G. B. Nando

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.

Thermal degradation characteristics of natural rubber vulcanizates modified with phosphorylated cashew nut shell liquid

Abstract The thermal and thermo-oxidative decomposition characteristics of Natural Rubber (NR) vulcanizates modified with Phosphorylated Cashew Nut Shell Liquid (PCNSL) have been studied by Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Differential Thermal Analysis (DTA). The PCNSL modified NR vulcanizate showed improved thermal stability in air, compared to that in nitrogen, which is presumed to be due to the formation of intermediate thermally stable structures in the former. The kinetic parameters for the initial stage of degradation in air and in nitrogen have been evaluated by the Freeman-Carroll method. The higher value for activation energy for thermo-oxidative degradation of PCNSL modified NR (15.10kCal/mol) and Integral Procedural Decomposition Temperature, IPDT (366 °C). as against that for unmodified NR (13.04 kCal/mol and 347 °C, respectively) indicate the improved thermal stability of the rubber.

Modification of natural rubber with phosphatic plasticizers: a comparison of phosphorylated cashew nut shell liquid prepolymer with 2-ethyl hexyl diphenyl phosphate

Abstract The vulcanization characteristics, tensile properties, thermal decomposition characteristics and flame retardancy of Natural Rubber (NR) modified with phosphorylated cashew nut shell liquid (PCNSL) prepolymer has been studied and compared with 2-ethyl hexyl diphenyl phosphate (Santicizer-141), at concentrations ranging from 10 to 20xa0phr. The PCNSL modified NR vulcanizates showed higher tensile properties and resistances to thermo-oxidative decomposition and flame compared to that containing similar dosages of Santicizer. Kinetic parameters for themo-oxidative decomposition, obtained from dynamic thermogravimetry, indicated a higher degree of condensed phase reactions for the PCNSL modified NR vulcanizates, especially at higher heating rates and in presence of higher concentrations of PCNSL.

Vulcanization of natural rubber modified with cashew nut shell liquid and its phosphorylated derivative: a comparative study

Abstract The vulcanization characteristics of unfilled natural rubber (NR) compounds was studied in presence and absence of cashew nut shell liquid (CNSL) and its phosphorylated derivative (PCNSL) by using an oscillating disc rheometer at various temperatures. The case of crosslinking in the presence of PCNSL and the active role of PCNSL in the crosslinking reaction was shown by the comparatively higher values of the cure rate index and lower values of the activation energy of vulcanization.

Scanning Electron Microscopy Studies of Fractured Natural Rubber Surfaces

Abstract A tensile ruptured gum specimen shows formation of crystalline regions at an angle of 45° to the flow lines, whereas a tensile ruptured filled specimen shows formation of depression. A tear fractured gum specimen shows again the formation of crystallites at an angle of 45° to the flow lines. Tear fractured filled specimens show the enhancement of crystallinity throughout the matrix, but the surface is rough. Flex fractured gum specimen show a large number of cracks on the surface while the filled vulcanizate shows formation of balls presumably due to coiling of polymer chains on the filler surface. An abraded gum surface shows dimple structure, while a filled vulcanizate indicates coarse ribbed structure. Addition of lignin, in general, reduces the crystallinity of tensile and tear fractured samples and increases the fibrosity of flex cracked and abraded samples.

Thermal degradation of short kevlar fibre thermoplastic polyurethane composite

Abstract The thermal degradation of short kevlar fibre-thermoplastic polyurethane (TPU) composites has been studied by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). TGA showed that the thermal degradation of TPU takes place in two steps with peak maxima ( T 1 max and T 2 max ) at 383°C and 448°C, respectively. In the presence of 10–40 phr of short kevlar fibres, T 1 max and T 2 max were shifted to lower temperatures. The temperature of onset of degradation was increased from 245 to 255°C at 40 parts per hundred rubber (phr) fibre loading. Kinetic studies showed that the degradation of TPU and kevlar-TPU composite follows first-order reaction kinetics. The DSC study showed that there is an improvement in thermal stability of TPU in the presence of 20 phr of short kevlar fibres.

Cure characteristics and physicomechanical properties of natural rubber modified with phosphorylated cashew nut shell liquid prepolymer—A comparison with aromatic oil

Natural rubber (NR) has been modified with 10 phr each of phosphorylated cashew nut shell liquid (PCNSL) prepolymer and an aromatic oil (spindle oil) in a typical semi-efficient vulcanization (SEV) system. Despite the lower chemical crosslink density, the PCNSL modified NR vulcanizate showed higher tensile strength, elongation at break, thermal stability, and resistances to fatigue failure and thermo-oxidative decomposition, as compared to the vulcanizate containing the same dosage of spindle oil.

Mechanical Properties and Fracture Behavior of Short PET Fiber-Waste Polyethylene Composites:

Plastics used in the packaging industry, especially in the form of carry bags and pouches, manifest a formidable threat to the environment because of their non-biodegradable nature. Addition of both natural and synthetic fibers to these materials improves their performance, replacing the conventional materials like wood, metal, and ceramics in the majority of industrial applications. Short polyethylene terephthalate (PET) fiber-reinforced composites from waste high density polyethylene (WPE) such as carry bags/pouches collected from municipal solid waste and neat high density polyethylene (HDPE) were prepared in a Brabender Plasticorder using melt-mixing technique under optimum processing conditions. Physico-mechanical properties of these short PET fiber-reinforced WPE and neat HDPE composites were determined using standard procedures. It is observed that the mechanical strength is enhanced by increasing the fiber-loading up to 50% by weight. Maleic anhydride (MAH) grafting was done onto the WPE matrix and the resulting composites were evaluated for their mechanical properties. The thermal stability of the WPE-PET fiber composites also improves significantly with fiber-loading as well as upon grafting the WPE with MAH. Flexural strength exhibited an increase of 59% from 25.4 to 40.5 MPa, proving MAH-grafted WPE (MAH-g-WPE) to have good compatibilizing ability.

Rheological Behavior of Low-density Polyethylene (LDPE)- Polydimethylsiloxane Rubber (PDMS) Blends

The rheological behavior of different blends of low-density polyethylene (LDPE) and polydimethylsiloxane rubber (PDMS) has been investigated at different temperatures (160, 180, and 200 C) and shear rates (61.3-613.1 s 1) with varying proportions of ethylene methylacrylate copolymer (EMA) and silica filler loading by using a Monsanto Processability Tester (MPT). The EMA copolymer is used as a chemical compatibilizer for the blend systems. The melt viscosity increases with the increase in the PDMS proportion and the filler loading but decreases with the increasing proportion of the EMA. The melts of all the blends are pseudoplastic in nature. The flow behavior index (n)of the blends decreases with the increase in the PDMS proportion and the silica filler loading but increases with the increase in the EMA proportion and the temperature. The activation energy of flow for the blends decreases with an increase in the PDMS proportion and the silica filler loading. But it decreases initially with an increasing proportion of EMA, reaches a minimum value at 6 wt% and then increases. The die swell increases with an increase in the shear rate but decreases continuously with an increase in the PDMS proportion and the silica filler loading. But it becomes the maximum at 6 wt% of EMA for the compatibilized blends. The phase morphology studied by Scanning Electron Microscopy (SEM) shows an improved dispersion for a 50/50 blend of LDPE-PDMS and it further improves with the incorporation of 6 wt% of EMA as well as the blend containing 10 wt% of silica filler loading. The surface finish of the extrudate for the blend containing 10 wt% of silica filler is better compared to that with 20 wt% of silica filler.

Self-adhesion of natural rubber modified with phosphorylated cashew nut shell liquid

The self-adhesion strength of natural rubber (NR) compounds modified with phosphorylated cashew nut shell liquid (PCNSL) prepolymer has been studied with respect to variations in contact time, contact pressure, storage time, and concentration of PCNSL. The self-adhesion strength of NR as measured from the 180° peel test showed a maximum at 10 phr of PCNSL. The adhesion between substrates containing various concentrations of PCNSL (from 0 to 20 phr) also reached a maximum at a PCNSL concentration of 10 phr in one of the substrates. An increase in self-adhesion strength with storage time was observed for the PCNSL-modified NR compounds, which is presumed to be due to the time-dependent interfacial diffusion.