Curing Mixture Research Articles

Cold-curing mixtures based on biopolymer lignin complex for casting production in single and small-series conditions

<abstract> <p>This study proves that lignin-based biopolymer materials can be employed as starting materials for the synthesis of novel casting binders that fulfill the current level of characteristics. The optimal concentration of the binder in the mixture was experimentally determined to be 5.8%–6.2%. It has been demonstrated in practice that the employment of ammonium salts as a technical lignosulfonate (TLS) modifier can result in the provision of cold (room temperature) curing of a mixture based on them. It was proposed to use as a technological additive that boosts the strength characteristics of a mixture of substances carboxymethyl cellulose (CMC). In a variety of adhesive materials, it is utilized as an active polymer base. The concentration limits for using CMC in the mixture are set at 0.15%–0.25%. To improve the moldability of the combination, it was suggested that kaolin clay be used as a plasticizing addition. The concentration limits for using a plasticizing additive are set at 3.5%–4.0%. The produced mixture was compared to the analog of the alpha-set method in a comparative analysis. It was discovered that the proposed composition is less expensive, more environmentally friendly, and enables the production of high-quality castings. In terms of physical, mechanical, and technological properties, the created composition of the cold curing mixture is not inferior to analogs from the alpha-set method. For the first time, a biopolymer-based binder system containing technical lignosulfonate with the addition of ammonium sulfate and carboxymethyl cellulose was used in the production of cast iron castings on the case of a cylinder casting weighing 18.3 kg from gray cast iron grade SCh20. Thus, it has been proved possible for the first time to replace phenol-based resin binders with products based on natural polymer combinations. For the first time, a cold-hardening mixture based on technological lignosulfonates has been developed without using hardeners made of very hazardous and cancer-causing hexavalent chromium compounds. But is achieved through a combination of specialized additives, including kaolin clay to ensure the mixture can be manufactured, ammonium sulfate to ensure the mixture cures, and carboxymethyl cellulose to enhance the strength properties of the binder composition. The study's importance stems from the substitution of biopolymer natural materials for costly and environmentally harmful binders based on phenolic resins. This development's execution serves as an illustration of how green technology can be used in the foundry sector. Reducing the amount of resin used in foundry manufacturing and substituting it with biopolymer binders based on technological lignosulfonates results in lower product costs as well as the preservation of the environment. Using lignin products judiciously can reduce environmental harm by using technical lignosulfonates, or compounds based on technical lignin. The combination is concentrated on businesses with single and small-scale manufacturing because it is presumable that this is merely the beginning of the investigation. This study confirms the viability of creating a cold-hardening combination based on technical lignosulfonates in practical applications and supports this with the castings produced, using the creation of a gray cast iron cylinder casting as an example.</p> </abstract>

Formation of heterocyclic aromatic amines in grilled pork depending on the pre-thermal treatment method

Electric grilled pork pretreated using four methods was analyzed for heterocyclic aromatic amines: 2-amino-3,8-dimethylimidazo [4,5-f] quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP). It was found that pre-thermal treatment of pork led to both a decrease and an increase in the content of heterocyclic aromatic amines in grilled steaks. In contrast to the control sample, the sample pretreated with an oil-based marinade exhibited a 3.2-fold decrease in the amount of MeIQx and 4.82-fold decrease in the amount of PhIP. The sample pretreated with a water-based marinade exhibited a 1.75-fold decrease in the amount of PhIP and a 3.81-fold increase in the amount of MeIQx. The sample pretreated with a dry curing mixture with red hot pepper exhibited a 3.5-fold increase in the amount of MeIQx and a 2.44-fold increase in the amount of PhIP. The sample pretreated with a dry curing mixture with paprika showed a 8.21-fold increase in the amount of MeIQx and a 3.65-fold increase in the amount of PhIP compared to the control sample. The study has shown that pretreatment of meat leads to both an increase and a decrease in the amount of heterocyclic aromatic amines formed during high-temperature thermal treatment depending on the non-meat ingredients used.

Synthesis and characteristics of novel 2-hydroxy-3-mercaptopropyl terminated polyoxypropylene glyceryl ether as an epoxy hardener of epoxy-based adhesives

Two epoxy hardeners with different molecular weights of 2-hydroxy-3-mercaptopropyl terminated polypropylene glyceryl ether (HMP-t-PGE) were synthesized as crosslinkers of bisphenol-A epoxy resin via the thiol-epoxy click reaction. After analyzing the curing characteristics and thermal behaviors of the formulated curing mixture with/without an amine-type curing catalyst, it was found that the molecular weight of the HMP-t-PGE hardener affected the curing kinetics and final properties of the epoxy networks. The thiol group of the low-molecular-weight (low-MW) HMP-t-PGE hardener was more reactive with the epoxy group than both the high-molecular-weight (high-MW) HMP-t-PGE hardener and the mercaptopropanoate-terminated polypropylene glyceryl ether (MP-t-PGE) hardener. When the high-MW HMP-t-PGE hardener was applied as the adhesive on mild steel substrate, the apparent adhesion strength was enhanced by up to ∼400% from that of MP-t-PGE hardener (assessed in single lap joint shear tests). By contrast, the low-MW HMP-t-PGE hardener enhanced the adhesion strength by only ∼230%. The high reactivity and excellent adhesion achieved by the thiol-epoxy click reaction at room temperature can be exploited in two-package epoxy adhesive applications such as quick repairs, tooling, and general bonding.

Suppressing Creep and Promoting Fast Reprocessing of Vitrimers with Reversibly Trapped Amines

AbstractWe report a straightforward chemical strategy to tackle current challenges of irreversible deformation in low Tg vitrimers at operating temperature. In particular, vinylogous urethane (VU) vitrimers were prepared where reactive free amines, necessary for material flow, were temporarily shielded inside the network backbone, by adding a small amount of dibasic ester to the curing mixture. The amines could be released as reactive chain ends from the resulting dicarboxamide bonds via thermally reversible cyclisation to an imide moiety. Indeed, (re)generation of the required nucleophilic amines as network defects ensured reprocessing and rapid material flow at higher temperature, where exchange dynamics are (re)activated. As a result, VU vitrimers were obtained with limited creep at service temperature, yet with good reprocessability at elevated temperatures. Thus, by exerting strong control on the molecular level over the availability of exchangeable functional groups, a remarkable improvement of VU properties was obtained.

Suppressing Creep and Promoting Fast Reprocessing of Vitrimers with Reversibly Trapped Amines.

We report a straightforward chemical strategy to tackle current challenges of irreversible deformation in low Tg vitrimers at operating temperature. In particular, vinylogous urethane (VU) vitrimers were prepared where reactive free amines, necessary for material flow, were temporarily shielded inside the network backbone, by adding a small amount of dibasic ester to the curing mixture. The amines could be released as reactive chain ends from the resulting dicarboxamide bonds via thermally reversible cyclisation to an imide moiety. Indeed, (re)generation of the required nucleophilic amines as network defects ensured reprocessing and rapid material flow at higher temperature, where exchange dynamics are (re)activated. As a result, VU vitrimers were obtained with limited creep at service temperature, yet with good reprocessability at elevated temperatures. Thus, by exerting strong control on the molecular level over the availability of exchangeable functional groups, a remarkable improvement of VU properties was obtained.

The Influence of Acid Whey on the Lipid Composition and Oxidative Stability of Organic Uncured Fermented Bacon after Production and during Chilling Storage.

The aim of this research was to evaluate the effect of acid whey on changes in the fatty acid profile, oxidative stability, physico-chemical parameters, and microbiological and sensory quality of traditional organic uncured fermented Polish bacon after production and during chilling storage. Three different treatments of fermented bacon were produced: C—control bacon with a nitrite curing mixture; T—bacon with a nitrate curing mixture; and AW—bacon with acid whey and NaCl. The acid whey used in the production of uncured fermented pork bacon positively changed the sensorial characteristics, directly after the ripening process, and had a positive effect in terms of a decrease in the pH of the product. All of the fermented bacon treatments in general were of good microbiological quality. A higher lactic acid bacteria (LAB) level was observed in the AW treatment after the fermentation process, and the bacteria number did not change during storage, whereas in the C and T treatments, the LAB level increased during storage (p < 0.05). The application of acid whey did not limit the formation of secondary oxidation products (TBARS) during bacon ripening (1.68 mg MDA kg−1), but had a reduced value during storage time (0.73 mg MDA kg−1). The highest polyunsaturated fatty acid (PUFA) levels, after ripening and after four weeks of refrigerated storage, were found in the C treatment. In the AW treatment, it was found that the PUFA level increased; likewise, the content of n-3 and n-6 fatty acids increased, while saturated fatty acids (SFAs) decreased during storage (p < 0.05). The opposite tendency was observed in the C treatment. After four weeks of storage, the PUFA/SFA ratio was the lowest in the nitrate treatment, and higher values of the PUFA/SFA ratio were obtained in the acid whey and nitrite treatment (p < 0.05).

Combined use of superabsorbent polymers and nanosilica for reduction of restrained shrinkage and strength compensation in cementitious mortars

In cementitious mixtures with a low water-to-cement ratio, autogenous shrinkage and cracking due to restrained shrinkage pose a severe problem. To reduce the risk of autogenous shrinkage cracking, internal curing by means of superabsorbent polymers (SAP) was applied. The drawback is that macropores are created upon the release of water by the polymers. The latter reduces the mechanical properties of the material. To counteract this strength reduction, nanosilica is introduced to the internal curing mixture. The effect of additives on the restrained shrinkage of mortar was evaluated by means of the restrained shrinkage ring test accompanied by acoustic emission (AE). AE enabled the monitoring of the hydration process, indicating when the absorbed water was released by the SAPs, while it also pointed out the moment of fracture of the ring. Results showed that combining SAPs and nanosilica, a mixture was created that decreased shrinkage while maintaining the mechanical properties of the reference material.

Influence of freeze-dried acid whey addition on biogenic amines formation in a beef and deer dry fermented sausages without added nitrite.

ObjectiveAim of this study was to evaluate the influence of freeze-dried acid whey addition and the use a game meat (fallow deer) on a microbial content and the biogenic amines formation in dry fermented sausages.MethodsThe experiment involved dry fermented sausages made in two variants from beef and from fallow deer. Each variant was divided into five groups: control (with a curing mixture), reference (with a sea salt), sample with a liquid acid whey and two samples with the addition of reconstituted freeze-dried acid whey in different concentrations. Changes in lactic acid bacteria (LAB), Enterobacteriaceae content and biogenic amines content were determined.ResultsThe microbial content changes suggest that addition of acid whey slightly affected LAB content in comparison with the control and reference sample, but the addition of freeze-dried acid whey resulted in a reduction of Enterobacteriaceae content in the sausages from fallow deer or a similar level in the beef sausages compared with the control and reference sample. Both changes in LAB and Enterobacteriaceae content were more evident in case of sausages made from fallow deer. Addition of acid whey (liquid and a higher amount of freeze-dried) and use of fallow deer meat to produce the sausages resulted in a significant reduction of total biogenic amines content.ConclusionThe addition of acid whey (liquid and higher amount of freeze-dried) resulted in a significant reduction of total biogenic amines content in dry fermented sausages made from fallow deer meat.

Исследование влияния состава посолочных смесей на процесс окисления липидов мясных систем

Lipids are the most unstable substances that take part in oxidation process in meat and meat products. Table salt (sodium chloride) which is considered as a pro-oxidant factor has significant effect on the development of meat products oxidative deterioration. The main objective of the research was to study the effect of curing mixture compositions which have low sodium content on the intensity and dynamics of lipids oxidation process in model systems, raw meat and final products during storage. Semi-smoked sausages were taken as an example. The author studied curing mixtures in which 30% of sodium chloride was replaced with one of the following components: potassium chloride, calcium chloride, magnesium chloride. Compositions included potassium chloride and calcium chloride at the ration of 1 to 1, mixture of sodium chloride with yeast extract. The results of the study of the oxidation process in model systems and meat systems with different curing mixtures conform to each other which shows that the mixtures which contain potassium chloride, magnesium chloride and composition of potassium chloride and calcium chloride help slow down oxidation process. According to the results of semi-smoked sausages organoleptic analysis, which were cooked using different curing compositions, the traditional characteristics of the product are obtained when one uses curing mixture which consists of 70% of sodium chloride and 30% of potassium chloride and calcium chloride composition. The dynamics of changes in acid-degree value, peroxide value and thiobarbituric value during semi-smoked sausage storage cooked using that curing mixture indicates that lipid fraction oxidation process stabilizes.

Effect of incorporation of masonry residue on the properties of self-compacting concretes

This paper presents the results of an experimental study about the effects of the incorporation of masonry residue (RM) on self-compacting concretes (SCCs). RM was composed of ground red clay bricks and cement Portland mortar. It was studied the influence of this RM addition on self-compactability properties of SCCs such as slump flow, V-funnel flow and L-box, and mechanical properties such as compressive, indirect tensile and flexure strength were determined. The Portland cement was partially replaced from 0% to 50% of RM in volume for the SCC blends. All the mixtures fulfilled the properties in fresh state, and specifically in the slump flow the mixtures presented a flow between 660 mm and 700 mm. As for the mechanical properties, the compressive strength was affected at different curing ages (7, 28 and 90 days) for all replacement levels showing much lower resistances if compared to the reference mixture (0% of RM); however, at longer days of curing (180 and 360 curing days) mixtures with 12.5%, 25% and 37.5% of RM showed similar or greater resistance.

New Approaches to Production of Turkish-type Dry-cured Meat Product "Pastirma": Salt Reduction and Different Drying Techniques.

In this study, the possible changes in the quality characteristics of pastırma, Turkish-type dry-cured meat product, produced by using two different salts (NaCl-KCl) in a curing mixture and two different production techniques (natural and controlled condition) were examined. Moisture, pH, salt, sodium, potassium, TBA, fat, water activity, instrumental colour, texture, and sensory analyses were implemented in order to determine the possible effects of these applications. Fat, aw, pH, colour, tiobarbituric acid (TBA), texture, salt, Na and K values may allow these desired modifications in pastirma production to be limited. The substitution of 15% KCl instead of NaCl was acceptable in terms of the sensorial properties of the pastirma. However, the sensory analyses did not allow for using a higher KCl instead of NaCl because both the hardness and chewiness in the texture of the pastirma samples salted with 30% of KCl were not scored positively. Besides this, negative effects, which may occur during the pastirma production under natural conditions, can be eliminated by the production being under controlled conditions.

Concrete pavements curing evaluation with non-destructive tests

This study was completed by the Texas A&M Transportation Institute (TTI). The ground penetrating radar (GPR) technology and percometer were implemented for newly constructed highways. The GPR identifies the subsurface condition, which permits the user to determine the moisture availability for potential concrete curing. For this purpose, a GPR data acquisition program and data analysis system were developed by utilizing antenna. A combination of GPR information evaluation and curing quality evaluation is performed to diagnose the effectiveness of the applied curing compounds in terms of the moisture retention capability. Dielectric constant (DC) measurements were also taken on concrete specimens to indicate the free moisture content of the surface concrete. The new procedure consists of using measured relative humidity and temperature to calculate an Effectiveness Index (EI). EI and DC measurements indicate potentials to differentiate the curing quality of rigid pavement construction. Researchers examined the relationship between the Non-Destructive Testing (NDT) data and the actual concrete properties to develop “acceptability of quality” limits based upon the NDT data. The field investigations were conducted on two continuously reinforced concrete paving (CRCP) projects’ microfiber and internal curing mixtures.

Quality Characteristics of Cured Semi Dried Camel Meat Treated with Different Medicinal Plants as Natural Preservatives Sources

The aim of the study is to determine the quality characteristics of produced curing and semi dried camel meat contained some medicinal plants of thyme, rosemary, clove and ginger as natural preservatives. Camel meat samples were sliced and divided into five batches; one batch recorded as control sample was treated by the curing mixture (black pepper, cumin, spices mixture, dried onion, dried garlic and salt). To evaluate the effect of different natural preservatives sources of thyme, rosemary, clove and ginger, 3.0% of the aforementioned natural preservatives was mixed with the aforementioned curing mixture and used for curing the four batches of sliced camel meat. After curing process, cured sliced camel meat (control and treated with the natural preservatives) were conducting to drying process at 35 ± 3 OC for 36 h in a drying cabinet. The quality characteristics of prepared dried camel meat were evaluated such as chemical composition, microbiological characteristics and sensory characteristics. Based on the microbiological and sensory characteristics, it could be suggested that the selected medicinal plants specially thyme and rosemary could be used as natural preservatives for preparing semi dry camel meat without negative effects.

THE STUDY OF FACTORS AFFECTING THE ACTIVITY OF MEAT ANTIOXIDANT SYSTEM

Oxidation of lipids and myoglobin in raw meat are interrelated processes that affect the overall meat quality. The intensity of oxidation processes in meat raw material is regulated by its own antioxidant system (catalase, peroxidase, glutathione, etc.), the activity of which should be considered in the development of new technological solutions. Oxidation of lipids and myoglobin, directly affect the quality and safety of meat products, and reducing of the intensity of these processes contributes to the life time of raw meat, as well as that of finished products. The paper presents the study results of the salt curing mixture, including combination with yeast extract, affecting on the activity of the antioxidant system of the main types of raw meat pork and beef. The basic systems, minced pork and beef being subjected to salting with curing salt (sodium chloride) and curing mixture consisting of 70% sodium chloride and 30% of composition KCl + CaCl2 at the ratio of 1:1 are investigated. The influence of curing mixture on the intensity of oxidation of lipids and myoglobin of raw meat of different species is stated. It is found, that reducing the amount of sodium chloride in curing composition of the mixture brings down oxidative changes of heme pigments and meat lipids. Introduction of yeast extract into raw meat, in the amount of 2% enhances the inhibitory effect on oxidation in raw minced meat.

Experimental Study on the Wet Fly Ash Stabilized by Cement

Through unconfined compressive strength tests and triaxial compression tests made by sea water wet fly ash, fly ash solidified by cement, and the analysis with water wet strength of the material solidified fly ash formation mechanism, getting their basic mechanical properties and index. The results showed that curing water wet fly ash cement has good stability and durability, mixing curing mixture strength with age of stable growth, increased strength by adding cement content. The pilot research on the retaining structure, embankment reinforcement and ground improvement has important engineering applications such as theory and practice of value.

Effect of nanosilica on the kinetics of cure reaction and thermal degradation of epoxy resin

Nanocomposites from nanoscale silica particles (NS), diglycidylether of bisphenol-A based epoxy (DGEBA), and 3,5-diamino-N-(4-(quinolin-8-yloxy) phenyl) benzamide (DQPB) as curing agent were obtained from direct blending of these materials. The effect of nanosilica (NS) particles as catalyst on the cure reaction of DGEBA/DQPB system was studied by using non-isothermal DSC technique. The activation energy (Ea) was obtained by using Kissinger and Ozawa equations. The Ea value of curing of DGEBA/DQPB/10% NS system showed a decrease of about 10 kJ/mol indicating the catalytic effect of NS particles on the cure reaction. The Ea values of thermal degradation of the cured samples of both systems were 148 kJ/mol and 160 kJ/mol, respectively. The addition of 10% of NS to the curing mixture did not have much effect on the initial decomposition temperature (Ti) but increased the char residues from 20% to 28% at 650°C.

Influence of Curing Conditions on Strength Development and Strength Predictive Capability of Maturity Method

Applicability of the maturity method to ternary systems with fly ash (FA) and silica fume (SF) has been investigated through laboratory and field studies. The laboratory study explored the impact of the combined effect of initial curing conditions and mixture composition on the compressive strength development and strength predictive capability of the maturity method. It was demonstrated that the maturity method can be used effectively to predict compressive strength of ternary concrete containing ordinary portland cement, FA, and SF. However, the accuracy of this method was strongly influenced by the amount of moisture supplied during early stages of curing and to a lesser extent by relative amounts of FA and SF in the mixture. Further (intermittent) moist curing of field trial batch (FTB) concrete (potentially simulating natural precipitation) was found to have a beneficial effect on strength development and, consequently, on the accuracy of strength prediction using the maturity method. Thus, even an occasional supply of moisture to high-performance concrete (especially at early age) may significantly minimize potential strength losses. Finally, applicability of the maturity method to ternary bridge deck concrete made and placed under field conditions and exposed to ambient temperature variations was verified. The predicted strength of bridge deck concrete was found to be approximately 10 MPa lower than the actual strength, irrespective of age. However, a correction factor was established to account for different air content in field concrete (compared with FTB concrete that was used for development of maturity function), which resulted in much more accurate strength estimates.

CHARACTERIZATION OF A LAMB HAM: FATTY ACIDS AND VOLATILE COMPOUNDS COMPOSITION

ABSTRACT The study presents and characterizes a little‐known product that is processed manually on the cottage industry scale. The product, called “violino” of lamb, is a cured and matured lamb thighbone of sheep of the Lamon × Bergamasca breed. The sheep graze on pasturelands, and the lambs are weaned at 60–70 days of age. They are then raised out in the field and the pasture feeding is supplemented with a commercial concentrate based on maize and soybean. At 7–8 months the lambs are slaughtered, and the thighs are cured with a curing mixture and ripened for 60 days. The study determined, on the fresh thighs, the proximate composition and fatty acid profile; and on the cured thighs (violino), the proximate composition, fatty acid profile and the volatile composition influenced by curing, salting and spicing. The results revealed the cured ham lamb to have a reduced fat content, a high polyunsaturated fatty acids/saturated fatty acids ratio and a high protein content. The processing, performed completely manually, resulted in a niche product that has the possibility of being produced on a bigger scale, which would favor breeders in that they would profit from being able to sell not just the fresh lamb meat but also a cured end‐product. Given the consumer demand for typical products, this lamb ham, known as lamb violino, could be a sought‐after product.

New polythiourethane hardeners for epoxy resins

AbstractNew mercaptan‐terminated polythiourethanes were synthesized from low‐molecular‐weight dimercaptan oligomers and diisocyanates. The characteristic bands in the FT‐IR spectra, and the specific peaks in the 1H‐NMR spectra correlate rather well with the proposed structures of these polymers. Chemical analysis of the epoxy group conversion and swelling measurements were conducted in order to determine the crosslink densities of the cured epoxy resins. The curing characteristics and thermal behaviour of the formulated curing mixtures indicate that the epoxy/polythiourethane stoichiometry and thermal history during cure may greatly affect the curing mechanism and final properties of the epoxy networks. Mechanical studies indicated that the application of polythiourethane hardeners improves the flexibility with increasing tensile strength and impact toughness. The prepared polythiourethane hardeners have an acceptable odour and give a perfectly homogeneous system with the epoxy resins and have good storage stability with other coreactants such as diamines. Copyright © 2005 Society of Chemical Industry

Mathematical Modeling of Microbial Growth of Pretreated Refrigerated Minced Goat Meat (Black Bengal Variety)

ABSTRACT: Minced goat meat (Black Bengal variety) was stored aerobically and refrigerated at 4°C for 15 d after washing with hot water followed by different combination pretreatments including acetic acid-glucose, a curing mixture, and tea liquor and honey mixture. It was observed that pretreated samples exhibited better physicochemical (pH, water-holding capacity, thiobarbutyric acid value, and extract release volume), sensory, and microbial characteristics compared with the control goat meat samples, which were not washed and pretreated (P < 0.05). Microbial characterization of goat meat samples was evaluated with respect to aerobic bacterial, yeast, and mold growth during its storage. Microbial growth characteristics were modeled by 2 nonlinear regression models of sigmoidal functions, specifically, a logistic equation and modified Gompertz equation. In this study, the modified Gompertz equation was found to be more suitable to explain the microbial growth characteristics. Tea liquor and honey pretreatment was most effective in controlling aerobic bacterial growth, whereas acetic acid-glucose pretreatment was most effective in controlling yeast and mold growth. Storage life of pretreated samples was >15 d, whereas storage life of the control sample was <5 d.