Shear strength of adhesively bonded polyolefins with minimal surface preparation

Interest in polyethylene and polypropylene bonding has increased in the last years. However, adhesive joints with adherends which are of low surface energy and which are chemically inert present several difficulties. Generally, their high degree of chemical resistance to solvents and dissimilar solubility parameters limit the usefulness of solvent bonding as a viable assembly technique. One successful approach to adhesive bonding of these materials involves proper selection of surface pre-treatment prior to bonding. With the correct pre-treatment it is possible to glue these materials with one or more of several adhesives required by the applications involved. A second approach is the use of adhesives without surface pre-treatment, such as hot melts, high tack pressure-sensitive adhesives, solvent-based specialty adhesives and, more recently, structural acrylic adhesives as such 3M DP-8005^® and Loctite 3030^®.In this paper, the shear strengths of two acrylic adhesives were evaluated using the lap shear test method ASTM D3163 and the block shear test method ASTM D4501. Two different industrial polyolefins (polyethylene and polypropylene) were used for adherends. However, the focus of this study was to measure the shear strength of polyethylene joints with acrylic adhesives. The effect of abrasion was also studied. Some test specimens were manually abraded using 180 and 320 grade abrasive paper. An additional goal of this work was to examine the effect of temperature and moisture on mechanical strength of adhesive joints.     

Strengthening of reinforced concrete beams in flexure by partial jacketing

This work investigates the structural behaviour of reinforced concrete beams strengthened in bending by the addition of concrete and steel on their tension sides using expansion bolts as shear connectors, technique here denominated partial jacketing. The experimental program comprised tests on eight full-scale reinforced concrete beams, simply supported, with rectangular cross section (150 mm × 400 mm) and 4,500 mm length. Five of these beams were strengthened in bending by partial jacketing, while the other three did not receive any strengthening and served as reference beams. The flexural reinforcement ratio in the beams varied between 0.49% and 2.33% and the beams target concrete strength was 35 MPa. On the basis of the obtained test results, the studied strengthening technique proven to be efficient in terms of increasing the resistance and stiffness of the beams. The used expansion bolts as shear connectors proven to be practical and added ease to the application of this technique.     

Boundary elements with equilibrium satisfaction: a consistent formulation for plate bending analysis considering Reissner’s theory

The present paper presents a self-equilibrated boundary element formulation for elastostatic analysis of Reissner’s plate bending problems. In this formulation, rigid body movements are introduced to the generalized displacement fundamental solution, resulting in modified boundary element matrices with inherent equilibrium satisfaction. The procedure is quite general and easy to implement into existing boundary element codes. In the end of the paper, numerical examples are presented, illustrating the benefits of the proposed formulation.     

Measurement of density distribution of a cracking catalyst in experimental riser with a sampling procedure for gamma ray tomography

By scanning a riser the number of the gamma ray trajectories and the beam width involve temporal, spatial and density resolutions as they are closely correlated parameters. Therefore, evaluation of parameters and their interaction quantification, certainly, are required in the imaging process. Measuring the density distribution of the catalyst from the FCC - fluid cracking catalytic process in an experimental riser in single beam tomographic system, density resolution is evaluated and correlated with spatial resolution. The beam width Δs inside riser is measured and a criterion for determining spatial resolution is proposed. Experiments are carried out to demonstrate resolution effects of three Δs values: 3.30 × 10⁻³, 6.20 × 10⁻³ and 12.00 × 10⁻³ m. The gamma beam profile is modeled and a sampling rate according to Nyquist criterion is analyzed. The 4.3%, 8.1% and 15.6% ratios of Δs/R to internal riser radius are correlated to counting time in the sampling procedure. Results are discussed by comparison with values from literature.     

Performance of sunflower oil with high levels of oleic and palmitic acids during industrial frying of almonds,peanuts, and sunflower seeds

High-oleic, high-palmitic sunflower oil (HOHPSO) is a seed oil from a new mutant sunflower line characterized by increased levels of both oleic acid (>50%) and palmitic acid (>25%) and a high oxidative stability. In this study, its performance at frying temperature was compared with that of palm olein in thermoxidative assays (4 h, 180°C). Also, industrial discontinuous frying of almonds, peanuts, and sunflower seeds (200 kg of each product) was carried out to define both the performance of HOHPSO and the main changes undergone by the foods. The evaluation of polar compounds and their distribution in the main groups, i.e., polymers, oxidized monomers, and DAG, as well as changes in tocopherols and oxidative stability, demonstrated the excellent behavior of HOHPSO during thermoxidation and frying. The increase in polar compounds and the loss of tocopherols and stability were much lower for HOHPSO than for palm olein under identical heating conditions. Only 1.3% polar compounds were formed during industrial discontiuous frying for 4 h and the oil stability increased, probably due to the formation of antioxidant compounds. As for the foods, the FA composition of the surface oil was clearly different from that corresponding to the internal oil, the former denoting the presence of HOHPSO in high concentration, particularly in fried sunflower seeds. Changes in oil stability of the foods attributable to the frying process clearly demonstrate the interest in using a highly stable oil such as HOHPSO to protect the surface against oxidation during food storage.     

An environmentally acceptable primer for galvanized steel: Formulation and evaluation by SVET

The object of this paper was to formulate a two-pack wash primer employing aluminium phosphosilicate as active anticorrosive pigment instead of basic zinc chromate. The anticorrosive action of the primer was evaluated by the polarization technique and the scanning vibrating electrode technique (SVET). The exposed surface was then examined by scanning electron microscopy (SEM) and the surface composition determined by energy dispersive X-ray (EDX) analysis. The primer was finally integrated in a complete paint scheme whose anticorrosive performance was evaluated by the salt spray chamber and electrochemical impedance spectroscopy. The adhesion of the primer plus a painting system was also evaluated by standard ASTM D 3359-90 test method. The wash primer pigmented with zinc chromate was used as reference. Results indicated that basic zinc chromate could be replaced by the more eco-friendly wash-primer containing aluminium phosphosilicate.     

Continuous enzymatic production of biodiesel from virgin and waste sunflower oil in supercritical carbon dioxide

A continuous process for biodiesel production in supercritical carbon dioxide was implemented. In the transesterification of virgin sunflower oil with methanol, Lipozyme TL IM led to fatty acid methyl esters yields (FAME) that exceeded 98% at 20 MPa and 40 °C, for a residence time of 20 s and an oil to methanol molar ratio of 1:24. Even for moderate reaction conversions, a fractionation stage based on two separators afforded FAME with >96% purity. Lipozyme TL IM was less efficient with waste cooking sunflower oil. In this case, a combination of Lipozyme TL IM and Novozym 435 afforded FAME yields nearing 99%.     

Effect of mechanical stress on biofilms challenged by different chemicals

In this study a methodology was applied in order to ascertain the mechanical stability of biofilms, by using a stainless-steel (SS) rotating device immersed in a biological reactor where biofilms formed by Pseudomonas fluorescens were allowed to grow for 7 days at a Reynolds number of agitation of 2400. The biofilms developed with this system were characterised in terms of amount of total, extracellular and intracellular proteins and polysaccharides, amount of mass, metabolic activity and mechanical stability, showing that the biofilms were active, had a high content of extracellular constituents and an inherent mechanical stability. In order to assess the role of chemical agents on the mechanical stability, the biofilms were exposed to chemical agents followed by mechanical treatments by submission to increase Reynolds number of agitation. Seven different chemical agents were tested (two non-oxidising biocides, three surfactants and two oxidising biocides) and their effects on the biofilm mechanical stability were evaluated. The increase in the Reynolds number increased the biofilm removal, but total biofilm removal was not found for all the conditions tested. For the experiment without chemical addition (only mechanical treatment), the biofilm remaining on the surface was about 76%. The chemical treatment followed by the subsequent mechanical treatment did not remove all the biofilms from the surface. The biofilm remaining on the SS cylinder ranged from 3% to 62%, depending on the chemical treatment, showing that the chemical treatment is far from being a cause that induces massive biofilm detachment and even the synergistic chemical and mechanical treatments did not promote biofilm removal. Some chemical agents promoted an increase in the biofilm mechanical stability such as glutaraldehyde (GTA), benzalkonium chloride (BC), except for the lower concentration tested, and sodium dodecyl sulphate (SDS), except for the higher concentration tested. Treatments that promoted biofilm removal, to an extent similar to the control experiment (without chemical treatment), were BC, for the lower and the higher concentration of SDS. Cetyltrimethyl ammonium bromide (CTAB), ortho-phthalaldehyde (OPA), sodium hydroxide (NaOH) and sodium hypochlorite (SHC) promoted the weakening of the biofilm mechanical stability.     

Preparation of alkenyl succinic anhydrides from vegetable oil FAME

Sunflower oil and oleic motif-enriched sunflower oil methyl esters were used to prepare alkenyl succinic anhydrides. A classic batch reactor was selected to carry out the synthesis. The range in which the temperature, reaction time, and molar ratio between the number of moles of maleic anhydride and the equivalent number of double bonds present in the unsaturated vegetable oil methyl esters (the most influential factors in the process) varied was determined in a preliminary study. A secondorder Doehlert uniform network design was used to investigate the influence of the temperature and molar ratio for all the methyl esters on the yield of alkenyl succinic anhydride from methyl oleate, the conversion of methyl oleate, the formation of side reaction products, the Gardner color of the product, and viscosity. The optimal reaction conditions for obtaining the maximal yield (around 95%) of alkenyl succinic anhydride from methyl oleate were 235°C, a molar ratio of 1.5, and a reaction lasting 8 h. However, the products synthesized under these conditions showed high viscosity (215 cP), a very dark color (18+ Gardner color), and a high content of undesirable side products (4%), which hindered their direct industrial use. The increase in the product viscosity was probably due to the formation of side reaction products. A molar ratio of less than 1.5 led to a less viscous product, although with a lower alkenyl succinic anhydride content.     

Pigment parameters determining spanish virgin olive oil authenticity: Stability during storage

The chlorophyll and carotenoid pigment composition in 12 mono-variety virgin olive oils was examined every 30 d during 1 yr of storage at 15°C in darkness. The oil authenticity parameters, as defined by the ratio of chlorophylls/carotenoids and the ratio of minor carotenoids/lutein, remained stable throughout storage, irrespective of the variety and degree of ripeness of the source fruit. The percent of violaxanthin, percent of lutein, and total pigment content, the classifying variables chosen as the best possible discriminators among olive varieties, also remained stable during storage. The prediction model for olive variety, which was based on a discriminant multivariate analysis of the observed values of these variables, gave a correct classification in 99.6% of the oils analyzed. The discriminant criterion established remained valid after 1 yr of oil storage. The detection of chlorophyll derivatives other than those associated with the physical extraction process was seen as a quality index, as small, analytically detectable transformations in the structure of pigments were indicative of oil storage.