Microstructure and mechanical properties of polyurethane/nylon/montmorillonite nanocomposite

Nanocomposite of polyurethane (PU), Nylon66 (nylon), and montmorillonite (MMT) was prepared by a twin screw extruder, and the dispersion of MMT and the mechanical properties of the nanocomposite were analyzed. Dimethyl hydrogenated tallow 2-ethylhexyl ammonium modified Cloisite 25A (C25A) and methyl tallow bis-2-hydroxyethyl ammonium modified Cloisite 30B (C30B) were used as MMT. XRD and TEM analysis indicated that the continuous melt mixing by a twin screw extruder was effective in MMT dispersion. C30B having hydroxyl group on its surface has better dispersion than C25A in the PU/nylon matrix. Maximum stress and strain at break were the maximum at 1 wt% MMT regardless of matrix composition, and decreased at higher MMT content. Best MMT dispersion was also observed at 1 wt% MMT for the entire matrix composition. Aggregation of MMT occurred at MMT content higher than 1 wt%. Nylon addition also induced the aggregation of MMT because of the high polarity of nylon surface. Dispersion of MMT was very important in improving the mechanical properties of PU/nylon nanocomposite.     

Effect of matrix viscosity on clay dispersion in preparation of polymer/organoclay nanocomposites

The viscosity effect of matrix polymer on melt exfoliation behavior of an organoclay in poly(ε-caprolactone) (PCL) was investigated. The viscosity of matrix polymer was controlled by changing the molecular weight of poly(ε-caprolactone), the processing temperature, and the rotor speed of a mini-molder. Applied shear stress facilitates the diffusion of polymer chains into the gallery of silicate layers by breaking silicate agglomerates down into smaller primary particles. When the viscosity of PCL is lower, silicate agglomerates are not perfectly broken into smaller primary particles. At higher viscosity, all of silicate agglomerates are broken down into primary particles, and finally into smaller nano-scale building blocks. It was also found that the degree of exfoliation of silicate layers is dependent upon not only the viscosity of matrix but thermodynamic variables.     

Effect of glycerol cross-linking and PDI on the shape memory effect and mechanical properties of polyurethane

A series of shape memory polyurethane (PU) copolymers synthesized from 1,4-phenyldiisocyanate (PDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD) as a chain extender, and glycerol as a cross-linking agent were tested for the mechanical properties and the shape memory effect at the temperature 20 °C above melting temperature (T _m), and were compared with other PUs synthesized from 4,4′-methylene-bis-phenyldiisocyanate (MDI), PTMG, and BD. Mechanical properties and shape memory effect were improved substantially by adopting both PDI and glycerol. Interestingly, enthalpy of melting and T _m were not affected by the glycerol content. Vibration and shock absorption ability was investigated by measuring both loss tan δ and storage modulus with dynamic mechanical analyzer (DMA).     

Structural,thermal, and mechanical properties of polyurethane foams prepared with starch as the main component of polyols

In this study, rigid polyurethane foams were prepared using starch as the main component of polyols and their structural, thermal, and mechanical properties were investigated. The starch content in polyols was 30∼50 wt.%. The prepared polyurethane foams had a cell structure. When the starch content and -NCO/-OH molar ratio (TS4-05, TS3-07, and TS3-05) was low, polyurethane foams were not formed. To confirm the formation of a urethane linkage between -OH of the starch and -NCO of the 2,4-TDI, FT-IR spectroscopic analysis was performed. The thermal properties of polyurethane foams were analyzed by DSC and TGA. DSC thermograms showed two endothermic peaks: a sharp peak at a lower temperature and a broad peak at a higher temperature. Both peaks were shifted to higher temperature with starch content in polyols and -NCO/-OH molar ratio. Thermal degradation of polyurethane foams began at a lower temperature and ended at a higher temperature than that of starch. The impact resistance, compressive stress and modulus of polyurethane foams increased with -NCO/-OH molar ratio and starch content.     

Effect of nanoclay incorporation method on mechanical and water vapor barrier properties of starch-based films

The objective of this study was to investigate the influence of nanoclay incorporation procedure on the mechanical and water vapor barrier properties of starch/nanoclay composite films. Cassava starch films were prepared with (nanocomposite) and without nanoclay (control) in two steps: firstly the production of extruded pellets and secondly thermo-pressing. The nanocomposite films were prepared via two different methods: in D samples the nanoclay was dispersed in glycerol and subsequently incorporated into the starch; and in ND samples all ingredients were added in a single step before the extrusion. All the composite-films were prepared with cassava starch using 0.25 g of glycerol/g of starch and 0.03 g of nanoclay/g of starch. Control samples showed V_A-type crystallinity induced by the manufacturing process and the nanocomposites presented a semicrystalline and intercalated structure. The nanoclay improved the water vapor barrier properties of the starch film and this effect was more pronounced in D samples, where the water vapor permeability (K^w) was 60% lower than that of the control samples. The K^w reduction was associated with decreases in the effective diffusion coefficient (approximately 61%) and in the coefficient of solubility (approximately 22-32%). On the other hand, the incorporation of nanoclay increased the tensile strength and the rigidity of the films and this effect was more significant when the nanoclay was dispersed in glycerol. Thus, the incorporation of nanoclay into starch-based films is a promising way to manufacture films with better mechanical and water vapor barrier properties.     

Effect of coir fiber content and compatibilizer on the properties of unidirectional coir fiber/polypropylene composites

The main objective of this research was to study the effect of fiber content variation and stearic acid (SA) treatment on the fundamental properties of unidirectional coir fiber (CF) reinforced polypropylene (PP) composites. Several percentages of filler contents were used (10–40 wt %) in order to gain insights into the effect of filler content on the properties of the composites. Coir/PP composites were fabricated by compression molding, and the properties of composites were studied by physico-mechanical and thermal properties. The results from mechanical properties such as tensile strength (TS), tensile modulus (TM) and impact strength (IS) of the CF/PP composites were found to be increased with increasing fiber content, reached an optimum and thereafter decreased with further increase in fiber content. Treatment of the coir with SA as the coupling agent enhanced the mechanical properties, crystallization temperature and crystallinity of virgin PP and water desorption of the resulting composites, resulting from the improved adhesion between the CF and PP matrix. Scanning electron micrographs (SEM) of the tensile fractured samples showed improved adhesion between fiber and matrix upon treatment with SA. Interfacial shear strength (IFSS) of the composites was measured by single fiber fragmentation test (SFFT).     

Effect of surfactant functionalization of multi-walled carbon nanotubes on mechanical,electrical and thermal properties of epoxy nanocomposites

The present paper compares the mechanical, electrical and thermal properties of epoxy nanocomposites (prepared by solution blending method) by adding four different multi-walled carbon nanotubes (MWCNTs), which are pristine, cationic, anionic and non-ionic surfactant functionalized MWCNTs, respectively. This investigation focused on the effects of dispersion of MWCNTs on the physical properties. Systematical characterization on the dispersion of MWCNTs in different solvents were did via UV-Vis spectrophotometer. The Hansen solubility parameters (HSPs) and dispersion of MWCNTs in solvent and epoxy were both changed after surfactants introduced especially for the non-ionic surfactant. Finally, mechanical, fracture toughness, electrical and thermal properties of epoxy composites were found can be improved because of good dispersion of MWCNTs (especially non-ionic surfactant).     

Effect of water and fiber length on the mechanical properties of polypropylene matrix composites

This paper presents the results of a current study on polypropylene matrix composites processed by injection, with two different glass fiber lengths and five different volume fractions. Physical and mechanical properties were obtained, namely flexural strength, stiffness modulus and fracture toughness. The mechanical properties of the composites increased significantly with the increase of the fibers volume fraction in agreement with the Counto model. The effect of water immersion time was also analysed. Immersion in water promotes a marked decrease in mechanical properties in the early seven-ten days, and afterwards tends to stabilize. Water causes a decrease of the relative strength which increases with fiber volume fraction and reaches about 29 % and 32 % for 20 % of 4.5 mm fiber length and for 25 % of 12 mm fiber length respectively, after 28 days immersion in water. Fracture toughness increases with fiber volume fraction and is always higher for 12 mm fiber length composites than for 4.5 mm fiber length composites.     

Preparation and properties of waterborne polyurethanes based on triblock glycol (CL)4.5-PTMG-(CL)4.5 for water vapor permeable coatings: Effect of soft segment content

A series of waterborne polyurethanes (WBPU) were prepared from 4,4-dicyclohexylmethane diisocyanate (H₁₂MDI), 2,2-bis(hydroxylmethyl) propionic acid (DMPA), ethylenediamine (EDA), triethylamine (TEA), and triblock glycol [TBG, (ε-caprolactone)_4.5-poly(tetramethylene ether) glycol (MW=2000)-(ε-caprolactone)_4.5: (CL)_4.5-PTMG-(CL)_4.5, MW=3000] as a soft segment. Two melting peaks of TBG at about 14°C and 38°C were observed indicating the presence of two different crystalline domains composed of CL and PTMG dominant component. The effect of soft segment content (60–75 wt%) on the colloidal properties of dispersion, and thermal and mechanical properties of WBPU films, the water vapor permeability (WVP) and water resistance (WR) of WBPU-coated Nylon fabrics, and the adhesive strength of WBPU-coated layer and Nylon fabrics was investigated. As soft segment contents increased, the water vapor permeability of WBPU-coated Nylon fabrics increased from 3615 to 4502 g/m²day, however, the water resistances decreased from 1300 to 500 mmH₂O.     

Glucose cross-linking of polyurethane copolymer and its impact on the elevation of mechanical properties and shape memory effect

Effect of glucose cross-linking on the shape memory and mechanical properties of polyurethane (PU) block copolymer was investigated. Glucose was selected due to its large number of free hydroxyl groups, easy availability, miscibility with other reactants, and cyclic structure. The glycerol cross-linking did not affect the molecular interaction and phase separation of hard and soft segments in polyurethane structure as judged from IR and DSC analysis. Viscosity of glucose cross-linked PU increased after cross-linking due to the cross-linked structure. Maximum stress drastically improved with the adoption of glucose as a cross-linker together with a slight increase in strain at break. Shape recovery also increased with the adoption of glucose as a cross-linker, and shape recovery was not diminished after four cyclic shape recovery tests. In contrast, shape retention significantly decreased if glucose was included for two different hard segment contents. Finally, glucose cross-linking was compared with other cross-linkers used in shape memory polymer and the advantage of glucose cross-linking was discussed.     

Dyeing and fastness properties of a reactive disperse dye on PET, nylon, silk and N/P fabrics

Dyeing and color fastness properties of a reactive disperse dye containing an acetoxyethylsulphone group on PET, Nylon, silk and N/P fabrics were examined. The reactive disperse dye exhibited almost the same dyeing properties on PET fabric as a conventional disperse dye except the level of dye uptake. The most appropriate pH and dyeing temperature for the dyeing of Nylon fabric were 7 and 100°C respectively. The build-up on Nylon fabric was good and various color fastnesses were good to excellent due to the formation of the covalent bond. Application of the reactive disperse dye on silk fabric at pH 9 and 80°C yielded optimum color strength. The rate of dyeing on Nylon fabric was faster than that on PET fabric when both fabrics were dyed simultaneously in a dye bath, accordingly color strength of the dyed Nylon was higher. The reactive disperse dye can be applied for one-step and one-bath dyeing of N/P mixture fabric with good color fastness.     

Temperature variations during grain filling obtained in growth tunnel experiments and its influence on protein content,polymer build-up and gluten viscoelastic properties in wheat

The aim of this study was to investigate effects of temperature during grain filling on gluten quality characteristics at a lower to moderate temperature range. Experiments with two wheat varieties grown in field covered by polypropylene tunnels during grain filling were performed in two seasons. Mean day temperature differences achieved within the tunnel were approximately 2–2.5 °C from the open to the closed end. There were significant effects of temperature on grain maturity time, thousand grain weight and protein content. The resistance to stretching of the gluten doughs increased with the increasing day temperatures. This was reflected in the proportion of unextractable polymeric proteins (UPP). The results suggest that increases in temperature within this temperature range affect the polymerization of polymeric proteins, giving higher molecular weights, and hence increased Rmax and stronger gluten. The two varieties differed in their response to temperature. In addition, there were seasonal variations in gluten functionality that may be associated with fluctuations in day temperatures between the seasons.     

Effect of press cycle time and resin content on physical and mechanical properties of particleboard panels made from the underutilized low-quality raw materials

In this study, the influence of press cycle time and resin content (RC) on some of the physical and mechanical properties of single-layer particleboard manufactured from the low-quality raw materials were determined. Eucalyptus (Eucalyptus camaldulensis), mesquite (Prosopis juliflora), saltcedar (Tamarix stricta) and date palm (Phoenix dactylifera) wood, which is underutilized invasive species in southern parts of Iran, were used as alternative raw materials for particleboard manufacturing. Variable factors were as resin content (9, 10 and 11%) and press time (PT) (4, 5 and 6 min). Other parameters such as type of resin (UF), hardener content (2%), type of hardener (NH₄Cl), press-closing time (4.5 mm/s), board density (0.75 g/cm³), press pressure (30 kg/m²) and press temperature (160 °C) were held constant. The experimental panels were tested for their mechanical strength including modulus of elasticity (MOE), modulus of rupture (MOR), internal bonding (IB) and physical stability properties (thickness swelling) according to the procedures defined by European Union (EN) Standard. Overall results showed that most panels made from above-mentioned materials exceed the EN Standards for IB, MOE and MOR. The mechanical properties of particleboard were improved as the resin content increased from 9 to 11%. The results indicated that the polymerization of resin and wood is better at 11% resin content and 5 min of press time. However, thickness-swelling (TS) values were higher (poor) than requirements. Panels made of mesquite, saltcedar and date palm with a resin content of 11% and pressed for 5 min is adequate for general uses while eucalyptus with a resin content of 11% and pressed for 6 min is suitable for interior decoration.     

Study of the impact of wheat flour type,flour particle size and protein content in a cake-like dough: Proton mobility and rheological properties assessment

The study of food products is always a challenge due to the number of components involved and the interactions that may occur between them. Water is a particular ingredient which interacts with all hydrophilic compounds, although affinities may differ for limiting water amount. During this study, results obtained using ¹H NMR on cake dough were compared in terms of the effects of flour type (soft or medium hard), the addition of gluten (5%–20%) and the use of soft flour fractions (flour particle fractions smaller or larger than 50 μm). T₂ values and the signal intensities of different proton populations were studied as a function of the wheat protein contents of dough samples. Physicochemical characterization methods were used to better understand how the origin and particle size of flour might impact the hydration properties and mobility of a model system. Increasing the protein content in dough samples was related to an increase of the mobility of fat protons and of the least mobile proton population (relaxation times ranging from 175 to 180 ms and from 5 to 7 ms, respectively).     

Effect of boron phosphate on the mechanical, thermal and fire retardant properties of polypropylene and polyamide-6 fibers

The effect of boron phosphate (BPO₄) nanoparticles on the mechanical, thermal, and flame retardant properties of polypropylene (PP) and polyamide 6 (PA-6) fibers are investigated by tensile testing, thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), and micro combustion calorimeter (MCC). The addition of BPO₄ reduces the mechanical properties of the both PP and PA-6 fibers. According to the TGA results, the addition of BPO₄ does not change the thermal behavior of PP fiber and slightly reduces the thermal stability of PA-6 fiber by about 30 °C. According to MCC results, the addition of BPO₄ does not change the effective total heat evolution and heat release rate (HRR) peak for PP fibers. Although the inclusion of BPO₄ does not change the total heat evolution of PA-6 fiber, it reduces the HRR peaks due to increase in barrier effect of char.     

Effects of additives on the rheological and mechanical properties of non-conventional fresh handmade tagliatelle

The effects of the following additives on the amaranth (A), quinoa (Q) and oat (O) dough rheological properties and the extruded tagliatelle dough mechanical characteristics were evaluated: carboxymethylcellulose of sodium (CMC), whey protein isolate (WPI), casein (CAS), chitosan (CHIT) and pregelatinized starch (PS). The amaranth, quinoa and oat rheological dough properties and amaranth, quinoa and oat tagliatelle mechanical characteristics were compared to those of their respective controls (ACTRL, QCTRL and OCTRL) and of the SEMOLINA sample. The storage modulus (G′) and loss modulus (G″) values of the quinoa and oat doughs with PS were similar to those of the semolina dough. For all tagliatelle samples, WPI reduced the elastic modulus or Young's modulus towards that of the semolina tagliatelle. Moreover, the additives did not have particular influence on the tenacity with the exception of the amaranth tagliatelle added with WPI.     

Effect of inorganic fillers and ammonium polyphosphate on the flammability,thermal stability,and mechanical properties of abaca-fabric/vinyl ester composites

In order to comply with the safety environment requirements, this research is being carried out for reinforcing inorganic additives to improve fire retardancy of composite. In the present study, abaca fabric/vinyl ester (AF/VE) composites were prepared by vacuum assisted resin transfer (VARTM) molding process. For improving flame retardant property of the composites, three different types of halogen free inorganic fillers, i.e. nano-clay (NC), halloysite nanotubes (HNT) and ammonium polyphosphate (APP) were used. The flammability, thermal stability and mechanical properties of composites have been investigated by Horizontal burning test, Thermogravimetric analysis (TGA), tensile, and flexural test respectively. FESEM was used to observe the morphology of the fractured surface of the tensile specimens. Taguchi method was used to optimize the process and minimize the number of experiments for fillers addition. The results showed that the flame retardancy and thermal stability increased with increasing percentage of fillers, but mechanical properties slightly decreased simultaneously.     

Effect of fertilisation, development stage, mechanical impact and heating during processing on subsurface hardening in pre-peeled potatoes (Solarium tuberosum L.)

Summary Studies of the effect of fertilisation stress, harvest time, machine sorting, storage time, peeling and blanching of potatoes (Solarium tuberosum L.) were carried out. Mechanical impact by sorting before storage did not have a significant effect on hardness of pre-peeled potatoes. Potato hardness decreased significantly with the storage time for raw potatoes following an exponential function. Treatment of potatoes in a damage drum for 5 minutes (36 drops from 35 cm) increased the subsurface hardening, production of brick-like cells and deposition of suberin. Potato hardness throughout the whole potatoes increased with blanching time by blanching at 85 and 95 °C. It was concluded that development of potato hardiness occur because of two mechanisms. That is: 1) wound healing by periderm formation with deposition of suberin and: 2) activation of methyl esterase activity by blanching and subsequent crosslinking of demethoxylated pectin by calcium ions, respectively.     

The effects of extrusion on the content and properties of dietary fibre components in various barley cultivars

Wholemeal flour from five Czech spring barley materials was processed in a single-screw extruder at 130 °C, addition of 20% water and a screw speed of 220 rpm. Two barleys (AF Cesar, AF Lucius) were hulless cultivars with a standard starch composition, while three barleys (KM 2624, KM 2460-1, KM 2460-2) were hulled waxy lines. The effect of extrusion on content of different dietary fibre fractions was determined. Also the changes of the molar mass of β-glucan were studied. Regardless of the barley genotype (standard starch or waxy), the extrusion had no significant effect on arabinoxylan content. A significantly higher beta-glucan and soluble dietary fibre content in barley cultivars with standard starch composition was observed after extrusion. The content of insoluble dietary fibre decreased significantly in all extruded flours. The molar mass of water-extractable beta-glucan increased independently of the barley variety after extrusion. But the increase in beta-glucan extractability due to extrusion was not observed.     

Effects of crop properties, weather conditions and mechanical treatments on the wilting rate of dipliod and tetraploid Italian ryegrass for silage

The relationship between rate of water loss of Italian ryegrass (Lolium multiflorum) and crop properties, weather conditions and mechanical treatments were studied on a field scale, as was the importance of the variables and their combined effects on influencing the wilting process. Eleven forage-drying experiments were performed between 1992 and 1994 on diploid and tetraploid cultivars cut at different growth stages, ranging from early elongation to flowering, under environmentally variable conditions. The rate of drying was measured until a moisture content of 1 g water g^?1 dry matter (DM) (500 g kg^?1) was reached, or for a maximum of 2 days by calculating the rate of water loss from two consecutive hourly weights of swath portions placed on trays. Multiple regression analysis was used to correlate the drying rate (k) with crop properties and with meteorological and mechanical treatment variables. The interaction between potential evapotranspiration (ET₀) and the moisture content of grass at cutting (M_grass appeared to be the most important variable, from the twenty-one tested, in influencing K. This variable shows that the same quantity of energy available for evaportaion acts in different ways when the water content of the crop at cutting differs. The rate of water loss is also influenced by the M^grass itself, surgacae density of the swath, tedding and the weather conditions on the first day of drying. The value of M^grass at cutting is greatly greatly dependent on crop maturity and ploidy. The tetraploid cultivars, with a higher inital moisture content, lost water more slowly than diploid cultivars did. Because the date of cutting cannot be delayed, owing to the decline in nutrive value, it is helpful to select for cultivars with low moisture contents at cutting, as well as applying mechanical treatment (spreading and tedding), in order to keep the wilting period as short as possible. A validated drying model can be useful for operational purposes to understand the drying process and to assess technological choices for forage drying.