Subasini Lenka

Synthesis and characterization of polymers from cashewnut shell liquid (CNSL), a renewable resource II. Synthesis of polyurethanes

Abstract A novel copolyester was synthesized by solution polycondensation of terephthaloyl chloride with 4-[(4-hydroxy-2-pentadecenylphenyl)diazenyl] phenol (HPPDP) and 1,4-butane diol. The monomer (HPPDP) has been synthesized from 3-pentadecenyl phenol, a renewable resource and a by-product of the cashew industry characterized earlier [1] . The copolyester was characterized through elemental analysis, 1 H -NMR, IR, and UV spectroscopy. Dilute solution viscosity of its solution was also determined by viscometry. The intrinsic viscosity [η] was 0.98 dl/gm. The melting temperatures of the copolyester were 63 and 127°C as observed from Differential Scanning Calorimetric (DSC) studies. Thermogravimetric analysis show that degradation commences at 290°C in nitrogen atmosphere. Wide-angle X-ray diffraction study of the copolyester indicates absence of any crystallinity, whereas DSC studies indicate the presence of two melting peaks. Thus, it is presumed that the copolyester has short range crystallinity.

Synthesis of polyurethane from cashew nut shell liquid (CNSL), a renewable resource

A novel thermoplastic polyurethane was prepared from cardanol, a renewable resource and a waste of the cashew industry. Cardanol was recovered from cashew nut shell liquid (CNSL) by double vacuum distillation. It was characterized by CHN analysis and IR, 1H-NMR, and 13C-NMR spectroscopy techniques. Cardanol is a meta-substituted long chain phenol. The long aliphatic chain unit substituent was found to be a monoene. The monomer, 4-[(4-hydroxy-2-pentadecenylphenyl)diazenyl]phenol was prepared from cardanol. It was a dihydroxy compound as characterized by CHN analyzer, UV, and 1H-NMR spectroscopy. The polyurethane was synthesized from this dihydroxy compound by the treatment with 4,4′-diphenylmethane diisocyanate (MDI) in dimethylformamide (DMF) solvent at 80–90°C under nitrogen atmosphere. The polymer was characterized by 1H-NMR, FTIR, and UV spectroscopy. The elemental analysis was done for determining the percentage content of C, H, and N, and the intrinsic viscosity [η] of polymer showed 1.85 dL/gm. Thermogravimetric investigations (TGA) of the cardanol, the dihydroxy compound, and the polyurethane were performed to study their decomposition. The semicrystalline nature of the PU was confirmed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analyzer (DMTA). The wide-angle X-ray diffraction (WAXS) study of PU shew a broad amorphous halo indicative of absence of crystallinity in the polymer, which has been explained as due to strong hydrogen bonding in the hard phase. PU may possibly be useful as a telecommunication and as a nonlinear optical material.

Polymers from renewable resources. IX. Interpenetrating polymer networks based on castor oil polyurethane poly(hydroxyethyl methacrylate): Synthesis, chemical, thermal, and mechanical properties

A number of polyurethanes were synthesized by reacting castor oil with hexamethylene diisocyanate, varying the NCO/OH ratio. The polyurethanes were reacted with 2-hydroxyethyl methacrylate ( HEMA) to prepare the interpenetrating polymer networks (IPNs) using benzoyl peroxide as the initiator and ethylene glycol dimethacrylate (EGDM) as the crosslinker. The IPNs are partly soluble in some of the solvents and are less resistant to alkali, but more resistant to acid. The solvent absorption is more pronounced in benzene than in toluene. A novel computerized LOTUS package was used to calculate the kinetic parameters. All the IPNs decomposed with 2-4% weight in the temperature range of to 200°C; 10% weight loss occurs at 300°C and 40% weight loss occurs at 400°C. There is a rapid weight loss from 10 to 90% in the temperature range of 400-500°C. From the kinetic data, it is clear that the degradation process of the IPNs is slower in the temperature range 300-400°C and faster in the temperature range of 440-560°C.

Redox Polymerization Initiated by Metal Ions

Abstract During the last four decades there has been rapid development of the use of redox systems [1–30], that is, systems containing both an oxidizing and reducing agent, for the initiation of vinyl polymerization. Polymerizations which are initiated by the reaction between an oxidizing and a reducing agent may be called redox polymerizations.

Interpenetrating polymer networks composed of castor oil-based polyurethane and 2-hydroxy-4-methacryloyloxy acetophenone

2-Hydroxy-4-methacryloyloxy acetophenone, a vinyl monomer, was prepared by reacting 2,4-dihydroxy acetophenone with methacryloyl chloride in presence of triethylamine in methyl ethyl ketone. The vinyl monomer was characterized by Fourier transform infrared spectra and Proton magnetic resonance spectra to confirm the various functional groups in the monomer. The liquid prepolyurethanes obtained from castor oil, toluene-2,4-diisocyanate, and hexamethylene diisocyanate, varying the NCO/OH ratio, were interpenetrated with the above vinyl monomer containing ethylene glycol dimethacrylate, using radical polymerization initiated by benzoyl peroxide. The interpenetrating polymer networks were obtained as transparent tough films by transfer moulding. They were characterized for thermal behavior with evaluation of kinetic parameters. From the kinetic data, it is clear that the degradation process of the interpenetrating networks is slower in the temperature range of 270-390°C and faster in the range of 390-510°C. Thermal stability also varies with the change in diisocyanates. The morphology was examined by scanning electron microscopy (SEM). The resulting two-phase morphology was found to be sensitive to change in monomer concentration.

Grafting of vinyl monomers onto silk using redox systems. Yellowing of silk

The aim of this study is to investigate the influence of temperature, initiator concentration, and vinyl monomer on silk yellowing during grafting. A series of silk fabrics was treated at four different temperatures (70, 75, 80, and 88°C), with different concentrations of initiator in the range 1–4% owf, with and without methacrylamide (MAA) or 2-hydroxyethyl methacrylate (HEMA). By treating silk with ammonium persulphate (APS), in the absence of a monomer, the degree of silk yellowing increased linearly with increasing both initiator concentration and treatment temperature, indicating that the initiator plays a specific role in enhancing silk yellowing through macroradical formation. The graft copolymerization of MAA (with APS as the initiator) caused only slight changes in the intensity of silk yellowing compared to blank-treated fabrics. On the other hand, the use of HEMA resulted in a deeper yellowing of silk fabrics, especially in the 70–80°C temperature range, due to its higher reactivity and to the tendency to form a homopolymer, leaving unreacted macroradicals on silk fibroin backbone. Compared to APS, other initiators, such as 2,2′-azobis(isobutyronitrile) (AIBN) and 2–2′-azobis-(2-amidino propane) dihydrochloride (ADC), caused a significantly lower degree of silk yellowing when tested in the absebce of a monomer. The yellowness of silk fabrics tended to increase by grafting with HEMA, while decreased by grafting with MAA. The use of variable amounts of monomer (25–150% owf) did not influence the degree of yellowing with ADC as the initiator. The results reported in this study show that the extent of yellowing induced on silk fabrics by grafting MAA and HEMA with APS as the initiator can be limited by a suitable selection of the processing parameters (initiator concentration, temperature). Moreover, the use of both AIBN and ADC appears promising, owing to their negligible effect on silk yellowing.

Polymers from renewable resources. XX. Synthesis, structure, and thermal properties of semi‐interpenetrating polymer networks based on cardanol–formaldehyde‐substituted aromatic compounds copolymerized resins and castor oil polyurethanes

A large number of improved high-temperature stable semi-interpenetrating polymer networks (semi-IPNs) were synthesized by condensing copolymerized resins with castor oil-based polyurethane using ethylene glycol dimethacrylate (EGDM) as a crosslinker. The structures of these semi-IPNs were studied using various characterization techniques such as IR and nuclear magnetic resonance (NMR) spectra, and the thermal behavior of the semi-IPNs was also studied by thermogravimetric analysis (TGA). A plausible degradation mechanism was suggested in our previous communication.

Polymers from renewable resources: XXII: Studies on synthesis and thermal properties of interpenetrating polymer networks derived from castor oil-isophorone diisocyanate-cardanyl methacrylate/poly (cardanyl methacrylate)

Abstract A large number of interpenetrating polymer networks (IPNs) based on polyurethane of castor oil and isophorone diisocyanate with cardanyl methacrylate and its homopolymer were synthesized using benzoyl peroxide (BPO) as initiator and ethyleneglycol-dimethacrylate (EGDM) as cross-linking agent. The solvent absorptivity behaviour of different IPNs have been studied. The thermal properties have been studied and the kinetic parameters involved in the thermal degradation of the IPNs have been evaluated by using the computerised LOTUS package method.

Unperturbed Dimension of Polymer Molecules from Viscosity Measurements in Different Solvents

Abstract An expression for the determination of the cross-over point concentration, CX, of the polymer in a number of solvents has been derived, and an expression relating Cx with the unperturbed dimension of polymer molecules (r0 2)½ has been proposed. The unperturbed dimensions for polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, polyacrylonitrile, and polyvinyl pyrrolidone have been calculated.

Grafting Vinyl Monomers onto Silk Fibers. V. Graft Copolymerization of Methyl Methacrylate onto Silk with Potassium Permanganate as Initiator

Abstract The graft copolymerization of methyl methacrylate onto silk fibers in aqueous solution with the use of manganese (IV) ions as initiator was investigated. The rate of grafting was determined by varying monomer, acidity of the medium, temperature, nature of silk, and the reaction medium. The graft yield increases significantly with increase of manganese (IV) concentration up to 15 meq/liter; with further increase of manganese (IV) concentration, the graft yield decreases. The effect of the increase of monomer concentration brings about a significant enhancement in the graft yield up to 7%, and with further increase of monomer concentration the graft yield decreases. The graft yield is considerably influenced by chemical modification prior to grafting. The effect of some inorganic salts and anionic surfactants on the rate of grafting has been investigated.