Process optimization and removal of phenol formaldehyde resin coating using mechanical erosion process

Consumption of coated abrasive discs in various automobile and pipe fitting application is increasing, due to its good surface finish. Coated abrasive disc consists of single layer of abrasive grain bonded to a fibre backing. The major portion of the disc is comprised of fibre backing. But the sustainability of the fibre backing is low and is dumped as waste after usage. The present work deals with the removal of resin coating and recovery of fibre backing from the spent coated abrasive discs using physical separation process such as sand blasting technique. Initially, the recovery experiment was carried out based on L16 orthogonal array. The factors and levels chosen for the experiments were erodent pressure (0.2, 0.4, 0.6 and 0.8 MPa), erodent size (36, 60, 80 and 120 grit), disc orientation (30, 45, 60 and 75°) and number of times flexing (5, 10, 15 and 20). The experimental result shows that erodent size and erodent pressure have a major impact on recovery of the fibre backing. The surface structure of the recovered backing was analysed using scanning electron microscopy and optical microscopy. The recovered backing was very much useful for the coated abrasive industry as the flexible backing and support material for abrasive grain coating.

A model study on the impact of metal ions on pre-vulcanization of concentrated natural rubber latex and dipped-products

A model study on the influence of some heavy metal ions on the stability and vulcanization efficiency of uncompounded and compounded high-ammonia natural rubber (HANR) latex was carried out by an exogenous addition and then determined by Brookfield viscometer, mechanical stability time (MST) tester, and tensile testing machine. The case of pre-vulcanized HANR latex with different aging times was determined by the change in the volatile fatty acid (VFA) number, MST, and viscosity. The compounded HANR latex was coagulated by adding Mn2+and Mg2+ while it was unaltered by adding Zn2+, Fe2+, and Cu2+ ions, leading to their colloidal stability. Therefore, these metal ions were chosen further to study the pre-vulcanization of compounded HANR latex. The presence of Zn2+, Fe2+, and Cu2+ in the latex is responsible for the delay in the vulcanization process and changes the appearance of compounded latex. Before compounding, the addition of such metal ions led to the reduction in tensile strength of the obtained gloves. At the same time, there was no effect on the tensile properties of the gloves made from the compounded HANR latex containing the metal ions.

Effect of basalt and polypropylene fibers on crumb rubber mortar with Portland cement and calcium aluminate cement binders: Strength and artificial neural network prediction model

This paper aims to study the influence of basalt fiber (BF) and polypropylene fiber (PPF) in crumb rubber (CR) mortar made of two different types of cement, including ordinary Portland cement (OPC) and calcium aluminate cement (CAC). CR was used to partially (5%, 10%, 15%, and 20% by volume) replace the fine aggregate in OPC and CAC mortars. BF and PPF were added (0.1%, 0.3%, and 0.5% by total volume) in the CR mortars. The consistency, density, compressive, and flexural strength of cement mortars were investigated. The use of CAC cement slightly increased the consistency; however, the results showed that the CR replacement and the addition of both fiber types tend to reduce the consistency in OPC and CAC mortars. Significant reduction in the density of fiber-added CR mortar was found with increasing CR content, whereas the influence of both PPF and BF was minimal. The fiber-added CR mortar made of both binder and fiber types in general exhibited a reducing trend in the 28 days compressive strength when increasing CR and fiber contents. Nevertheless, an enhancement in the compressive strength of CAC mortar with 20% CR was found with the addition of 0.1% of both fibers. The use of CR and addition of the fibers generally decreased the flexural strength of mortar made of both binder types; however, the addition of 0.3% BF in mortars containing 15–20% CR positively affected the flexural performance. Finally, the artificial neural network (ANN) approach demonstrated the ability to predict the compressive strength of fiber-added CR mortars. The model showed a considerably insignificant mean square error (MSE) of 1.4–1.5 and high plot regression (R) results of 0.97–0.98.

Temperature glass and conductivity behavior of epoxy deproteinized natural rubber in ternary blend of EDPNR/PMMA/LiCF3SO3

The temperature glass behavior of epoxy deproteinized natural rubber/polymethylmethacrylate/lithium trifluoromethanesulfonate (EDPNR/PMMA/LiCF3SO3) and the conductivity behavior of EDPNR in the ternary blends were studied by DSC and multichannel potentiostat. The DSC result revealed the temperature glass of the EDPNR was shifted to the right with the increase of lithium salt amount in these binary blends composition. However, in the ternary blends of EDPNR/PMMA/LiCF3SO3 the temperature glass revealed the miscibility of these ternary blends. Two different temperature glass values were obtained when the ratio of EDPNR in EDPNR/PMMA was less than 80 wt.%. The ionic conductivity of EDPNR could be improved by increasing the amount of lithium salt up to 35 wt.%, after this amount the ionic conductivity of EDPNR was significantly decreased. While in the ternary blends, the highest ionic conductivity value was found at the ratio 80/20 of EDPNR/PMMA. Furthermore, the factors influencing the temperature glass and conductivity behavior of EDPNR were systematically studied in this work. The results demonstrated an intimate correlation between temperature glass and conductivity behavior of EDPNR.

Thermal aging behaviors of the waste tire rubber used in bitumen modification

Considering the application scenarios of rubber granules from waste tires in the bitumen modification process (wet or dry process), both aerobic and anaerobic aging of rubber may occur. The current study aims to investigate the thermal aging behavior of waste tire rubber samples using nanoindentation and environment scanning electron microscopy (ESEM) tests. Both aerobic and anaerobic aging tests with different durations were conducted on rubber samples. The complex moduli of aged rubber samples were measured by nanoindentation tests. The surface morphology and elemental composition of aged samples were obtained by ESEM tests together with the energy dispersive X-ray analysis. Results have shown that for both aerobic and anaerobic aging, the equilibrium modulus derived from the complex modulus curve first increases and then decreases with aging time. However, the time needed for the aerobically aged sample to reach the maximum equilibrium modulus is shorter than the anaerobic case. Aging results in crack propagation and an increase of sulfur content on the rubber surface until it reaches the peak. The degree of crosslinking reflected by sulfur content for anaerobic aging is higher than aerobic aging. The morphological change and elemental change of rubber correlate well with the change of mechanical properties. The aging of rubber from the waste truck tire at 180°C can generally be separated into two stages: crosslinking dominant stage and chain scission dominant stage.

Enhancing cellular structure, mechanical properties, thermal stability and flame retardation of EVA/NR blend nanocomposite foams by silicon dioxide-based flame retardant

Flame retardant rubber foams of ethylene vinyl acetate (EVA)/natural rubber (NR)/layered silicate blends filled with silicon dioxide (SiO2) were prepared by using azodicarbonamide (ADC) as a blowing agent. Specifically, SiO2 was added in EVA/NR blend nanocomposites to produce good flame retardant foams. The properties of EVA/NR blend nanocomposite foams with different SiO2 loading (0, 20, 30, 40 parts per hundred rubber, phr) were investigated through transmission electron microscopy (TEM), scanning electron microscopy (SEM), rheological property test, mechanical property measurement, flammability tests, thermogravimetry analysis (TGA) and pyrolysis-gas chromatography-mass spectrometry (Pyrolysis-GC-MS). Compared with the simple EVA/NR blend nanocomposite, the added SiO2 increased the blend compatibility between EVA and NR phases and melt strength/viscosity of the EVA/NR blend nanocomposites, thus promoting cellular structure of the EVA/NR nanocomposite foams. Increasing SiO2 loading resulted in higher cell density, smaller cell size, and lower volume of void. These improvements caused higher strength and elastomeric recovery. The LOI test results showed that flame retardancy of the EVA/NR blend nanocomposite foams increased at higher SiO2 loading as a result of formation of insulation silicon dioxide-based char. TGA and pyrolysis-GC-MS analyses also validated the finding that the silicon dioxide-based char in the foamed samples containing higher SiO2 loading was more effective on improving thermal stability, which was responsible for lower material combustibility and better flame retardancy. Based on our finding, it was concluded that a good flame retardant EVA/NR blend nanocomposite foam with the best improvement in strength and elastomeric recovery was achieved when combined with 40 phr SiO2.

Ground tire rubber/polyamide 6 thermoplastic elastomers produced by dry blending and compression molding

This study investigates the addition of ground tire rubber (GTR) into virgin polyamide 6 (PA6) to produce thermoplastic elastomer (TPE) blends. In particular, a wide range of GTR concentration (0–100% wt.) was possible by using a simple dry blending technique of the materials in a powder form followed by compression molding. The molded samples were characterized in terms of morphological (scanning electron microscopy), physical (density and hardness) and mechanical (tension, flexion and impact) properties. The results showed a decrease in tensile and flexural moduli and strengths with GTR due to its elastomeric nature. However, significant increases were observed on the tensile elongation at break (up to 167%) and impact strength (up to 131%) compared to the neat PA6 matrix. Based on the results obtained, an optimum GTR content around 75% wt. was observed which represents a balance between high recycled rubber content and a sufficient amount of matrix to recover all the particles. These results represent a first step showing that a simple processing method can be used to produce low cost PA6/GTR compounds with a wide range of physical and mechanical properties.

Ultraviolet light exposure degradation effect on the properties of nanocrystalline cellulose-reinforced polyvinyl alcohol composite film

PVA used in packaging applications has been faced with a UV light degradation challenge, which often reduces its durability while in use. The UV light stability enhancement effect of nanocrystalline cellulose (NCC) reinforcement in PVA was studied. Polyvinyl alcohol composite film was reinforced with NCC from palm oil waste (PVA-NCC film) and exposed to UV light (22 W, SUV-16 254 nm) for different time duration to study the material durability enhancement. The percentage weight loss of the samples was measured to observe the UV light degradation effect. Furthermore, the samples’ structural, morphological, and tensile properties were studied before and after exposure to UV light with FT-IR, scanning electron microscopy (SEM), and tensile test. The results showed physical degradation, morphological and tensile properties enhancement of PVA with NCC’s addition. The addition of NCC to the PVA matrix reduced the degradation rate under UV light significantly. Also, the percentage of weight loss was observed to change with the exposure time to UV light.

Reusing ground tire rubber powder as thermoplastic elastomers with excellent superhydrophobicity and self-cleaning performance

A simple, effective and inexpensive method was proposed to reuse ground tire rubber (GTR) powder by preparing a superhydrophobic surface via a molding process. The obtained superhydrophobic surface was based on low-density polyethylene (LDPE) / ground tire rubber (GTR) thermoplastic elastomers (TPEs) where the styrene-butadiene-styrene block copolymer (SBS) was used as compatibilizer and series sandpapers were used as templates. The mechanical properties, hydrophobic properties, surface morphology and self-cleaning property were investigated systematically. The results showed that both of the mechanical properties and superhydrophobicity could be greatly improved with a certain amount of SBS. The superhydrophobic surface based on molded LDPE/SBS/GTR (weight ratio = 40/15/60) TPE exhibited excellent superhydrophobicity (with a contact angle of 164.6° ± 3.0° and a tilt angle of 4.4° ± 1.9°). Furthermore, abundant tearing microstructure could be found obviously by morphology observation. Optical images indicated the surface possessed of low adhesion force and self-cleaning property.

Waste cooking oils as processing aids for eco-sustainable elastomeric compounding

This work focuses on the replacement of mineral oils with bio-based waste cooking oils in rubber compounding. Two different waste cooking oils from potatoes and chicken frying process were analyzed by means of chemical and rheological tests to evaluate the chemical composition, the oxidative stability and the viscosity. Waste oils have been introduced in elastomeric compounds as substitute for typical processing aids (i.e. lubricants). Cure kinetics of rubber compounds was studied by rheological characterization. Mechanical properties of vulcanized samples were determined by means of tensile tests, hardness tests and dynamic mechanical analysis. The waste oils showed a rheological behavior very similar to the mineral oils conventionally employed in rubber manufacturing leading to almost the same processability of the resulting compound. The waste oils did not significantly affect the vulcanization kinetics of the rubber compound, as expected for conventional lubricants. Waste cooking oils and mineral oil show analogous influence on mechanical properties of cured compounds. At increasing oil content, the elongation at break and the tensile strength increased whereas the values of Elastic Modulus at 100% strain, the Storage Modulus and Shore A Hardness decreased with respect to the oil-free sample. These results are very promising, confirming the possibility to replace the mineral oils, in a good practice of circular economy.