国外知名钙/锌稳定剂没有差别,在热老化性能和力学性能方面还优于该国外知名钙/锌稳定剂。     

Hydrothermic aging of plasticized poly(vinyl chloride): Its effect on the dielectric,thermal, and mechanical properties

Accelerated hydrolytic aging (according to the NFT 5166 method) was performed on samples of poly(vinyl chloride) (PVC) plasticized with dioctylphthalate (DOP) and dinonyladipate (DNA) at different concentration ratios. The aging test consisted of immersing the samples in boiling water at 100°C. The samples were removed from water regularly, that is, every 2 h, for mechanical, thermal, and dielectric characterizations. Thermograms of PVC plasticized with DOP revealed no migration of the plasticizer independent of the concentration used. Moreover, the thermal stability of the samples was not affected by the hydrothermal aging. However, for PVC samples plasticized with DNA, a small amount of the plasticizer migrated from the polymer matrix with a considerable effect on the thermal stability. In fact, the data indicated a decrease in the decomposition temperature from 275 to 225°C, particularly for samples containing 50% (w/w) DNA immersed up to 10 h. The mechanical results showed that for a plasticizer content greater than 30% (w/w), the strain at break obtained for samples plasticized with DNA was lower than that for samples plasticized with DOP because the DNA molecules were more likely to be removed by water on account of their polarity and dimension. Finally, the dielectric measurements showed that the permittivity of all the PVC samples plasticized with DOP and immersed in boiling water was higher than that of the virgin samples. On the contrary, the permittivity of the aged unplasticized PVC was less than that of the nonimmersed samples. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3447–3457, 2003     

PVC modification with biobased poly(hydroxyalkanoates)

Supported by numerous calculated and empirical data, a miscibility between polyvinylchloride (PVC) and biobased poly(hydroxyalkanoates) (PHAs), PHAs along with its utilization in plasticization, toughening, and processing improvement is discussed in unplasticized and plasticized (semirigid to flexible) PVC compounds. The long‐term thermal stability of PVC stabilized with BaZn salts is shown to be improved in the presence of PHAs and the short‐term stability (initial color hold) slightly reduced. The biobased PHAs are also shown to improve UV stability of PVC by offsetting the yellowing of PVC and not causing additional photodegradation. The transparence and durability of PVC are found to be unaffected by the presence of minor phase of otherwise biodegradable PHA. The discussed PHAs offer a new, ecologically attractive, and simplified approach to PVC formulation in which multiple processing and modifying additives could be replaced with a single product, eliminating both undesirable additive interactions and the need to stabilize unstable ingredients. J. VINYL ADDIT. TECHNOL., 21:259–271, 2015. © 2014 Society of Plastics Engineers     

Rheological and thermodynamic interaction effects in plasticized polyvinyl chloride compounds

Earlier work reported the superposition of flow curves for plasticized compounds of vinyl chloride homopolymer with corresponding curves for unplasticized resin. Viscosity shift factors for three plasticizer systems plotted against temperature define an apparent fusion temperature for the bulk polymer. A Brabender Plasticorder, used as a temperature-scanning rheometer, determined fusion temperatures for various plasticized PVC compounds. These data confirm a fusion temperature for bulk polymer near 205°C, and permit calculation of Flory-Huggins χ parameters over substantial ranges of composition and temperature. The thermodynamic parameter correlates well with viscosity shift factors for compounds with polymer volume fractions below 0.6. The possibility is therefore raised of calculating flow characteristics for plasticized PVC compounds from knowledge of χ only. The temperature and composition dependence of χ, estimated for the system PVC-diiso-octyl phthalate, is similar to reported variations in simpler polymer-diluent systems. Thus, PVC-plasticizer systems may follow analogous thermodynamic rules.     

Molecular orientation behaviour of uniaxially stretched poly(vinyl chloride) film: 1. Birefringence: effect of plasticizers and draw ratio above and below Tg

In order to investigate the orientation behaviour of a non-crystalline chain polymer, plasticized and unplasticized poly(vinyl chloride) films (PVC) are chosen for investigation. The following two orientation distribution functions are postulated to calculate the second moment of the molecular orientation: (a) for the unplasticized film drawn below the glass transition temperature the distribution function derived from an affine deformation mechanism is applied; (b) for the all plasticized films or for the films drawn above the glass transition temperature a compound distribution function derived from the affine deformation mechanism and that of a rubber-like chain (Langevin model) proposed by Roe et al is applied. The parameters which are included in the distribution function, viz. the ratio of the affine part to the Langevin part, the ratio of polyene to carbonyl in a heat treated film and the segment number of the Langevin chain, can be evaluated experimentally. The intrinsic birefringences of normal and heat treated unplasticized and plasticized films are estimated theoretically on the basis of additivity of band polarizabilities. The calculated birefringences and orientation distribution functions show good agreement with measured values.     

N-substituted maleimides as thermal stabilizers for rigid polyvinylchloride

N-substituted maleimides have been investigated as thermal stabilizers for rigid polyvinylchloride (PVC) at 180°C in air by measuring the rate of dehydrochlorination and the extent of discoloration of the polymer. The results reveal the higher stabilizing efficiency of these products relative to basic lead carbonate, dibutyl tin maleate, and cadmium-barium stearate stabilizers commonly used in industry. The induction period (Ts) increases as a function of the positive resonance effect of the substituents (+R). Moreover, the investigated stabilizers impart better color stability for the degraded samples as compared with the stearate stabilizer. The stabilizer efficiencies are attributed to their radical trapping potency which intervenes with the radical degradation process of PVC, while the good color stability is due to the ability of the stabilizer to interact with the conjugated double bonds formed on the PVC chains as a result of degradation. A mechanism illustrating the stabilizer's action is proposed.     

新型稀土复合多功能稳定剂在PVC-U微发泡板材中的应用II.稀土稳定剂对配方体系性能的影响

研究了稀土稳定剂对PVC U微发泡板材配方体系的静态、动态热稳定性的影响 ,及对泡孔结构和制品性能的影响 ,并在此基础上 ,确定了稀土稳定剂在配方体系中应采用的添加量     

Silane cross-linking of PVC. I. Grafting of mercaptoalkylalkoxysilanes onto PVC: Properties of the grafted and cross-linked product

The reaction of poly(vinyl chloride) (PVC) with mercaptoalkyltrialkoxysilanes yielded silane-grafted PVC that can be cross-linked by the hydrolytic mechanism. The grafting of the silanes on the plasticized and unplasticized PVC was carried out at 180° C during processing in the presence of basic lead-containing stabilizers. The reaction is favorably affected by the presence of plasticizers and lubricants containing polar, preferably ester, groups. The silane-grafted and cross-linked polymers have satisfactory thermal stability. The results of strength measurements at elevated temperatures after cross-linking by water indicate that the material obtained has greatly improved parameters that are suitable for a number of applications. © 1993 John Wiley & Sons, Inc.     

Poly(vinyl chloride) films plasticized with novel poly‐nadic‐anhydride polyester plasticizers

In this work, several novel poly‐nadic‐anhydride polyester plasticizers were developed to be used in poly(vinyl chloride) (PVC) film fabrication for the first time. Mechanical properties of the films, the compatibility of plasticizers in PVC resin, as well as testing of migration of the plasticizers, were performed in order to evaluate the efficiency of plasticization. Scanning electron microscopy, Fourier‐transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry were used to characterize the unplasticized and plasticized polymer. The results demonstrated that the as‐prepared poly‐nadic‐anhydride plasticized PVC film significantly improved the plasticization efficiency of PVC film based on the increase in the break in elongation of the films. According to scanning electron microscopy analysis, the poly‐nadic‐anhydride polyester plasticizers presented good compatibility with PVC resin. In volatility and extraction tests, PVC films plasticized with the poly‐nadic‐anhydrides showed enhanced migration resistance. The plasticizing effects induced by the poly‐nadic‐anhydride polyester plasticizers were also confirmed by a glass transition temperature shift toward lower temperatures in the plasticized films. J. VINYL ADDIT. TECHNOL., 23:321–328, 2017. © 2015 Society of Plastics Engineers     

二氧化钛对聚氯乙烯热稳定性能的影响

通过刚果红法实验研究了不同种类和用量的二氧化钛（TiO2）对使用复合铅盐稳定剂的硬质聚氯乙烯（PVC—U）脱氯化氢反应的影响,同时研究了不同用量的TiO2对使用不同热稳定剂的PVC—U脱氯化氢反应的影响。结果表明：①在复合铅盐稳定体系中,金红石型TiO2会导致PVC—U的热稳定性的下降,而锐钛型TiO2会提高PVC—U的热稳定性;②金红石型TiO2后期的包覆处理也对PVC—U的热稳定性有影响;③金红石型TiO2（R930）在复合铅盐热稳定体系中会导致PVC—U的热稳定性下降,而在Ca／Zn热稳定体系中,则能提高PVC—U的热稳定性。     

复合酯润滑剂对透明u-PVC稳定作用的研究

研究了复合酯润滑剂对透明未增塑聚氯乙烯（u－PVC）热稳定作用的影响。结果表明，与有机锡的稳定作用相比，复合酯润滑剂具有突出的抑制u－PVC初期变色的能力，改善了熔体流动性，及具有较好的辅助热稳定作用。     

Stabilization of rigid poly(vinyl chloride) by 5,6,7,8-Tetrahydro-2-mercapto-4-(p-methoxyphenyl)-3-quinolinecarbonitrile

The chemical 5,6,7,8-Tetrahydro-2-mercapto-4-(p-methoxyphenyl)-3-quinolinecarbonitrile (TMQC) has been investigated as a thermal stabilizer for rigid poly(vinyl chloride) (PVC) at 180°C in air. The results reveal the higher stabilizing efficiency of the investigated material, as shown by the longer induction period obtained in its presence relative to those produced by commonly used industrial stabilizers. Ultraviolet irradiation of the polymer stabilized by TMQC gives a lower extent of discoloration compared to that of unstabilized PVC. Reaction of TMQC with the polymer in solution also has been studied in order to investigate the mechanism of stabilization.     

About one possibility to investigate the synergism between PVC - stabilizers statistically

The possibility of studying the presence of synergism between stabilizers was treated, by applying experimental design, which is suitable for studying mixture's properties. The method of “pseudocomponents” was used with the particular three-component stabilizing system - calzium-zinc complex, tris-(nonyl-phenyl)phosphite and α-Phenylindole. As thermal stability criteria the induction time, colour stability and dynamic thermal stability in Brabender Plastograph were chosen. Regression relationships in the form of canonic equations of third order were obtained. Using the derived equations and computer, "composition-properties" diagrams were plotted. The abovementioned diagrams described adequately the stabilizing effect of the system in the investigated area of stabilizer concentrations, and it was shown that optimum results were obtained when about 20 percent of the primary stabilizer were replaced by 10 percent of each co-stabilizer. This synergistic effect is most pronounced for the initial colour of the PVC-compound.     

Effect of temperature,shear and blending conditions on the relaxation properties of milled and compression molded plasticized PVC compounds

Blended, milled, and compression molded plasticized PVC compounds containing 30 wt percent of DIOP plasticizer were studied by combination of low effective frequency relaxation methods. The compounds were found to be heterogeneous and the ratio of plasticized and unplasticized phases dependent on the processing parameters. There is a correlation between the mechanical strength and the phase structure of the system.     

Stabilization of poly(vinyl chloride) against photo‐degradation using dienophilic compounds

As dienophilic compounds, N‐ aminophenylmaleimides would be expected to act as radical traps and thus, could be investigated as organic photo‐stabilizers for rigid poly(vinyl chloride) (PVC). Their stabilizing efficiencies were evaluated by measuring the extent of discoloration and the change in the mechanical properties of the photo‐irradiated polymer. Their stabilizing efficiencies were compared with phenyl salicylate, which is a commonly used industrial photo stabilizer. The results have proved the higher stabilizing efficiency of all the investigated materials as compared with phenyl salicylate. The stabilizing efficiency of the aminomaleimides is attributed to their radical trapping potency which intervenes with the radical degradation of the photo‐irradiated PVC. Moreover, it was found that these materials lower the extent of discoloration of the polymer during later stages of degradation. This improvement in the color stability is most probably attributable to the ability of the aminomalemides to react by a Diels–Alder reaction with the conjugated double bonds created on the polymeric chains as a result of the degradation of the polymer. Finally, the results illustrate the blending of aminomaleimide derivatives with phenyl salicylate improve the photo stabilization of the polymer as shown from the absorbance coefficient Δa values, and this improvement attains its maximum when both the investigated stabilizers and phenyl salicylate are taken in equivalent ratios. The observed synergism is attributed to the combination of the mechanisms by which both stabilizers function. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

PVC—U耐压供水管管件专用料的研究

就用于耐压输水管管件的未增塑聚氯乙烯（PVC－U）的配方选取及材料性能进行了研究。通过不同型号PVC树脂混配,获得了具有良好加工性能和力学性能的树脂配混料,通过低含量铅系稳定剂卫生级有机锡混合使用,获得了既有较好稳定效果,又有价格优势的稳定体系。本工作考察了润滑剂用量、增韧剂和硅烷偶联剂品种对体系性能的影响。同时还首次使用高强度聚酯纤维和超高相对分子质量聚硅氧烷树脂作为PVC－U体系的改性剂,并探讨了各自的改性效果。结果发现因界面作用极弱,聚酯纤维并未有预期的增韧效果,但超高相对分子质量聚硅氧烷树脂能起到良好的改善流动性、增加表面光洁度的作用。