Exposure of thermoplastics to methanol–gasoline blends: A material compatibility study

Alcohols are increasingly being looked upon as the most viable alternative to the conventional sources of energy. Methanol is the first member of the alcohol family and can be easily synthesized from syngas. It is an attractive blend to gasoline due to its advantageous properties. There is a necessity to make sure that the infrastructure is ready to adapt these alternative fuels. Hence, the aim of this study is to assess the degradation of widely used thermoplastics in fuel tanks, pipes, and the fuel injection system, namely, polytetrafluoroethylene (PTFE), polyethyleneterephthalate (PET), and high density polyethylene (HDPE) post exposure to methanol–gasoline blends (P100, M15, and M30) for a period of 4, 10, and 30 days. The effects of the exposure were examined by comparing changes in gain/loss of mass, hardness, elongation, and tensile strength. The surface morphology changes of the polymeric coupons were characterized by scanning electron microscopy and their elemental analysis was done by energy dispersive X-ray spectroscopy. The studied materials were found to gain mass in the order HDPE > PTFE >PET. The decrease in hardness was found to be more in HDPE followed by PTFE and PET. PTFE and PET showed reduction in strength but an increase in tensile strength was observed for HDPE post exposure to fuel blend. Highest change in elongation was found in HDPE followed by PTFE and PET. The changes were found to be the least in P100 followed by M15 and maximum in M30 blends for all immersion periods.

Fourier transform infra-red spectroscopy to determine formaldehyde to phenol ratio of phenol formaldehyde resole

A model has been proposed to determine the formaldehyde (F) to phenol (P) ratio [F/P] of resole with the help of Fourier transform infra-red spectroscopy. The study is based on the comparison of IR absorbance of the dominant peaks corresponding to the formaldehyde and phenol contents in the resin. This study can be of much use in adhesive coating industries to employ the F/P ratio as a quality tool as well as for competition resin benchmarking. It can also be utilized for understanding the kinetics of the reactions between phenol and formaldehyde. Detailed qualitative analyses of various resoles with different formulations have been discussed in this paper, which can be of potential help for the standard analysis of the commercial resins. The validation of results confirms that the most fitting model offers an error less than 7%. Interestingly, this model can also be applied with blends of different Phenol formaldehyde resoles.

Influence of the curing system on the physical-mechanical, dynamic properties, and aging resistance of ethylene–propylene–diene monomer formulations for applications at high temperatures

The effects of three curing systems on rheometric, morphological, physical-mechanical, thermal, and dynamic properties of ethylene–propylene–diene monomer (EPDM) composites was investigated. The influence of thermo-oxidative aging on crosslink density and physical-mechanical properties was studied. Based on a standard composition for application at high temperatures, EPDM formulations with semi-efficient vulcanization systems (ES), efficient vulcanization systems (ED), and peroxide curing systems (EP) were prepared. Experimental results indicated that EPDM compounds cured with efficient vulcanization systems exhibit the highest scorch time with an intermediate maximum torque value at 150°C. The filler dispersion in the elastomeric matrix was greater than 94%; however, the ED formulation showed a more pronounced decrease, with the increase in deformation indicating a greater filler–filler interaction. In comparison with those cured with peroxide and semi-efficient systems, EPDM formulations cured with an efficient system presented better thermal resistance and the crosslink density was sufficient to maintain the mechanical integrity, leading to an intermediate hardness value, tensile strength, modulus, and greater elongation at breaking. In summary, the results indicated that the efficient curing system was the most appropriate to be used in the envelope’s manufacture, due to the better performance of the mechanical properties associated with the better resistance to thermal aging.

Controlling foamability of polypropylene/γ-irradiated ethylene acrylic elastomer blends by extent of crosslinking and domain microstructure of elastomer

Foams of polypropylene/elastomer blends can often lead to softer foams which may not be desirable every time. Incorporating rigidity to the foams can often be made possible by preferentially crosslinking the elastomer phase prior to blending. Although foamability of polypropylene/elastomer blends has been understood in the scientific community, the influence of the extent of crosslinking in the elastomer phase is not yet understood well. The purpose of this investigation is to identify the influence of the extent of elastomer crosslinking and the blend morphological attributes (achieved by varying screw speed during melt mixing) on foamability of polypropylene/partially crosslinked elastomer blends. Crosslinking of ethylene-acrylic elastomer is carried out using gamma radiation with several doses (0, 12.5, 25, 50 kGy) before melt blending and, subsequently, 10 wt.% of the irradiated elastomers (prior optimized) are mixed with polypropylene in a micro-compounder at three different screw speeds. The microstructure development in blends is characterized by scanning electron microscopy. Frequency sweep rheological analysis is done for selected blends to identify the ease of foamability among the series of blends. Foaming of blends is done with supercritical carbon dioxide in batch mode at three different temperatures. The density reduction along with the microcellular morphology development of blends with foaming is analyzed with the screw speed, the extent of crosslinking, and foaming temperature; furthermore, the individual input parameters (the elastomer domain size, controlled by the screw speed and the extent of crosslinking, controlled by gamma radiation dose) are optimized based on the foam morphology. A uniform and good foamability were achieved at 155 and 160°C for blends with elastomers, irradiated at 12.5 and 25 kGy radiation doses. The lowest density foam (0.37 g/cc) was obtained for polypropylene with 12.5 kGy irradiated crosslinked elastomer mixed at 200 rpm at 160°C foaming temperature. The final elastomer domain dispositions within the foam morphologies are characterized and the plausible foaming mechanism is proposed.

Flexible crosslinking of polyurethane using grafted poly(dimethylsiloxane) with Epichlorohydrin and Bisphenol A end groups and its impact on the mechanical properties and low-temperature flexibility

Poly(dimethylsiloxane) (PDMS) was grafted onto polyurethane (PU), and Epichlorohydrin and Bisphenol A were attached to the free ends of PDMS groups and used to link the grafted PDMS to thereby introduce flexible crosslinks between the PU chains. The flexible crosslinks enhanced the crosslink density and solution viscosity of PU but did not change the melting and crystallization behaviors of the soft segments of PU. In particular, the flexible PDMS crosslinks increased the maximum tensile stress by up to 300% and the maximum tensile strain up to 180%. The shape recovery capability at 10°C and the shape retention capability at −25°C were maintained above 90% with the flexible crosslinking. Grafted PDMS moderately improved the low-temperature flexibility of PU due to its flexibility at low temperature. The flexible crosslinks of grafted PDMS successfully improved the tensile strength, shape recovery, and low-temperature flexibility of the PU.

Studies on reinforcing effect of industrial nano silica in chloroprene vulcanizates containing carboxy-terminated liquid natural rubber

Maleic anhydride was chemically attached to depolymerized natural rubber, and the product was named as carboxy-terminated liquid natural rubber (CTNR). The CTNR can act as a potential plasticizer in chloroprene (CR) vulcanizates. This paper describes the use of commercial nano silica (NS) as a promising cost-effective filler, which can enhance the tensile properties and ageing resistance of the CR vulcanizates incorporated with CTNR (CR-CTNR). The enhancement in properties may be attributed to the increased bound-rubber content owing to the large surface area of the nano-sized filler. The characteristics of the NS-filled CR vulcanizates containing CTNR (NS CR-CTNR) were compared with those containing amorphous silica. The NS CR-CTNR vulcanizates showed superior ageing and oil resistance due to the finer rubber filler interaction modified by ionic cross linking.

Thermal, mechanical, and electrical properties of difunctional and trifunctional epoxy blends with nanoporous materials

In the present study, the aim is to synthesize the particulate nanocomposites with difunctional and trifunctional epoxy blend as matrix and synthesized nanoporous materials as fillers. Organic/inorganic hybrid networks were prepared by the novel solvent free method. Viscoelastic, thermal, and electrical properties of di- and trifunctional epoxy and the effect of different nanoparticles in the particulate nanocomposites have been studied by dynamic mechanical analyzer, thermogravimetry (TGA), and dielectric strength. Epoxy mixed with different compositions of TGPAP and particulate nanocomposites by the addition of different types of nanomaterials shows higher storage modulus than the pure epoxy. The addition of TGPAP and nanofillers decreases the thermal stability of epoxy matrix. The evolved gas analysis (TG-FTIR) was also done in order to study the products formed during degradation. An increase in dielectric strength and impact strength (4%) was also observed in the particulate nanocomposites.

The effect of OMMT reinforcement and annealing treatment on mechanical and thermal properties of Polyurethane Copolymer nanocomposites

This study focuses on a new fabrication of nanocomposite based on Polyurethane Copolymer (PUC) intercalated with organo-modified montmorillonite nanoparticles (OMMT), via an efficient combination of solution mixing and melt blending processes. The combination of solution mixing and melt interaction processes produced PUC/OMMT nanocomposites with enhanced properties. The OMMT filled PUC was characterised by TEM and tensile test. The effect of thermal treatment process was also studied due to subsequent microphase separation of PUC resulting from microdomain miscibility. TEM observation recognised a decent dispersion state of OMMT within PUC, owing to their exfoliated and intercalated structure. This morphology was greatly influenced by induced thermal treatment. The dynamic mechanical thermal analysis (DMTA) revealed that storage modulus and glass transition temperature of the nanocomposites increased with OMMT incorporation. The tensile modulus and tensile strength of nanocomposites showed an improvement with the addition of OMMT.

Investigation of the effects of welding variables on the welding defects of the friction stir welded high density polyethylene sheets

Modern thermoplastic materials are used in an expanding range of engineering applications, such as in the automotive industry, due to their enhanced stress-to-weight ratios, toughness, a very short time of solidification, and a low thermal conductivity. Recently, friction stir welding has started to be used in joining processes in these areas. There are many factors that affect weld performance and weld quality in friction stir welding (FSW). These factors must be compatible with each other. Due to the large number of welding variables in friction stir welding processes, it is very difficult to achieve high strength FSW joints, high welding performance, and control the welding process. Welding variables that form the basis of friction stir welding; machine parameters, tool variables, and material properties are divided into three main groups. Each welding variable has different effects on the weld joint. In this study, friction stir welds were made on high density polyethylene (HDPE) sheets with factors selected from machine parameters and welding tool variables. Although the welding performance, quality, and strength gave good results in some conditions, successful joints could not be realized in some conditions. In particular, welding defects occurring in the combination of HDPE material with FSW were investigated. Welding quality, defects, and performances were examined with macrostructure. In addition, the tensile strength values of some the joints were determined. The main purpose of this study is to determine the welding defects that occur at the joints. The causes of welding defects, prevention methods, and which weld variables caused were investigated. Welding parameters and welding defects caused by welding tools were examined in detail. In addition, the factors causing welding defects were changed in a wide range and the changes in the defects were observed.