Are Omega 3 Fatty Acids and Depression Related to Each Other?
Omega 3 fatty acids like DHA and EPA are found in fish oil and they are required for proper development of the nervous system. It is therefore a general finding that omega 3 fatty acids and depression (and other psychological illnesses) are related to each other.
Omega 3 fats prevent depression, anxiety, bipolar disorder, schizophrenia and Alzheimer’s disease. All these diseases are related to mental health and occur as a result of severe DHA deficiency in the body.
DHA is required for proper nerve transmission and it is also one of the basic building blocks of the brain. Omega 3 fats if taken in adequate amounts also affect a person’s mood and behavior. It has also been found that postpartum depression in women also occurs as a result of DHA deficiency.
Pregnant women need DHA and EPA in large amounts because their baby obtains all the nutrients from the mother’s blood. It should also be kept in mind that our body is incapable of producing omega 3 fats on it own. Because of this reason they are known as essential fatty acids and should be consumed through diet.
Infants receive their share of DHA and EPA from their mother’s milk. The importance of omega 3 fats and the connection of omega 3 fatty acids and depression can also be judged by the fact that human milk contains large quantities of both DHA and EPA.
Hyperactivity in growing children is also a mental disorder and it occurs when babies fail to receive adequate amounts of DHA from their mother’s milk. All these facts tell us how important DHA is for overall health and well-being. The significance of DHA in our everyday diet cannot be overemphasized.
However, there is one problem with the consumption of DHA and EPA. There are not many food sources available that contain good amounts of both fats. Only fish, seafood, flax seed oil, some other plant oils, walnuts and tofu contain DHA and EPA in good amounts.
A healthy alternative is to consume fish oil capsules and other omega 3 supplements available on the market. These supplements are pure and totally harmless. They can be consumed by people of all ages since they do not cause any side effects. Other alternative foods can also be used like omega 3 enriched eggs and canned fish.
It is advisable to consume at least 3 fish oil capsules on a daily basis to fulfill omega 3 requirements.
Classification of Amino Acids
Though 300 amino acids occur in nature, about 20 amino acids are found in proteins. All the amino acids are required by the body but some are known as indispensable nutritionally essential amino acids, as these cannot be synthesized in the body, and their deficiency disturbs nitrogen equilibrium, growth, nutrition, maintenance, and life span. The others are termed as dispensable in the diet as there amino acids can be synthesized in the body, but they are more important to the cell than the essential ones. There are 10 essential amino acids in humans.
Arginine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine. Arginine and Histidine are considered nutritionally semiessential, since they can be synthesized but not in quantities sufficient to permit normal growth. Two other amino acids, Cysteine and Tyrosine may be formed form the essential amino acids Methionine and Phenylalanine, respectively.
The others are Alanine, Asparagine, Aspartate, Glutamate, Glutamine, Glycine, Proline, and Serine. These are formed from amphibolic intermediates by short anabolic pathways, or from other dietary amino acids.
Proteins form different sources vary considerably in the quality and quantity of their amino acid contents, and thus their food values differ. The building blocks of proteins are amino acids. While proteins contain substances in addition to amino acids, their biologic properties are determined largely by the kinds of amino acids, present, the order in which they are linked together, and thereby the spatial relationship of one amino acid to another.
First class proteins of high biological value contain all essential amino acids and are capable of providing growth and maintenance. Almost all animal proteins, glutein of wheat, and glutelin of maize belong to this class. Second class proteins of low biological value are different in some of the essential amino acids and unsuitable for growth and maintenance. Generally most of the vegetable origin proteins, and gelatin of animal origin fall in this category. A diet supplying 12% energy from protein in adequate.
Certain amino acids, like Glycine and Glutamic acid, appear to be involved in the transmission of impulses in the nervous system.
The metabolism of amino acids rise to many compounds of biomedical importance: as decarboxylation of certain amino acids produces the corresponding amines like Histamine and Gama-aminobutyric acid (GABA) having biologic functions.
The protein values in food items are calculated from the functions, content, and the factor used is 6.25 for all foodstuffs. The amount of nitrogen in gm per 100 gm of edible portion of a foodstuff is given in col. 2 of table below. The col. 3 to 14 of the table further indicate content of 12 amino acids in mg per gm of nitrogen. So to calculate:
Protein =N (col.2) x6.25 in gm per 100 gm of edible portion of foodstuff. Amino acid= N x 6.25xAmino Acid (any of col. 3-14) in mg in 100 gm of food. Know more about 20 amino acids.
The Benefits of Omega 3 Fatty Acids
Medical specialists have been aware of omega 3 fatty acids’ benefits on the human body for more than 40 years now and for all this time, they have tried to discover more and more positive effects.
The overall conclusion is that, indeed, the essential omega 3 fatty acids play a very important role in our health. In addition, they have discovered that during the years, the modern man’s diet has become poorer, poorer in omega 3 fats, and richer in omega 6 fatty acids. While omega 6 fats are also important for human health, they have also inflammatory properties and there must be a balance between the two types of fats in the human body. Medics have also tried to find out what foods contain the richest amounts of essential fats, because the human body cannot produce naturally these acids.
The best omega 3 medical supplements are made out of fish oil, cold-water fish having the richest natural concentrations of fatty acids. Medics have been prescribing omega 3 supplements to people suffering from heart conditions, as studies have shown that the risk for heart attacks is lowered by up to 45% compared to people who do not have enough fatty acids in their diet. You do not have to suffer from a heart condition to benefit from the omega 3’s positive actions, as these supplements also have protective properties.
The circulatory system is also protected by these fats, as the bad cholesterol levels are reduced if the person is lowering the amounts of omega 6 fats and increases the amount of omega 3 acids in the diet. In addition, a series of mental conditions are ameliorated by taking omega 3 supplements: the risk for developing dementia is reduced by up to 50% in people eating the proper amount of essential fats. Patients suffering from depression, bipolar disorder and borderline personality disorder also witness improvements in their symptoms by increasing the amount of omega 3 fats. The human brain is mostly comprised of fats and having proper concentrations of essential fatty acids enables a better and more efficient neuron to neuron communication.
Medics also witnessed an improvement in insulin sensitivity in diabetes sufferers. Because of the anti-inflammatory properties of omega 3 fats, these medical supplements are also prescribed to people suffering from arthritis and other inflammatory medical conditions. The benefits of omega 3 fatty acids are clearly important and they should not be neglected by any person concerned of his or her health.
Omega 3 Fatty Acids and Bone Health
After many years in which scientists suspected that omega 3 fatty acids play an important role in bone development and protection, a team of medical researches from Cambridge University has discovered that indeed, these essential fats have a beneficial effect over our bones.
Moreover, the omega 3 fatty acids obtained from plants are the most efficient in protecting bone cells. Omega 3 fats have been known for years to have anti-inflammatory properties and elderly people had been prescribed supplements to ameliorate their cardiovascular and inflammations. However, compared to omega 3 supplements obtained from marine sources, the omega 3 fats obtained directly by the human body from plants proved to have an increased efficiency in protecting the bones. The richest plants in omega 3 essential fats are soybean, canola oil, walnuts and flaxseed.
The medical research mentioned above had been conducted on 23 people, 20 men and three women. The test lasted for 6 weeks and they had been split in three groups, each having a certain diet. After the test has ended, medical tests performed on the test group that had a richer diet in omega 3 rich plant showed an increased level of all blood markers indicating bone health. Two main markers have substantially increased, one that indicates bone formation and another that indicates bone resorption or breakdown. Our bones have a hard time to stay together once the body grows older, two types of cells affecting them: osteoblasts and osteoclasts.
Because of this process, special chemicals are released that can be traced in blood tests. In very severe cases, osteoporosis can occur, a medical condition in which bone and joint integrity is compromised. If the amount of bone cells that are being absorbed is lower than the number of bone cells being created, the bones will remain healthy. This is the purpose of any bone care medication, but until now, medics had a very hard time trying to determine the most efficient way of protecting bones against osteoporosis.
The indication that essential omega 3 fatty acids help increase the amount of bone cells produced and lowers the number of bone cells destroyed is very important for the medical community, as until now little treatment was known for osteoporosis. Medics used to treat people of bone conditions rather than prescribing protective medication and these latest discoveries may help people understand that an omega 3 rich diet can help them fight a lot of age related medical problems.
N-3 fatty acids and sudden death - Cardiovascular Disease - long chain n-3 polyunsaturated fatty acids
The Physician’s Health Study reported that fish consumption was associated with a reduced risk of sudden death from cardiac causes, but not a reduced risk of myocardial infarction. Experimental data suggests that long chain n-3 polyunsaturated fatty acids found in fish, primarily eicosapentaenoic fatty acids, have antiarrhythmic properties.
Prospective data on blood levels of long chain n-3 fatty acids and sudden death from cardiac causes are sparse and there have been no randomized trials of the effects of these fatty acids in the diet or as supplements among persons without a history of cardiovascular disease (CVD), who represent over half of all cases of sudden death from cardiac causes. Therefore, a recent study in the New England Journal of Medicine tested the hypothesis that the long chain n-3 fatty acids found in fish are associated with reduced risk of sudden death from cardiac causes in those without known CVD, in men enrolled in the Physician’s Health Study.
A prospective, nested case-control analysis among apparently healthy men who were followed for up to 17 years in the Physicians’ Health Study were enrolled in this trial. In the beginning the physicians completed questions on their health status and risk factors for CVD. Dietary intake offish was determined at 12 months with a food frequency’ questionnaire. The fatty acid composition of previously-collected blood was analyzed by gas-liquid chromatography for 94 men in whom sudden death occurred as the first manifestation of CVD and for 184 controls.
The mean level of total long-chain n-3 fatty acids was significantly lower among the men who died suddenly than among the controls. In contrast, the levels of the other fatty acids, including the short chain n-3 polyunsaturated fatty acids, saturated fall), acids, monounsaturated fatty acids, n-6 polyunsaturated fatty acids, and trans unsaturated fatty acids, did not differ significantly between the two groups. As compared with men whose blood levels of long chain n-3 fatty acids were in the lowest quartile, the relative risk of sudden death was significantly lower among men with levels in the third and fourth quartile.
The authors acknowledge that a limitation of this study was the single baseline measurements of fatty acid levels, which may not accurately reflect the levels of long-chain n-3 fatty acids over long periods. However, Albert, et al., state that this limitation cannot seriously affect the strong inverse association observed between long-chain n-3 fatty acid levels and sudden death. Taken together with previous data from observational studies, the results suggest that increasing the intake of n-3 fatty acids by eating more fish or by taking supplement is an intervention that could be applied to this segment of the population at low cost and little risk.
Going to the dogs…and cats…and horses - Ingredients in Use: Omega-3 Fatty Acids
Essential Nutrient Research Corporation (ENRECO[TM] Inc.), a division of Natural Ovens Bakery Inc., Manitowoc, Wisc., provides consumers and their pets an education as to the benefits of dog treats high in omega fatty acids and antioxidants. With its use of flaxseed and tuna oil to create a pet food with 5% omega-3s and 2% omega-6s, this product, which has been on the market for a bit, was ahead of its time.
Although the company also uses flaxseed in human-oriented products such as breads, muffins, cookies and supplements, its website notes a range of animal foods and feeds such as Omega Gold[TM] for pigs, Omega Horseshine[TM] for horses, and Super Egg Stabilized Flax for chickens.
The company highlights current research that suggests, in pet foods, the ratio of omega-6s to omega-3s should be between 2:1 and 5:1. “However, commercial pet foods have ratios of 20:1 to 50:1, causing them to be extremely omega-3 deficient.”
Statistically, pet foods have been the most popular category for omega fatty acid use, with references to benefits for skin and coats, the most common claim worldwide.
Spread it around - Ingredients in Use: Omega-3 Fatty Acids
Spectrum Naturals, Petaluma, Calif., and omega fatty acids have been a winning combination for some time. Organic vinaigrette salad dressings in balsamic, ginger-garlic and raspberry were introduced back in 1999 in the U.S., with a similar line turning up in the U.K. in 2000. The source is flax oil.
More recently, “omega mayonnaise” has been hitting retail shelves. Spectrum Naturals introduced Organic Omega-3 Mayonnaise (shown here), “which helps provide consumers with the essential fatty acid omega-3, a nutrient that is essential to the body and must be obtained from outside food sources’ claims the company. A 16-fl.-oz. container retails for $4.99 at health food stores nationwide.
The GNPD noted that Heart Beat Foods, Div. GFA Brands, Inc., Cresskill, N.J., introduced Smart Balance Light mayonnaise in March of this year. The label notes that the “right balance of fats helps improve cholesterol ratio.” It claims half the fat and calories of regular mayonnaise, is fortified with vitamin E and–retailing at $2.39 for a 16-fl.-oz. glass jar–is also less than half the price. The omega-3s are likely from the canola and/or soy oil, as no other primary sources are mentioned.
Measurement of Organochlorines in Commercial Over-the-Counter Fish Oil Preparations: Implications for Dietary and Therapeutic Recommendations for Omega-3 Fatty Acids and a Review of the Literature
Context.-The consumption of fish high in omega-3 fatty acids is advocated by the American Heart Association to decrease the risk of coronary artery disease. However, fish contain environmental toxins such as mercury, polychlorinated biphenyls, and organochlorine pesticides, which may negate the beneficial cardiovascular effects of fish meals. Toxin levels vary depending on both the fish source and the specific toxin, and neither farm-raised nor wild fish are toxin free. Fish oil supplements also prevent the progression of coronary artery disease and reduce cardiovascular mortality. However, only sparse data exist on the level of toxins in fish oil. In a previous study we showed that the amount of mercury in 5 over-the-counter brands offish oil was negligible.
Objective.-To determine the concentrations of polychlorinated biphenyls and other organochlorines in 5 overthe-counter preparations of fish oil.
Design.-The contents of 5 commercial fish oil brands were sent for organochlorine analysis.
Results.-The levels of polychlorinated biphenyls and organochlorines were all below the detectable limit.
Conclusions.-Fish oil supplements are more healthful than the consumption of fish high in organochlorines. Fish oils provide the benefits of omega-3 fatty acids without the risk of toxicity. In addition, fish oil supplements have been helpful in a variety of diseases, including bipolar disorder and depression.
Fish possess antiatherogenic properties, presumably because of their high content of essential omega-3 polyunsaturated fatty acids (ie, eicosapentaenoic acid or docosahexaenoic acid). Several studies demonstrate the benefits of fish consumption in patients with cardiac disease, including a decreased mortality following myocardial infarction.1-16 In addition, regular fish intake is recommended to decrease the risk of coronary artery disease.6 On the other hand, many studies have illustrated that certain fish contain high levels of environmental toxins, such as mercury, polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides, and related compounds.6,7 Some of these toxins may negate the cardiovascular health advantages of fish meals.6
Concentrated omega-3 fatty acids are found in fish oil supplements and may provide benefits similar to fish without the exposure to harmful environmental toxins.1 Daily fish oil ingestion slows the progression of coronary artery disease.5 Furthermore, fish oil supplements have been shown to stabilize mood in bipolar disorder, relieve depression in pregnancy, and decrease inflammation in some autoimmune diseases.8-15 In a previous study, we showed that several over-the-counter brands of fish oil supplements contained negligible amounts of mercury compared with fish and suggested that the consumption of fish oils may be preferable to eating fish.16 However, mercury is not the only toxin potentially in fish oil supplements.
Organochlorines have at least 1 aromatic ring and include PCBs, which have 2 aromatic rings. Organochlorines can be divided into pesticide OCs (ie, dichlorodiphenyltrichloroethane [DDT]) and nonpesticide OCs (ie, PCBs). PCBs are unwanted byproducts of a variety of industrial processes and are still found in transformers and capacitors that were manufactured before PCBs were banned in 1977. PCBs persist in the environment because of their resistance to degradation, and they bioconcentrate in fish along the food chain. PCBs and related compounds have adverse dermatologic, reproductive, developmental, endocrine, hepatic, and immunologie effects.17-19 DDT is the best-known OC pesticide. Similar to PCBs, OC pesticides such as DDT are resistant to degradation and accumulate in fish and in the environment. Exposure to OC pesticides may cause neurotoxicity and cardiac and pulmonary dysfunction.17,18,20
The levels of PCBs, OC pesticides, and related compounds in fish have received considerable attention in the press recently.21,22 Articles warn the public about the hazards of toxins in certain fish and discuss the use of fish oil as an alternative. Commercially available fish are either farm raised or wild. Researchers have addressed concerns about the source of fish and its associated contaminants. A recent Wall Street journal article stated that farm-raised salmon had higher levels of certain toxins than wild salmon. Consequently, people who regularly consume farmraised salmon may have an increased risk of cancer later in life. On the other hand, toxins such as mercury are detected at equal or higher concentrations in wild fish, so neither farm-raised nor wild fish appear superior.17,23-27 In this study, we examined the levels of a common group of environmental toxins, organochlorines, in 5 over-the-counter fish oil preparations to further evaluate whether advocating fish oil over fish is potentially warranted.
MATERIALS AND METHODS
Five commercial over-the-counter brands of fish oil supplements were purchased from retail or Internet sources. The brands included Omega Brite (Waltham, Mass), Natrol (Chatsworth, Calif), Sundown (Boca Raton, Fla), Kirkland (Houston, Tex), and CVS (Woonsocket, RI). The capsules were punctured, and approximately 5 mL of the liquid contents were sent in a citrate tube to National Medical Services (Willow Grove, Pa) for OC analysis (a-chlordane, 1,1 -dichloro-2,2-bis(;i-chlorphenyl)ethane [DDD], dichlorodiphenyldichloroethene [DDE], DDT, dieldrin, ychlordane, heptachlor, heptachlorepoxide, hexachlorobenzene, lindane, methoxychlor, oxychlordane, polybrominated biphenyls (PBBs), PCBs, trans-nonachlor). The OC levels were measured by gas chromatography with electron capture detection. This methodology has been described previously.28-30 The lower limits for detection of PCBs and other OCs in this assay are 400 parts per billion (ppb) and 200 ppb, respectively.
Omega-3 Fatty Acids and CHD Prevention - coronary heart disease
Mounting evidence shows that omega-3 polyunsaturated fatty acids (PUFAs) prevent cardiac death and nonfatal myocardial infarction. The types of PUFAs that have been most often studied include eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and a-linolenic acid (ALA). Dietary sources of PUFAs include meat, poultry, fish, vegetable oils, salad dressings, and grain products. Fatty cold-water fish such as halibut, mackerel, herring, and salmon are good sources of EPA and DHA. Soy and pinto beans, walnuts, and flaxseed are good sources of PUFAs, as are vegetables such as leeks and purslane. Oils high in ALA include canola, soybean, and flaxseed. Harper and Jacobson review evidence supporting the value of PUFAs in preventing coronary heart disease (CHD).
Epidemiologic studies that confirmed the relationship between PUFAs and decreased CHD include comparisons of the rates of heart disease among Eskimos and Greenlanders who ate higher amounts of PUFAs versus Danes whose diet contained a much lower PUFA intake. In the U.S. Physicians Health Study, U.S. male physicians aged 40 to 84 years who ate more fish had a decreased risk of sudden cardiac death. A higher intake of ALA among participants in the Nurses Health Study correlated with a lower relative risk of fatal CHD.
The omega-3 PUFAs are probably cardioprotective through several mechanisms. They have antiarrhythmic and antithrombotic effects, and improve endothelial function. Atherosclerotic plaque formation has been shown to be inhibited by ingestion of EPA and DHA. Total cholesterol and triglyceride concentrations are lowered with consumption of fish oil without a drop in high-density lipoprotein levels. Working mostly through anti-atherogenic effects, it is mainly the marine-derived PUFAs, EPA, and DHA that have the clearest value. The benefit of ALA needs further clarification.
Prospective trials have confirmed the benefit of PUFAs on CHD. In a large prospective study, men who had recovered from a myocardial infarction and were assigned to eat fish or take fish oil capsules had a significant decrease in all-cause mortality. A prospective study of a Cretan Mediterranean diet, high in fruits and vegetables, rich in monounsaturated fatty acids (olive oil), and high in ALA, among a population who had survived a first myocardial infarction, demonstrated a significant reduction of risk for cardiovascular death and nonfatal myocardial infarction. Other prospective diet-based studies have demonstrated similar beneficial results.
The authors conclude that PUFAs are useful in secondary prevention of CHD. In the U.S. diet, the principal sources of PUFAs are vegetable oils and fish. Guidelines recommend increased consumption of ALA, EPA, and DHA. For persons who cannot tolerate an increase in fish to one to two fish meals per week, supplements are available, including a vegetarian source derived from algae. One or two fish-oil capsules containing 750 to 1,000 mg EPA can be used as an alternative. Cod liver oil is a good source of PUFAs but also contains high amounts of vitamins A and D. Although more evidence is needed to confirm the value of PUFAs in the primary prevention of CHD, it would be prudent to increase ingestion of PUFA-containing foods (see accompanying table).
Foods High in Omega-3
Polyunsaturated Fatty Acids
Fish (mostly EPA and DHA) Plants (mostly ALA)
Mackerel Flaxseed
Atlantic herring Butternuts (dried)
Albacore tuna English walnuts
Chinook salmon Soybeans (raw)
Anchovy Leeks
Coho salmon Wheat germ
Greenland halibut Purslane
Rainbow trout Almonds
Atlantic cod Pinto beans
EPA = eicosapentaenoic acid; DHA = docosahexaenoic acid;
ALA = a-linolenic acid.
Information from Harper CR, Jacobson TA. The fats of life.
The role of omega-3 fatty acids in the prevention of coronary
heart disease. Arch Intern Med 2001;161:2190.
Harper CR, Jacobson TA. The fats of life. The role of omega-3 fatty acids in the prevention of coronary heart disease. Arch Intern Med October 8, 2001;161:2185-92.
EDITOR’S NOTE: The cardioprotective value of omega-3 fatty acids is becoming more widely accepted. Data tell us that the type of fat is more important than the total amount of fat in the diet. Replacing saturated fat with unsaturated fat is more effective in lowering CHD risk than simply reducing total fat intake. Clear evidence of reduced cardiac mortality has been demonstrated in studies using omega-3 fatty acids for secondary prevention of cardiac morbidity and mortality. Other potential benefits of consumption of fatty fish may include decreased risk of prostate cancer (Terry P, et al. Fatty fish consumption and risk of prostate cancer. Lancet 2001;357:1764-6) and decreased rates of depression (Mischoulon D, Fava M. Docosahexanoic acid and v-3 fatty acids in depression. Psych Clin North Am 2000;23:785-94). When recommending fatty acid supplements, physicians must monitor patients closely, keeping in mind the lack of data about long-term safety.
Crosslinking of Cotton Cellulose in the Presence of Alpha-Amino Acids: Part II: Reaction Kinetics of the Mixed Reagents
ABSTRACT
Two kinds of alpha-amino acids are used to combine with dimethylol-dihydroxyethyleneurea (DMDHEU) as crosslinking agents, and the specific rate constants and other activation parameters are discussed. Prom the results, we find that the rate constants for the various crosslinking agent systems are in the order of DMDHEU > DMDHEU-aspartic acid > DMDHEU-glutamic acid. The energies needed to crosslink are in the rank of DMDHEU-glutamic acid > DMDHEU-aspartic acid > DMDHEU. The values of enthalpy and entropy for DMDHEU are lower than those for DMDHEU-alpha-amino acids, and enthalpy values for DMDHEU are significantly lower than those for DMDHEU-alpha-amino acids. The data of various activation parameters reveal that the reaction state of DMDHEU-alpha-amino acids is different from that of DMDHEU. Additionally, the reactions between aluminum sulfate and aspartic acid are confirmed by infrared spectra.
Our previous study [4, 13] showed that the -OH groups of both cellulose and dimethyloldihydroxyethyleneurea (DMDHRU) can react with the vinyl and/or epoxy group of alkyl di-allyl ammonium salts and the -COOH and -NH^sub 2^ of alpha-amino acids in the pad-dry-cure process. The physical properties and surface migration of DMDHEU-alkyl di-allyl ammonium salts and DMDHEU-alpha-amino acids are different from those for DMDHEU. It is well known that reaction rate constants are affected by varying the functional groups on crosslinking agents [1, 2, 7, 15]. Our recent study [5] showed that adding alkyl di-allyl ammonium salts to the aqueous solutions of DMDHEU did change the activation parameters of the crosslinking reaction.The effects of adding various alpha-amino acids in the aqueous padding solution of DMDHEU on the crosslinking reaction are interesting. Detailed information of the specific rate constants and other activation parameters for the DMDHEU-alpha-amino acids and DMDHEU treated fabrics is lacking. In this paper, we examine and discuss those activation parameters calculated using the method described by Ziifle et al. [2, 15].
Experimental
In this study, we used desized, scoured, and bleached cotton fabric with 60 ends (20’s) and 60 picks (20’s). The crosslinking agents were DMDHEU (dimethyloldihydroxyethyleneurea) and alpha-amino acids of aspartic acid and glutamic acid. Aluminum sulfate was reagent grade, as were the other chemicals.
For reaction kinetic studies, the cotton fabric samples were padded twice to about 90% wet pick-up with freshly prepared DMDHRU-alpha-amino acid solutions (0.36M, the mole ratio of DMDHEU to alpha-amino acids was 3 to 1) in the presence of the aluminum sulfate catalyst (0.036M). An queous padding solution of DMDHEU alone was also used for comparison. In order to obtain the changes in the bound nitrogen contents of the heated fabrics with the heating temperatures, padded fabric samples were heated at 80, 90, and 100°C for different time intervals, then soaped, washed, and dried. Nitrogen contents were determined using the Kjeldahl method.
Infrared spectra of the samples were obtained with a KBr disk technique [10]. Samples were prepared to a dry weight of 1.8 mg after storage in 1-dram vials over P^sub 2^O^sub 5^ for 3 days. Spectral-grade KBr (250-300 mg) was ground, transferred to individual sample vials, dried in an oven at approximately 200°C for several hours, and stored in an oven at 110°C. Samples were ground and mixed with the KBr and pressed in an evacuated die under suitable pressure. The IR spectra of aluminum sulfate, aspartic acid, and cured aluminum sulfate-aspartic acid (0.5 to 1 mole ratio of aluminum sulfate to aspartic acid was mixed, dissolved in water, then coated on a piece of glass and dried at 80°C) were examined to confirm the interaction of aluminum ion with the aspartic acid molecule in this study.
Results and Discussion
The data in Table 1 show the changes in the nitrogen content of cotton fabrics treated with DMDHEU-aspartic acid (sample, 1), DMDHEU-glutamic acid (sample 1), and DMDHEU (sample 0) with heating time. All samples were catalyzed by aluminum sulfate. The table reveals that the nitrogen contents of the treated fabrics increase with increased heating time for all cases. Figures 1, 2, and 3 show the relationships between the nitrogen contents and heating time intervals at different heating temperatures for samples 0, 1, and 2, respectively. The initial shape of slightly concave upward in all cases, which can be attributed to the time needed to raise the temperature of the fabric in the oven [2, 12]. The lower nitrogen bonded on the cotton fabrics for the DMDHEU-alphaamino acid crosslinking agents clearly reveal that the reaction between alpha-amino acids and cellulose molecules (and/or DMDHEU molecule) takes place only a little in the kinetic runs.
Semilogarithmic plots of (%N^sub 0^ - %N)/%N^sub 0^ versus heating time are shown in Figures 4-6 for samples 0, 1, and 2, respectively. %N^sub 0^ is the nitrogen content of the treated fabric after the pad-dry-cure process-padded to 90% wet pick-up, dried at 80°C for 5 minutes, and cured at 135°C for 3 minutes; the samples are thought to be fully cured at these conditions [8, 9]. %N is the bound nitrogen after a given time interval at the temperature indicated (80, 90, and 100°C). For all cases, straight lines are obtained, the linearity indicating that the reaction is pseudo-first-order for the time shown.