scholarly journals Low Density Wood Particleboards Bonded with Starch Foam—Study of Production Process Conditions

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 1975 ◽  
Author(s):  
Sandra Monteiro ◽  
Jorge Martins ◽  
Fernão D. Magalhães ◽  
Luísa Carvalho
Keyword(s):  
Mechanical Performance ◽  
Hold Time ◽  
Operating Conditions ◽  
Process Conditions ◽  
Low Density ◽  
Thickness Swelling ◽  
Hot Plate ◽  
Pressing Time ◽  
Two Stages ◽  
Platen Temperature

It has been shown that wood particleboards bonded with sour cassava starch can display low density combined with good physico-mechanical performance, thanks to starch being able to produce a strong foam that fills the interparticular space. Here we optimize the pressing conditions for the production of these panels. The procedure involved hot-plate pressing in two stages: (1) lowering the top platen to a specified thickness for a duration designated as pressing time, followed by (2) raising the top platen to allow panel expansion for a duration designated as hold time. The parameters studied were the pressing time (10 to 150 s), the hold time (290 to 890 s), and the top platen temperature (80 to 190 °C). The hold time and pressing time showed to be crucial parameters. The best operating conditions corresponded to 600 s of press cycle time, comprising 60 s of pressing time and 540 s of hold time. The top platen temperature used was 190 °C. The particleboards produced had a density of 405 kg·m−3, an internal bond strength of 0.44 N·mm−2, and a thickness swelling of 13.2%. This can be considered as very good performance, taking into account the panels’ low density.

Managing Transient Operating Conditions of Hyper Compressors

2014 ◽  
Author(s):  
Marcello Agostini ◽  
Cosimo Carcasci ◽  
Alessio Cristofani
Keyword(s):  
High Pressures ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Process Conditions ◽  
Operator Experience ◽  
Start Up ◽  
Reactor Operating ◽  
Two Stages ◽  
Gas Expansion ◽  
Plant Automation

Special reciprocating compressors are required to reach the very high pressures necessary to feed the reactors used in LDPE plants. The working conditions of the compressors are determined by the reactor operating pressures and are considered for evaluation of the loads, torsional, pulsation and vibration conditions. Performance and safety are key considerations and operator experience is essential for optimal and safe plant operation. Plant automation contributes to safety and optimizes process conditions. The compressor start-up and shutdown procedures, commonly detailed in maintenance manuals, are analyzed studying the operating parameters to draw up guidelines for avoiding damage to plunger seals and keeping loads within design limits, without compromising the design performance. The multiple gas compositions of co-polymers and the fact that gas expansion can cause a reduction in temperature, need adequate consideration to avoid damage caused by polymer inside the compressor cylinders. The paper will also give recommendations on the necessary procedures to reach the operating pressures with correct distribution of the total pressure ratio between the two stages. These will also include the requirement of minimum pressure on the plunger head to maintain contact with the crosshead and avoid failure of such a brittle component.

scholarly journals Properties of low-density cement-bonded composite panels manufactured from polystyrene and jute stick particles

2019 ◽  
Vol 65 (1) ◽  
Author(s):  
Md Nasim Rana ◽  
Md Nazrul Islam ◽  
Suresh Kumar Nath ◽  
Atanu Kumar Das ◽  
Md Ashaduzzaman ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Modulus Of Elasticity ◽  
Expanded Polystyrene ◽  
Modulus Of Rupture ◽  
Low Density ◽  
Processing Conditions ◽  
Thickness Swelling ◽  
Pressing Time ◽  
Jute Fibers ◽  
Bonded Composite

Abstract This study was conducted to evaluate the properties of cement-bonded composite (CBC) manufactured using jute stick particles and expanded polystyrene (EPS) beads to reduce the density of CBC for mitigating the main limitation of CBC in its applications. The CBCs were manufactured by using cement, jute stick particle, EPS and jute fiber by cold pressing having the pressure of 5 MPa and pressing time of 24 h. CBCs were also manufactured by replacing the jute stick particles with EPS beads, the processing conditions remaining the same. There were at least 5 replications for each type of board. Waste jute fibers were added for improving the degenerated mechanical properties of CBC caused by the addition of EPS beads. Important physical properties, i.e., density, water absorption (WA) and thickness swelling (TS) and mechanical properties, i.e., modulus of elasticity (MOE) and modulus of rupture (MOR) of the manufactured CBCs were tested following the Malaysian Standards. Higher percentage of EPS beads significantly reduced the density of CBCs and the lowest density (0.91 ± 0.02 g/cm3) was found when the EPS beads replaced 30% jute stick particles. As expected, mechanical properties decreased with the gradual replacement of jute stick particles by EPS beads. However, the degraded mechanical properties significantly increased when waste jute fibers were added in the CBCs. Addition of EPS beads in CBCs reduced the density, which might increase the potentiality for the utilization of cement-bonded composites for various applications.

scholarly journals Physico-mechanical properties of plywood bonded with ecological adhesives from Acacia mollissima tannins and lignosulfonates

2017 ◽  
Vol 78 (3) ◽  
pp. 34813 ◽  
Author(s):  
Naima Rhazi ◽  
Mina Oumam ◽  
Abdessadek Sesbou ◽  
Hassan Hannache ◽  
Fatima Charrier-El Bouhtoury
Keyword(s):  
Mechanical Properties ◽  
Mechanical Performance ◽  
Phenol Formaldehyde ◽  
Waste Product ◽  
Formaldehyde Emission ◽  
Extraction Methods ◽  
Press Temperature ◽  
Pulp Industry ◽  
Pressing Time ◽  
Chemical Conditions

The objective of this research was to develop ecological adhesives for bonding plywood panels using lignosulfonates, a common waste product of the wood pulp industry, and natural tannin extracted from Moroccan bark of Acacia mollissima using different process. Natural tannin and lignin were used in wood adhesives formulation to substitute resins based on phenol and formaldehyde. To achieve this, the lignosulfonates were glyoxalated to enhance their reactivity and the used tannins obtained by three different extraction methods were compared with commercial mimosa tannin. The proportion of Acacia mollissima tannins and lignosulfonates, the pressing time, the pressing temperature, and the pressure used were studied to improve mechanical properties, and bonding quality of plywood panel. The properties of plywood panels produced with these adhesives were tested in accordance with normative tests. Thus, the tensile strength, and the shear strength were measured. The results showed that the performance of the plywood panels made using biobased tannin adhesives was influenced by physical conditions such as pressure, press temperature as well as by chemical conditions, such as the tannin-lignin ratio. It exhibited excellent mechanical properties comparable to commercially available phenol-formaldehyde plywood adhesives. This study showed that biobased adhesives formulations presented good and higher mechanical performance and no formaldehyde emission.

Low-Density Phenolic Syntactic Foams: Processing and Properties

2007 ◽  
Vol 26 (4) ◽  
pp. 229-244 ◽  
Author(s):  
Bibin John ◽  
C.P. Reghunadhan Nair ◽  
K.N. Ninan
Keyword(s):  
Phenolic Resin ◽  
Mechanical Performance ◽  
Volume Fraction ◽  
Mechanical Analysis ◽  
Low Density ◽  
Syntactic Foams ◽  
Novolac Resin ◽  
High Concentration ◽  
Volume Percentage ◽  
Propargyl Ether

Low-density phenolic syntactic foams with different volume percentages of microballoons were processed and their mechanical performance has been evaluated in terms of tensile, flexural, compressive and the corresponding specific properties. Tensile and flexural strength increased with volume fraction of microballoon and optimized at 72–74 percentage by volume of microballoon. Both the properties decreased with further addition of microballoon. The corresponding specific properties also manifested a similar order. Compressive and specific compressive strength decreased with increase in microballoon volume percentage. The flexural and compressive modulus values followed the same trend as the strength values. The properties of phenolic syntactic foams were compared with syntactic foams based on an addition cure phenolic resin, Propargyl Ether Novolac resin (PN). The mechanical properties of the latter were inferior to those of phenolic syntactic foams. The morphology of the failed samples as examined by SEM showed that failure occurred by a combination of matrix and microballoon failure at low microballoon loading whereas it occurred by microballoon cracking and resin to microballoon debonding at high concentration of filler. The dynamic mechanical analysis of phenolic and PN resin syntactic foams showed a higher use temperature for PN system in comparison to phenolic.

Research on Combined Processing Technology of Superficial Layers Hardened Steel

2016 ◽  
Vol 841 ◽  
pp. 21-28
Author(s):  
Petrică Corabieru ◽  
Stefan Velicu ◽  
Anişoara Corabieru ◽  
Dan Dragos Vasilescu ◽  
Ionel Păunescu
Keyword(s):  
Solid State ◽  
Liquid Phase ◽  
Cooling Rate ◽  
Hold Time ◽  
Hardened Steel ◽  
Operating Conditions ◽  
Technological Parameters ◽  
Surface Layers ◽  
Durability Analysis ◽  
Machined Parts

The novelty technology lies in the fact that the hardening of the surface layers is carried out both in liquid phase and in the solid state. Technology comprises three main stages with 12 technological phases.Experimentation highlights the viability of the technological procedure. The results of tests and verifications are the basis of the analysis of combined machined parts behavior in conditions similar to the operating conditions and of the analysis of the dependence between operation behavior and durability. Analysis of the results revealed the fact that failure to technological parameters: casting temperature; hold time at high temperatures; cooling rate after microalloying in liquid phase, gives rise to possible faults of the combined treated parts.

Linking Microbial Community Dynamics in BIOX® Leaching Tanks to Process Conditions: Integrating Lab and Commercial Experience

2017 ◽  
Vol 262 ◽  
pp. 38-42 ◽  
Author(s):  
Mariette Smart ◽  
Robert J. Huddy ◽  
Catherine J. Edward ◽  
Charl Fourie ◽  
Trust Shumba ◽  
...  
Keyword(s):  
South Africa ◽  
Community Structure ◽  
Microbial Community ◽  
Research University ◽  
Community Dynamics ◽  
Operating Conditions ◽  
Process Conditions ◽  
Significant Shift ◽  
Engineering Research ◽  
Microbial Community Dynamics

In the commercial BIOX® process, an acidophilic mixed bacterial and archaeal community dominated by iron and sulphur oxidising microorganisms is used to facilitate the recovery of precious metals from refractory gold-bearing sulphidic mineral concentrates. Characterisation of the microbial communities associated with commercial BIOX® reactors from four continents revealed a significant shift in the microbial community structure compared to that of the seed culture, maintained at SGS (South Africa). This has motivated more detailed study of the microbial community dynamics in the process. Microbial speciation of a subset of the BIOX® reactors at Fairview mines (Barberton, South Africa) and two laboratory maintained reactors housed at Centre for Bioprocess Engineering Research, University of Cape Town, has been performed tri-annually for three years by quantitative real-time polymerase chain reaction. The laboratory BIOX® culture maintained on Fairview concentrate was dominated by the desired iron oxidiser, Leptospirillum ferriphilum, and sulphur oxidiser, Acidithiobacillus caldus, when operated under standard BIOX® conditions. Shifts in the microbial community as a result of altered operating conditions were transient and did not result in a loss of the microbial diversity of the BIOX® culture. The community structure of the Fairview mines BIOX® reactor tanks showed archaeal dominance of these communities by organisms such as the iron oxidiser Ferroplasma acidiphilum and a Thermoplasma sp. for the period monitored. Shifts in the microbial community were observed across the monitoring period and mapped to changes in performance of the commercial process plant. Understanding the effect of changes in the plant operating conditions on the BIOX® community structure may assist in providing conditions that support the desired microbial consortium for optimal biooxidation to maximize gold recovery.

scholarly journals Prefabricated Urban Underground Utility Tunnels: A Case Study on Mechanical Behaviour with Strain Monitoring and Numerical Simulation

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Yonggang Xiao ◽  
Jubing Zhang ◽  
Jie Cao ◽  
Changhong Li
Keyword(s):  
Numerical Simulation ◽  
Working Conditions ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Low Cost ◽  
Side Wall ◽  
Operating Conditions ◽  
Land Occupation ◽  
Depth Analysis ◽  
Simulation Results

The prefabricated urban utility tunnels (UUTs) have many advantages such as short construction period, low cost, high quality, and small land occupation. However, there is still a lack of in-depth analysis of the mechanical performance of the prefabricated urban utility tunnel (UUT) structure with bolted connections under different working conditions. In this paper, the force performance of a prefabricated UUT in Tongzhou District, Beijing, was studied under different working conditions using two methods: field monitoring and numerical simulation. The multichannel strain monitor was used for monitoring, and the internal wall concrete and bolt strain change data under the two conditions of installation and backfill were obtained. Combined with the construction process of the UUTs, a three-dimensional numerical model was established by COMSOL, where the build-in bolt assembly was used to simulate the longitudinal connection of the tunnel. The simulation results were compared with the measured data to verify the rationality of the computational model. The simulation results showed that the concrete and bolts on the inner wall of the tunnel work well under the two conditions of installation and backfilling; The deformation of the top plate of the prefabricated tunnel was approximately parabolic, with the largest vertical displacement (0.37 mm) in the middle and the most sensitive to the vertical load in the central part of the roof. The central portion of the side wall had the largest displacement (0.17 mm) in the inner concave. The tensile stress of bolt 3 increased the most (30.75 MPa) but was still much smaller than the yield strength of the bolt. The concrete and bolts of the UUT were found to work well through force analysis under operating conditions. In conclusion, analysis of structural forces and deformation failure modes will help design engineers understand the basic mechanisms and select the appropriate UUT structure.

Effect of vulcanization time on crosslink density and aging performance of natural rubber composites

2020 ◽  
Vol 62 (8) ◽  
pp. 858-862
Author(s):  
Ece Unur Yilmaz ◽  
Ahu Kor Dayioglu ◽  
Seda Balaban
Keyword(s):  
Natural Rubber ◽  
Crosslink Density ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Operating Conditions ◽  
Rubber Composites ◽  
Rubber Mixture ◽  
Natural Rubber Composites ◽  
Different Temperatures ◽  
Auto Parts

Abstract Natural rubber composites are widely used in the automotive industry because of their improved viscoelastic characteristics that are mostly governed by crosslink density. However, rubber parts suffer deterioration of performance over long service lives. Therefore, optimization of crosslink density and prediction of changes in physico-mechanical properties over time at elevated temperatures is extremely important for the production of safe auto parts. In this work, the effect of vulcanization time on crosslink density and thus the performance and lifetime of natural rubberbased auto parts was investigated. The natural rubber mixture prepared in this context was vulcanized for 3, 5, 10 and 15 minutes at a constant temperature of 160 °C. The crosslink density of each vulcanizite was determined by equilibrium swelling tests and the Flory-Rehner equation. The maximum crosslink density (10.75 × 10-5 mol × cm-3) and the minimum permanent compression set values (10 % at 70 °C and 25 % at 100 °C) were recorded for the sample vulcanized for 10 minutes (v10). Aging behavior of the samples were investigated by stress relaxation tests performed at 85 °C, 100 °C and 120 °C. The service lives of the vulcanizites at different temperatures were predicted by linear Arrhenius fits of degradation times. The sample vulcanized for 10 minutes (v10) was shown to exhibit a service life of 2282 hours at 70 °C in air and the optimum physico-mechanical performance under real operating conditions. The performance and lifetime prediction procedure used in this work could be employed in an early design of rubber components for specific applications.

scholarly journals PRODUCTION OF PARTICLE BOARDS USING POLYSTYRENE AND BAMBOO WASTES

2017 ◽  
Vol 36 (3) ◽  
pp. 788-793
Author(s):  
SA Abdulkareem ◽  
AG Adeniyi
Keyword(s):  
Physical Properties ◽  
National Standards ◽  
Low Density ◽  
Thickness Swelling ◽  
The Matrix ◽  
Curing Methods

This investigation was able to produce incredibly strong particleboards using bamboo and resinous material obtained from Polystyrene wastes. The particleboards were prepared by mixing the bamboo fibres and Polystyrene based resin (PBR) followed by flat press process at different ratio (v/v). Physical properties were measured, with reference to normal and oven curing methods, according to the ASTM D-1037 standard. Thickness Swelling (TS) of the samples were measured after 2 and 24 hours of immersion in water at 25oC temperature. It was found that the physical properties of particleboards with 20%, 30% and 40% PBR content were all in agreement with low density particleboard classification of American National Standards Institute (ANSI). TS increased as the PBR content decreased in the matrix. Obtained properties convincingly indicate superior bonding ability of the synthesised resinous polystyrene over known industrial adhesives typically used for particleboard production. http://dx.doi.org/10.4314/njt.v36i3.18 

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