Emulsion Graft Research Articles

γ‐Radiation–induced emulsion graft copolymerization of MMA onto jute fiber

AbstractGraft copolymerization of methyl methacrylate (MMA) onto jute substrate was carried out using gamma radiation (60Co) both by the preirradiation and “simultaneous irradiation and grafting” methods in an aqueous emulsion system. The variation of graft weight with radiation dose, intensity of radiation, and irradiation environment was investigated. In the case of the preirradiation method, irradiation in air produced up to 30% graft weight compared to only 20% obtained when the irradiation was conducted in nitrogen environment. In this method the graft copolymerization reaction was initiated by reactive species having different life times, some of which were very long. In simultaneous irradiation and grafting method, the graft weight passes through a maximum value (∼15%) with radiation dose and graft weight limited due to excessive homopolymerization. A comparative study on the mechanical properties of samples grafted by both preirradiation and simultaneous irradiation and grafting methods was carried out. The results showed that the method of grafting has significant influence on the mechanical properties of grafted jute. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 132–140, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/adv.10016

Microphase separation in poly(acrylonitrile–butadiene–styrene) (ABS) studied with paramagnetic spin probes. I. Electron spin resonance spectra

AbstractMicrophase separation in poly(acrylonitrile–butadiene–styrene) (ABS) was studied as a function of the butadiene content and method of preparation with electron spin resonance (ESR) spectra of nitroxide spin probes. Results for the ABS polymers were evaluated by comparison with similar studies of the homopolymers polybutadiene (PB), polystyrene (PS), and polyacrylonitrile (PAN) and the copolymers poly(styrene‐co‐acrylonitrile) (SAN) and poly(styrene‐co‐butadiene) (SB). Two spin probes were selected for this study: 10‐doxylnonadecane (10DND) and 5‐doxyldecane (5DD). The probes varied in size and were selected because their hydrocarbon backbone made them compatible with the polymers studied. The ESR spectra were measured in the temperature range 120–420 K and were analyzed in terms of line shapes, line widths, and hyperfine splitting from the 14N nucleus; the appearance of more than one spectral component was taken as an indication of microphase separation. Only one spectral component was detected for 10DND in PB, PS, and PAN and in the copolymers SAN and SB. In contrast, two spectral components differing in their dynamic properties were detected for both probes in the three types of ABS samples studied and were assigned to spin probes located in butadiene‐rich domains (the fast component) and SAN‐rich domains (the slow component). The behavior of the fast component in ABS prepared by mass polymerization suggested that the low‐Tg (glass‐transition‐temperature) phase was almost pure PB. The corresponding phase in ABS prepared by emulsion grafting also contained styrene and acrylonitrile monomers. A redistribution of the spin probes on heating occurred with heating near the Tg of the SAN phase, suggesting that the ABS polymers as prepared were not in thermodynamic equilibrium. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 415–423, 2002; DOI 10.1002/polb.10109

Grafted stock synthesis of ABS at the ultimate high ratio of polybutadiene to poly(styrene‐co‐acrylonitrile)

AbstractThis study describes the emulsion grafting of styrene and acrylonitrile onto 60–70% polybutadiene (PB), in the presence or absence of tert‐dodecanetiol as a chain transfer reagent with a radical initiator, and the properties of the obtained grafted stock. There was no significant difference in terms of effect of the initiation mode on the grafting efficiency resulting from the high grafting reactivity of PB. However, the grafted stock with 70% PB prepared in the presence of tert‐dodecanetiol and the adequate selection of an initiation system gave a homogeneous dispersion of the PB particles into poly(styrene‐co‐acrylonitrile) (SAN) matrix. The initiation system involves tert‐butyl peroxylaurate, tert‐butyl peroxyacetate, and tert‐butyl peroxyisopropylcarbonate coupled with ferrous sulfate. The efficient coverage of the SAN grafted layer around 70% PB particles was observed by TEM to eventually give excellent impact resistance, high surface gloss, and good thermal resistance. The absence of tert‐dodecanetiol resulted in a toughness reduction of ABS. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3462–3470, 2001

Emulsion graft polymerization: mechanism of formation of dispersions

Three stages of the kinetics of graft polymerization of methyl acrylate onto water soluble polymers have been investigated. Polymer particles of graft copolymers contained polyacrylic chains, monomer and water during the whole process. Graft copolymer, formed on the first stage of the polymerization, is a stabilizer of polymer particles in water dispersion. The distribution of monomer between water phase and polymer particles showed that the polymerization proceeds generally in the particles. Nephelometric investigations and adsorption titration of dispersions showed that the adsorption saturation of dispersion particles can change during the process and its final value is high for graft copolymers of water soluble cellulose derivatives and nitrolignin.

Properties of PHMS-g-p [butylacrylate (BA)-N-hydroxyl-methyl acrylamide (NMA)] graft copolymer emulsions

Emulsion graft copolymerization of poly(hydrogenmethylsiloxane) (PHMS) and butyl acrylate (BA) in the presence of functional comonomer N-hydroxyl-methyl acrylamide (NMA) was conducted by batch emulsion copolymerization to modify the properties of polysiloxane. Morphology of graft copolymer particles was characterized by transmission electron microscopy. The effect of polymerization method, PHMS content, initiator concentration, and NMA content on stability of emulsion, morphology, size of particle, and rheological properties were investigated. It has been found that stability of emulsion is better by semicontinuous emulsion polymerization than that of batch emulsion polymerization and it increased with increasing PHMS-NMA concentration. Increasing PHMS concentration and NMA concentration, the particle size and the viscosities increase. The property of resistance to electrolytes of graft copolymer emulsions and swelling property of film were also discussed. Results showed PHMS-g-P [butylacrylate (BA)-N-hydroxyl-methyl acrylamide (NMA)] graft copolymer emulsion has good resistance to electrolytes and the water absorption of its film increases with increasing BA-NMA content grafted onto PHMS. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2209–2217, 1999

Novel emulsion graft copolymerization onto the silylmethyl group of poly(dimethylsiloxane)

The influence of radical initiators upon the emulsion graft copolymerization of styrene and acrylonitrile onto poly(dimethylsiloxane) (PDMS) was studied. As initiators, a series of peroxides and hydroperoxides were coupled with ferrous sulfate, among which the tert-butyl peroxylaurate system gave the highest grafting efficiency (30%). The tert-butyl peroxylaurate initiator fulfills the criteria for efficient radical grafting by generating only the tert-butoxy radical, which is reluctant to form a carbon radical via β-scission, being highly hydrophobic, and not carrying a tertiary hydrogen that may be abstracted by a radical. 13C-NMR analysis of the products showed that the grafting occurred on the silylmethyl groups of PDMS to give 10–25 grafts per polymer and graft ratio in the range 44–140%. The PDMS graft copolymers thus obtained could be used as surface-modifying agents to improve the lubricity and water-repellency of ABS [poly(styrene-co-acrylonitrile)-graft-polybutadiene]. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2607–2617, 1997

Some features of the heterophase emulsion graft polymerization of glycidyl methacrylate to polycaproamide fibre

-- The special features of the graft polymerization of glycidyl methacrylate to polycaproamide fibre have been discovered. An anomalous effect of the copper compound and of hydrogen peroxide in the composition of the redox system on the rate of graft polymerization of glycidyl methacrylate has been found.

Mechanical behavior of dual-rubber-modified SAN

The use of either an SBS block copolymer or an emulsion-made methyl-methacrylate-grafted rubber alone failed to give any significant increase in the toughness of brittle poly(styrene-co-acrylonitrile) (SAN), even at concentrations up to 50%. However, a combination of the two rubber modifiers produced a strong synergistic toughening. All specimens were prepared by injection molding; however, annealing to relax orientation did not significantly alter this synergistic effect. The use of mechanical dilatometry showed that post-yield deformation of blends containing both modifiers involved some crazing just after yielding but subsequent deformation was mostly due to shear yielding. Addition of SBS alone to SAN resulted in a mixed crazing/shear yielding mode of post-yield deformation with the relative proportions of the two mechanisms being constant up to failure. In contrast, the small emulsion graft particles alone gave rise to a predominant shear yielding deformation. A qualitative mechanism for the synergism is discussed.

Special features of the emulsion graft polymerization of styrene to cellulose fibres

Special features of the emulsion graft polymerization of styrene to cellulose fibres

High Level Grafting of Grapevines

High-level cleft or notch grafts made on <i>Vitis vinifera</i> L. grapevines at 2 to 3 feet above the ground surface were equally successful although the notch grafts made smoother unions. Bark grafts were less successful. Notch grafts made in mid-April, about a month after bud burst but prior to bark slippage, were equal or superior to earlier grafting. Painting the scions and the black asphalt-water emulsion grafting compound with white interior latex or vinyl paints improved the success of either early or late grafts. These paints reduced moisture loss from the scion wood.

Effect of oxygen on intensity exponents of radiation‐induced polymerization rates

AbstractGamma radiation‐induced graft polymerization to natural rubber in benzene solution (solution grafting), graft polymerization to natural rubber latex (Emulsion grafting), and emulsion polymerization of three vinyl monomers—styrene (St), methyl methacrylate (MMA) and acrylonitrile (AN), were carried out under air atmosphere to compare the radiation intensity exponent of each polymerization rate under air atmosphere with that under nitrogen atmosphere or under vacuum. The intensity exponents of the solution grafting both under air atmosphere and under exclusion of air were found to be numerals near one half. This indicates prevailing normal radical mechanism. However, the intensity exponents of the emulsion grafting under air atmosphere were found to be 0.94, 1.00, and 0.82 for St, MMA, and AN, respectively, and those of the emulsion polymerization under air atmosphere, 0.16 and 0.15 for St and MMA, respectively, although those of both emulsion grafting and emulsion polymerization under exclusion of air were found to be numerals near to one half except for that of emulsion polymerization of AN. For emulsion grafting, the initiating species is considered to be trunk polymer radical but the terminating species is assumed to be the radical(s) produced in the water phase in the presence of oxygen. For emulsion polymerization, both initiating and terminating species are assumed to be the radical(s) produced in the water phase in the presence of oxygen.