Interpenetrating polymer networks from polyurethanes and poly(methyl acrylate)

Simultaneous two-component interpenetrating polymer networks (IPNs) of polyurethane (PU)–poly(methyl acrylate) (PMA) were prepared, as well as the corresponding pseudo-IPNs. A comparison was made between the full IPNs, pseudo-IPNs, and the respective homopolymers. Their ultimate mechanical properties were obtained and the dynamic glass transition temperatures (T_g's) were found using a thermomechanical analyzer. At all compositions, a single T_g(except 50–50 wt %) was found.     

Interpenetrating polymer networks from castor oil based polyurethanes and poly(ethyl acrylate)

Polyurethanes were obtained by the reaction of hydroxyl groups of castor oil with hexamethylene diisocyanate, isophorone diisocyanate or diphenylmethane diisocyanate using an NCO/OH ratio of 1.6. These polyurethanes were swollen in ethyl acrylate monomer and subsequently polymerized by radical polymerization initiated with benzoyl peroxide in the presence of the crosslinking agent ethylene glycol dimethacrylate. A series of interpenetrating polymer networks (PU/PEA IPNs) were obtained as tough films by casting in glass moulds. The characteristics of these films were determined: resistance to chemical reagents, thermal behaviour (DSC, TGA), tensile strength, Young's modulus, elongation at break (%) and Shore A hardness. The morphology was determined by scanning electron microscopy, and the dielectric properties such as electrical conductivity, dielectric constant (ε′), dielectric loss (ε″) and loss tangent (tan δ) were studied.     

Interpenetrating polymer networks from castor oil-based polyurethanes and polystyrene,XXV

Interpenetrating polymer networks (IPNs) of castor oil-based polyurethanes and polystyrene were prepared by simultaneous polymerization. The liquid prepolyurethanes were formed by reacting the hydroxyl functionality of castor oil with isophorone diisocyanate using different stoichiometric NCO/OH ratios. These prepolyurethanes were mixed with styrene monomer and subsequently polymerized by free radical polymerization initiated by benzoyl peroxide in the presence of the crosslinker 1,4-divinyl benzene. The interpenetrating polymer networks. PU/PS IPNs, were obtained as tough and transparent films by the transfer moulding technique. These IPNs were characterized by the static mechanical properties (tensile strength, Young's modulus and % elongation), thermal properties and morphology. The dielectric relaxation properties (σ, E′, E″ and tanδ) of the IPNs at different temperatures were studied.     

Interpenetrating polymer networks from caster oil-based-polyurethanes and poly(ethyl acrylate). VII

Liquid prepolyurethanes were synthesized from castor oil and toluene-2, 4-diisocyanate (TDI) under different experimental conditions and varying NCO/OH ratios. All these prepolyurethanes were subsequently reacted with ethyl acrylate/ethylene glycol dimethacrylate mixtures by radical polymerization using benzoyl peroxide as initiator to obtain interpenetrating polymer networks (IPNs) by transfer molding. The novel polyurethane/poly(ethyl acrylate) IPNs are found to be tough films. These IPNs are characterized in terms of their resistance to chemical reagents, thermal behavior (DSC, TGA), mechanical behavior including tensile strength, Young's modulus, and elongation. The dielectric properties, namely electrical conductivity (σ), dielectric constant (ε′), dielectric loss (ε″), and loss tangent (tan δ) were computed. The mechanothermal behavior was analyzed by dynamic mechanical spectroscopy. The morphological behavior was studied by scanning electron microscopy.     

Semi-interpenetrating polymer networks from castor oil-based polyurethanes and chlorinated rubber

Semi-interpenetrating polymer networks (semi-IPNs) were prepared by crosslinking castor oil in the presence of chlorinated rubber. Crosslinking in toluene solution was effected with 2,4-toluene diisocyanate or hexamethylene diisocyanate at various NCO/OH ratios. The semi-IPNs were obtained as tough films and were characterized by their mechanical, thermal, morphological and electrical properties.     

Interpenetrating polymer networks from castor oil based polyurethane and poly(methyl methacrylate), III

Liquid prepolyurethanes (PPU) were obtained from castor oil and toluene-2,4-diisocyanate under different experimental conditions varying NCO/OH ratio. All these prepolyurethanes were subsequently interpenetrating with poly(methyl methacrylate) made by radical polymerization initiated with benzoyl peroxide. The novel PPU/PMMA interpenetrating polymer networks were obtained as though films by transfer moulding. They were characterized by thermal studies (DSC and TGA) and mechanical properties viz., tensile strength, modulus of elasticity, and percent elongation at break. The morphological behaviour was analyzed by scanning electron microscopy.     

Interpenetrating polymer networks of castor oil polyester and poly(methyl methacrylate)

The physical and mechanical properties of interpenetrating polymer networks (IPNs) and semi-I IPNs of the castor oil polyester network and poly(methyl methacrylate) were investigated. In the semi-I IPNs, the second component was a copolymer of poly(methyl methacrylate) and polystyrene (PS) or poly(methyl methacrylate) and poly(n-butyl acrylate) (PnBA). The dynamic mechanical properties indicated the semi-I IPNs to be more compatible than the IPNs. The degree of molecular mixing was higher than that for IPNs. The impact strength showed a gradual increase with the increase in the percentage of PS or PnBA in the copolymer. The effect of the copolymerization of the second component on transparency was investigated. The transparency of the semi-I IPNs increased with the increasing composition of PnBA, but reduced with the increasing composition of PS. These results are discussed in light of existing theories.     

Interpenetrating polymer networks from castor oil based polyurethanes,XI

Under different experimental conditions, various liquid polyurethanes (PU) were synthesized from castor oil and isophorone diisocyanate varying NCO/OH ratio. These polyurethanes were then subsequently interpenetrated with n-butyl acrylate (nBA) monomer and ethylene glycol di-methacrylate as crosslinker by radical polymerization using benzoyl peroxide as an initiator. This leads to the formation of novel PU/PnBA interpenetrating polymer networks (IPNs) by transfer molding. These IPNs were characterized by their resistance to chemical reagents, thermal behavior (TGA), mechanical properties, namely; tensile strength, Young's modulus, elongation at break (%) and hardness (Shore A). The morphology of the IPNs was studied by Scanning Electron Microscopy. The dielectric behavior was computed in terms of electrical conductivities, dielectric constant (ε′), loss tangent (tan δ) and dielectric loss (ε″).     

Preparation and properties of castor oil-based polyurethanes

Four series of polyurethane elastomers were synthesized using diphenylmethane diisocyanate (MDI) and castor oil as the polyol. Two types of MDI (crude and distilled) were used. The temperature of reaction and the effect of excess isocyanate above stoichiometric were also varied. The structure of the polyurethanes was analyzed using wide-angle X-ray diffraction, scanning electron microscopy, and density and differential scanning calorimetry (DSC). Thermomechanical and dynamic mechanical (TMA and DMA) as well as mechanical measurements were carried out. The results have shown considerable influence of the type of MDI, excess of isocyanate, and temperature of preparation on the properties of the polyurethanes synthesized.     

Interpenetrating polymer networks from castor oil and dibasic acids

Prepolyesters were obtained from castor oil and dibasic acids, viz oxalic, malonic, succinic, glutaric, adipic, suberic and sebacic acid. These prepolyesters (PPE) were subsequently interpenetrated with methyl methacrylate containing 1% ethylene glycol dimethacrylate as crosslinker by radical polymerization initiated with benzoyl peroxide. The novel PPE poly(methyl methacrylate) PPE/PMMA interpenetrating polymer networks (IPNs) were obtained as powder. They were characterized by solubility behaviour, IR spectral study and thermal behaviour.     

Interpenetrating polymer network of poly(vinyl chloride) and polymethacrylates

A curable polymeric composite was prepared using equal weights of poly(vinyl chloride) (PVC), reactive polyfunctional methacrylate monomers, and inorganic fillers. Peroxide initiated in situ polymerization of the polyfunctional methacrylate monomers in the PVC matrix produced an interpenetrating polymer network (IPN) structure. The polymerization kinetics and the degree of polymerization were investigated using differential scanning calorimetry (DSC), carbon-13 nuclear magnetic resonance (¹³C NMR), and solvent extraction. All measurements indicated that during polymerization, the PVC is either crosslinked by or grafted onto the methacrylate three-dimensional network structure. The rheological properties of the composite were measured before curing using a Rheometrics mechanical spectrometer and found to exhibit mainly viscous behavior and diminished elasticity. The PVC and the methacrylate monomers form a two-phase system when mixed at room temperature. However, when heated to 100°C the PVC dissolves in the monomers and forms a one-phase optically clear blend with a single glass transition temperature. In the presence of peroxide, the one-phase blend is stable and does not separate out upon cooling and storing at room temperature.     

Semi-interpenetrating polymer networks from castor oil-based polyurethane and nitrokonjac glucomannan

New semi-interpenetrating polymer networks (semi-IPNs) coded as PUNK were successfully synthesized from castor oil-based polyurethane (PU) prepolymer and 10–40 wt % nitrokonjac glucomannan (NKGM) containing a degree of substitution of 2.4 and a weight-average molecular weight of 4.75 × 10⁴. The semi-IPN sheets that were 100 μm thick were cured more speedily than PU, with curing times of 5 h for PUNK and 16 h for PU at 50–70°C. The structure and miscibility of the semi-IPN sheets were studied by Fourier transform infrared spectroscopy, ultraviolet spectroscopy, and scanning electron microscopy. The results showed that a strong intermolecular interaction caused by hydrogen bonding between NKGM and PU exists in PUNK, resulting in good miscibility. When the NKGM content of the semi-IPNs sheets was 20 wt %, the tensile strength and light transmittance were obviously higher than that of the PU sheets. The NKGM in the semi-IPN sheets plays an important role not only in accelerating the cure but also in improving the mechanical properties and biodegradability. As a new material prepared from renewable resources, PUNK has potential applications because of its biodegradability. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2076–2083, 2001     

Fabrication and apparent kinetic study of poly(methyl methacrylate)/poly(octyl acrylate) and poly(octyl acrylate)/poly(methyl methacrylate) latex interpenetrating polymer networks

Two latex interpenetrating polymer networks (LIPNs) were synthesized with methyl methacrylate (MMA) and octyl acrylate (OA) as monomers, respectively. The apparent kinetics of polymerization for the LIPNs was studied. This demonstrates that network II does not have a nucleus formation stage. The monomers of network II were diffused into the latex particles of network I and then formed network II by in situ polymerization. It indicates that the polymerization of network I obeys the classical kinetic rules of emulsion polymerization. But the polymerization of network II only appears a constant‐rate stage and a decreasing‐rate stage. The apparent activation energies (E_a) of network I and network II of PMMA/POA were calculated according to the Arrhenius equation. The E_a values of POA as network I (62 kJ/mol) is similar to that of POA as network II PMMA/POA (60 kJ/mol). However, the E_a value of PMMA as network II POA/PMMA (105kJ/mol) is higher than that of PMMA as network I (61 kJ/mol). Results show that the E_a value of the network II polymerization is related to the properties of its seed latex. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Dielectric relaxations in poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate)

A comparative study is undertaken of the dielectric relaxation spectra of poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate), taking into consideration the spectra of the corresponding polymers in the series of the polymethacrylates. The three polymers, PMA, PEA, and PBA, present an α relaxation zone clearly separated from the secondary relaxations. Its shape is not altered with temperature, and it is possible to construct a master curve. With increasing length of the side chain, its distribution of relaxation times broadens and the temperature of the maximum of the relaxation decreases. A β relaxation with decreasing intensity as the length of the side chain increases is clearly perceptible in PMA and PEA, but almost not perceptible at all in PBA. In PEA this relaxation appears split into two peaks. Computer simulation of restricted motions of the side chain discard an origin similar to that of the γ relaxation in PPA or PBA for the lowest temperature component of the relaxation, and suggests the conjunction of two rotation mechanisms in this relaxation for the polyacrylates. For the experimental temperatures of our tests a γ relaxation shows up only in PBA. Its apparent activation energy, higher than in related polymers of the polymethacrylate series, suggests that the tighter packing of monomeric units in polyacrylates leads to a significant increase in the intermolecular contribution to the potential energy barrier responsible for the relaxation.     

Synthesis and characterization of novel renewable castor oil-based UV-curable polyfunctional polyurethane acrylate

In recent years, a lot of interest has been given to renewable resources for their environmental friendliness and potential biodegradability in the synthesis of urethane-derived polymers. In this work, UV-curable castor oil-based polyfunctional polyurethane acrylate (COPUA) was prepared by the reaction of isophorone diisocyanate (IPDI) with castor oil and pentaerythritol triacrylate (PETA). The structures and molecular weights of the targeted IPDI–PETA and COPUA were characterized by FTIR, ¹H NMR, and GPC, respectively. In addition, the effect of reactive diluent content on damping properties, thermal stabilities, and mechanical properties of COPUA was characterized by dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and universal test machine. DMA revealed the copolymers had a glass transition temperature (T _g) from 31.81 to 48.09°C. TGA showed that thermal initial decomposition temperatures were above 344.5°C, indicating the copolymers had certain thermal stability. Finally, some physical properties of curing films were studied by the contact angle and water absorption, and the results showed that the coatings exhibited good hydrophobicity. The COPUA obtained from castor oil can be used as eco-friendly materials and other applications alternative to the use of other petrochemicals in coatings.     

Thermal stability of poly(methyl methacrylate-co-butyl acrylate) and poly(styrene-co-butyl acrylate) polymers

Thermal stability of poly(methyl methacrylate-co-butyl acrylate) and poly(styrene-co-butyl acrylate) modified with a small amount of acrylic acid and/or N-methylolacrylamide as a crosslinking agent was studied in this work. Programmed thermogravimetric analysis has been used to study the effect of copolymer composition on thermal stability, over a temperature range from 50 to 450°C, under a constant flow of nitrogen. Kinetic parameters of thermal degradation, activation energy, pre-exponential factor, and reaction order were obtained by using MacCallum-Tanner's approach. Kinetic data indicate that the thermal degradation of the investigated copolymer systems is the first order reaction, and that the increase of activation energy may be an indication of thermal stability changes in copolymer systems.     

Interpenetrating polymer networks derived from epoxide-amine adducts in either polymer network

A new type of interpenetrating polymer network was synthesized via photoinitiated free-radical polymerization of α,ω-methacryloyl terminated macromonomers prepared from epoxide-amine-adducts, followed by thermal addition polymerization of bisphenol-A diglycidyl ether and 4,4′-diaminodiphenylsulfone or 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.0.^2,6]decane. The interpenetrating polymer networks are optically transparent and show only one glass transition temperature ranging from -10 to 130°C, as a function of the macromonomer/addition polymer mixing ratio. The presence of a single phase was confirmed by scanning electron microscopy (SEM).     

Interpenetrating polymer networks based on thermoplastic polyurethanes (TPUS) and cis-1,4-polyisoprene

Semi-interpenetrating polymer networks based on two elastomers, cis-1,4-polyisoprene (PI) and thermoplastic polyurethane elastomers (TPUs) were prepared in varying compositions. The PI component was cross-linked using peroxide initiators. Modulus and mechanical properties were investigated as a function of composition and temperature. Slight synergisms were observed in mechanical properties, particularly for compositions containing 10% PI by weight. Little or no molecular mixing is shown by differential scanning calorimetry (DSC) for these two-phase materials. © 1994 John Wiley & Sons, Inc.     

Synthesis of casein-g-poly(methyl acrylate). II

The synthesis of casein-g-poly(methyl acrylate) was studied using the potassium peroxydisulfate–ascorbic acid redox system. The effect of synthetic variables has been investigated in the light of rates of conversion of monomer, graft copolymerization and homopolymerization, percent grafting, and grafting efficiency. The results are compared with the system initiated by pure potassium peroxydisulfate alone.