Photocrosslinking of azidated poly(vinyl chloride) coated onto plasticized PVC surface: Route to containing plasticizer migration

The migration of phthalate esters which are commonly employed for plasticizing poly(vinyl chloride) (PVC) is a significant problem in PVC-based medical devices as well as in packaging used for food stuffs and pharmaceuticals. Medical-grade PVC resin was treated with sodium azide in dimethylformamide (DMF) to prepare the azide polymer. The polymeric azide was coated onto the surface of plasticized PVC sheets by dipping in a solution of the polymer in tetrahydrofuran (THF). Crosslinking of the azide polymer was accomplished by irradiating the surface using a 125 W UV lamp for various lengths of time. Migration of the plasticizer di 2-(ethylhexyl phthalate) (DEHP) from coated and uncoated samples was examined in n-hexane at 30°C. It was found that 50–80% reduction in migration of DEHP could be effected from plasticized PVC in comparison with the controls in 72 h by this technique depending on the concentration of the coating solution, coating thickness, azide concentration, and irradiation dose. © 1995 John Wiley & Sons, Inc.     

Hg(II) removal with polyacrylamide grafted crosslinked poly(vinyl chloride) beads via surface‐initiated controlled/“living” radical polymerization

Polyacrylamide grafted crosslinked poly (vinyl chloride) beads (PAM‐PVC) were prepared by the surface‐initiated controlled/“living” radical polymerization (SI‐CLRP) methodology from the crosslinked poly(vinyl chloride) beads with surface modification with diethyldithiocarbamyl groups under UV irradiation. The macroiniferter, diethyldithiocarbamyl crosslinked poly(vinyl chloride) beads (DEDTC‐PVC) were prepared by the reaction of the surface C? Cl groups with sodium N,N‐diethyl dithiocarbamate. The “grafting from” polymerization exhibited some “living” polymerization characteristics and the percentage of grafting (PG%) increased linearly with polymerizing time and achieved 47.6% after 6 h UV irradiation. The beaded polymer with polyacrylamide surface was also characterized with Fourier transform infrared (FTIR) and scanning electron microscope (SEM). Its adsorption property for Hg(II) ion was also investigated preliminarily. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3385–3390, 2006     

Aminosilane grafting of plasticized poly(vinyl chloride) I. Extent and rate of crosslinking

The grafting of poly(vinyl chloride) (PVC) by reactive aminosilane compounds, which make them moisture-curable, has been investigated. Plasticized poly-(vinyl chloride) has been successfully grafted with aminosilane during extrusion. The grafted polymer was crosslinked in the presence of moisture. Although the hydrolysis and condensation of the crosslinking agent is very rapid, the speed of the reaction is controlled by the rather slow diffusion of water in the plasticized PVC. This water diffusion speed follows Fick's Law and is strongly dependent on temperature. To achieve a high crosslinking speed, the extruded PVC has to be placed in warm water or in a steam heated vessel. The effects of catalyst concentration, moisture concentration, and immersion time and temperature on the rate and degree of crosslinking were investigated. Since the formulation used contained a tin stabilizer, the addition of a tin catalyst to the immersion water had little effect. Crosslinking did occur in samples stored at room temperature due to the presence of moisture, but the reaction rate was increased substantially if the sample was immersed in water. Reaction rate was very temperature dependent and followed an Arrhenius relationship. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2111–2119, 1997     

Modification of polyvinylchloride in solution or suspension by nucleophilic substitution

Nucleophilic displacement of chlorine from polyvinylchloride (PVC) suspended either in water or in solution can be achieved using a nucleophile such as a sodium thiolate (R? S^?, Na⁺). The nucleophilicity of the salt increases if an ether linkage exists in a β position to the thiol group [R? O? (CH₂)₂? S^?, Na⁺]. Addition of a solvent such as cyclohexanone (which is a good solvent for PVC) to the slurry increases substantially the degree of substitution. Elemental analysis shows that every chlorine displaced from the polymer is replaced by a thiolate group; thus almost no dehydrochlorination occurs. It is possible to obtain by this method a grafted polymer in which 33% of the chlorine atoms are replaced by the β-ether thiolate group. The resulting polymer behaves like an internally plasticized PVC. The higher the degree of substitution of chlorine, the greater the flexibility of the grafted polymer is. Other compounds, such as lauryl thiolate and diethyl dithiocarbamate, also were used as nucleophiles, the latter one resulting in a brittle crosslinked polymer whenever sulfur was above 2%. Grafting of polytetrahydrofuran from PVC also was achieved using tetrahydrofuran as solvent and silver-perchlorate as catalyst. The resulting flexible grafted polymer is believed to consist of longer chains of polytetrahydrofuran grafted from few displaced chlorine atoms along the PVC chain.     

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.     

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 characterization of fullerene functionalized poly(vinyl chloride) (PVC) and dehydrochlorinated PVC using atom Transfer Radical Addition and AIBN based fullerenation

The research presented details chemical modifications of poly(vinyl chloride) (PVC) and its derivative, dehydrochlorinated PVC (DH‐PVC) through the use of two grafting techniques, namely a normal fullerenation, using AIBN (2,2′‐Azoisobutyronitrile), and the atom transfer radical addition (ATRA). The products were characterized and the presence of new FTIR peaks at 528 and 577 cm^?1 along with new ¹H‐NMR signal at 3.9 ppm, suggested that fullerenes has been grafted to the polymer molecules. Percentage of C₆₀ in the fullerene grated products determined by UV/Visible spectroscopy initially increased with the amount of fullerene used to a maximum value (～5.66 % wt) before decreasing again. It was also determined that the C₆₀ content of the fullerene grafted PVC product prepared by using ATRA, was notably greater than that obtained using the normal fullerenation approach, regardless of the amount of C₆₀ used. When the dehydrochlorinated PVC was used as the starting polymer for fullerenation, the fullerene grafted DH‐PVC using ATRA, was markedly insoluble in many common solvents (THF and dichlorobenzene). This was not the cases for the fullerene grafted DHPVC prepared via an AIBN based fullerenation. Furthermore, the electrical conductivity values of the modified PVC products determined by using a four‐point probe method were found to increase linearly with the amount of C₆₀ present. Overall our data suggest that the suitable and efficient techniques for grafting C₆₀ onto PVC and DHPVC chains are ATRA and AIBN‐based fullerenation, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2410–2421, 2013     

Ultrafiltration membranes obtained by grafting hydrophilic monomers onto poly(vinyl chloride)

The grafting of vinylacetate (VAc) or hydroxyethylmethacrylate (HEMA) onto poly(vinyl chloride) (PVC) has been performed by means of γ-rays or chemical initiators. The grafted polymer so obtained has been separated by selective extraction and submitted to IR spectroscopy in order to check the amount of grafting. The grafting percentage was measured as a function of the grafting conditions. Using the above-mentioned polymer, dissolved again in DMF, asymmetric ultrafiltration membranes have been prepared by the phase inversion technique. The membranes have been tested with Dextran solutions. Their performances have been studied as functions of the grafting amount. The values of rejection and permeating flux demonstrated the effectiveness of the treatment in enhancing the performances of PVC ultrafiltration membranes.     

Optical, electrical and discharge profiles for (PVC + NaIO4) polymer electrolytes

A sodium ion conducting polymer electrolyte based on poly (vinyl chloride) (PVC) complexed with NaIO₄ was prepared using a solution-cast technique. Optical properties such as direct and indirect optical energy gap, and optical absorption edge were investigated in pure and doped PVC films from their optical absorption spectra in the 200–600 nm wavelength region. The direct optical energy gap for pure PVC lies at 3.14 eV while it ranges from 2.60 to 3.45 eV for different composition doped films. Similar behavior was observed for the indirect optical energy gap and absorption edge. It was found that the energy gaps and band edge values shifted to higher energies on doping with NaIO₄ up to a dopant concentration of 10 wt%. Measurements of ionic conductivity and transference number were made to investigate the order of conductivity and charge transport in this polymer electrolyte. Transference number values show that the charge transport in this polymer electrolyte is predominantly due to ions (t _ion = 0.93). The conductivity increases with increase in concentration of the salt and with temperature. Using this electrolyte, cells were fabricated and their discharge profiles were studied under constant load. Miscibility studies were performed using X-ray diffraction (XRD) and Fourier Transform Infrared analysis (FT-IR) measurements.     

Synthesis of chloromethyl benzimidazole grafted polybenzimidazole with enhanced UV absorption and its effect as a stabilizer on the ultraviolet-aging behaviors of poly(vinyl chloride) films

Poly(vinyl chloride) (PVC) is particularly susceptible to UV damage, and its durability can be reduced substantially when it is exposed to outdoor environments. In this study, high-molecular-weight polybenzimidazole (PBI) was synthesized and then grafted with 2-chloromethyl benzimidazole. The polybenzimidazole grafted with 2-chloromethyl benzimidazole (PBI-g-CMBeIm) could absorb over 99% of UV light in the region 220–420 nm. Then, PVC–PBI-g-CMBeIm blend films were prepared by a solution-casting method, and the effects of the PBI-g-CMBeIm content and UV-irradiation time on the properties of these films were investigated. The results show that the benzimidazole moieties incorporated into the macromolecular chain of PBI provided additional conjugation units, and this allowed the films to have a stronger UV absorption and broader λ range. The yield strength of the PVC–PBI-g-CMBeIm blend films irradiated for 1000 h ranged from 16.5 to 27.7 MPa; this increased 3.2–14.4 MPa compared with that of the pure PVC. The strength retention rate of the pure PVC was 28.8%, whereas that of the PVC–PBI-g-CMBeIm blend films was in the range 34.1–55.2%. The addition of PBI-g-CMBeIm also effectively increased the thermal degradation temperature of the blend films and slowed down their thermal degradation rate. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47626.     

Photodegradation of plasticized poly(vinyl chloride) stabilized by different types of thermal stabilizers

Photodegradation of plasticized poly(vinyl chloride) (PVC) stabilized by different thermal stabilizers including organic calcium complex and mercaptide organotin was investigated. Plasticized PVC sheets prepared by an open twin‐roller mill and plate vulcanizing machine were exposed to xenon‐arc light with the irradiance of 0.51 W/(m²·nm) at 65°C. A much better color stability displayed by mercaptide organotin than organic calcium complex has been confirmed by digital photos and color difference. This can be explained that the more effective mercaptide organotin minimizes the amount of thermal damage from processing thus favours subsequent UV weathering. Carbonyl index and decomposition activation energy (E_a1) obtained from attenuated total refection‐Fourier transform infrared spectra (ATR‐FTIR) and thermogravimetric (TG) analysis, respectively, further indicate that plasticized PVC sheets containing mercaptide organotin have more excellent UV resistance. Mechanical tests reveal that photodegradation of PVC is accompanied by the predominant process of chain scission on the surface of samples. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Photoinitiated surface grafting of synthetic fibers,III. Photoinitiated surface grafting of poly(ethylene terephthalate) fibers

Photoinitiated surface grafting of acrylic acid (AA), acrylamide (AM) and 4-vinyl pyridine (VP) onto poly(ethylene terephthalate) (PET) fibers (a commercial textile yarn) has been studied using benzophenone (BP) as photoinitiator. A continuous process as previously described has been applied, which involves presoaking of the PET yarn in a solution of initiator and monomer in acetone and UV irradiation in nitrogen atmosphere. The resulting grafted polymer on the fiber surface has been analyzed by ESCA, titration of carboxy groups (grafted AA), and dye absorption. The relative ESCA intensities (RI) of O1s/C1s and N1s/C1s are used as measure for grafted AA, AM and VP, respectively, after recording the RI-values for ungrafted fibers. For grafting with AA, the RI-values increased from 32.8% (background) to 48.6% after 20 s irradiation time. The amount of carboxy groups measured by titration increased from 0.045 to 0.106 mmol/m². Assuming an even coverage of grafted AA polymer, this means a grafted layer of 4.8 nm thickness. After grafting, the adsorption of the dye Crystal Violet (CV) from aqueous solution increased by about 3 times. With AM as monomer, the RI-values increased from 2.6 (background) to 14.8% and the adsorption of a direct dye Sirius Lichtbordo B-LL increased by about 6 times. With VP as grafted monomer, the RI-values increased from about 2.6 (background) to 5.1% and the adsorption of the direct dye increased by about 4 times.     

Ultrafiltration membranes obtained by poly(acrylonitrile) grafted onto poly(vinylchloride)

Acrylonitrile (AN) has been grafted onto Polyvinylchloride (PVC) dissolved in Dimethylformamide (DMF) by means of gamma rays from a Co⁶⁰ source. The grafting yield has been studied as a function of irradiation dose and initial AN/PVC ratio in the solution.

The ratio PAN/PVC has been evaluated both in the grafted copolymer and its fractions by infrared spectroscopy. Ultrafiltration membranes have been prepared from the grafted PVC and its fractions, using the phase inversion technique.

The UF performances have been studied as a function of PAN grafted %.

The results show that both water flux and rejection increase with the grafting. Electron microscopy has also been employed to investigate the membrane structure.     

Photostabilization of poly(vinyl chloride) by protective coatings

The light stability of poly(vinyl chloride) plates has been substantially increased by protecting their surface with a UV‐cured acrylic clearcoat containing both a UV absorber and a HALS radical scavenger. To ensure a long‐lasting adhesion, the coating was photochemically grafted onto the PVC substrate. The coated PVC sample remained transparent, non‐colored, and glossy upon accelerated QUV‐B weathering for up to 3000 hours. An additional advantage of this method of photostabilization is to improve some of the surface properties of the coated polymer, such as its resistance to solvents, abrasion, and scratching. The method was also successfully used to recover highly photodegraded PVC and make it even more weathering‐resistant than the original polymer.     

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.     

Grafting of Hindered Amine Stabilizer in Poly(propylene) Films under γ‐Irradiation

Summary: In this paper, the grafting of a hindered amine stabilizer (HAS) is studied in isotactic poly(propylene) (PP) films under γ‐irradiation. The HAS used has a definite structure that combines a hindered amine functionality and a UV‐absorbing unit (benzylidene malonate ester group) detectable at 308 nm in the UV spectrum of PP film and 314 nm in chloroform. The stabilizer is added to the polymer at various concentration ratios: 0.1, 0.2, and 0.3 wt.‐%. The percentage of HAS grafting in the PP film at various additive concentrations is determined as a function of γ‐radiation dose in the range of 0–100 kGy by direct spectroscopic measurements through the absorption band of the stabilizer in the UV spectra of the PP film. The percentage of free HAS extracted with chloroform from the PP film versus the radiation dose is determined by UV spectroscopy for all the additive concentrations used. This study reveals that only 80% of the HAS is grafted on the 100 kGy irradiated PP matrix independent of the additive concentration used. However, the percentage of HAS grafted on PP films displays an exponential dependence on γ‐radiation dose. These results are consistent with the data obtained on the free HAS content. γ‐Irradiation grafting of HAS in the PP is accompanied by the oxidative degradation of the polymer substrate that is evaluated by increasing the carbonyl index and reducing significantly the oxidation induction time of the PP films.

The percentage of hindered amine stabilizer grafted to the PP film as a function of γ‐radiation dose.     

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     

Surface modification of polyacrylonitrile (PAN) fibers by grafting of natural polymer-soybean protein (SP)

Summary A novel method of modifying polyacrylonitrile (PAN) fibers by grafting of soybean protein (SP) onto it was studied. The reactant of PAN-g-SP fiber was prepared based on chlorination of the hydrolyzed PAN fiber. The effects of chlorination and grafting conditions on the grafting efficiency were investigated. The grafting efficiency first increases with the increase of the addition of thionyl chloride (SOCl₂), chlorination time and temperature and then levels off. In grafting reaction, grafting efficiency increases at first and then declines significantly with increasing addition of sodium hydroxide (NaOH), grafting temperature and time. The grafted polymer was characterized by FT-IR spectroscopy, X-ray diffraction and SEM images. The results indicated that SP was grafted onto the PAN fiber. PAN-g-SP also exhibits good hygroscopicty and proper mechanical properties.     

Novel multimonomer‐grafted polypropylene preparation and application in polypropylene/poly(vinyl chloride) blends

A novel grafted polymer was prepared in one step through free‐radical melt grafting in a single‐screw extruder. It was shown that the addition of styrene (St) to the melt‐grafting system as a comonomer could significantly enhance the grafting degree of methyl methacrylate (MMA) onto polypropylene (PP) and reduce the degradation of the PP matrix by means of Fourier transform infrared and melt flow rate testing, respectively. Then, the potential of using multimonomer‐grafted PP, which was designated PP‐g‐(St‐co‐MMA), as the compatibilizer in PP/poly(vinyl chloride) (PVC) blends was also examined. In comparison with PP/PVC blends, the average size of the dispersed phase was greatly reduced in grafted polypropylene (gPP)/PVC blends because of the addition of the PP‐g‐(St‐co‐MMA) graft copolymer. The tensile strength of the gPP/PVC blends increased significantly, and the impact strength was unchanged from that of the pure PP/PVC blends. The results of differential scanning calorimetry and scanning electron microscopy suggested that the compatibility of the PP/PVC blends was improved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Chemical Functionalization of Graphene Oxide by Poly(styrene sulfonate) Using Atom Transfer Radical and Free Radical Polymerization: A Comparative Study

Poly(sodium styrenesulfonate)-functionalized graphene was prepared from graphene oxide, using atom transfer radical polymerization and free radical polymerization. In atom transfer radical polymerization route, the amine-functionalized GO was synthesized through hydroxyl group reaction of GO with 3-amino propyltriethoxysilane. Atom transfer radical polymerization initiator was grafted onto modified GO (GO-NH₂) by reaction of 2-bromo-2-methylpropionyl bromide with amine groups, then styrene sulfonate monomers were polymerized on the surface of GO sheets by in situ atom transfer radical polymerization. In free radical polymerization route, the poly(sodium 4-styrenesulfonate) chains were grafted on GO sheets in presence of Azobis-Isobutyronitrile as an initiator and styrene sulfonate monomer in water medium. The resulting modified GO was characterized using range of techniques. Thermal gravimetric analysis, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy results indicated the successful graft of polymer chains on GO sheets. Thermogravimetric analysis showed that the amount of grafted polymer was 22.5 and 31?wt% in the free radical polymerization and atom transfer radical polymerization methods, respectively. The thickness of polymer grafted on GO sheets was 2.1?nm (free radical polymerization method) and 6?nm (atom transfer radical polymerization method) that was measured by atomic force microscopy analysis. X-ray diffractometer and transmission electron microscopy indicated that after grafting of poly(sodium 4-styrenesulfonate), the modified GO sheets still retained isolated and exfoliated, and also the dispersibility was enhanced.