In this study, we present the fabrication of nitrile butadiene rubber/waste leather fiber (NBR/WLF) composites with different weight percentages of WLF and NBR (0/100, 20/80, 30/70, 40/60, 50/50, 60/40 wt/wt). WLF was prepared by cutting the scrap leathers from the waste product of the Vietnamese leather industry. Subsequently, in order to make the short fibers, it was mixed by a hammer mill. The characteristics of WLF/NBR composites such as mechanical properties (tensile strength, tear strength, hardness), dynamic mechanical properties, toluene absorption, and morphology were carefully evaluated. As a result, the tensile strength and tear strength become larger with increasing WLF content from 0 to 50 wt% and they decrease when further increasing WLF content. The highest tensile strength of 12.5 MPa and tear strength of 72.47 N/mm were achieved with the WLF/NBR ratio of 50/50 wt%. Both hardness and resistance of the developed materials with toluene increased with increasing WLF content. The SEM results showed a good adhesion of NBR matrix and the WLF. The increasing of storage modulus (E’) in comparison with raw NBR showed good compatibility between WLF and NBR matrix. This research showed that the recycled material from waste leather and NBR was successfully prepared and has great potential for manufacturing products such as floor covering courts and playgrounds, etc.
Graphene has been demonstrated to be one of the most promising candidates to use as filler to improve the electrical, thermal, chemical and mechanical properties of natural rubber due to exceptional high surface area, superior electrical and thermal conductivity, and remarkable gas impermeability resistance. In this study, graphene nanoplates (GNPs) were mass-produced by a one-step chemical exfoliation of natural graphite and used as a filler for the fabrication of GNPs@natural rubber composite by a simple mixing method. The resultant GNPs/rubber composite was characterized by using scanning electron microscopy (SEM), and a rheometer. The prepared graphene nanoplates had a thickness of less than 10 nm and a lateral size of tens of microns. The GNPs@rubber composite revealed an exceptional improvement of abrasion loss up to seven to ten fold, along with an approximately 400%, 200% and 30% increment of elongation at break, tear strength and tensile strength, respectively. Other mechanical properties, such as hardness, compression set and rebound, as well as the effect of the GNPs loadings on the mechanical properties of the composite, were also investigated in detail.
Cationic polyacrylamide (CPAM) emulsifier is widely applied in the wastewater treatment industry, mining industry, paper industry, cosmetic chemistry, etc. However, optimization of input parameters in the synthesis of CPAM by using the traditional approach (i.e., changing one factor while leaving the others fixed at a particular set of conditions) would require a long time and a high cost of input materials. Onsite mass production of CPAM requires fast optimization of input parameters (i.e., stirring speed, reaction temperature and time, the amount of initiator, etc.) to minimize the production cost of specific–molecular–weight CPAM. Therefore, in this study, we synthesized CPAM using reverse emulsion copolymerization, and proposed response surface models for predicting the average molecular weight and reaction yield based on those input parameters. This study offers a time–saving tool for onsite mass production of specific–molecular–weight CPAM. Based on our response surface models, we obtained the optimal conditions for the synthesis of CPAM emulsions, which yielded medium–molecular–weight polymers and high conversion, with a reaction temperature of 60–62 °C, stirring speed of 2500–2600 rpm, and reaction time of 7 h. Quadratic models showed a good fit for predicting molecular weight (Adj.R2 = 0.9888, coefficient of variation = 2.08%) and reaction yield (Adj.R2 = 0.9982, coefficient of variation = 0.50%). The models suggested by our study would benefit the cost–minimization of CPAM mass production, where one could find optimal conditions for synthesizing different molecular weights of CPAM more quickly than via the traditional approach.
Selection of a suitable thermal aging process could render desirable mechanical properties of the rubbers or blended rubbers. In this work, the effect of the aging processes on the mechanical properties and activation energies of natural rubbers (NR) and NR/chloroprene rubbers (CR) blends with low CR contents (5–10%) was investigated. Three aging processes including heat aging (at 110°C for 22 hours), mechanical aging (under dynamic loading to 140% strain for 16000 cycles), and complex aging (heat and mechanical aging) were studied. The results revealed that the compatibility of CR in natural rubber matrix had a significant effect on the dynamic properties of the blended rubber and negligible effect on the static properties. The changes in activation energies of the blended rubber during aging processes were calculated using Arrhenius relation. The calculated changes (ΔUc, ΔUd, and ΔUT) in activation energies were consistent with the results of mechanical properties of the blended rubber. Interestingly, the change in activation energies using complex aging conditions (ΔUc) was mostly equal to the total changes in activation energies calculated separately from heat aging (ΔUT) and mechanical aging (ΔUd) conditions. This indicates that, in complex aging conditions, the heat and dynamic loading factors act independently on the properties of the blended rubber.
In this study, the flame-retardant treatment for cotton fabric has been done by using the commercial organophosphoruscompounds labelled Pyrovatex CP New (PR). Knittex FFRC (K), a formaldehyde-free crosslinking agent, has been usedto enhance the link between Pyrovatex CP New and Cellulose molecules. The flame-retardant treatment process forcotton fabric has been done by the pad-dry-cure technique. The purpose of the study is to predict the optimal PyrovatexCP New and Knittex FFRC concentrations with the highest fire resistance efficiency, minimum loss for mechanicalproperties and minimum formaldehyde release for the treated fabric. To achieve this goal, the response surfacemethodology (RSM) was used to find the relationship between the controlled experimental factors and the observedresults. The central composite design type face centred (CCF) was applied as experimental design. According to thisexperimental design, 10 experiments were carried out. The chemical uptake rate, vertical flammability characteristics,LOI value, tensile strength and formaldehyde-free content of the untreated and treated samples were determined. Fourresponse models between the reagent concentrations and the add-on amount, LOI value, warp and weft tensile strengthof the treated fabric were obtained by the assistance of software Design-Expert V 10.0.8. The R-squared values of thesemodels were above 80% confirming their significances. The optimal conditions when combining three parameters (LOI,warp tensile strength and weft tensile strength) were selected as 450 g/l Pyrovatex CP New and 107,575 g/l KnittexFFRC with the assistance of Design-Expert software
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