Search

The effects of weight fraction and length of short bamboo and glass fibers on flexural strength and inter-laminar shear strength (ILSS) of vinyl ester resin and unsaturated polyester (USP) resins were investigated. The bamboo fibers were isolated from the bamboo plant by treating them with dilute solution of sodium hydroxide (0.1 and 1N NaOH) for 72 h and then boiling them in a pressure cooker for 30 min. The fibers were separated, dried, and cut into 5 or 10mm lengths. Composites were fabricated using vinyl ester resin or USP resin as binders. The flexural properties of glass/bamboo fiber reinforced vinyl ester resins were higher than those based on USP resins. This may be due to better wetting of the fibers by VE resins due to their low viscosity and possibility of hydrogen bond formation with hydroxyl group on bamboo fibers. Hybrid composites were fabricated using 50wt% of fibers. The wt% of bamboo fibers in these hybrid composites was varied as 25, 50, and 75wt% of chopped glass fibers (5 mm). Replacement of 25wt% of glass fibers did not affect the flexural modulus and a marginal increase in ILSS was observed. However, replacement of 75% glass fibers by bamboo fibers resulted in a significant decrease in flexural strength, modulus and ILSS. [ABSTRACT FROM AUTHOR]

The paper demonstrates the efficacy of natural rubber-g-poly (styrene-co-acrylonitrile) (NR-g-SAN) copolymers as impact modifier for SAN. The impact behaviour of SAN /NR-g-SAN blends were studied as a function of cross-link density of NR, percent grafting, rubber content in the blend and the AN content in the grafted chain. The cross-link density of NR had no significant effect on impact strength of the blends whereas increase in percent grafting (PG) of the rubber significantly improved the impact strength. Thus the impact strength increased four times when the PG of the rubber was increased from 34.2 to 65%. Further increase in PG decreased the impact strength. Similar trend was observed on increase in the rubber content, the maximum impact strength was observed at 20% rubber. The impact strength also depended on the acrylonitrile content of the grafted chain. Tensile and flexural strength and modulus of these blends were not influenced by PG and AN content in the grafted chain whereas these properties decreased with the increase in the rubber content. Scanning electron microscopic studies of the impact fractured surfaces showed cavitation of rubber particles and craze induced matrix deformation. Dynamic mechanical studies confirmed the two-phase structure of these blends. [ABSTRACT FROM AUTHOR]

This article describes the graft copolymerization of methyl methacrylate (MMA) on to natural rubber (NR) by emulsion polymerization using cumene hydroperoxide and tetraethylene pentamine as redox initiators in NR latex. The effect of surfactants, crass-link density of NR, NR/MMA ratio, and mode of addition of monomer on particle morphology is investigated by a transmission electron microscope (TEM). The percent grafting increases with the increasing MMA content while the graining efficiency decreases. Secondary nucleation of poly(methyl methacrylate) (PMMA) is observed when oleic acid is used as a surfactant, while sodium dioctyl sulphosuccinate (SDSS) and nonionic nonyl phenol poly(ethylene oxide), give core-shell morphology. In all the samples, the smaller rubber particles are heavily coated with PMMA while the larger particles are coated only at higher MMA content. At a given feed rate of the monomer, higher cross-link density of NR results in a more uniform shell. Ultramicrotomed sections of the latex particles show an interpenetrating network-like structure. [ABSTRACT FROM AUTHOR]

The sulphonation of commercially available PEEK in powder form (Gatone™, Gharda Chemicals Limited, India) was carried out using conc. H2SO4 under different reaction conditions. The duration of reaction was varied from 3-5 h, polymer concentration 4-10% (w/v) and temperature 35-50°C. Structural characterisation of sulphonated polymers was done by elemental analysis, FT-IR and1H-NMR spectroscopy. The degree of sulphonation as calculated from1H-NMR and elemental analysis (S-content) was found to be in the range of ~ 50-80%. Multistep mass loss was observed in thermogravimetric traces (recorded in N2 atmosphere). The first step (50-225 ± 25°C) was due to loss of moisture (1-10%) and second step (250-425 ± 25°C) has been attributed to volatilization of SO3 from the sulphonic group. The backbone degradation takes place above 450°C. The mechanical properties and proton conductivities of various sulphonated samples was also evaluated. [ABSTRACT FROM AUTHOR]

Structurally different poly(arylene ether sulphone) (PES) copolymers were synthesized by reacting stoichiometric amount of dichlorodiphenyl sulphone (DCDPS) with bisphenols. The molar ratio of bisphenol-A and phenolphthalein (ESP)/hydroquinone (ESH)/resorcinol (ESR) was varied to prepare nine copolymer samples. Structural characterization was done by FT-IR and 1H-NMR studies. The initial decomposition temperature as well as temperature of maximum rate of mass loss in ESR and ESH copolymers were similar and a marginal decrease in these decomposition temperatures were observed by increasing the isopropylidine units in the backbone. High char residue at 800°C was observed in polymers having high content of phthalein units. [ABSTRACT FROM AUTHOR]

Thermal behaviour of blends based on N,N'-bis(4-itaconimidophenyl) ether (IE) and 4,4'-bis(4-allyl-2-methoxyphenoxy) benzophenone (R1) or 4,4'-bis(2-allylphenoxy) benzophenone (R2) are described in this paper. The reactive diluent content was varied from 5-50% (mass/mass) in these blends. A decrease in the melting point and exothermic peak temperature was observed with increasing mass percent of reactive diluent. Thermal stability of blends was affected at high mass percentage of reactive diluents. [ABSTRACT FROM AUTHOR]

Focuses on flame retardation of epoxies by addition of phosphorus-containing additives or incorporation of phosphorus in the epoxy monomer or hardeners. Discussion of the mechanism of flame retardation and correlation of phosphorus content of resins with anaerobic char yield; Effect of phosphorus on curing characteristics of resins; Thermal stability of cured resins.

Examines the state of the art of the unsaturated polyester (UP) thermoset resins. Characterization of UP resins; Classification of UP resins; Synthesis of UP by the reaction of unsaturated and saturated dibasic acids with dihydric alcohols.

Extensive experimental and computational studies have been carried out on survivability of buildings, vehicles, combat helmets etc exposed to various high‐velocity projectiles such as explosives, bullets, sharpenal etc. Such explosive attacks have necessitated the development of protective techniques for mitigation of blast. Retrofitting the above mentioned structures with light weight materials such as fibrous composites, coatings or both seems to be of foremost importance. The present review focuses mainly on experimental techniques reported in last 15 years for blast mitigation. The topics covered include introduction, applications and properties of FRP coatings, types of explosives and other details of charge, testing procedures and performance evaluation of protected structures. Proposed mechanism for improvement in blast mitigation of protected structures has also been discussed. POLYM. COMPOS., 39:1389–1402, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Different 1-substituted-(pyrrole alkyl)phosphonic acid derivatives have been designed as adhesion promoters to graft polypyrrole layers on several substrates. These compounds contain two reactive, terminal moieties: the phosphonic acid group as anchor to the oxide surface and the pyrrolyl group, which functions as starting unit for surface polymerisation. Both groups are connected by an alkyl spacer ranging from 4 to 12 methylene units. The short- and long-chain derivatives were synthesized for the first time to study their self-assembling properties and their effectiveness to be used as an adhesion promoter for grafting covalently bound polypyrrole layers on oxide substrates. Surfactant-like properties of the long chain derivatives and their behaviour in water for pyrrole polymerization were also investigated, as will be discussed in future papers. In this first paper of the series, the synthesis and characterization of the monomers are presented. The structure of the molecules was proven by 1H-NMR, 31P-NMR and FT-IR spectroscopy. Thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) revealed that the stability of the compound depended on their chain length: the longer the alkyl chain, the more stable the monomer. On the other hand, reactivity decreased with increasing chain length, as proven by cyclic voltammetry measurements (CV). [ABSTRACT FROM AUTHOR]

Optimum temperature and pH for the isolation of soy protein isolate (SPI) from soy protein concentrate (SPC) were established. Enzymatic hydrolysis of SPI with enzymes of different specificities such as trypsin, chymotrypsin, papain and urease was carried out and the products of hydrolysis were characterized by molecular mass determination [sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)] and thermal techniques [differential scanning calorimetry (DSC) and thermogravimetric analysis (TG)]. Enzymatic hydrolysis resulted in a significant reduction in molecular masses. However the thermal stability of hydrolysed SPI was similar to native SPI indicating that it is independent of molecular mass. DSC studies indicated an increase in temperatures of endothermic transition associated with SPI denaturation and loss of absorbed moisture in samples of lower molecular masses. [ABSTRACT FROM AUTHOR]

Reviews the synthesis, characterization, physicochemical, thermal and mechanical properties of polymeric binders containing pendant azido group. Preparation of azido polymers; Physical properties of azido polymers; Thermal behavior; Photodecomposition of the polymers.

Disusses the effect of structure on thermal behavior of homopolymers and copolymers of itaconimides. Synthesis of itaconimides; Characterization of itaconimides; Polymerization; Modifications of itaconimides polymers.