Similar Tensile Strength Values Research Articles

Thermo-Mechanical Properties of Polypropylene Composites Filled with Recycled Office Waste Paper

ABSTRACT The high production of paper, followed by a more significant concern with environmental and economic issues, has led to greater relevance to paper recycling and its raw uses as composite filler. Composites of polypropylene with 10, 20, and 30 wt.% of recycled office waste paper were produced by injection molding and characterized by mechanical and thermal properties. All composites presented a slight reduction of 15°C in thermal stability compared to the polymeric matrix. Moreover, as the filler amount increased, the degree of crystallinity was reduced proportionally. The mechanical test showed similar tensile strength values among neat polymer andcomposites but also showed an increase in the composite’s tensile modulus, related to the stiffness of the natural filler. The composite with a higher percentage of waste paper (30 wt.%) maintained equivalent properties as neatpolypropylene and other composites (10 and 20 wt.%). Thus, 30 wt.% composites proved to be an excellent material with less synthetic polymer percentage, keeping thermal and mechanical properties comparable to the neat PP.Furthermore, this composite does not need chemical treatment or additives harmful to the environment. It is suitable for future applications in various plastic products such as packaging and domestic utensils.

Physicochemical, Mechanical, and Structural Properties of Bio-Active Films Based on Biological-Chemical Chitosan, a Novel Ramon (Brosimum alicastrum) Starch, and Quercetin

The properties of biological-chemical chitosan (BCh) films from marine-industrial waste and a non-conventional Ramon starch (RS) (Brosimum alicastrum) were investigated. Blended films of BCh/RS were prepared to a volume ratio of 4:1 and 1:4, named (BChRS-80+q, biological-chemical chitosan 80% v/v and Ramon starch, BChRS-20+q, biological-chemical chitosan 20% v/v and Ramon starch, both with quercetin), Films from commercial chitosan (CCh) and corn starch (CS), alone or blended (CChCS-80+q, commercial chitosan 80% v/v and corn starch, CChCS-20+q commercial chitosan 20% v/v and corn starch, both with quercetin) were also prepared for comparison purposes. Films were investigated for their physicochemical characteristics such as thickness, moisture, swelling, water-vapor permeability, and water solubility. In addition, their mechanical and structural properties were studied using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA) and Scanning Electron Microscopy (SEM) techniques. Antioxidant activity was evaluated as radical scavenging, and antimicrobial effect was also determined. The BCh and RS films presented similar tensile strength values compared with commercial biopolymers. Only films with chitosan presented antioxidant and antimicrobial activity. The FTIR spectra confirmed the interactions between functional groups of the biopolymers. Although, BChRS-80+q and BChRS-20+q films exhibited poor mechanical performance compared to their commercial counterparts, they showed good thermal stability, and improved antioxidant and antimicrobial activity in the presence of quercetin. BChRS-80+q and BChRS-20+q films have promising applications due to their biological activity and mechanical properties, based on a novel material that has been underutilized (Ramon starch) that does not compete with materials for human feeding and may be used as a coating for food products.

Effect of Chemical Treatment and Length of Raffia Fiber (Raphia vinifera) on Mechanical Stiffening of Polyester Composites.

In recent decades, the unique characteristics of natural fibers have promoted their use as reinforcement in polymeric composites. This is verified in several industrial sectors, from packaging to automotive and civil construction. Among the natural fibers, the raffia fiber extracted from the palm tree Raphia vinifera and introduced in the Amazon region a long time ago; started to be considered for the production of polymeric composites only in recent years. For the first time, the effect of raffia fiber length and its alkali treatment on the mechanical properties of a polymer composite was disclosed. Tensile tests were performed in composites with raffia fibers randomly dispersed into terephthalate-based unsaturated polyester resin. The results showed an increase in the Young’s moduli, confirmed by ANOVA, for the composite with both untreated and alkali-treated fibers in comparison to the plain polyester, which characterizes a stiffening effect. The composites with alkali treated fibers exhibited similar tensile strength values for all lengths; however, their strengths are lower than those for the untreated condition due to a weak raffia fiber/polyester matrix adhesion. Therefore, this work fills the current knowledge gap on raffia fiber incorporation in polyester matrix and valorizes this abundant Brazilian resource, providing additional information towards the use of raffia fiber in polymer composites.

Materials characterisation and mechanical properties of Cf-UHTC powder composites

Ultra-high temperature ceramic composites based on carbon fibre, Cf, preforms impregnated with hafnium diboride, HfB2, powder and then densified with carbon by chemical vapour infiltration, CVI, have been mechanically tested to measure the room temperature flexural, interlaminar shear, compressive and tensile strengths. The latter was also measured at 1000 °C. All the composites suffered a degree of delamination during the different mechanical tests but the strength values obtained were at least equal to, or better than, those previously reported in the literature for ultra-high temperature ceramic (UHTC)-based composites. Importantly, in spite of the oxidation of the tensile samples tested at 1000 °C, similar tensile strength values were obtained at both temperatures, suggesting that the materials can resist elevated temperatures. The samples tested at higher temperature did show greater evidence of fibre pull out, possibly due to a weaker fibre-matrix interface as a result of oxidative degradation. The results also suggested that the 0° orientation plies in the Cf preform structure offered greater resistance to mechanical stresses; this suggests that composites can now be designed to offer even greater strength values.

Effects of soldering methods on tensile strength of a gold-palladium metal ceramic alloy

The tensile strength obtained by conventional postceramic application soldering and laser postceramic welding may require more energy than microwave postceramic soldering, which could provide similar tensile strength values. The purpose of the study was to compare the tensile strength obtained by microwave postceramic soldering, conventional postceramic soldering, and laser postceramic welding. A gold-palladium metal ceramic alloy and gold-based solder were used in this study. Twenty-seven wax specimens were cast in gold-palladium noble metal and divided into 4 groups: laser welding with a specific postfiller noble metal, microwave soldering with a postceramic solder, conventional soldering with the same postceramic solder used in the microwave soldering group, and a nonsectioned control group. All the specimens were heat treated to simulate a normal porcelain sintering sequence. An Instron Universal Testing Machine was used to measure the tensile strength for the 4 groups. The means were analyzed statistically with 1-way ANOVA. The surface and fracture sites of the specimens were subjectively evaluated for fracture type and porosities by using a scanning electron microscope. The mean (standard deviation) ultimate tensile strength values were as follows: nonsectioned control 818 ±30 MPa, microwave 516 ±34 MPa, conventional 454 ±37 MPa, and laser weld 191 ±39 MPa. A 1-way ANOVA showed a significant difference in ultimate tensile strength among the groups (F3,23=334.5; P<.001). Follow-up multiple comparisons showed a significant difference among all the groups. Microwave soldering resulted in a higher tensile strength for gold and palladium noble metals than either conventional soldering or laser welding. Conventional soldering resulted in a higher tensile strength than laser welding. Under the experimental conditions described, either microwave or conventional postceramic soldering would appear to satisfy clinical requirements related to tensile strength.

Comparing bond strength and water resistance of alkali-modified soy protein isolate and wheat gluten adhesives

The tensile strength of beech substrates bonded with dispersions of alkali-denatured soy protein isolate (SPI) and wheat gluten (WG) was measured for comparison of bond strength and resistance to cold water. The proteins were denatured with 0.1 M NaOH (pH 13). Dispersions with different protein concentration and viscosity were investigated. The adhesive properties were studied at different press temperatures (90, 110, and 130 °C) and press times (5, 15, and 25 min). Two types of application methods were used in order to overcome the problem with different viscosity of the dispersions. In addition, SPI was denatured at two different pH levels (approximately 10 and 13) and with two different concentrations of salt (158 μM and 0.1 M), in order to compensate for the different isoelectric points of the proteins. The adhesive properties of WG powder with different particle sizes were also compared. The tensile strengths of the wood substrates were measured according to somewhat simplified versions of the European Standards EN 204 and EN 205. The bond lines were studied with light microscopy. The results indicate that the adhesive properties of SPI are superior, particularly with regard to water resistance. However, the water resistance of WG was to some extent improved when starved adhesive joints could be avoided. Similar tensile strength values were obtained for the dispersions of alkali-denatured SPI regardless of pH or salt concentration. No apparent difference in adhesive strength was observed for the WG dispersions from powder with different particle sizes.

Sorption isotherm and plasticization effect of moisture and plasticizers in pea starch film.

Pea starch films were produced with various plasticizers (glucose, fructose, mannose, sorbitol, and glycerol). Effects of plasticizer content (4.34 to 10.87 mmol/g of dry starch) and storage relative humidity (RH) (11.3% to 75.4%) on moisture content (MC), tensile strength (TS), elongation (E), modulus of elasticity (EM), and water vapor permeability (WVP) were evaluated using response surface methodology. MC was influenced strongly by RH. Glycerol-plasticized films had the highest MC, indicating that water molecules played a more important role in plasticizing starch films. Monosaccharide-plasticized films and polyol-plasticized films had similar TS values. However, monosaccharide-plasticized films had higher E values and lower EM values than polyol-plasticized films, meaning monosaccharides had better efficiency in plasticizing starch films. Recrystallization happened in glucose- and sorbitol-plasticized films when they were stored in high RH. Sorption isotherm studies showed the similar adsorption and desorption profiles for all 3 monosaccharide-plasticized films and a hysteresis. The Flory-Huggius model fitted experimental data best for starch films, while the BET model fitted the data marginally.

Starch-chitosan hydrogels prepared by reductive alkylation cross-linking.

Starch-chitosan hydrogels were produced by oxidation of soluble starch to produce polyaldehyde and subsequently cross-linked with chitosan via reductive alkylation. The swelling ratio of starch-chitosan membranes was increased gradually with increasing starch ratio, but it was always lower than the native chitosan. In dry state, starch-chitosan membranes with low starch ratio (0.16, 0.38) showed similar tensile strength values to those of native chitosan while these values decreased with increasing starch ratios (0.73-1.36). Membranes in physiological buffer solution (PBS) gave a tensile modulus between 2.8 and 1.0 MPa, decreasing with increasing starch ratio (0.16-1.36 (Wstarch/Wchitosan)). When the membranes were incubated in PBS only, a moderate weight loss was observed for the first two weeks. Original weights of low starch weight ratio membranes (0-0.38) were at near 85%, while high ratio samples (0.73-1.55) were kept around 70% after three months. However, for the membranes incubated in alpha-amylase solution, very fast weight loss was observed. For low starch ratio membranes (0.16, 0.38, 0.73), the residual original weights were measured to be 11%, 6%, 20%, while for high ratio membranes (1.04 and 1.36) these were 45% and 30%, respectively, after two months of enzyme incubation. Scanning electron microscopy analysis of alpha-amylase degraded membranes exhibited rough surface morphology.