Molecular structure and storage hardening of natural rubber: Insight into the reactions between hydroxylamine and phospholipids linked to natural rubber molecule

The effect of hydroxylamine on the molecular structure and storage hardening of natural rubber (NR) was investigated by the treatment of deproteinized NR (DPNR) latex with hydroxylamine. The hydroxylamine treatment decreased the content of long‐chain fatty acid ester groups in DPNR from about 2–0.7 mol per rubber molecule. The molecular weight and molecular weight distribution changed apparently after treatment with hydroxylamine. The relative intensity of the ¹H NMR signals corresponding to phospholipids at the α‐terminal group decreased after the hydroxylamine treatment. The Huggins ‘k’ constant of hydroxylamine‐treated DPNR showed the liberation of linear rubber molecules caused by decomposition of branch points derived from phospholipids. The absence of storage hardening in hydroxylamine‐treated DPNR was observed to be caused by not only the reaction of hydroxylamine and aldehyde groups but also the removal of phospholipids as well as the breakdown of phospholipid aggregations as a result of hydroxylamime, contributing to the establishment of a newly proposed mechanism of hydroxylamine on the inhibition of storage hardening in NR. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43753.     

Reducing and stabilizing the viscosity of natural rubber by using sugars: Interference of the Maillard reaction between proteins and sugars

This work is an extension of previous work elucidating the reduction and stabilization of solid natural rubber (NR) viscosity by using sugars. Various amounts of glucose, fructose, sucrose, and maltose were incorporated into fresh NR (FNR), deproteinized NR (DPNR), and synthetic polyisoprene (IR) latexes. The results revealed that all sugars cannot decrease the Mooney viscosity of FNR, while only monosaccharides, that is, glucose and fructose, can significantly decrease the Mooney viscosity of both DPNR and IR by way of a lubrication mechanism. The proteins in FNR can diminish the capability of glucose and fructose to decrease the Mooney viscosity. Furthermore, glucose was found to reduce the occurrence of storage hardening in DPNR by interacting with polar groups of phospholipids at the rubber chain ends. Measurements of browning intensity as well as analysis of Maillard reaction products together with the NR protein–glucose model compound were utilized to confirm that the reduction and stabilization of the viscosity of NR using monosaccharides were interfered by the Maillard reaction between the proteins in NR and the monosaccharides.     

Effect of hybrid nanofluids mixture ratio on the performance of a photovoltaic thermal collector

Solar photovoltaic-thermal (PV/T) collectors, are hybrid collectors used to convert solar radiation into usable thermal and electrical energy. Recently, the field of research on PV/T is has focused on improving the efficiency of the PV/T collector by replacing the conventional heat transfer fluids (HTFs) with nanofluids. This article investigates the effect of hybrid nanofluids mixture ratio on the useful energy and overall efficiency of a PV/T collector operating with Al₂O₃-ZnO water nanofluid as the HTF. Experiments to measure the thermophysical properties of the hybrid nanofluids were conducted for various temperatures, volume concentrations, and mixture ratios, furthermore, accurate correlation models were proposed. Metrological data and energy output readings collected from the PV solar farm at Cyprus International University were used to validate our model. The study observed that at the optimum mixture ratio (0.47 of Al₂O₃ in the hybrid), the electrical, thermal, and exergy efficiencies of the PV/T collector are 13.8%, 55.9%, and 15.13% respectively. Also, the cell temperature drops by 21% when the mass flow rate is 0.1 kg/s as compared to when it is 0.01 kg/s. Finally, the study concludes that by using the Al₂O₃-ZnO hybrid nanofluid an overall peak thermal efficiency of 91% can be attained, and this represents a 34% enhancement in the collector's performance when compared to water.     

Compatibility enhancement of silica and natural rubber compound using UVA-induced silane-grafted saponified skim natural rubber

Silane coupling agents are potential reagents widely used to improve the compatibility between silica and less polar rubber, especially natural rubber (NR). Nevertheless, high temperature is generally required to generate the interaction between the components during the mixing process. Accordingly, an alternative method by grafting the silane coupling agent onto the rubber molecules would be a desirable approach to develop a compatibilizer for the silica-filled NR compound. In this work, skim NR was used as a starting material due to its linear structure. The optimal conditions of the grafting reaction were found to be 1 phr of an alkoxy silane and 5 phr of benzoyl peroxide under 8 min of UVA irradiation time. These conditions were applied for producing the rubber material used in the mixing process of STR 5L and silica. The cure characteristics, silica dispersion and mechanical properties of the rubber compounds were improved, suggesting that the modified rubber was an efficient material for increasing the compatibility between silica and NR.     

Decarbonization of EU energy sector: techno-feasibility analysis of 100% renewables by 2050 in Cyprus

Clean Technologies and Environmental Policy - Cyprus continues to be one of the European Union’s most energy import-dependent countries. It is of worthy note that Cyprus is also the only...     

Pre‐Vulcanization of Large and Small Natural Rubber Latex Particles: Film‐Forming Behavior and Mechanical Properties

The pre‐vulcanized large rubber particle (LRP) and small rubber particle (SRP) latices are independently prepared to investigate their film‐forming process and mechanical properties after being cast into films. The surface morphologies and roughness of both LRP and SRP films are found to be dependent on crosslink densities. The networks inside each rubber particle (RP) restrict particle deformation resulting in residual contour of RP within the film surface. For highly crosslinked RP, the collapse of the top surface of the RPs in the LRP films appears to create many “crater‐like” structures within the film surfaces, while they present only protruding particles within the SRP and blend films. This seems to indicate that LRPs are easier to coalesce and form film than SRPs. Additionally, dynamic and mechanical properties and strain‐induced crystallization (SIC) behaviors of the latex films, are effectively enhanced after pre‐vulcanization. The pre‐vulcanized LRP films perform better tensile properties and SIC than the SRP can.