Monomer Diluent Research Articles

Study of the Defects and Water Absorption Behavior in Jute-reinforced Polymer Composites using Film Neutron Radiography

Neutron radiography method has been adopted to study the defects and water absorption behavior in jute-reinforced polymer composites using the thermal neutron radiography facility of 3MW TRIGA MARK-II Research Reactor of Atomic Energy Research Establishment, Savar Dhaka, Bangladesh. The composite is prepared with jute fabrics and a formulated solution composed of a urethane triacrylate oligomer, reactive monomer diluents, and an additive urea under Co-60 radiation. Optical density of the neutron radiographs is adopted for measurements in both the cases. Densitometric measurements of the neutron radiographs show that in the composite, the associated solutions are diffused and exposed by dose uniformly. The water absorption of the composite with time is negligible.

Evaluation of two Bis-GMA analogues as potential monomer diluents to improve the mechanical properties of light-cured composite resins

The aim of this study was to investigate the influence of new diluent agents, diluent ratio and filler content, on relevant mechanical properties of several novel composite resins containing Bis-GMA as resin matrices, and to compare these with the properties of composites based on TEGDMA, a conventionally used diluent. Two Bis-GMA analogues were synthesized and 20 experimental composite resins were prepared combining three monomer mixtures (Bis-GMA/TEGDMA, Bis-GMA/CH3 Bis-GMA and Bis-GMA/CF3 Bis-GMA), at three dilution rates (85/15, 10/90, 0/100) and three levels of hybrid filler content (barium aluminosilicate glass): 0, 10 and 35%. Flexural strength (FS), modulus of elasticity (ME) and microhardness (VHN) of the composites were evaluated. Five specimens of each material were prepared for each mechanical test, light-cured over 120 s and stored in water at 37 degrees C for 1 week. Three-point bending test was used for FS measurement and VHN was quantified by using a Vickers microindentor. Data were analyzed by ANOVA and Student-Newman-Keuls tests (P<0.05). Materials with CH3 Bis-GMA showed an enhanced VHN. Mean FS was higher for matrices containing TEGDMA. Overall, dilution favored FS and VHN but not ME. Filler loading specially improved ME and VHN. Results correlate with an increase in the extent of polymerization due to the higher flexibility of the less viscous comonomer starting system and the hydrophobic character of the Bis-GMA analogues.

Relationship Between Physical-Mechanical Properties and Glass Transition Temperatures of UV-Cured Polymers

A urethane acrylate oligomer (LR 8739) was used in combination with functional monomer diluents and codiluents possessing different glass transition temperatures (Tg 's) to prepare thin polymer films under ultraviolet (UV) radiation. The amount of photoinitiator (Irgacure 184) and radiation dose intensity were optimized. The UV-cured films prepared at the optimized parameters were characterized to determine pendulum hardness, gel content, and tensile properties; these properties were correlated with glass transition temperatures of the UV-cured polymer films. The Tg values of the film were calculated on the basis of the Fox equation. The effect of codiluents on these properties was also investigated in consideration of the Tg values of the polymeric films prepared in the presence of codiluents.

Study of radiation-Cured thin films of aliphatic and aromatic urethane acrylate prepolymers

Eighty different formulations have been developed with aliphatic (M1200) and aromatic (M1100) urethane diacrylate oligomers in combination with eight functional monomer diluents and five comonomers. Thin polymer films were prepared with these formulations under electron beam (EB) and ultraviolet (UV) radiation. These films were then characterized. Glass transition temperatures (Tg) of the homopolymer of monomer diluents were correlated with physical properties of these films. Effects of modes of radiation, backbone structures of oligomers, and monomer functionalities on properties of the cured films are discussed. © 1998 John Wiley & Sons, Inc. Adv Polym Techn 17: 259–267, 1998

Characterization of Radiation-Induced Thin Films of Urethane Oligomer

Forty different formulations were developed with urethane diacrylate (M1200) oligomers (containing an aliphatic backbone chain) in the presence of eight different functional monomer diluents additives and five co monomers (co additives). Thin films, prepared with these formulations under ultraviolet (UV) and electron beam (EB) radiations, were characterized. The theological properties were correlated with glass transition temperature (T g) of the co monomer diluents. Results obtained with M1200 under UV and EB radiations are discussed and compared with those of aromatic urethane (M1100) films, previously reported.

Synthesis, characterization, and application of tetraethylene glycol diacrylate crosslinked polystyrene support for gel phase peptide synthesis

Styrene and tetraethylene glycol diacrylate (TTEGDA) were copolymerized by the free radical aqueous suspension polymerization technique, employing toluene as the monomer diluent at 80°C. The resulting beads were functionalized by chloromethylation. The copolymer was characterized by IR and high-resolution solid-state 13C-NMR techniques. Scanning electron microscopy was employed to observe shape, size, and morphological features of the crosslinked bead copolymer. The swelling capacities of the copolymer were measured in various solvents. Reactivity of the amino functionalized polymer was compared with divinylbenzene-polystyrene (PS) resin. Stability of the copolymer was tested under various peptide synthetic conditions. High capacity chloromethyl TTEGDA-crosslinked PS was employed as a solid support in the synthesis of the hydrophobic peptide Boc(Ala-Leu-Ala)4-OMe. The coupling and deprotection steps in the synthetic scheme proceeded in near quantitative yields, supporting the positive role of the flexible and hydrophilic crosslinking agent. The fully protected 12-residue peptide was cleaved from the support by a transesterification procedure in 85% overall yield and characterized by thin-layer chromatography, amino acid analysis, and 1H-NMR. © 1996 John Wiley & Sons, Inc.

Effect of diluents on the thermal and mechanical properties of electron beam cured films of urethane acrylates

In the formulation of an oligomer and a reactive monomer, a second diluent (called co-monomer) has been incorporated in order to study their influence on the tensile properties, thermal behaviour (shape memory), 180° folding test and deformation stability of the electron beam (EB) cured films. Incorporation of co-monomer into the oligomer/monomer system has been advantageous as it can produce more shape memorised films than the oligomer/monomer system; it can also induce shape memory character in the film whose Tg values are lower than 0°C. This is unique. There is a good correlation among Tg monomer diluent, tensile properties and shape memory temperature of the cured films.

Synthesis and characterization of phenyl acrylates crosslinked to hydroquinone diacrylate

Styrene, glycidyl methacrylate, phenyl methacrylate, and 2,4,6-tribromo and 4-acetylphenyl acrylates are copolymerized with hydroquinone diacrylate (4 mol%) by a free-radical aqueous suspension polymerization technique employing chlorobenzene as the monomer diluent at 8O°C. Optical microscopy showed the formation of both translucent and opaque resins depending upon the interactions of the diluent with the polymer. The copolymer supports were microporous and basically hydrophobic in nature. The swelling capacities of the copolymers are measured in various solvents

Synthesis and characterization of styrene‐based polymer supports

AbstractA number of reactive styrene derivatives 3a – h was synthesized and copolymerized in suspension with styrene and divinylbenzene to produce beaded styrene‐based resins 5a – h, carrying bromo, methoxy, chloromethyl, hydroxymethyl, hydroxyethyl, or α‐hydroxy‐4‐methoxybenzyl groups. The swelling behaviour of selected samples of these resins was studied in tetrahydrofuran, toluene, dichloromethane, dioxane, ethyl acetate, dimethylformamide, and methanol. Swellability data are given for resin samples having different percentages of crosslinking and for those produced in the presence of chlorobenzene as a monomer diluent (or polymerization solvent). The significance of the swellability data are briefly discussed in terms of the nature of solvent, the degree of crosslinking and the effect of the monomer diluent on the matrix structure. Details of a series of model reactions of the resin‐bound functional groups are also given, and the results are discussed on the basis of resin swellability and polymer‐substrate compatibility.

Elastomeric electron beam-cured coatings: Structure–property relationships. I. Oligomer structure

Mechanical properties of electron beam-cured films were studied as a function of oligomer structure and monomer diluent. In films cast from polyester acrylourethane oligomers, increasing the chain length between the two acrylate groups on each end resulted in a decrease in breaking strength from 7000 psi to 1000 psi in Young's modulus from 200,000 psi to 700 psi, and in glass transition temperature from 50 to −25°C, while the ultimate elongation increased from 20% to 210%. These properties were virtually independent of dose above 1 Mrad. The elongations were compared with literature values at equivalent degrees of crosslinking and found to fall within the range, but on the low elongation side of the distribution. It was speculated that the crosslinks' functionality would equal the average degree of polymerization of the double bond at each end of the oligomer, resulting in multirayed, star-shaped crosslinks with less flexibility than those with the usual functionality of 3 or 4, and methods for reducing this functionality were investigated. Addition of active monomers effected only minor change, but diethylaminoethyl acrylate was found to be very helpful in increasing the extensibility of these films considerably. This behavior can be explained by assuming that this monomer has a significant chain transfer constant, which should reduce the degree of polymerization of acrylic endgroups, producing a looser structure.

Morphology of nascent polyolefins prepared by Ziegler‐Natta catalysis

AbstractThe morphology of nascent (i.e., as‐polymerized) Ziegler‐Natta polymers was studied by optical and electron microscopy and x‐ray and electron diffraction. Observations were made on six polyolefins: polyethylene, polybutene, polypropylene, polystyrene, poly‐4‐methylpentene‐1, and polyisoprene. These polymers were synthesized by using conventional techniques by polymerizing the undiluted monomer or monomer–diluent mixtures with a preformed heterogeneous catalyst obtained by reacting a titanium halide and aluminium alkyl. After the reactions were terminated the polymers were subjected to suitable purification treatments and stored in the wet state. Observations in the optical microscope revealed that, in most cases, the polymers is formed as discrete hollow particles with a fibrous texture, but in a few instances, depending upon experimental conditions, it could also form as fibrous sheets or webs. More detailed observations in the electron microscope showed that the polymer is composed of a profusion of fibrils 200–1000 A. in width and of indefinite length. The fibrils themselves have a fine structure as indicated by the presences of lamellae running prependicular to their length. Various interpretations of this appaerent structure are discussed. The x‐ray and electron diffraction studies show that the molecular chain axis is oriented prependicular, or nearly so, to the plane of fibril lamellae and suggest that the molecules are folded within the lamellae in a manner analogous to conventional polymer single crystals. As fibril formation is observed under most conditions of polymerization it is considered to be basic to the mechanism of Ziegler‐Natta catalysis. It is proposed that the fibrils are formed by the crystallization of polymer chains growing from the active sites on the catalyst surface. The process is likened to root growth in whiskers, new materials being added at the base or root. The detailed mechanism of fibril formation and of the organization of the fibrils into larger structural formations are obscure, but several possibilities are discussed.