Heat stabilizers for poly (vinyl chloride). I. Synergistic systems based on calcium/zinc stearate

Synergism in poly(vinyl chloride) stabilization was studied by the determination of the dynamic and static stability of 34 different formulations. Nine ratios of Ca/Zn stearate were tested. Both the static and the dynamic stability increased almost linearly with the calcium stearate content, but unfortunately the initial discoloration increased as well. Melt viscosity decreased with an increasing content of calcium stearate. This was mainly caused by the difference in lubrication effect between calcium stearate and zinc stearate. Several co-stabilizers (synergists) for the Ca/Zn system were also evaluated. Among these, polyols were found to be the most effective. The addition of Polyol T 34, which was prepared through a coprecipitation of trimethylol propane and pentaerythritol, resulted in excellent initial color and improved transparency. Trimethylol propane and di-trimethylol propane were also powerful in this respect. The best static stability was observed for compounds containing mannitol and sorbitol, although these formulations were slightly discolored. Pentaerythritol and di-pentaerythritol were very effective in extending the static stability, but they were not useful for the improvement of initial color. Well-known complexing agents like EDTA and dimethylglyoxime were surprisingly ineffective as synergists. The addition of tris(nonylphenyl) phosphite resulted in a somewhat higher thermal stability, but not in any significant color improvement.     

Stabilization of poly(vinyl chloride). III. Synergism between metal soaps and masking agents on the stabilization of poly(vinyl chloride)

The stabilization mechanism by synergetic metal soaps containing complementary colors was previously reported. With increased heating times, the color of heated poly(vinyl chloride) (PVC) films containing Cd/Ba and Zn/Ca synergetic soaps markedly deviated from the polyene color. These color deviations usually decreased the thermal stability of PVC. Discoloration from polyene color to blue appeared especially on PVC films containing Zn/Ca synergetic soap and was concomitant with a marked decrease in thermal stability. The stabilization of PVC containing synergetic metal soaps can be improved by masking or removing the excessive color. In this work, the addition of various masking agents, such as ethylenediaminetetraacetic acid, o-phenanthroline, triethanolamine, urea, N,N′ -dimethylolurea, melamine, stearylamide, and lactams, to PVC containing synergetic metal soaps was investigated. It was shown that these masking agents do markedly slow down the discoloration of PVC.     

Stabilization of poly(vinyl chloride). I. Change in color of poly(vinyl chloride) compounded with some metal soaps

Poly(vinyl chloride) (PVC) with one or more metal salts added was colored by the action of heat to investigate the stabilization mechanism. The coloration and the color difference of heated PVC compound films varied according to the metal salt added. The decoloration of the colored compound films was advanced markedly in THF, DMF, acetone, and ammonia. On the other hand, the heated achromatic PVC film containing Cd/Ba soaps underwent an opposite change, from colorless to yellow orange, in the above materials. This means that the coloration of heated compound films may result from the formation of some complex (for example, π complex of the polyene with the metal chloride). Furthermore, the colored film with cadmium stearate was decolored by roll mixing with the colored film containing barium stearate. These results indicate that the stabilization with metal soaps may be founded on a physical phenomenon such aa an effect of complementary color.     

Stabilization of poly(vinyl chloride). V. Synergism between metal soaps and polyols upon stabilization of poly(vinyl chloride)

The marked discolorations observed on aged poly(vinyl chloride) (PVC) containing synergetic metal soaps, in the early heating stage, were due to the excessive coloration of π complex of metal chloride and double bonds in the polyene chain. These excessive colorations were inhibited by masking the excessive metal chloride with some masking agents, thereby slowing down the abrupt discoloration of PVC. In this paper, the masking effect of various alcohols such as 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, hexylene glycol, glycerol, 1,2,4-butanetriol, trimethylolethane, trimethylolpropane, meso-erythritol, pentaerythritol, sorbitol, and dipentaerythritol is investigated. The polyhydric alcohols, except dihydric alcohols, showed superior masking effect and markedly improved the thermal stabilization effects of synergetic metal soaps. The mechanism for the synergetic effects between polyols and metal soaps should be based on the masking effect of polyols, owing to the formation of the colorless complex of polyols with excess metal chlorides obtained from the metal soap.     

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.     

Lanthanum histidine with pentaerythritol and zinc stearate as thermal stabilizers for poly(vinyl chloride)

Lanthanum histidine [La(His)₂·(NO₃)·2H₂O or La(His)₂] was synthesized via the reaction of histidine and lanthanum nitrate, and it was investigated as a stabilizer for poly(vinyl chloride) (PVC). The results show that La(His)₂ exhibited a stabilizing effect on PVC as a long‐term stabilizer because it prolonged the stability time of PVC to 76 min, which was about 24 times longer than the stability time of the pure PVC. The stabilizing effect of La(His)₂ as a costabilizer with pentaerythritol (Pe) and zinc stearate (ZnSt₂) was also studied. The results show that the use of La(His)₂ with Pe or Pe/ZnSt₂ improved the stability time of PVC. La(His)₂/Pe/ZnSt₂ provided PVC with a good initial color and long‐term stability, and when it was prepared at mass ratios of 0.8:2.4:0.8 and 1.6:1.6:0.8, the stability times of PVC were improved to 86 and 88 min, respectively. As a nontoxic stabilizer, La(His)₂/Pe/ZnSt₂ has the potential to replace the toxic stabilizers widely used in PVC manufacturing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42878.     

Modification of poly(vinyl chloride). XIX. Electroplating of poly(vinyl chloride)

As a preliminary treatment in the PVC-electroplating procedure, treatment with dimethylformamide followed by sensitization leads to a finely roughened and a highly hydrophilic surface with reducing power. This is caused by the formation of an ionic complex compound between dimethylformamide and tin(II) chloride absorbed in the PVC surface. A much more finely and deeply etched surface which exhibits higher adhesion through the mechanical interlocking effect is obtained with the PVC blends containing the plasticizer with a low value of interaction parameter and with a solubility parameter approximate to that of PVC. Adhesion of the metal layer to the PVC surface thus obtained is improved about 1.5 times by thermal aging at 120°C for 20 min.     

Synergetic effect of dimerized pentaerythritol esters with synergetic metal soap on the stabilization of poly(vinyl chloride)

The synergetic effect of dimerized pentaerythritol esters, as novel costabilizer, with metal soap, the mixture of zinc and calcium stearates, as stabilizer, on the undesirable discoloration of poly(vinyl chloride) (PVC) by heating was investigated. The dimerized pentaerythritol esters were prepared by the esterification of pentaerythritol using stearic acid and the dimerization of the obtained pentaerythritol ester using unsaturated dicarboxylic acid. This dimer was used to improve its poor compatibility with PVC. The degree of esterification for pentaerythritol was varied from half to the full amount of hydroxyl groups. Both stabilizer and costabilizer were compounded into poly(vinyl chloride) through roll mixing. As a result, the dimerized pentaerythritol esters showed good dispersibility in poly(vinyl chloride). The effect of suppressing the discoloration was obtained in the systems used, not only the half‐esterified type but also the full‐esterified type, although it had no hydroxyl group. The abrupt discoloration was caused by the formation of a π complex between cool color producing metal chloride, i.e., zinc chloride from the metal soap and double bonds from the dehydrochlorination in poly(vinyl chloride) chain. Usually, the hydroxyl group containing compounds are said to be useful for suppressing the discoloration because the hydroxyl group captures the metal chloride. In the costabilizing effect of the full esterified type, it was clarified from the X‐ray photoelectron spectroscopic analysis and infrared spectrum observations for the model mixtures, that the decomposition of the ester group could occur, and the excess zinc chloride was captured as colorless zinc carboxylate. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2029–2037, 2001     

Stabilization of poly(vinyl chloride). X. Synergisms between epoxidized polybutadienes and metal soaps on the stabilization of poly(vinyl chloride)

Effects of epoxidized 1,2- or 1,4-polybutadienes on the zinc stearate/calcium stearate synergetic soap-induced thermal stabilization of poly(vinyl chloride) (PVC) were investigated by colorimetry. The remarkable stabilization effects of epoxidized polybutadienes could not be observed on the PVC films without synergetic soaps, while the stabilization of PVC was markedly enhanced by combined use of epoxidized polybutadienes with synergetic soaps. Excessive coloration of cool color-producing zinc chloride-polyene complexes that were the source of abrupt discoloration of stabilized PVC was retarded by using epoxidized polybutadienes together with synergetic soap. The synergism of epoxidized polybutadienes was enhanced with increasing epoxy contents. Moreover, the effect is also clearly dependent on degree of dispersion of epoxidized polybutadienes in PVC. Further colorimetries, infrared (IR), and X-ray photoelectron spectroscopies on the various PVC-containing epoxidized polybutadienes and zinc chloride indicated that the epoxy groups capture the zinc chloride. The synergistic effect between epoxidized polybutadienes and metal soap was ascribed to epoxidized polybutadienes serving as acceptors for the excessive cool color-producing zinc chloride produced by zinc stearate to retard the abrupt discoloration of stabilized PVC. The plate-out phenomenon appeared during the molding process of PVC-containing epoxy compounds was considerably retarded by epoxidized polybutadienes which modified polyols. The polyol-modifying epoxidized polybutadienes also exhibited a marked effect on PVC stabilization with metal soap.     

Stabilization of poly(vinyl chloride). II. Stabilization mechanism through metal soaps by complementary color action

In a previous paper, it was pointed out that the stabilization mechanism through metal soaps might be affected by an effect of complementary color. In this work, the colors of heated poly(vinyl chloride) (PVC) films mixed with various metal soaps were investigated by using a differential colorimeter and a spectrophotometer. Monochromatic coloration was observed with PVC, PVC–Ca stearate, and PVC–Ba stearate systems. On the other hand, the phenomenon of color mixing was observed with PVC–Zn stearate, PVC–Cd stearate, PVC–Zn/Ca stearate, and PVC–Cd/Ba stearate systems. In particular, achromatic color remained with PVC–Zn/Ca stearate and Cd/Ba stearate systems for longer heating periods. This means that the stabilization mechanism for PVC compounded with metal soaps should be effected finally by subtractive complementary colors situated between polyene color and the color effected with the metal complex, in addition to being subject to the usual chemical stabilization mechanisms.     

Modification of poly(vinyl chloride). XXXIV. Crosslinked poly(vinyl chloride) via paste-processing

A novel PVC-crosslinking technique using 6-dibutylamino-1,3,5-triazine-2,4-dithiol (DB) was applied for a paste processing to produce a crosslinked PVC product. The paste formulation recommended in the present study consisted of 100 parts of PVC (Zeon 121), 60 parts of dioctyl phthalate, 0.2 parts of MgO, and 6 parts of a 50% solution of DB-Na in butylcarbitol, which gave a highly crosslinked and transparent sheet with an excellent stability for thermal discolouring. The increasing viscosity behaviour of the paste during storage is explained by the effect of interparticle attracting forces of DB-Na which coordinates to the ether oxygen atoms in the glycol derivatives adsorbed on the surface of PVC particles. The increased viscosity can be reduced by addition of 3 parts of N-butyl-benzene-sulfonamide. The tension-distortion properties at elevated temperatures were remarkably improved at the crosslinked product compared with the uncrosslinked. The mechanical properties of the two crosslinked products produced via paste processing and roll-blending are compared in regard to the differences of the uniformity of crosslinking units.     

Stabilization of poly(vinyl chloride). VIII. Synergisms between epoxy compounds and metal soaps

Effects of bisphenol A type epoxy compounds involving various average molecular weights on the zinc stearate/calcium stearate and the cadmium stearate/barium stearate synergetic soaps induced thermal stabilization of poly(vinyl chloride) (PVC) were investigated by colorimetry. The remarkable stabilization effects of epoxides could not be observed on the PVC films without synergetic soaps, while the stabilization of PVC was markedly enhanced by combined use of epoxides and synergetic soaps. The appearance of excessive coloration of cool color producing metal chloride–polyene complexes which were an origin of abrupt discoloration of stabilized PVC was retarded by using epoxides together with synergetic soaps. Moreover, as for PVC with or without synergetic soaps, the epoxy compounds did not inhibit the formation of longer polyene chains which were a chromophore for yellow orange of aged PVC. Further colorimetries and IR or X-ray photoelectron spectroscopies on the various PVC containing epoxy compounds and zinc chloride indicated that the epoxy groups caught the zinc chloride. The synergetic effect between epoxy compounds and synergetic metal soaps is ascribed to the action that the epoxides serve as an acceptor for the excessive cool color producing metal chloride produced from zinc stearate and cadmium stearate to retard the abrupt discoloration of stabilized PVC.     

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     

Investigation of lanthanum trioxypurine with zinc stearate and pentaerythritol as complex thermal stabilizers for poly(vinyl chloride)

Lanthanum trioxypurine (LaTr) was triumphantly synthesized by reacting trioxypurine and lanthanum nitrate at neutral condition and was characterized by elemental analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The thermal stability effect of LaTr with its assistant thermal stabilizers about zinc stearate (ZnSt₂) and pentaerythritol (Pe) on poly(vinyl chloride) (PVC) was investigated by Congo red test, discoloration test, UV–vis spectroscopy test, and thermal decomposition kinetics. The results showed that the addition of LaTr as thermal stabilizer could significantly enhance static stability time and long‐term stability of PVC. It could be mainly attributed to the anions in the structure of LaTr, could efficiently absorb the hydrogen chloride released by PVC, and have ability to replace unstable chlorine atoms on structure of PVC. Moreover, the mixing of LaTr, Pe, and ZnSt₂ could reveal an excellent synergistic effect and both promote the initial color and the long‐term thermal stability of PVC. The thermal stability of PVC reached the optimal state when the ratio of LaTr/Pe/ZnSt₂ was 1.8/0.6/0.6. In addition, compared with the reaction energy E_a and UV–vis spectroscopy test's result of PVC samples, the order of PVC's thermal stability was PVC/LaTr/Pe/ZnSt₂ > PVC/LaTr/Pe > PVC/LaTr. The result was further ascertained that LaTr/Pe/ZnSt₂ showed excellent synergistic effect and could be used as an excellent complex thermal stabilizer for PVC. J. VINYL ADDIT. TECHNOL., 25:347–358, 2019. © 2019 Society of Plastics Engineers     

Preparation and characterization of magnesium stearate,cobalt stearate,and copper stearate and their effects on poly(vinyl chloride) dehydrochlorination

Preparation and characterization of pure metal soaps and investigation of their effects on poly(vinyl chloride) (PVC) dehydrochlorination were the objectives of the present study. Magnesium stearate (MgSt₂), cobalt stearate (CoSt₂), and copper stearate (CuSt₂) were prepared by a precipitation method. An aqueous sodium stearate (NaSt) solution was mixed at 500 rpm with respective metal salt solutions at 75^oC. The precipitates that formed were collected by filtration, washed with water, and ultimately dried at 105^oC under reduced pressure. Lamellar crystals that melted on heating were obtained. Solid‐liquid phase transitions were observed by optical microscopy at 160^oC, 159^oC, and 117^oC for MgSt₂, CoSt₂, and CuSt₂, respectively. However, the melting points of MgSt₂, CoSt₂, and CuSt₂ were determined as 115^oC, 159^oC, and 111^oC, respectively, by analysis by differential scanning calorimetry. The onset temperature of the mass loss was the lowest at 255^oC for CuSt₂ and the lowest activation energy for thermal decomposition was 18 kJ/mol for CuSt₂. CoSt₂ was effective in extending the induction time of PVC dehydrochlorination at both 140^oC and 160^oC. The activation energy calculated from stability time decreased from 175 kJ/mol for a blank PVC sample to 114, 105, and 107 kJ/mol for MgSt₂, CoSt₂, and CuSt₂‐containing PVC samples, respectively. All three metal soaps accelerated the dehydrochlorination of PVC. J. VINYL ADDIT. TECHNOL., 21:235–244, 2015. © 2014 Society of Plastics Engineers     

Chlorinated poly(vinyl chloride) stabilization by pentaerythritol/calcium‐zinc stearate mixtures: The fate of pentaerythritol

The stabilization effect of pentaerythritol (Pe) combined with calcium and zinc stearates (CaSt₂/ZnSt₂) on chlorinated poly(vinyl chloride) (CPVC) is investigated. Congo red and dynamic thermal stability data indicate that Pe alone has a mild stabilizing effect on the degradation of CPVC. Addition of mixed CaSt₂/ZnSt₂ to this system leads to a significant improvement in stability. Thermogravimetric studies indicate that premature weight loss, not observed with either Pe alone or with CaSt₂/ZnSt_2, is observed when the combined Pe/CaSt₂/ZnSt₂ systems are employed to stabilize CPVC. Fourier transform infrared (FTIR) spectroscopy and electrospray ionization mass spectrometry (ESIMS) both indicate that condensation (oligomerization) and chlorination of Pe occur when Pe and Pe/CaSt₂/ZnSt₂ systems are employed to stabilize CPVC. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Stabilization of poly(vinyl chloride) by elemental sulfur

The process of stabilization of a poly(vinylchloride) elemental sulfur in thermal and thermooxidative destruction conditions is investigated. The high stabilizing efficiency of elemental sulfur is revealed at the destruction of plasticized poly(vinylchloride) compared with the efficiency of phenolic antioxidants. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Modification of poly(vinyl chloride). XXXIII. Novel poly(vinyl chloride) foam crosslinked with 6-dibutylamino-1,3,5-triazine-2,4-dithiol

The formulation for producing the PVC foam crosslinked with a novel crosslinking agent such as 6-dibutylamino-1,3,5-triazine-2,4-dithiol (DB) was studied to determine the processing conditions. DB was almost consumed by radical combination with a coexistent blowing agent such as azobisformamide to give a high-density foam with excessively low crosslinking density. Blowing agents such as p-toluenesulfonylhydrazide (TSH) and 4,4′-oxybis(benzenesulfonylhydrazide) (OBSH) gave a crosslinked foam of low density, while a combination of the two crosslinking agents had moderate crosslinking reaction rate. The formulation recommended in the present study consists of PVC Zeon 101EP or Zeon 121 for paste, 100 parts; DOP, 100 parts; DB, 3–5 parts; OBSH or TSH, 10 parts; MgO, 1–3 parts; and RP101 (mixture of Ba, Ca, and Zn stearate), 2 parts, which gave colorless and insoluble foam of apparent density 0.14 under hot pressing at 180°C. The molded foam could be released without extraction of heat from a hot mold for fusion and expansion.