Preparation of high PMMA grafted particle SiO2 using surface initiated free radical polymerization

In this work, a convenient surface-initiated free radical graft-polymerization method, by which polymethacrylic acid (PMAA) with a high grafting density was grafted on silica gel particles, was put forward, and it was feasible and effective. The coupling agent γ-aminopropyltrimethoxysilane (AMPS) was first bound onto the surfaces of silica gel particles, obtaining the modified particles AMPS-SiO₂. So a redox initiation system was constituted with the amino groups on the surfaces of AMPS-SiO₂ particles and ammonium persulphate in the solution. A great deal of primary free radicals on the surfaces of AMPS-SiO₂ particles is produced via the redox initiating reaction, so that the surface-initiated free radical graft- polymerization of methacrylic acid (MAA) on the silica gel particles was realized, giving the grafted particles PMAA/SiO₂ with a high grafting degree (about 30 g/100 g) of PMAA. The effects of the main factors on the surface initiated graft polymerization were examined and the corresponding mechanism was investigated in depth. The experimental results show that for this surface-initiated free radical graft-polymerization of MAA, the suitable temperature is 40 °C. If the temperature is over 40 °C, the graft polymerization will be affected negatively, and the grafting degree of PMAA will decline because of the intense heat decomposition of ammonium persulphate. During the graft polymerization, the grafted polymer layer that has formed is a hindrance to the subsequent graft polymerization. The used amount of initiator and the monomer concentration affect the graft polymerization greatly. The appropriate reaction conditions are as follows: reaction time of 10 h, initiator persulphate amount of 1.1% (it implies the mass percent of the monomer), and monomer MAA concentration of about 5% (it drives at the mass percent of the solution).     

Role of nanoclay in determining microfibrillar morphology development in PP/PBT blend nanocomposite fibers

In this work, a new and highly efficient method of surface-initiated free radical graft-polymerizations on the surfaces of silica gel particles was put forward, and the graft-polymerization of methacrylic acid (MAA) was conducted. This method was convenient, feasible and highly effective. Coupling agent ??-mercaptopropyltrimethoxysilane(MPTS) was first bonded onto the surfaces of silica gel particles, obtaining the modified particles MPTS-SiO₂, onto which mercapto groups were chemically attached, so a redox initiation system of graft-polymerization was constituted by the mercapto group on the surfaces of MPTS-SiO₂ particles and the cerium (IV) salt in the solution. And then the surface-initiated free radical graft-polymerization of MAA on the surfaces of silica gel particles was carried out, resulting in the grafted particles PMAA/SiO₂ with a very high grafting density (35?g/100?g) of PMAA. The grafted particles PMAA/SiO₂ were characterized by infrared spectrum (FTIR), scanning electron microscope (SEM) and thermogravimetric analysis (TGA). The effects of the main factors on the new surface-initiated graft polymerization were emphatically examined, and the corresponding mechanism of the graft-polymerization was investigated in depth. The experimental results show that the mercapto group-cerium salt system analogous to the hydroxyl group-cerium salt system, can also effectively initiate vinyl monomers to be graft-polymerized on the surfaces of solid particles, and furthermore, it is a highly effective surface-initiated graft-polymerization method. In this graft-polymerization system, several factors such as sulfuric acid concentration, the used amount of cerium salt and the reaction temperature affect the grafting density greatly. For the graft-polymerization of MAA, the appropriate reaction conditions are as follows: reaction time of 3?h, reaction temperature of 50?°C, cerium concentration of 5.0?×?10^?3?M, acid (H⁺ ion) concentration of 0.15?M and MAA concentration of 0.5?M.     

Latexes of starch-based graft polymers containing polymerized acrylonitrile

The scope of graft reactions to produce starch-based latexes was extended by graft polymerization of acrylonitrile (AN) onto gelatinized cationic starch possessing quaternary amine functionality and by graft terpolymerization of AN and t-butylaminoethyl methacrylate (TBAEM) onto gelatinized starch by cerium (IV) initiation at 25°C. Grafting onto starches containing highly basic quaternary amines gave polyacrylonitrile [poly(AN)] grafts having about one fourth the number-average molecular weight (M?_n) (178,000–232,000) of those produced by grafting AN onto starches containing the less basic tertiary amine groups. Sonification at 20 KHz of graft polymerization reaction mixtures having up to 8% solids reduced viscosities from 400–3000 cP to 10–40 cP. Diameters of dried particles measured about 300–1500 Å. Shaker-type agitation during grafting onto starch having quaternary amine groups produced poly(AN) chains with lower M?_n values than those produced during blade stirrer-type agitation. M?_n values of grafted poly(AN) decreased with increasing reaction time, degree of substitution of amine in the starch, gelation time of cationic starch at 95°C, and cerium (IV) concentration. AN was copolymerized with TBAEM at molar ratios of 14–85:1 in grafting onto gelatinized starch to yield copolymer side-chain grafts analyzing 8–52:1 of polymerized AN to TBAEM moieties.     

Graft polymerization of acrylamide onto UV-irradiated films

Graft polymerization of acrylamide was attempted onto the surface of films preirradiated with UV radiation. The films employed are nylon 6, polypropylene, and ethylene–vinyl acetate copolymers. Following UV irradiation in air on films without photosensitizer, they were placed in monomer solution, degassed, and then heated to 50°C to effect the graft polymerization. After rigorous removal of homopolymers, polyacrylamide chains were found to be grafted in the surface region of the films to amounts up to several hundred micrograms per square centimeter of films. An ESCA study revealed the UV-irradiated but not yet grafted surfaces to be oxidized, and formation of peroxides was strongly suggested by the reaction of irradiated films with 1,1-diphenyl-2-picrylhydrazyl. It is likely that the initiator responsible for the graft polymerization is peroxides generated at and near the film surfaces upon UV irradiation. The grafted films became very slippery when contacted with water, in contrast with the films UV-irradiated but not yet grafted.     

Glow-discharge-induced graft polymerization of acrylic acid onto poly[1-(trimethylsilyl)-1-propyne] film

Graft polymerization of acrylic acid onto poly[1-(trimethylsilyl)-1-propyne] [poly(TMSP)] film was examined. The water contact angle of poly(TMSP) film decreased remarkably from 90 to 15° by plasma treatment, which gradually increased up to 40° after several days. When the film exposed to a glow discharge was heated in an aqueous solution of acrylic acid at 80°C for 24 h, graft polymerization proceeded on the film surface, which was confirmed by ATR-IR and ESCA spectra. Graft polymerization effectively occurred above a threshold temperature (80°C). The water contact angle of the grafted film was about 30°, and did not change with time. In contrast, when a poly(TMSP) film exposed to UV irradiation was heated in an aqueous solution of acrylic acid, graft polymerization took place not only on the film surface but also inside the film.     

Peroxydiphosphate–metal ion–cellulose thiocarbonate redox system‐induced graft copolymerization of vinyl monomers onto cotton fabric

The grafting of methacrylic acid (MAA) and other vinyl monomers onto cotton cellulose in fabric form was investigated in an aqueous medium with a potassium peroxydiphosphate–metal ion–cellulose thiocarbonate redox initiation system. The graft copolymerization reaction was influenced by peroxydiphosphate (PP) concentration, the pH of the reaction medium, monomer concentration, the duration and temperature of polymerization, the nature of vinyl monomers, and the nature and concentration of metallic ions (activators). On the basis of a detailed investigation of these factors, the optimal conditions for the grafting of MAA onto cotton fabric with the said redox system were as follows: [Fe²⁺] = 0.1 mmol/L, [PP] = 2 mmol/L, [MAA] = 4%, pH‐2, grafting time = 2 h, grafting temperature = 70°C, and material/liquor ratio = 1 : 50. Under these optimal conditions, the graft yields of different monomers were in the following sequence: MAA ? acrylonitrile > acrylic acid > methyl acrylate > methyl methacrylate. The unmodified cellulosic fabric (the control) had no ability to be grafted with MAA with the PP–Fe²⁺ redox system. The percentage of grafting onto the thiocarbonated cellulosic fabric was more greatly enhanced in the presence of iron salts than in their absence. This held true when the lowest concentrations of these salts were used separately. A suitable mechanism for the grafting processes is suggested, in accordance with the experimental results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1879–1889, 2003     

Improved synthesis of poly(MAA)–starch graft copolymers

Graft copolymerization of methacrylic acid (MAA) onto starch using a potassium persulfate/sodium thiosulfate redox initiation system was investigated. Emphasis was placed on the promotion of graft formation while minimizing homopolymerization. This could be achieved through a thorough investigation into the major factors affecting the polymerization reaction such as the state of the starch, redox ratio of the initiator, monomer and initiator concentrations, time and temperature of polymerization, and material-to-liquor ratio. The results obtained imply that the magnitude of the polymer yield including total conversion, graft yield, and homopolymer are determined by these factors. The yield is favored under the influence of higher temperature, longer time, short liquor, and increased monomer and initiator concentrations. A poly-(MAA)–starch graft copolymer is the main product of the polymerization reactions only when starch was preswelled (through cooking prior to grafting). Moreover, this grafted product could be precipitated by more dilution with water and easily separated by filtration. Hence, the results of the current work formed the basis of a novel method for the synthesis of poly(MAA)–starch graft copolymers. The mechanisms involved in the synthesis are reported. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1709–1715, 1998     

A comparative study on effects of two kinds of polymerization methods on grafting of polymer onto silica surface

In this article we present the result of a comparative study of two kinds of polymerization methods—solution polymerization (sol. poly.) and dispersion polymerization (dis. poly.) for grafting polymer onto silica. As a model for the grafting polymerization reaction, styrene was chosen as the monomer and azo diisobutyronitrile (AIBN) as the initiator. The study aims at supplying theoretical reference for better selecting polymerization method to graft polymer on the silica particle surface. First, monolayers of 3‐methacryloylpropyl trimethoxysilane were chemically bonded onto the surfaces of micrometer‐sized silica gel particles, and so double bonds were immobilized onto the silica surface. Second, the copolymerizations between the immobilized double bonds and the monomer styrene were carried out, homopolymerizations of styrene followed, and finally polystyrene was grafted to the silica surfaces. Two kinds of polymerization methods, sol. poly. and dis. poly., were adopted respectively, and the effects of polymerization methods on grafting process were examined mainly. At the same time, the effects of different polymerization conditions on the grafting degree were researched. It was found that in the dis. poly. system the grafting degree is obviously higher than that in the sol. poly. system under the same polymerization conditions, and the grafting degree can go up to 47%, i.e. 47g/100g. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5808–5817, 2006     

Plasma induced grafting of PSt onto titanium dioxide powder. II

Grafting of polystyrene (PSt) onto titanium dioxide powder was investigated in this study. The graft polymerization reaction was induced by N₂ plasma treatment of the surfaces of the titanium dioxide powder. IR and XPS results showed that PSt was grafted onto the titanium dioxide powder. The crystal structure of the titanium dioxide powder observed by XRD spectra was unchanged after plasma graft polymerization. In the grafting reaction, the grafting yield increased with the plasma power, the plasma treatment time, and the grafting reaction, but it increased first then decreased after reaching 50°C. The type of monomers also has an effect on the grafting yield. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2112–2117, 2005     

Ce(IV)‐induced graft copolymerization of methacrylic acid on electrospun polysulphone nonwoven fiber membrane

Ce(IV)‐induced graft copolymerization of methacrylic acid (MAA) on polysulphone (PSU) surface is studied. After pretreatment either by formaldehyde solution or by air glow discharge plasma, the PSU fiber membrane was immersed in MAA solution with Ce(IV) and heated under 80°C under N₂ protection. The MAA was induced by the Ce(IV) redox initiation system to polymerize on the PSU fiber membrane surface. It was found that the pretreatment of the membrane is a very necessary condition for the graft copolymerization to obtain high graft degree. For both the formaldehyde and the air glow discharge plasma pretreated membrane, the graft degree increase with the reaction time. To study the reaction mechanism, control experiments were carried out. Membrane surfaces were characterized by ATR‐FTIR and XPS. The reaction mechanism of the graft copolymerization was discussed based on the experimental data. The effect of the graft copolymerization on the membrane's structure and water permeability was finally studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3835–3841, 2006     

Preparation of iminodiacetic acid-type composite chelating material IDAA-PGMA/SiO2 and preliminary studies on adsorption behavior of heavy metal ions and rare earth ions

A kind of iminodiacetic acid (IDAA)-type composite chelating materials was prepared by first graft polymerization and subsequent polymer reaction. Monomer glycidyl methacrylate (GMA) was grafted on micron-sized silica gel particles in the manner of “graft through” in a solution polymerization system, resulting in the grafted particles poly(glycidyl methacrylate) (PGMA)/silicon dioxide (SiO₂). Subsequently, the ring-opening reaction of the epoxy groups of the grafted PGMA was carried out with IDAA as reaction reagent, resulting in the bonding of IDAA groups onto PGMA/SiO₂ and obtaining the composite chelating material IDAA-PGMA/SiO₂ particles. The effects of the main factors on the graft polymerization of GMA and the bonding reaction of IDAA were examined emphatically, and the adsorption behavior of IDAA-PGMA/SiO₂ particles toward several kinds of heavy metal ions and rare earth ions was preliminarily explored. The experiments results show that: (a) to obtain the grafted particles PGMA/SiO₂ with high grafting degree, in the graft polymerization step, the reaction temperature and the used amount of initiator should be controlled. The suitable temperature is 70°C and the appropriate used amount of initiator is 1.4 % of the monomer mass. Under the optimal conditions, the grafted degree of PGMA can reach 17.50 g/100 g. (b) It is feasible to introducing of IDAA groups onto PGMA/SiO₂ particles via ring-opening reaction of epoxy groups of the grafted PGMA under alkaline conditions, and the bonding rate of IDAA group can get up to 70% based on epoxy groups of the grafted PGMA. (c)The composite chelating material IDAA-PGMA/SiO₂ possesses very strong chelating adsorption ability for heavy metal ions, and especially toward Pb²⁺ ion, the adsorption capacity can reach 24 g/100 g. (d) The adsorption ability of IDAA-PGMA/SiO₂ for rare earth ions is weaker than that for heavy metal ions. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Benzoyl peroxide-induced graft polymerization of 2-methyl-5-vinylpyridine onto polyester/wool blend

Graft polymerization of 2-methyl-5-vinylpyridine (MVP) onto polyester/wool blended fabric was carried out using benzoyl peroxide as initiator. The graft polymerization reaction was conducted under a variety of conditions. The graft yield increased by increasing benzoyl peroxide concentration from 0.559 mmole/l. to 1.657 mmole/l. Further increase in benzoyl peroxide concentration (i.e., up to 2.795 mmole/l.) decreased grafting. Increasing the MVP concentration from 4% to 10% caused a significant enhancement in grafting. The same held true for raising the polymerization temperature within the range of 65°–85°C. The grafting reaction proceeded initially at a fast rate and decreased with time to a slower rate. The grafted samples showed improved dyeability toward acid dye, increased density, and decreased moisture regain as compared with the untreated blend. Furthermore, a tentative mechanism for initiation of grafting was suggested.     

Graft copolymerization of methacrylic acid onto guar gum,using potassium persulfate as an initiator

Graft copolymerization of methacrylic acid (MAA) onto guar gum (GG) was carried out by free radical initiation mechanism by using potassium persulfate (PPS) as an initiator. It was found that % grafting, grafting efficiency, and % conversion were all dependent on the concentration of PPS, MAA, reaction temperature, and reaction time. Using PPS, the maximum % grafting was ascertained to be 241 at the optimum conditions of 60°C reaction temperature, 3 h of reaction time, 1.1 mmol of PPS, and 0.058 mol of MAA. Plausible mechanism for grafting reaction was suggested. The graft copolymer formed was characterized by Fourier transform infrared and differential scanning calorimetry. The graft copolymer formed could find applications in drug delivery. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 618–623, 2006     

Optimal amidoximation conditions of acrylonitrile grafted onto polypropylene by photoirradiation-induced graft polymerization

To prepare amidoxime (AO) adsorbents for uranium recovery from seawater, the optimum conditions for graft polymerization and amidoximation of acrylonitrile (AN) group and alkaline treatment of the AO group have been investigated in terms of the uranium adsorption capacity. AN has been grafted onto polypropylene (PP) fabric by photoirradiation-induced graft polymerization with benzophenone as the photoinitiator. A concentration of AN ≤1.0M, a photoirradiation time of 2 h, and a reaction temperature of 60°C proved to be optimal for the grafting of AN onto PP. The grafted AN groups were effectively converted into AO groups upon reaction with ≥5.0% (w/v) hydroxylamine solution at pH 7.0−9.0 for ≥16 h at 60−80°C. Although widely used for this purpose, we have shown that methanol is not an essential solvent for the amidoximation reaction. Conditioning of the AO group with KOH solution (alkaline treatment) proved to be effective for enhancing the uranium adsorption capacity of amidoximated PP-g-AN-AO fabric, which increased logarithmically with the conditioning time. The AO group density in the PP-g-AN-AO fabric increased linearly with the degree of AN grafting, whereas the uranium adsorption capacity of PP-g-AN-AO fabric conditioned with KOH reached a maximum at a degree of AN grafting of approximately 60%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The graft polymerization of acrylamide onto paper preirradiated with high energy electrons

The graft polymerization of acrylamide onto filter paper preirradiated in air with electrons from a 200-keV accelerator has been shown to lead to weight increases of up to 210%. The degree of grafting depends on the radiation dose, the moisture content of the paper, and the time interval between irradiation and grafting, but is independent of the radiation dose rate. The degree of grafting increases with the monomer concentration of the reaction medium, and increases as the grafting temperature is reduced. Irradiations in the presence of O₂ or N₂ and the effect of ferrous ions in the grafting solution indicated that peroxides derived from cellulose do not contribute significantly to the initiation reactions up to 60°C. The results are consistent with the degree of grafting depending primarily on the concentration of trapped radicals present in the paper at the time of copolymerization. The cellulose in the grafted material was degraded and the grafted acrylamide was isolated and its molecular weight measured and compared with a calculated value. The moisture regain characteristics of the grafted material are reported.     

Surface graft copolymerization of poly(methyl methacrylate) onto waste tire rubber powder through ozonization

Grinding of tires offers a promising opportunity for recycling waste rubber because fine waste tire rubber particle may be used as fillers and property modifiers in thermoplastic, elastomer, and thermoset blends. However, due to the lack of reactive sites on the WTR surface, the adhesion between WTR powder and matrix is poor. In this article, ozonization of waste tire rubber (WTR) powder was performed to produce some “immobile” reactive points (hydroperoxide groups) on the WTR surface. The free radical generated by the decomposition of hydroperoxide groups on WTR surface, was used to initiate graft polymerization of methyl methacrylate (MMA) onto the surface of WTR powder. The experimental results showed that MMA was successfully grafted onto the surface of WTR. The hydrophilicity of the MMA grafted WTR (MMA‐g‐WTR) was improved. The concentration of hydroperoxide groups and the graft degree were both increased with ozonization time. With increasing of polymerization time and polymerization temperature, the grafting degree increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Hydrophilic and adhesive properties of methacrylic acid-grafted polyethylene plates

Methacrylic acid (MAA) was grafted onto polyethylene (PE) surfaces by simultaneous irradiation with UV rays in the liquid phase to estimate hydrophilic and mechanical properties for MAA-grafted PE plates. The amount of grafted MAA increased sigmoidally with UV irradiation time, and the higher grafted amount was obtained at higher monomer concentrations. With an increase in grafting of MAA, the wettabilities from the contact angles of water were enhanced and the refractive indices from the ellipsometry decreased. Though the contact angles remained constant above the grafted amount of 0.02 mmol/cm², the refractive indices approached the value of PMAA around 0.009 mmol/cm², indicating that the PE surfaces were fully covered with grafted PMAA chains. Then, at a fixed grafted amount, the grafted layer can absorb more water and the grafted PE plates possessed higher tensile shear adhesive strength, in case grafting was carried out at lower monomer concentrations. Surface properties depended on the density of carboxyl group at the surfaces of grafted layers, whereas adhesive properties depended on the structural properties of grafted chains as well as on the density of carboxyl group of the whole grafted layers.     

Surface structure of low density polyethylene films grafted with acrylic acid using corona discharge

Chemical composition, morphology, and crystalline structure of low density polyethylene (LDPE) films surface grafted with acrylic acid (AA) using corona discharge were studied by attenuated total reflection infrared (ATR-IR), electron spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD) techniques. The grafted film surface is covered with grafted chains. After grafting for 3.0 h in 20% aqueous solution of AA, the depth of the grafted layer is more than 10 nm. A grain structure was observed on the grafted surfaces which was probably caused by the isolated dispersion of active sites generated by corona discharge, and these active sites initiated the graft copolymerization. However, surfaces of grafted films were smoother than that of ungrafted ones. DSC curves of grafted films show a small peak at about 100°C due to vaporization of adsorbed water. The longer the graft copolymerization time, i.e. the higher the graft degree of AA on LDPE, the higher the amount of adsorbed water. The position of each peak in WAXD patterns, crystal axial length, crystal plane distance and crystal grain size remain almost unchanged during the graft copolymerization time of 2.0 h. However, when the graft copolymerization time reaches 3.0 h, twin peaks at about 21.4° and 22.0° are observed, indicating that a different crystal form is formed at longer copolymerization time, i.e. at a higher graft degree.     

聚丙烯微波辐照固相接枝改性研究

采用微波辐照技术在聚丙烯(PP)上接枝马来酸酐(MAH),研究了反应时间、PP粒径、过氧化苯甲酰含量、PP溶胀时间、MAH含量、苯乙烯用量等对接枝率和接枝效率的影响,利用化学分析和红外光谱分析(FTIR)对接枝聚丙烯(PP-g-MAH)进行了分析和表征.结果表明,溶胀PP经微波辐照5 min即可实现MAH在PP上的接枝聚合,接枝率最高达到2.1%.     

Preparation and property of porous hydroxyapatite as an inorganic dispersant used in suspension polymerization

The porous hydroxyapatite (HAP) for suspension polymerization dispersant was prepared using calcium carbonate and phosphoric acid as raw materials. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and BET nitrogen adsorption. The results show that the prepared HAP has a porous structure, low particle density, large specific surface area, uniform particle size and does not agglomerate easily between the particles. The preparation conditions for the HAP were optimized as follows: solid content of calcium carbonate aqueous suspension 90 g/L, concentration of phosphoric acid 1.0 mol/L, reaction/aging temperature 50°C, and aging time 3 h. The HAP prepared under optimal preparation conditions has 106.8 m²·g^-1 of specific surface area, which is about 1.5–1.8 times as much as that of Japanese HAP or commercial HAP. Its application result in the suspension polymerization of styrene show that the porous HAP dispersant has high surface activity, excellent suspension dispersibility and stability and can markedly improve the quality of polystyrene beads.