Nachweis von Polyensequenzen in thermisch gealtertem Polyvinylchlorid durch Resonanz-Ramanspektroskopie

A Raman spectroscopical method allowing the evaluation of polyene sequences in heat-treated polyvinylchloride (PVC) samples is described. The enormous increase of Raman scattering with increasing number of conjugated double bonds, utilizing the Raman resonance phenomenon, renders the laser Raman spectroscopy an extremely sensitive analytical method. A polyene sequence length of n ～ 20 could be deduced from the frequency of the resonance line. This frequency was independent of the amount of HCl split off within the limits of 1·10^?4 to 0,1 wt.-% HCl. The activation energy of HCl-elimination for a graft copolymer of vinyl chloride onto poly(ethylene-vinylacetate) was found to be E_A = 32,7 kcal/mole by both Raman spectroscopy and conventional detection from the elimination reaction. A commercial suspension PVC showed evidence of polyene sequence formation already at 60°C.     

Formation of conjugated carbon bonds on poly(vinyl chloride) films by microwave‐discharge oxygen‐plasma treatments

Conjugated polyene bonds on poly(vinyl chloride) (PVC) films were rapidly formed by the treatment of oxygen plasma produced by microwave discharge. Changes affecting the formation of conjugated carbon bonds on PVC were studied with respect to plasma emission diagnostic and surface properties of the film with fluorescence, refractant absorption spectroscopy, X‐ray photoelectron spectroscopy analysis, and Raman spectroscopy. The formation of polyene bonds on the film surface was responsible for both the dechlorination and dehydrogenation of PVC in the plasma atmosphere. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 589–594, 2005     

Structural and mechanistic aspects of the thermal degradation of poly(vinyl chloride)

A critical review of the title subject supports the following major conclusions. Thermal dehydrochlorination of poly(vinyl chloride) (PVC) begins with internal allylic chloride and tertiary chloride structural defects formed during polymerization. The tertiary chloride is associated with 2,4-dichloro-n-butyl, 1,3-di(2-chloroethyl), and chlorinated long branches. Mechanisms for the formation of all of the labile defects are well established. ‘Carbonylallyl’ structures and certain isotactic conformers of ordinary monomer units are unimportant as initiators of thermal dehydrochlorination. Both the initiation and the subsequent formation of conjugated polyene sequences occur via carbenium chloride ion pairs or by a closely related concerted four-center quasi-ionic route. Six-center concerted processes, pathways involving free radicals, and other mechanistic schemes suggested recently are not involved in polyene elongation. However, during thermal degradation, ordinary monomer units are converted into internal allylic chloride defects by a mechanism that may include the abstraction of hydrogen by triplet cation diradicals derived from polyene intermediates. Cyclization reactions seem likely to contribute to the termination of polyene growth. When PVC is thermolyzed in blends with other polymers, unusual kinetic phenomena are detected that remain to be fully explained.     

Struktur und Reaktivität heterosubstituierter Nitrile. XVI[1]. Kinetik und Mechanismus der Arylcyanatbildung aus Bromcyan und Phenolen

Structure and Reactivity of Heterosubstituted Nitriles. XVI. Kinetics and Mechanism of the Formation of Arylcyanates from Cyanogen Bromide and Phenoles The first-order and second-order rate constants of the reaction of cyanogen bromide with phenoles in the presence of tertiary aliphatic amines were determined in absolute acetone. The first step of the reaction is the nucleophilic attack of the tertiary amine at the cyanogen bromide. By a fast equilibrium reaction an N-cyano-N,N,N-trialkylammonium bromide is formed, which is attacked by the phenol as a nucleophile or dissociates in the slowest steps of the reaction. The nucleophilicity and the steric hinderance of the tertiary amine, and the nucleophilicity of the phenole as well determine, which of these reactions is favoured.     

Kinetics and mechanism of the thermal degradation of poly(vinyl chloride)

The kinetics of the thermal degradation of solid powdered poly(vinyl chloride) (PVC) under nitrogen was studied by thermogravimetry, rate of hydrogen chloride evolution, and rate of polyene sequence formation. These results are accommodated by a chain mechanism involving initiation by random dehydrochlorination at normal monomer residues of PVC, and a series of intermediates, each leaking to a stable conjugated polyene sequence. Structural irregularities such as allylic and tertiary chlorine are responsible for a fast initiation process at the very beginning of the degradation. Mean rate constants and activation parameters for random initiation, propagation, and termination reactions of the PVC degradation chain were calculated by simulation. Activation enthalpy/entropy correlations for the experimental data available for dehydrochlorination of chloroalkanes and chloroalkenes in the gas and in the liquid phase or nonpolar solvents and elementary reactions of PVC degradation show that initiation is an HCl elimination through a transition state of four centers requiring a synperiplanar conformation of the >CH–CCl< group, whereas propagation is a dehydrochlorination through a transition state of six centers requiring a cis configuration of the double bond.     

Stabilizations of molecular structures and mechanical properties of PVC and wood/PVC composites by Tinuvin and TiO2 stabilizers

Three different UV stabilizers, 2‐(2H‐benzotriazol‐2‐yl)‐4,6‐ditertpentylphenol (Tinuvin XT833), 2‐(2H‐benzotriazol‐2‐yl)‐p‐cresol (Tinuvin P), or rutile–titanium dioxide (TiO₂) were incorporated into poly(vinyl chloride) (PVC) and wood/PVC (WPVC) composite, and mechanical and physical properties and photostabilities were monitored. The polyene and carbonyl sequences of PVC increased with UV weathering time and with presence of wood flour. The yellowness index increased because of polyene and carbonyl productions, whereas the brightness increased because of the photobleaching of lignin in wood. The photostabilities of PVC and WPVC could be improved through the use of UV stabilizers. Tinuvin P was recommended in this work as the most effective stabilizer for PVC and WPVC composites. The stabilization effect was interfered by presence of wood particles. The mechanical property changes corresponded well to the structural changes under UV for neat PVC. For WPVC composites, the presence of wood particles played more significant effect on the mechanical properties during UV aging than the UV stabilizer. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

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.     

Effect of thermal stabilizers on the photo-oxidative degradation of solid poly(vinyl chloride)

It has been found that metal (Ba, Ca, Cd and Pb) stearates and pure stearic acid have stabilizing effects on the photodehydrochlorination of poly(vinyl chloride) (PVC) and the formation of polyene structures. On the other hand the same compounds accelerate photo-oxidation of PVC. From oxygen uptake measurements at different temperatures we calculated the energy of activation of photo-oxidation. It was found that metal stearates decrease the energy of activation of photo-oxidation processes of PVC, whereas stearic acid increases it. A synergistic effect of an equimolecular mixture of Ba and Cd stearates has also been observed.     

Dehydrochlorination of poly(vinyl chloride) modified with titanium dioxide/poly(ethylene oxide) based paint photocatalysts

The dehydrochlorination of poly(vinyl chloride) (PVC) film samples modified with titanium dioxide (TiO₂)/poly(ethylene oxide) (PEO) based paint photocatalysts [the addition of methyl linoleate (ML) or methyl oleate (MO)] was performed. After 24 h of UV photoirradiation, the sample with TiO₂/PEO showed that there existed a structure with the longest polyene length, whereas that with TiO₂/PEO/ML contained the most polyene structures. The chloroform‐soluble fraction of the sample with TiO₂/PEO contained a poly(vinyl alcohol) (PVA) structure instead of a polyene one and showed a novel method of PVA production via PVC photodegradation. The molecular weight curve of the fraction shifted slightly to a lower molecular weight compared to that without the photocatalyst; this showed that slight polymer chain scission occurred. The ¹H‐NMR and ¹³C‐NMR spectra showed that the content of PVA units was about 20%, and the PVA sequence was blocky. The fraction of the sample with TiO₂/PEO/ML contained the highest methyl group content; this showed that the branch degree was highest as was the polyene content. These highest contents were due to the existence of the grafted ML. Pyrolysis gas chromatography/mass spectroscopy measurements suggested that there existed more polyene and graft units in the chloroform‐insoluble fractions of the samples with TiO₂/PEO, TiO₂/PEO/ML, and TiO₂/PEO/MO, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40760.     

利用13C NMR技术探究叔胺溶液中HCO3-的生成

利用¹³C NMR技术对CO₂捕获叔胺溶剂进行了碳元素的定量研究,主要考察了对胺溶剂解吸热影响较大的HCO₃^-的生成规律。重点对叔胺分子结构中羟基官能团(-OH)、羟烷基数目、烷基支链及氮原子(N)所连接烷基链大小对胺溶剂生成HCO₃^-的影响。在20℃条件下分别对1 mol·L^-1具有不同CO₂负载的1-二甲基氨基-2-丙醇(1DMA2P)、N-甲基二乙醇胺(MDEA)、3-二甲氨基-1-丙醇(3DMA1P)、二乙氨基-2-丙醇(1DEA2P)、N,N-二乙基乙醇胺(DEEA)、N,N-二甲基乙醇胺(DMMEA)及三乙醇胺(TEA)溶液进行了¹³C NMR测试研究。实验结果显示:在相同浓度的叔胺水溶液中,同一CO₂负载下的叔胺-CO₂-水体系中HCO₃^-的含量顺序为:DMMEA > MDEA>3DMA1P > 1DMA2P > TEA > DEEA > 1DEA2P。通过对各叔胺分子结构中N原子的电子云密度大小及空间位阻效应分析,得出如下结论:3DMA1P分子中-OH官能团离N原子的距离大于其在DMMEA分子中的距离,导致其生成了较少的HCO₃^-;DMMEA分子中N原子上连接的烷基链小于DEEA分子中N原子上的烷基链,导致DMMEA溶液中生成了更多的HCO₃^-;MDEA分子中羟烷基数目少于TEA分子中的羟烷基数目,且MDEA比TEA多了一个甲基,导致MDEA溶液中含有更多的HCO₃^-;3DMA1P相比1DMA2P、DEEA相比1DEA2P分子中都少了一个甲基支链,导致3DMA1P溶液相比1DMA2P溶液、DEEA溶液相比1DEA2P溶液生成了更多的HCO₃^-。     

A comparative kinetics study of CO2 absorption into aqueous DEEA/MEA and DMEA/MEA blended solutions

The kinetics of CO₂ absorption into aqueous solutions of N,N‐diethylethanolamine (DEEA), and N,N‐dimethylethanolamine (DMEA), and their blends with monoethanolamine (MEA) have been studied in a stopped‐flow apparatus. The kinetics experiments were carried out at the concentrations of DEEA and DMEA varying from 0.075 to 0.175 kmol/m³, respectively, and that of MEA ranging between 0.0075 and 0.0175 kmol/m³, over the temperature range of 293–313 K. Two kinetics models are proposed to interpret the reaction in the blended amine systems and the results show that the model which incorporates the base‐catalyzed hydration mechanism and termolecular mechanism resulted in a better prediction. Furthermore, the kinetics behaviors of CO₂ absorption into two blended systems are comprehensively discussed according to their molecular structures. It can be concluded that the interaction between tertiary amines and primary amines as well as the alkyl chain length of tertiary amines have a significant influence on the kinetics. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1350–1358, 2018     

Effect of tertiary amines on yellowing of UV‐curable epoxide resins

The work reported demonstrates that the yellowness of UV‐curable epoxide resins can be improved by adding certain tertiary amines in appropriately determined amounts. According to the results of our experiments, 2.0 wt% benzoyl peroxide added to a resin effectively enhances the crosslinking density, and phenolic free radicals are produced during UV curing, which consequently induce yellowness via the reaction of oxygen and the free radicals. Imidazole (1‐amine) and tertiary amines, including 1,2‐dimethylimidazole (2‐amine), 2,4,6‐tris(dimethylaminomethyl)phenol (3‐amine), 1‐methylimidazole (4‐amine) and 2‐methylimidazole (5‐amine), were chosen to be added to resins, and their effects on UV conversion and yellowness were investigated. According to the experimental results, tertiary amines in the resin can provide a certain degree of improvement in yellowness index (ΔYI) and color parameter (ΔE*_ab) of the resin sample. Whatever the type of tertiary amine, it is found that the optimum content of amine in resin is 1.0 wt%. Also, among the studied amines, the 3‐amine exhibits the highest UV reactivity and the best efficiency for yellowness improvement with values of Δa*, Δb*, ΔYI and ΔE*_ab as low as ? 1.4, 6.23, 11.27 and 6.48, respectively. Copyright © 2007 Society of Chemical Industry     

Quaternary ammonium salts derived from jojoba oil

Quaternary ammonium salts derived from jojoba oil have been prepared either from jojobyl halides and tertiary amines or from dimethyljojobyl- and dimethylhomojojobylamines and alkyl halides. These salts have special potential as germicides, surfactants, emulsifiers and phase transfer reagents, for example. The jojobyl iodide and jojobyl mesylate react more readily with amines than the chloride, which is consistent with the expected relative leaving group reactivity of the different halides. The nucleophilicity of the tertiary amine, containing one long chain derived from jojoba oil, is similar to that of other tertiary amines containing only short alkyl chains. The salts are thermally stable up to 100–110 C.     

Thermal stability of poly(vinyl chloride)/layered double hydroxide nanocomposites

Effects of nanoscale dispersed layered double hydroxides (LDHs) on thermal stability of poly(vinyl chloride) (PVC) in thermal and thermooxidative degradation processes are investigated by dynamic and isothermal thermogravimetric analysis (TGA), discoloration test, fourier transform infrared (FTIR), and ultraviolet‐visible (UV‐vis) spectroscopic techniques. During both stages of thermal degradation, the degradation temperatures, including onset degradation temperature and temperature of the maximum degradation rate, increase, and the final residue yield of the PVC/LDH nanocomposites reaches 14.7 wt %, more than double that for neat PVC. The thermooxidative degradation process is more complex. During the first two stages, the presence of nanoscale dispersed LDH particles enhances the thermal stability, whereas in the last stage accelerates the thermal degradation possibly due to the accumulation of heat released. Additionally, the studies of the isothermal thermooxidative degradation process by FTIR and UV‐vis spectra indicate that both polyene backbone formation and some carbonyl groups are simultaneously developed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Stabilization of poly(vinyl chloride). VI. Synergetic effects of aminopolycarboxylates or nitrogen-containing agents with zinc stearate/calcium stearate soap

Discoloration such as zinc burning was observed in aged poly(vinyl chloride) (PVC) compounded with synergetic soaps. This discoloration was caused by excessive formation of cool color-producing π complexes formed between double bonds in polyene chain and zinc chloride or cadmium chloride produced from the corresponding metal soap. The appearance of excessive color of the π complexes was reduced by adding some masking agents into PVC admixed with synergetic soaps. In the present study differences in masking effects results by adding solid or an aqueous solution of aminopoly-carboxylates such as glycine, ethylenediaminetetraacetates, and nitrilotriacetates to PVC stabilized with zinc stearate/calcium stearate synergetic soap. The mechanism of synergetic effect between nitrogen-containing agents and synergetic soaps upon the stabilization of PVC is also investigated by colorimetry. The aqueous solution of aminopolycarboxylates exhibits a greater masking effect than the solid. The masking effect of aminopolycarboxylates depends on the ease with which they are fnely dispersed into PVC. Colorimetry indicated that the masking effect of aminopolycarboxylates and other nitrogen-containing agents depends on forming the colorless complex compound with the excessive cool color-producing metal chlorides.     

Photolysis of dialkyl phthalates and poly(vinyl chloride) plasticized with dialkyl phthalates at wavelengths exceeding 290 nm

When dialkyl phthalate plasticizers, neat poly(vinyl chloride), PVC, and PVC plasticized with dialkyl phthalate are subjected to near UV radiation at λ_inc > 290 nm, chemical alterations are induced by traces of impurities capable of absorbing light in this wavelength range. The main photoproducts formed in the case of neat phthalates are olefins, alcohols, and phthalic acid anhydride. Neat PVC undergoes C? Cl bond cleavage and, in addition, carbonyl and polyene groups are formed. The formation of carbonyl groups is a nonlinear (auto-accelerated) process whereas polyene generation occurs linearly with increasing irradiation time. The photolysis of phthalate-plasticized PVC is characterized by the decomposition of the plasticizer, evidenced by the decrease in the absorption band at 278 nm, and by the formation of carbonyl groups attached to PVC and the cleavage of C? Cl bonds as evidenced by the increase or decrease in the IR absorption bands at about 1710 and 617/639 cm^?1, respectively. Phthalates hardly influence the incorporation of carbonyl groups into PVC (an auto-accelerated process) and retard only slightly the cleavage of C? Cl bonds. By contrast, phthalates sensitize the incorporation of carbonyl groups upon irradiation at λ_inc = 254 nm. Within the error limit no effect of the chemical nature of the phthalate on the formation of photoproducts was detectable upon performing irradiations at λ_inc > 290 nm.     

Homogeneous Catalytic Cleavage of Saturated Carbon-Nitrogen Bonds

An evaluation of the catalytic reactivity of [CPD (CO)₂RuH]₂ (1) and (CPD)(CO)₃Ru (2) (where CPD = tetraphenylcyclopentadienone) with amines suggests that these complexes catalyze C-N bond cleavage by activating C-H bonds alpha to the nitrogen atom of tertiary, secondary and primary amines at ca. 140° C. When two different amines are used, transalkylation takes place. With secondary and primary amines, ammonia and tertiary amines are formed. A series of amine complexes (CPD)(CO)₂Ru.NR₃ (R = alkyl/H) was isolated from stoichiometric reactions of 1 or 2 with primary and secondary amines. It was found that tertiary amines do not generate complexes of the above type but rather unexpectedly give secondary amine complexes by cleavage of an alkyl group. The only isolatable tertiary amine complex is the moderately stable (CPD)(CO)₂RuNMe₃. All amine complexes were characterized by spectral and elemental analyses. Catalytic aspects of C-N bond cleavage were studied. Complexes (1) and (2) were found to react with primary, secondary and tertiary amines to generate imminium or eneamine species which subsequently undergo hydrolysis with water. This is in contrast to the Ru carbene mechanism previously proposed for cluster catalyzed C-N bond activation and cleavage. The two reactions are compared with respect to D for H exchange (with D₂O), water requirement and production of trace products during catalysis. A primary alcohol was found to substitute alkyl groups of a tertiary amine under the catalytic action of 1. A catalytic reaction cycle is proposed.     

Quaternarized cationic poly[(vinyl chloride)-co-(vinyl chloroacetate)] binary copolymer as non-migration antibacterial additive in PVC matrix

Antibacterial polyvinyl chloride (PVC) materials have drawn considerable attention since their wide application in medical devices. The objective of this study is to develop a novel quaternary ammonium cationic vinyl chloride copolymer, which can be potentially used as antibacterial additive in PVC matrix. Initially, the low average-number molecular weight poly[(vinyl chloride)-co-(vinyl chloroacetate)] (PVC-co-PVCA) is synthesized by precipitation copolymerization. Subsequently, quaternary ammonium cationic moieties with different lengths of alkyl chains are introduced into the copolymers via quaternization reaction between alkyl-dimethyl tertiary amines with acyl chloride groups. The successful synthesis of PVC-co-PVCA and quaternarized copolymers are carefully confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance (1H NMR), and x-ray photoelectron spectroscopy. The antibacterial behaviors of the quaternarized copolymers and its blends with PVC are investigated. The results reveal that all the PVC blends containing at least 5% by weight of quaternarized copolymer have superior bacteriostasis ratio (>99.6%) against both Escherichia coli (E.coli) and Staphylococcus aureus (S. aureus) due to the incorporation of quaternary ammonium groups. Meanwhile, the cationic copolymer exhibits excellent antifouling and much lower migration rate (<0.4%). These interesting consequences endow the quaternarized copolymers as alternative antibacterial agents possess a great deal of potential for use in PVC materials.     

Thermal Decomposition of Polymer Mixtures Containing Poly(vinyl chloride)

Thermal decomposition of a series of 1 : 1 mixtures of typical polymer waste materials [polyethylene (PE), poly(propylene) (PP), polystyrene (PS), polyacrylonitrile (PAN), polyisoprene, poly(methyl methacrylate) (PMMA), polyamide‐6 (PA‐6), polyamide‐12 (PA‐12), polyamide‐6,6 (PA‐6,6), and poly(1,4‐phenylene terephthalamide) (Kevlar)] with poly(vinyl chloride) (PVC) was examined using thermal analysis and analytical pyrolysis techniques. It was found that the presence of polyamides and PAN promotes the dehydrochlorination of PVC, but PVC has no effect on the main decomposition temperature of polyamides. The hydrogen chloride evolution from PVC is not altered when other vinyl polymers or polyolefins are present. The thermal degradation of PAN is retarded significantly, whereas that of the other vinyl polymers is shifted to a slightly higher temperature in the presence of PVC. Among the pyrolysis products of PAN‐PVC mixture methyl chloride was found in comparable amount to the other gaseous products at 500°C pyrolysis temperature.     

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.