Subsurface and bulk mechanical properties of polyurethane nanocomposite films

A series of exfoliated and intercalated polyurethane (PU) organoclay nanocomposites, polyurethane-graphite oxide (GO) and polyurethane carbon nanotubes (single-walled (SWNT) and multi-walled carbon nanotubes (MWNT)) were prepared by in situ polymerization. It is believed that the preparation of polymer/clay or polymer/CNTs nanocomposites with homogeneous dispersion of nanofillers in the matrices is a crucial step to developing high-performance polymer nanocomposites. The effects of various organoclays and carbon nanotubes (CNTs), polyol types and dispersion situation i.e. intercalation or exfoliation on viscosity were investigated. The interactions between the polyol and nanofillers and the mixing temperature play an important role in the occurrence of exfoliation and intercalation in polyurethane nanocomposite. The mechanism of exfoliation of clay was proposed based on the rheological data. The surface mechanical properties of the polyurethane nanocomposite films were investigated by means of nanoindentation. The results showed that the hardness and elastic modulus of the nanocomposites dramatically increased with the incorporation of nanofillers. This improvement was dependent on the content of nanofillers as well as the formation structure of organoclay in the polyurethane matrix. At 3wt% clay content, the hardness and elastic modulus of intercalated nanocomposites increased by approximately 16% and 44%, respectively, compared to the pure PU. For the exfoliated clay/PU nanocomposites, the improvement in these properties was about 3.5 (hardness) and 1.6 (modulus) times higher than the intercalated ones. For the polyurethane graphite oxide (GO) nanocomposites both the hardness and the elastic modulus were enhanced as a function of GO concentration. With incorporation of 4wt% GO, the hardness and modulus increased nearly ~400% and ~350%, respectively. Upon incorporation of only 1wt% SWNT, the hardness of polyurethane was greatly improved by about 150% from 3 MPa to 7.8 MPa and the modulus was improved by about 50% from 12MPa to 18.5 MPa. For only 1wt% MWNT, the hardness of polyurethane was improved by about 50% and the modulus is just slightly improved by about ~5%. The creep behaviour of bulk and sub-surface of the polyurethane nanocomposites were investigated by means of uniaxial conventional creep testing and nanoindentation, respectively. The results showed that the creep resistance of the PU was significantly improved by incorporation of nanofillers. The enhancement of creep resistance was dependent on the filler. With 1wt% clay, the creep resistance increased by approximately 50% for the intercalated system and 67% for the exfoliated system, respectively, compared to the pure PU. The elastic-viscoelastic (EVE) model was employed to examine the effect of organoclay loadings on the creep performance of PU nanocomposites. Results showed the model was in good agreement with the experimental data. A similar results were also noticed in polyurethane with GO and CNTs. The creep deformation decreases when the GO content increases, as expected from the addition of a rigid reinforcement of GO and CNTs into a polyurethane matrix. In scratch test, the results pronounced that with incorporation of nanofillers the scratch depth of polyurethane matrix was dramatically reduced

Mechanical And Physical Properties of Wood-Plastic Composites Made of Polypropylene, Wood Flour and Nanoclay

The focus of this study was to characterize mechanical and physical properties of experimental composition prepared from nanoclays (Cloisite® 20A), wood flour (WF) and polypropylene (PP). Nanoclays with different concentrations were used as reinforcing filler for wood plastic compositions (WPCs). Maleic anhydride grafted polypropylene (MAPP) was added as a coupling agent to increase the interaction between the components of wood-plastic composites. Nanoclay based wood-plastic composites were made by extrusion process and then injection molding. Mechanical and physical properties of the as-prepared composites were evaluated. The results of strength measurements showed that the flexural modulus of the composite was increased by 56.33 % with increasing of nanoclays contents to 5 wt. %, reaching approximately 3.58 GPa compared to WPC containing 0% of nanoclays. Moreover, the flexural and tensile strengths reached their maximum values when the concentrations of nanoclays was 2.5 wt. %. When maintaining the nanoclays at a low concentration, it was well dispersed in the WPC. However, when more nanoclays (4 –5 wt. %) was introduced, the enhancing effect began to diminish because of the agglomeration of nanoclays which caused poor interfacial adhesion. The addition of nanoclays decreased the average water uptake by 13 %, compared to the control sample (without nanoclays). The improvement of physical and mechanical properties confirmed that nanoclays has good reinforcement and the optimum effect of nanoclays was archived at 2.5 wt. %

Peranan universiti sebar manfaat AI

KECERDASAN buatan (AI) menjadi topik perbualan utama bukan sahaja dalam kalangan para akademik di universiti dan industri, malah kini ia mendapat tempat di hati masyarakat awam. Justeru, pendedahan awal mengenai AI sangat penting bagi memastikan ledakan teknologi itu dapat dimanfaatkan sebaik mungkin dan mengelakkan perkara-perkara memudaratkan hasil daripada AI

Elucidating the plasticizing effect on mechanical and thermal properties of poly(lactic acid)/carbon nanotubes nanocomposites

Poly(lactic acid) (PLA) is a biodegradable plastic and grabs attention in several applications such as biomedical implantation, film, packaging and clothing. Instead, PLA itself has a characteristic of brittleness, resulting in poor mechanical properties, and its slow ability in degradation leads to waste disposal problem. The present research aims to develop material in such a way to have a good combination of properties and optimum degradation ability. The PLA nanocomposites were prepared via melt blending that consisted of two types of carbon nanotubes (CNTs): unmodified carbon nanotubes (CNTs) and modified CNTs (mCNTs). The effect of 5 wt% poly (ethylene glycol) (PEG) as plasticizer on nanocomposites with CNTs material loading at 0.5 wt%, 1.0 wt%, 1.5 wt% and 2.0 wt% was studied. The analysis of physical properties was done using hardness testing and melt flow index (MFI). Neat PLA only gave around 69.0–77.6 Shore D in hardness test, while MFI exhibited around 36.1–39.4 g/10 min. PLA/mCNTs and PLA/PEG/mCNTs at 1.5 wt% exhibited the highest values of hardness testing which were 86.0 and 85.9 Shore D, respectively. In MFI study, the results were 70.0 g/10 min for PLA/mCNTs and 80.3 g/10 min for PLA/PEG/mCNTs. This proved that the PEG is useful in reducing the brittleness of nanocomposite. The full exfoliation of CNTs and mCNTs in the matrix observed from the X-ray diffraction analysis supported the excellent hardness and MFI properties. These nanocomposites also showed high thermal stability as obtained from differential scanning calorimetry and thermogravimetric analysis studies compared with neat PLA. The morphology study by field emission scanning electron microscopy analysis confirmed these findings through the existence of a smooth fracture surface, especially when PEG was loaded as evidence of good distribution of nanofiller in the matrix was established. Based on all analyses done, PLA/PEG/mCNTs were chosen as the good nanocomposite among others

Pure polyurethane and castor oil based polyurethane: Synthesis and characterization

In this study, the physico-chemical properties of high performance polyurethane synthesized from poly propylene glycol (PPG) in comparison with a combination of PPG and castor oil, is studied using the in-situ polymerization technique. The variations in properties of both types of polyurethanes are evaluated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and the thermogravimetric analysis (TGA) technique. Tensile strength properties were investigated by film tensile testing equipment. The results indicated the presence of large -CH stretching in the castor oil mixed polyurethane with a larger oxidative thermal stability over pure PPG polyurethanes. The tensile properties were found to be almost comparable in pure and mixed polymers, signifying the usage of mixed polymers in the future to overcome the environmental and economic crisis in polyurethane synthesis

Synthesis and Physicochemical Behaviour of Polyurethane-Multiwalled Carbon Nanotubes Nanocomposites Based on Renewable Castor Oil Polyols

Polyurethanes (PUs) are high performance materials, with vast industrial and engineering applications. In this research, effects of Multiwalled Carbon Nanotubes (MWCNTs) on physicochemical properties of Castor Oil based Polyurethanes (COPUs) were studied. MWCNTs were added in different weight percentages (0% to 1% wt) in a castor oil based polyurethane (COPUs-MWCNTs) nanocomposites. The composition, structure, and morphology of polyurethanes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), and element detection by energy dispersive spectroscopy (EDX) analysis, respectively. Thermal stability was studied by thermogravimetric analysis (TGA). Barrier properties and surface area studies were investigated by nitrogen permeability machine and BET technique. Mechanical properties were calculated by tensile universal testing machine. Results showed well dispersed MWCNTs in polyurethane matrix at different weight percentages. The best results were obtained with 0.3 wt% of MWCNTs in the composite. Surface area studies revealed presence of very few pores which is in a good agreement with barrier permeability, reduced up to ~68% in 1 wt% and ~70% in 0.5 wt% of MWCNTs in polymer matrix, with respect to pure COPUs samples

Thermal and structure analysis based on exfoliation of clay in thermosensitive polymer by in-situ polymerization

Poly(N-vinylcaprolactam) (PNVCL) offers superior characteristics as a thermoresponsive polymer for various potential applications. An attractive procedure, namely in-situ polymerization, was used to prepare NVCL/clay nanocomposite in different clay ratios. Organo-modified clay as C20 and B30 were employed in a range between 1–5% based on weight. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) were used to study thermal decomposition and to assess bond conversion during polymerization of the nanocomposite. This research was conducted to study PNVCL characteristics with the addition of clay as a nanocomposite. The stretch mode of the carboxylic group (C=O) and (C=C) was present in the band range about ~1635 cm–1 for the C20, but it was ranging between 1640 to 1664 cm–1 for the B30 of the nanocomposite. It was observed that the decomposition was different for each type of organoclay and the temperature peaked at 30 to 800 °C, to measure the degradation points at 5, 10, and 50%. Comparison results for FTIR and TGA showed that the best nanocomposite was found in the C20 (3%) case

Poly(lactic acid)/graphene oxide nanocomposites: A morphology study and mechanism of reaction

Because of environmental concerns, the use of biopolymer poly(lactic acid) (PLA) as a matrix has gotten a lot of attention. The graphite (Gt) was modified to produce graphene oxide (GO) using an acid treatment prior to mixing. The modified GO was validated by Fourier Transform Infrared Spectroscopy (FT-IR) and Ultraviolet-Visible Spectroscopy (UV-Vis) tests. Melt mixing produced PLA nanocomposites with 1.5 wt.% loadings of two distinct carbon-based materials, Gt and GO. The effect of a plasticizer of 5 wt.% poly(ethylene glycol) (PEG) on nanocomposites was also investigated. The morphology study by Field Emission Scanning Electron Microscopy (FESEM) analysis showed the GO loading gave a smooth surface morphology as compared with PLA/Gt. These findings were identified by the presence of a smooth fracture surface, particularly when PEG was loaded, as an indication of good nanofiller spreading in the matrix. The mechanisms of reactions for Gt and GO dispersion in the PLA matrix were proposed to prove the morphology analysis

Optimization and modeling of reactive conditions for free radical solution polymerization of SA-co-BA copolymer based on the yield using response surface methodology

In the recent years, response surface methodology (RSM) is one of the most common optimization methods employed in the chemical process. The satisfactory model for predicting the maximum yield in solution polymerization has been a challenge due to various conditions during the synthesis process. In this study, interactive impacts of three parameters which are reaction time, concentration of initiator, and reaction temperature on the yield in free radical polymerization of SABA copolymer using toluene as solvent was investigated using experimental design central composite design (CCD) model under response surface methodology (RSM). The result showed the optimization conditions were reaction time of 7 h, initiator concentration of 1 wt %, and reaction temperature of 90 oC with the corresponding yield of 97.31%. The analysis of the regression model (ANOVA) detected an R2 value of 0.9844, that the model is able to clarify 98.44% of the data variation, and just 1.23% of the whole differences is not clarified by the model. Three experimental validation runs were carried out using the optimal replicate conditions and the highest average yield value obtained is 97.15%. There is an error of about 0.97% as compared to the expected value.Therefore, the results indicate that this model is reliable and is able to predict the yield response accurately. it established that the regression model is extremely significant, indicating a strong agreement between the expected and the experimental values of SABA yield

Influence of poly (stearyl acrylate co-behenyl acrylate) as flow improvers on the viscosity reduction of Malaysian crude oil

Pipelines are the most appropriate means of transporting crude oils in different parts of the world. Nevertheless, the high viscosity of crude oil at low temperatures is one of the main challenges when transporting crude oils through the pipeline, which needs adequate and expensive methods of transporting crude oil, and wax depositions in the pipeline that is caused by high viscosity of crude oil. Therefore, several ways have been investigated to boost the mobility of crudes in stimulating pipeline transportation. In this study, poly (stearyl acrylate co-behenyl acrylate) (SA-co-BA) pour point depressant PPD copolymer was synthesized as flow improvers for reducing the viscosity of crude oil to improve the flowability. SA-co-BA copolymer has been synthesized by using free-radical polymerization method and characterized by FTIR. The viscosity of blank crude oil increases with decreasing temperature after the addition of (SA-co-BA) copolymer to the blank crude oil at various concentrations. The results exhibited that the mass ratio (1:2) at a concentration of 1000 ppm was the highest performance of viscosity reduction by 90.57% from 70 mPa.s to 6.6 mPa.s at 5 °C of crude oil temperature. The influence of the (SA-co-BA) copolymer was clearly seen on the viscosity reduction of crude oil at different conditions, because of the acrylate groups which have a long alkyl chain. It is observed that a major reduction in the viscosity of the crude oil sample was observed at low temperatures, which makes it a reasonable recommendation for offshore applications. The results of characterization revealed that FTIR characteristics showed absorption peaks at 2914.86 cm−1 and 2848.09 cm−1, respectively, as typical absorption peaks of CH3– and –CH2-. The ester group's sharp absorption peak C = O was recorded at 1731.71 cm−1. Therefore, SA-co-BA copolymer recorded an appreciable minimization in the viscosity of crude oil