Cyclopentadienylation of allyl-chlorine enriched PVC and degradation thereof

Summary Pendant cyclopentadienyl groups (Cp) have been introduced by treatment with Me₂CpAl into poly(vinyl chlorides) the allyl chlorine contents of which was augmented by mild chemical dehydrochlorination [PVC(A)]. Heating the cyclopentadienylated products [PVC(A)-Cp] led to gels, most likely by Diels-Alder addition, because the networks could be broken by strong dieno-philes, e.g., maleic anhydride. The thermal stability of PVC(A)'s was improved upon Me₂CpAl treatment due to the substitution of thermally unstable allylic chlorines by Cp groups. The thermooxidative stability of PVC(A)-Cp was reduced relative to that of PVC(A) on account of the high oxidizability of Cp groups in the resin.     

Phenylation of PVC with triphenylaluminum and related model reactions

It was theorized that the heat stability of PVC may be improved by exchanging the “weak” (allylic and tertiary) chlorines by groups of higher bond strength, e.g., phenyl. Thus PVC was phenylated by ?₃Al in carbon disulfide slurry for various times (1 to 5 hrs) and temperatures (from ?30 to +45°C). The ?₃Al concentration, temperature and time of ?₃Al treatment greatly affect the ultimate heat stability of PVC. Significant improvement in the heat stability was obtained by treating PVC in carbon disulfide at 25°C for 1 hr. The mechanism of phenylation was studied by model experiments in which the possible structural irregularities in PVC were simulated by small molecule chlorine compounds, i.e., 3-chloro-1-butene, 1,3-dichloro-1-butene, 4-choro-2-pentene were models for terminal and inchain allylic chlorines, t-butyl chloride was the model for tertiary chlorine at branch site, and isopropyl chloride simulated regular secondary chlorines. The reactions between ?₃Al and these chlorides were carried out at 35°C for various times and the NMR spectra were analyzed. The ?₃Al + tBuCl reaction in carbon disulfide gives t-butylbenzene (Wurtz coupling) and isobutylene oligomers. Evidently ?₃Al (or the ?₂AlCl formed) dehydrochlorinates tBuCl to isobutylene which rapidly oligomerizes in the presence of Lewis acids. In aromatic diluents, i.e., benzene, chlorobenzene, and o-chlorotoluene, Friedel-Crafts t-butylation of the diluent occurs; in mesitylene t-butylation is absent presumably because of steric hindrance and small amounts of t-butylbenzene are formed by Wurtz coupling. All the allyl chlorides examined are rapidly phenylated by ?₃Al in carbon disulfide at 35°C and yield the expected products: 3-chloro-1-butene → 1-phenyl-2-butene; 1,3-dichloro-1-butene → 1-chloro-3-phenyl-1-butene; 4-chloro-2-pentene → 4-phenyl-2-pentene. The kinetics of phenylation by ?₃Al of model compounds have been studied and the following rate constants were obtained: k_allyl = too fast to measure, k_tBuCl = 1.0, and k_iPrCl = 9 × 10^?4 l/mole min. Evidently the rate of the ?₃Al + RCl reaction is mainly determined by the stability of the R^⊕ intermediate: substituted allylic^⊕ ? tertiary^⊕ ? secondary^⊕.     

Cationic grafting of norbornadiene, indene, and 1,3-cyclohexadiene from PVC

Summary The synthesis of three novel graft copolymers consisting of a PVC backbone fitted with polynorbornadiene (PNbd), polyindene (PInd), polycyclohexadiene (PCHD) branches, i.e., PVC-g-PNbd, PVC-g-PInd, and PVC-g-PCHD, is described. The synthesis strategy was to initiate the grafting of norbornadiene (Nbd), indene (Ind), and 1,3-cyclohexadiene (CHD) by a PVC containing ∼ 1.6 active (tertary and allylic) chlorines in conjunction with Et₂AlCl. The products were characterized by solvent fractionation, molecular weight determination, T_g, and NMR spectroscopy. The effect of temperature on the grafting was investigated in the 20 to −50 °C range. Received: 8 October 2001/ Revised version: 22 April 2002/ Accepted: 23 April 2002     

Synthesis and properties of poly(vinyl chloride-g-2-methyl-2-oxazoline)

Summary Poly(vinyl chloride-g-2-methyl-2-oxazoline) copolymers were prepared by grafting from the allyl chloride sites of PVC with KI or AgOSO₃CF₃ as coinitiators. Use of AgOSO₃CF₃ led to higher grafting efficiencies and higher contents of poly(2-methyl-2-oxazoline) in the graft copolymers. DTA analyses of the P(VC-g-Me-Oxz) identified the thermal transitions of this copolymer; TGA analyses showed that the graft copolymers were less thermally stable than the constituent homopolymers. Unlike blends of P(Me-Oxz) and PVC, the graft copolymers could be molded easily; the graft materials exhibited greater flexural moduli but lower HDT's than PVC.     

Mechanical Properties and Thermooxidative Aging of a Ternary Blend,Pvc/Enr/Nbr,Compared with the Binary Blends of Pvc

In the quest to improve the thermooxidative aging of the poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend, nitrile rubber (NBR) was incorporated into the blend to yield a ternary blend of PVC/ENR/NBR. A Brabender Plasticorder with a mixing attachment was used to perform the melt mixing at 150°C and 50 rpm followed by compression molding. The mechanical properties, dynamic mechanical properties, and thermooxidative aging behavior of the ternary blend were compared with those of the binary blends (i.e., PVC/ENR and PVC/NBR). It was found that the ternary blend exhibits mechanical properties which are superior to those of PVC/ENR. A single glass transition temperature (T _g) obtained from dynamic mechanical analysis coupled with synergism in the modulus and some other mechanical properties indicate that PVC, ENR, and NBR form a single phase (miscible system) in the ternary blend. Di-2-ethyl hexylphthalate (DOP) plasti-cizer improves the aging resistance of the blends generally, whereas the presence of CaCO₃ as a filler only imparts minor influences on the properties and aging resistance of the blends.     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers)

Summary The unsaturated aliphatic dichlorides cis and trans Cl(CH₃)₂C-CH=CH-C(CH₃)₂Cl in conjunction with BCl₃ have been found to be excellent binifers and yield tert.-Cl capped polyisobutylenes PIB in CH₃Cl at –30°C. Intramolecular cyclization is absent and terminal chlorine functionality is F_n = 2.0±0.1. The normalized inifer constants have been determined: ^CItrans = 1.05, and ^CIcis = 3.8 and 1.05, respectively, for the first and second allylic chlorines in the cis isomer. The inequality of the chlorines have been analyzed. The cis and trans isomers have identical relative termination constants (k_t/k_p = 6×10^–3). The structure of the PIBs obtained has been analyzed by a variety of techniques. Model experiments with isobutylene/Cl-(CH₃)₂C-CH=CH-C(CH₃)₂Cl = 2/1 in the presence of BCl₃ gave the expected trans Cl(CH₃)₂CCH₂-(CH₃)₂C-CH=CH-C(CH₃)₂-CH₂C(CH₃)₂ -Cl. The end groups of polymers have been quantitated. The central position of the -CH=CH- residue in polymers has been demonstrated by molecular weight determinations i.e., the M_n of PIB has decreased by a factor of two after oxidative cleavage. The uniform distribution of -CH=CH-group across all polymeric species has also been established.     

Effects of 6-anilino-1,3,5-triazine-2,4-dithiol,zinc stearate,and barium stearate on the thermal stabilization of PVC

Individual action and synergistic effect in the combination of 6-anilino-1,3,5-triazine-2,4-dithiol (AF), zinc stearate, and barium stearate on the color stabilization of PVC were investigated. In this system, AF selectively reacts with allylic chlorine atoms in PVC. Consequently, unstable allylic chlorine units were converted to thermally stable allylic structures, thus retarding the development of polyene sequences. Zinc stearate accelerated the reaction of AF with allylic chlorine atoms in PVC, forming the zinc salts of AF (AFZ_nSt, St?C₁–H₃₅COO? ) by reacting with AF. Barium stearate reacted with ZnCl₂ which is formed in the above reaction to give St₂Zn and BaCl₂. Consequently, barium stearate led to the selective reaction of AF with allylic chlorine atoms in PVC and the remarkable retarding effect of discoloration of PVC.     

Studies on polyblends of poly(vinyl chloride) and acrylonitrile-butadiene-styrene terpolymer

Blends of poly (vinyl chloride) (PVC) and acrylonitrile-butadiene styrene (ABS) terpolymer were prepared in different ratios by a melt blending technique. ABS containing three different levels of rubber content were used. A quantitative assessment of ABS in PVC/ABS blends has been shown by infrared studies. ABS content has been shown as the presence of the characteristic acrylonitrile peak. Differential scanning calorimetry (DSC) studies have been carried out to study the glass transition (T_g) behavior of the blends. Two T_g values corresponding to PVC and styrene-acrylonitrile (SAN) copolymer have been observed. Thermogravimetric analysis (TGA) reveals a significant improvement in thermal stability of these blends as compared to PVC. Mechanical properties show a significant increase in the impact strength which is related to rubber content of the ABS used. Morphological studies have been carried out by scanning electron microscopy which support the observation that an increase in rubber content results in greater ductility.     

Thermal and mechanical properties of silane-crosslinked poly(vinylchloride)

A comparative study has been made of the crosslinking of plasticized PVC by grafting of γ-aminopropyltriethoxysilane (ASi) and sodium γ-mercaptopropyltrimethoxysilane (NaMSi) during processing. The influence of type of reagent and concentration, and the rheological behavior were investigated to obtain a crosslinked material with improved mechanical properties and good thermal stability. Depending on the reagent concentration, different gel contents, ranging from 0–100%, were obtained with both reagents. For all crosslinked systems the mechanical properties above T_g were improved. In the case of ASi-crosslinked PVC, the thermal stability deteriorated significantly but, for NaMSi-crosslinked PVC, thermal stability remains close to that of raw PVC, and the separation of the grafting and crosslinking processes is more viable in this case. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 865–872, 1998     

Synthesis and photodegradation of poly[2,5-bis(dimethylsilyl)furan]

Summary Poly[2,5-bis(dimethylsilyl)furan] (V), a copolymer with alternating furan and disilyl units, has been prepared by the Wurtz coupling of 2,5-bis(dimethylchlorosilyl)furan (II) with sodium metal dispersion in toluene. Lower molecular weight poly[2,5-bis(dimethylsilyl)furan] (IV) has been prepared by a similar condensation reaction with 2,5-bis(dimethylfluorosilyl)furan (III). IV and V have been characterized by ¹H, ¹³C and ²⁹Si NMR, IR, and UV spectroscopy as well as by GPC, TGA and elemental analysis. Photolysis of V in a benzene/methanol solution results in degradation of the polymer.     

Amphiphilic poly(vinyl chloride)‐g‐poly[poly(ethylene glycol) methylether methacrylate] copolymer for the surface hydrophilicity modification of poly(vinylidene fluoride) membrane

In this study, a comblike amphiphilic graft copolymer containing poly(vinyl chloride) (PVC) backbones and poly(oxyethylene methacrylate) [poly(ethylene glycol) methylether methacrylate (PEGMA)] side chains was facilely synthesized via an atom transfer radical polymerization method. Secondary chlorines in PVC were used as initial sites to graft a poly[poly(ethylene glycol) methylether methacrylate] [P(PEGMA)] brush. The synthesized PVC‐g‐P(PEGMA) graft copolymer served as an efficient additive for the hydrophilicity modification of the poly(vinylidene fluoride) (PVDF) membrane via a nonsolvent‐induced phase‐inversion technique. A larger pore size, higher porosity, and better connectivity were obtained for the modified PVDF membrane; this facilitated the permeability compared to the corresponding virgin PVDF membrane. In addition, the modified PVDF membrane showed a distinctively enhanced hydrophilicity and antifouling resistance, as suggested by the contact angle measurement and flux of bovine serum albumin solution tests, respectively. Accordingly, the PVC‐g‐P(PEGMA) graft copolymer was demonstrated as a successful additive for the hydrophilicity modification, and this study will likely open up new possibilities for the development of efficient amphiphilic PVC‐based copolymers for the excellent hydrophilicity modification of PVDF membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Graft copolymerzation of poly(vinyl chloride) with styrene. I. Synthesis and characterization

Graft copolymerization of poly(vinyl chloride) (PVC) partially dehydrochlorinated by heating in nitrobenzene was investigated using styrene as monomer and anhydrous AlCl₃ as cationic initiator in the temperature range of 0–35°C. Effect of monomer, catalyst, and PVC concentration on % graft-on was also evaluated. Introduction of labile sites in PVC by partial dehydrochlorination in nitrobenzene resulted in an increase in % graft-on. Intrinsic viscosity of PVC–g–polystyrene in THF initially increased with an increase in % graft-on. At higher % graft-on a decrease in [η] was observed.     

Thermal Behavior and Photovoltaic Performance of Fullerene Grafted Dehydrochlorinated Poly(Vinyl Chloride) in Bulk Heterojunction Solar Cells

This study describes the development of an alternative conducting polymer for organic photovoltaic cell application. Chemical structure of poly(vinyl chloride) (PVC) was modified by two reactions, dehydrochlorination followed by fullerenation. The aim of this work was to explore the feasibility of using this chemically modified PVC (C₆₀-g-DHPVC) as an electron acceptor phase in ITO/PEDOT:PSS/P3HT:acceptor/TiO_x/Al bulk heterojunction (BHJ) solar cell. From the result, it was found that the power conversion efficiency of the BHJ cell employing PCBM as an electron acceptor alone increased from 0.5% to the maximum value of 1.34%, after the addition of C₆₀-g-DHPVC.     

Polymeric plasticizers for PVC

High molecular weight plasticizers can be used if they have a low T_g and are miscible with PVC. For example, linear polyesters exhibit miscibility with PVC when their [CH₂]/[COO] ratio is intermediate; in that range, as “miscibility window” has been found. However, the degree of miscibility of miscible polymer blends vary with the structure of the polymers involved and thier concentration. The miscibility of these systems is often assessed by the measurement of a single T_g as a function of composition. A careful examination of experimental data of polyester/chlorinated polymer blends, as well as the use of the free volume theory, indicates that several of these systems exhibit a cusp as a function of composition, which is characterized by a critical volume fraction and a critical temperature. Specific examples are given.     

Effect of the molecular weight on the plasticization properties of poly(hexane succinate) in poly(vinyl chloride) blends

Blends of poly(vinyl chloride) (PVC) and poly(hexane succinate) (PHS) with various molecular weights were analyzed with respect to their mechanical properties, durability, and thermal stability. We found that the molecular weight of PHS played an important role in the plasticizing process, and the single glass-transition temperature (T _g) of the PVC blends measured by dynamic mechanical analysis supported the complete miscibility between PHS and PVC. The plasticizing efficiency of PHS increased as the molecular weight increased; this reflected the gradually increasing elongation at break and the decreased T _g of the PVC blend. Meanwhile, the higher molecular weight of PHS also improved the resistance of migration and thermal stability but decreased the biodegradability of the PVC blends; this was due to the strong intermolecular interactions between PHS and PVC. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47081.     

Compatibility and nonlinear viscoelasticity of polychloroprene/polyvinyl chloride blends with nitrile butadiene rubber as a compatibilizer

Miscible polychloroprene/polyvinyl chloride (CR/PVC) blends with nitrile butadiene rubber (NBR) as a compatibilizer were prepared. The effect of NBR on the compatibility between CR and PVC was mainly analyzed by studying the thermal behavior and the phase structure of CR/PVC blends. An obvious decrement in the T_g of PVC phase successfully provided an explanation for the compatibilization of NBR. Due to the improved compatibility between CR and PVC, the size of PVC particles in CR/PVC blends decreased a lot according to the scanning electronic microscopic images. The significant improvement of mechanical properties of CR/PVC blends was in good agreement with the better compatibility between CR and PVC phases. The softening effect of NBR on the nonlinear viscoelasticity of CR/PVC blends was also studied by RPA 2000. Temperature sweep test by RPA 2000, a less reported characterization method of T_g, was successfully applied to measure T_g of CR/PVC blends and study the compatibilization of NBR. The reason for better thermal stability and the thermal decomposition mechanism of CR/PVC blends were analyzed according to the results of TGA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42448.     

On the thermal degradation of poly(vinyl chloride). IV. Initiation sites of dehydrochlorination

A set of poly(vinyl chloride) samples were investigated with respect to their thermal stability. The dehydrochlorination rates were measured in nitrogen at 190°C by use of a very accurate, conductometric method. For all polymers studied, a significant molecular weight increase was observed after 0.4% conversion. With only one exception, samples exhibiting higher degradation rates showed higher absorptions (350–450 nm) after 0.4% dehydrochlorination. In addition, the relative amount of short polyene sequences was found to be higher for polymers with higher degrees of branching. The dehydrochlorination reaction was predominantly initiated at sites of internal unsaturation (allylic chlorines), but an initiation at tertiary chlorines and unstable end-groups could not be completely omitted. Head-to-head units, extraneous impurities, and syndiotactic sequences were found to be of minor importance in this respect.     

Experimental assessment of the thermodynamic theory of the compositional variation of Tg: PVC systems

The glass-transition temperatures (T_g's) and specific heats (C_p) of poly(vinyl chloride) (PVC) and PVC plasticized with 5–120 phr di(2-ethylhexyl) adipate (DOA) and tri(2-ethylhexyl) trimellitate (TOTM) have been determined by differential scanning calorimetry (DSC). Measured T_g's were compared to predictions by the Couchman and Karasz (C–K) thermodynamic theory, three related empirical equations, and a new equation obtained from the C–K relation by assuming the product T_gΔC_p to be constant. It was found that the T_g's of the PVC/TOTM mixtures are adequately predicted only by the C–K and the derivative relation. The T_g's of the PVC/DOA mixtures follow a sigmoidal or cusp-like dependence on plasticizer composition as has been observed for some other PVC/plasticizer mixtures. In this case, the approximation afforded by the C–K or derivative equations is still superior to the empirical models over a wide composition range. Dynamic mechanical analysis of the PVC/DOA mixtures suggests that the DSC transitions may consist of two overlapping phase transitions. The reported sigmoidal composition dependence of the DSC T_g's may therefore result from the measured T_g's being weighted towards the temperature corresponding to the predominant dynamic mechanical transition (i.e., the high T_g phase at low plasticizer concentrations and the low T_g phase at high plasticizer concentrations). In such cases of partial phase separation, the C–K or the derivative equation may be used to estimate the composition of the two phases at each overall plasticizer concentration.     

Ultrafine full-vulcanized powdered rubbers/PVC compounds with higher toughness and higher heat resistance

A new type of rigid PVC compound with higher toughness and higher heat resistance was prepared by using a new type of PVC modifier, ultrafine full-vulcanized powdered rubber (UFPR). The UFPRs used in this paper were butadiene nitrile UFPR-1 (NBR-UFPR-1) with particle size of about 150 nm and butadiene nitrile UFPR-2 (NBR-UFPR-2) with particle size of about 90 nm. Dynamic mechanical thermal analysis (DMTA) showed that glass transition temperature (T_g) of PVC in compounds increased from 77.52 °C of neat PVC to 82.37 and 85.67 °C, while the notched impact strengths increased from 3.1 kJ/m² of neat PVC to 5.2, 5.5 kJ/m², respectively. It can be found that both T_g and toughness of PVC have been improved simultaneously, and the smaller the particle size of NBR-UFPRs, the higher the T_g and the impact strength. The property could be attributed to larger interface and more interfacial interaction between NBR-UFPRs and PVC matrix. Transmission electron microscopy (TEM) showed that NBR-UFPRs could be well dispersed in PVC matrix.     

Electroinitiated polymerization and copolymerization of phenylacetylene

Summary A linear conjugated polymer [(C₆H₅C=CH)] _n, with a trans rich, cis-trans copolymer structure results from the electropolymerization of phenylacetylene.