What foods are most likely to cause gas. How can you reduce gas without eliminating nutritious foods from your diet. What are some effective strategies for managing digestive discomfort caused by certain foods.

The Science Behind Gas Formation in the Digestive System

Gas is a natural byproduct of the digestive process. It forms when bacteria in the large intestine break down certain components of food that were not fully digested in the small intestine. While gas production is normal, excessive gas can lead to discomfort, bloating, and embarrassing situations. Understanding which foods are more likely to cause gas can help individuals manage their symptoms and make informed dietary choices.

How Does Gas Form in the Digestive Tract?

Gas formation in the digestive system primarily occurs through two mechanisms:

1. Swallowing air while eating or drinking
2. Bacterial fermentation of undigested food in the large intestine

When certain foods are not fully broken down in the small intestine, they pass into the large intestine where bacteria ferment them, producing various gases as a byproduct. These gases, including hydrogen, carbon dioxide, and methane, must then be expelled from the body, either through burping or flatulence.

Beans: The Notorious Gas-Producers

Beans are often the first food that comes to mind when thinking about gas-causing foods. This reputation is well-deserved, as beans contain high levels of raffinose, a complex sugar that the human body struggles to digest.

Why Do Beans Cause Gas?

The gas-producing effect of beans is due to their high content of raffinose, a complex sugar that humans lack the enzyme to digest properly. As a result, raffinose passes through the small intestine undigested and reaches the large intestine, where bacteria break it down, producing hydrogen, carbon dioxide, and methane gas.

Strategies to Reduce Gas from Beans

• Soak beans overnight before cooking to help reduce their gas-producing potential
• Try using over-the-counter products like Beano, which contain enzymes that help break down complex sugars
• Gradually increase your bean intake to allow your digestive system to adapt

Dairy Products and Lactose Intolerance

Dairy products are a common source of digestive discomfort for many people, particularly those with lactose intolerance. Lactose, the sugar found in milk and dairy products, requires the enzyme lactase for proper digestion. When individuals lack sufficient lactase, consuming dairy can lead to gas, bloating, and other digestive issues.

Identifying Lactose Intolerance

Lactose intolerance symptoms typically appear within 30 minutes to 2 hours after consuming dairy products. Common signs include:

• Bloating
• Gas
• Abdominal cramps
• Diarrhea

Managing Dairy-Related Gas

For those who suspect lactose intolerance, several strategies can help manage symptoms:

1. Try lactose-free dairy products
2. Use enzyme supplements (like Lactaid) before consuming dairy
3. Explore non-dairy alternatives such as almond milk, soy milk, or oat milk
4. Gradually introduce small amounts of dairy to help your body adjust

Whole Grains: A Double-Edged Sword for Digestive Health

Whole grains are an essential part of a healthy diet, providing fiber, vitamins, and minerals. However, they can also be a significant source of gas for some individuals. The complex carbohydrates in whole grains, including fiber, raffinose, and starch, can be challenging for the body to break down completely.

Which Whole Grains Are Most Likely to Cause Gas?

While all whole grains have the potential to cause gas, some are more likely to do so than others. Grains that commonly cause gas include:

• Wheat
• Barley
• Rye
• Oats

Interestingly, rice is the only grain that typically doesn’t cause gas, making it a good option for those with sensitive digestive systems.

Balancing the Benefits and Drawbacks of Whole Grains

Despite their potential to cause gas, whole grains offer numerous health benefits and should not be eliminated from the diet without good reason. To reduce gas while still enjoying whole grains:

1. Start with small portions and gradually increase intake
2. Drink plenty of water to help move fiber through the digestive system
3. Consider soaking or sprouting grains before cooking to improve digestibility
4. Experiment with different types of whole grains to find those that agree best with your system

Cruciferous Vegetables: Nutritional Powerhouses with a Gassy Reputation

Cruciferous vegetables, including Brussels sprouts, broccoli, cabbage, and cauliflower, are known for their impressive nutritional profiles. However, they’re also infamous for causing excess gas in many individuals. Like beans, these vegetables contain raffinose, a complex sugar that can be difficult for the human digestive system to break down.

The Health Benefits of Cruciferous Vegetables

Despite their gas-producing potential, cruciferous vegetables offer numerous health benefits:

• High in fiber, vitamins, and minerals
• Rich in antioxidants and phytochemicals
• Associated with reduced risk of certain cancers
• Support heart health and digestive function

Strategies for Enjoying Cruciferous Vegetables with Less Gas

To reap the benefits of these nutritious vegetables while minimizing gas production:

1. Start with small portions and gradually increase intake
2. Cook vegetables thoroughly to break down some of the complex sugars
3. Consider using digestive enzyme supplements when consuming these vegetables
4. Experiment with different cooking methods, such as roasting or steaming, to find what works best for you

Carbonated Beverages: A Fizzy Source of Digestive Discomfort

Carbonated drinks, including sodas, sparkling water, and even some types of beer, can contribute significantly to gas and bloating. The bubbles in these beverages introduce extra air into the digestive system, which must be expelled one way or another.

How Do Carbonated Drinks Contribute to Gas?

Carbonated beverages cause gas through two main mechanisms:

1. Introducing additional air into the digestive system
2. Stimulating the release of excess stomach acid, which can lead to increased gas production

Alternatives to Carbonated Beverages

For those looking to reduce gas caused by carbonated drinks, consider these alternatives:

• Still water (plain or infused with fruits or herbs)
• Herbal teas
• Fresh fruit juices (in moderation)
• Smoothies made with non-gassy fruits and vegetables

Fruits High in Fructose and Sorbitol: Sweet but Potentially Troublesome

While fruits are an essential part of a healthy diet, some varieties can cause gas due to their high content of fructose (a natural sugar) and sorbitol (a sugar alcohol). These compounds can be challenging for the body to digest, leading to fermentation in the large intestine and subsequent gas production.

Which Fruits Are Most Likely to Cause Gas?

Fruits that commonly cause gas include:

• Apples
• Pears
• Peaches
• Prunes
• Mangoes
• Watermelon

Enjoying Fruits While Minimizing Gas

To reduce gas while still benefiting from the nutritional value of fruits:

1. Opt for lower fructose fruits like berries, citrus fruits, and bananas
2. Consume smaller portions of high-fructose fruits
3. Consider cooking fruits, which can make them easier to digest
4. Pair fruits with protein or healthy fats to slow down digestion and reduce gas formation

Hidden Gas-Producers: Processed Foods and Artificial Sweeteners

Processed foods and artificial sweeteners can be unexpected sources of gas for many individuals. These products often contain a variety of ingredients that can be difficult for the body to digest, leading to increased gas production.

How Do Processed Foods Contribute to Gas?

Processed foods can cause gas through several mechanisms:

• High content of refined sugars and artificial sweeteners
• Presence of additives and preservatives that may irritate the digestive system
• Combination of ingredients that can be challenging to digest simultaneously

Identifying and Avoiding Gas-Causing Ingredients

To reduce gas from processed foods and artificial sweeteners:

1. Read food labels carefully and avoid products with high fructose corn syrup, sorbitol, and other sugar alcohols
2. Choose whole, unprocessed foods whenever possible
3. Prepare meals at home using fresh ingredients to control what goes into your food
4. Gradually reduce intake of artificial sweeteners and observe any changes in gas production

By understanding which foods are most likely to cause gas and implementing strategies to manage their consumption, individuals can enjoy a varied diet while minimizing digestive discomfort. Remember that everyone’s digestive system is unique, so it’s essential to pay attention to your body’s responses and adjust your diet accordingly. If gas continues to be a significant problem despite dietary changes, consult with a healthcare professional to rule out any underlying digestive issues.

10 Foods That Cause Gas

Certain foods, including beans, dairy, and certain fruits and vegetables may cause gas. Some over-the-counter products and practices may help reduce it.

Whether we’d like to admit it or not, everyone gets gas from time to time. Gas is caused by swallowing air and the breakdown of food in your digestive tract. The consequences are usually burping, feeling bloated, or passing gas. On average, most people pass gas at least 14 times per day. Some people have more gas than others, which may be uncomfortable or embarrassing. However, gas itself is not cause for alarm.

Did you think we missed any foods? Share them here »

If you’re experiencing a lot of gas and bloating, making changes to your diet can help. Here are the types of foods that cause the most gas. Keep in mind that people’s bodies react differently, so if you make changes to your diet, avoid the foods you react to the most.

When you think of foods that cause gas, beans are probably at the top of the list. Beans contain a lot of raffinose, which is a complex sugar that the body has trouble digesting. Raffinose passes through the small intestines into the large intestines where bacteria break it down, producing hydrogen, carbon dioxide, and methane gas, which exits through the rectum.

To reduce gas without cutting out beans, one study found the over-the-counter product, Beano, effectively reduced gas for some people. Soaking the beans overnight can also help reduce gas.

Lactose is a sugar that’s found in milk and most dairy products, including cheese and ice cream. People who don’t produce enough of the enzyme lactase have difficulty digesting lactose, which is known as lactose intolerance. Increased gas is one symptom of lactose intolerance. If you suspect you’re lactose intolerant, you might reduce your symptoms by trying nondairy replacements such as almond milk or soy “dairy” products, or taking a lactase tablet before eating foods with lactose.

Whole grains such as wheat and oats contain fiber, raffinose, and starch. All of these are broken down by bacteria in the large intestine, which leads to gas. In fact, rice is the only grain that doesn’t cause gas.

Certain vegetables such as Brussels sprouts, broccoli, cabbage, asparagus, and cauliflower are known to cause excess gas. Like beans, these vegetables also contain the complex sugar, raffinose. However, these are very healthy foods, so you may want to talk with your doctor before eliminating them from your diet.

Sodas and other carbonated drinks can add significantly to the amount of air you swallow. When air gets into your digestive tract, it has to pass through somehow. This causes burping and may also increase how much gas you pass. Swapping soda for juice, tea, or water (with no carbonation) may help you reduce gas.

Fruits such as apples, peaches, pears, and prunes contain the natural sugar alcohol, sorbitol, which the body has trouble digesting. Many fruits also have soluble fiber, which is a type of fiber that dissolves in water. Sorbitol and soluble fiber must both also pass through the large intestines, where bacteria break them down to create hydrogen, carbon dioxide, and methane gas.

Like carbonated drinks, sucking on hard candy can cause you to swallow extra air. Many candies also use sorbitol as a sweetener. These two factors can contribute to extra gas.

Onions contain a natural sugar called fructose. Like raffinose and sorbitol, fructose contributes to gas when bacteria in the intestines break it down.

Gum seems an unlikely source for gas, but chewing it can make you swallow more air. Many sugar-free gums are also sweetened with sugar alcohols that are harder to digest, such as sorbitol, mannitol, and xylitol. If you burp a lot, your doctor may recommend that you stop chewing gum to reduce gas.

Processed foods are packaged goods, such as breads, snack foods, cereal, and salad dressing. These contain a variety of ingredients, including fructose and lactose. This combination can lead to increased gas.

8 Ways to Avoid Bloating After Eating

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After a wonderful meal, you’re ready to relax and move on to the rest of your day. But then it happens: Your pants feel tight, and your stomach feels twice its normal size. On top of that, you may even experience cramps, gas, and belching. These are all possible signs of bloating.

While some underlying health conditions sometimes cause bloating, it’s a common occurrence that may be fixed with changes to your eating habits. Here are some tips to help you avoid those uncomfortable bloating episodes.

Carbohydrates, fats, and proteins can all be triggers of bloating. However, certain foods may be worse than others, and digestive issues will vary from person to person. Common bloating triggers include:

• apples
• beans
• cruciferous vegetables such as broccoli, cauliflower, and cabbage
• dairy products
• lettuce
• onions
• peaches and pears

You don’t have to avoid these foods altogether. Instead, try eating one potential culprit at a time and reduce the quantity you eat if it causes any bloating. Get to know which foods in particular are causing issues. Here’s a list of 13 low-carb fruits and vegetables to eat.

Fibrous foods such as whole grains, beans, and legumes can be a common cause of bloating. While these foods are promoted as healthier than their refined counterparts, their high-fiber content leads to bloat in some people.

Fiber is an important part of a heart-healthy diet, but you should gradually increase the amount you eat. For example, instead of switching from refined white grains to whole grains all at once, try replacing one product at a time to see how your body reacts.

By now, you know that eating too much salt can cause a slew of long-term health problems, including high blood pressure. In the short term, an extra salty meal may lead to water retention, which causes bloating.

You can avoid excess sodium in your diet by using flavorful herbs instead of salt, and by reducing the amount of processed and packaged foods you eat.

Here’s another pitfall of high-fat meals: They take longer for your body to process. The fat moves slowly through the digestive tract, and this may cause bloat.

It also explains why your stomach feels like it wants to burst out of your clothing after a large, fattening meal, such as the traditional Thanksgiving dinner.

Not all fats are created equal though, and digestion can be different between trans, saturated, and unsaturated fats.

Pay attention to which types of fat may cause issues. If fried foods, which have saturated and trans fats, tend to cause issues, try a healthier, unsaturated fat such as avocado or nuts and seeds.

Limiting your intake of fried, processed, and refined foods can help with digestion and overall health.

Carbonated water and soda are leading culprits for bloating in the beverage world. As you consume these drinks, carbon dioxide gas builds up in your body. This can quickly lead to bloating, especially if you drink them quickly.

Plain water is best. Try adding a slice of lemon for some flavor without the bloat.

You may have a habit of scarfing down your food if you’re in a time crunch. You also swallow air when you do this, which can lead to gas retention.

You can beat the bloat by taking your time eating. Eating more slowly can also reduce your overall food intake, so you may find yourself tightening your belt rather than loosening it!

There is no denying the benefits of exercise for your overall health and well-being. As an added bonus, working out can also reduce the gas buildup that contributes to bloating. A short walk can alleviate bloating after a meal, if you’re up for it.

Digestive enzymes help break down food and absorb nutrients. One example is the anti-gas supplement a-galactosidase, which helps prevent gas buildup from certain foods.

While they’re usually advertised to prevent belching and flatulence, these pills also can relieve bloating. Depending on the brand, you may take these supplements on a daily basis, or as needed before meals per doctor’s orders.

There are many other digestive enzymes, including amylase, lipase, and protease, that you can take as well. These help break down carbs, fats, and proteins and can be found separately or in combination products over the counter.

In addition, probiotic supplements can help regulate the good bacteria in your gut, which can decrease bloat.

Shop for probiotic supplements.

Bloating is usually just your body’s natural response to certain foods or habits. But when bloating doesn’t ease up with dietary changes, it may be time to address the problem with your doctor.

This is especially the case if the bloating is accompanied with severe cramps and abnormal bowel movements. Possible underlying health problems include:

• Crohn’s disease
• food allergies
• irritable bowel syndrome (IBS)
• lactose intolerance
• celiac disease
• gluten sensitivity

You don’t have to put up with bloating forever. Remember that determining the cause will eventually help prevent uncomfortable bloating episodes. Work with a registered dietitian if you need extra help finding the right foods or supplement to help ease bloat.

Did You Know?

The American Heart Association and the U.S. Food and Drug Administration recommend no more than 2,300 mg of sodium per day — about the size of a teaspoon of salt. People who are more sensitive to sodium effects, such as those with hypertension or prehypertension, should aim for 1,500 mg or less.

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Various methods of curing adhesives.

Bulk and surface polymerization.

Most of the adhesives shown here are reactive polymers. Their transition from a liquid to a solid state is carried out as a result of various polymerization reactions. There are no universal adhesives in industrial production, each case requires a specific adhesive bond, here you will find a wide range of adhesives designed for specific uses and with special curing properties. The curing process of adhesives, depending on the method of polymerization, can be classified as follows:

• curing by anaerobic reaction

• as a result of exposure to ultraviolet rays (UV) (second polymerization method)

• by anionic reaction (cyanoacrylates)

• activated (modified acrylics)

• by moisture curing (urethanes, silicones)

• by heat curing (epoxies)

Anaerobic Reaction Curing Adhesives

Anaerobic adhesives are single-component materials that cure at room temperature without contact with oxygen. The curing component, which is in a liquid state, is inactive for as long as it is in contact with atmospheric oxygen. After the access of atmospheric oxygen to the adhesive stops, for example, after joining the parts, the process of rapid curing starts, especially if there is simultaneous contact with the metal. This process can be represented as follows: after the cessation of the influx of atmospheric oxygen, under the influence of metal ions (Fe, Cu), free radicals are formed that trigger the polymerization mechanism (Fig. 2).

Due to the capillary effect, adhesives can penetrate the smallest gaps. The adhesive is cured and wedged into the rough surface of the parts. The polymerization process is additionally stimulated as a result of contact between the adhesive and metal surfaces acting as a catalyst (Fig. 3). Due to the fact that passive materials have zero or minimal catalytic effect, activators are needed to achieve and accelerate the final polymerization. In such cases, one or both surfaces to be joined are first coated with a liquid activator and then with an adhesive. The components of the activator and inactive adhesive must not be mixed in advance.

Anaerobic adhesives have the following properties:

• extremely high strength

• good temperature resistance (-55 to +230 degrees Celsius)

• fast curing

• due to its one-component nature, easy to apply with the automatic dispenser

• finishing parts not required; allowed surface roughness (Ra) within – 8 – 40 microns

• parallel effect high and chemical resistance sealing

• good vibration resistance

• excellent resistance to dynamic loads

Anaerobic polymerization process for adhesives:

When exposed to oxygen, the adhesive is in a liquid state (1). After the adhesive enters the gap, the supply of oxygen stops (2), peroxides, as a result of reaction with metal ions, turn into free radicals. Free radicals stimulate the formation of polymer chains (3). The final curing (4) results in a solid structure consisting of crosslinked polymer chains.

* Use activator

to accelerate polymerization. 3: Impact on anaerobic polymerization of active and passive materials.

The curing process, especially the speed at which anaerobic products cure, depends mainly on:

• types of surfaces to be joined (fig. 4)

• gap dimensions between glued surfaces (Fig. 5)

• medium temperature (Fig. 6)

• type of activator used (fig. 7)

Dependence of the cure rate on the type of bonded material

Dependence of the cure rate on the gap between the surfaces

Effect of temperature on the cure rate

90 002 Effect on anaerobic polymerization of active and passive materials

About ultraviolet (UV) curing adhesives

The time it takes these adhesives to cure is affected by the intensity and length of the UV wavelengths. UV curing requires careful product selection and appropriate exposure to radiation. Photoinitiators are cleaved under the influence of UV rays. Free radicals, after transition to a different state, begin the polymerization process. Loctite’s UV curing systems emit a radiation spectrum suitable for Loctite products.

UV curing used for:

• bulk polymerization

• surface curing

• auxiliary polymerization

Polymerization of UV adhesives: 1 – in liquid state – photoinitiators and monomers do not react with each other. 2 – when exposed to UV, the transition of photoinitiators into free radicals occurs, 3 – which initiate linear polymerization. 4 – during the final curing, cross-linking of polymer chains occurs.

Electromagnetic spectrum diagram. Illustrates the types of radiation and waves of the electromagnetic spectrum with a suitable length.

About Bulk Cure

To achieve the greatest depth of cure, the UV wavelength should be 300 – 400 nanometers (UVA light, near ultraviolet) (Fig. 10).

About surface curing

The surface curing process is especially important when bonding or sealing with UV materials. If the UV source is not properly selected, the surfaces may not cure. To avoid this, the UV source must emit intense wavelengths of less than 280 nanometers (UVC light). This will effectively prevent unwanted contact between atmospheric oxygen (which does not allow the composition to polymerize on the surface) and the bonded surface, (Fig. 11).

Loctite UV systems use a high energy spectrum to ensure reliable polymerization and a non-tacky surface.

About the Co-Cure System

UV rays often do not reach all areas treated with adhesive. Therefore Loctite has developed adhesives containing curing aid systems for areas not exposed to UV:

• anaerobic
• humid
• activator
• thermal

Standard depth curing UV adhesives.

Standard curing UV adhesives surface.

It has already been mentioned that the correct wavelength and intensity of the radiation at the bonding point is necessary for UV curing. This means that the UV transparency of different materials (Fig. 12) will be one of the important criteria when choosing the most suitable adhesive. Special visible light curing adhesives have been developed for bonding parts made from PC (polycarbonate), PVC (polyvinyl chloride) and similar materials. Such adhesives are able to cure when exposed to UVA light, however, the highest quality polymerization is achieved when exposed to radiation with a high intensity – about 420 nanometers (visible part of the spectrum).

Transparency of plastics and glass for UV light.

UV curing adhesives have the following characteristics:

• high strength

• good gap filling

• very high cure rate up to manual strength level

• good environmental resistance

• ease of application using automatic dispensers, because these adhesives are one-component

About Cyanoacrylate Anionic Curing Adhesives

One-component cyanoacrylate adhesives polymerize during contact with slightly alkaline surfaces. As a rule, the ambient humidity (on the surface of the bonded materials and in the air) is sufficient to initiate the polymerization process and achieve a strong bond in a few seconds.

Moisture present on the joint surface neutralizes the stabilizer in the adhesive and starts the polymerization process between the surfaces. In order to obtain the fastest polymerization to manual strength, it is desirable to create zero gap conditions. Optimum results are obtained when the relative humidity of the working environment is between 40 and 60 percent and the temperature is at room temperature. Lower humidity increases the curing time (fig. 13) and higher humidity speeds up the process, but this acceleration can adversely affect the final bond strength.

The most common applications for UV sealants and adhesives are:

For bonding glass to metal or glass	3491
For bonding transparent plastics	3106, 3103, 322
For sealing electronic components (relays, etc. )	3016
For gluing electronic components – surface mounting	3608
For protective coating of printed circuit boards (in electronics)	394, 5293
For sealing/bonding in high temperature applications	5091, 5088
For spigot joints of metal parts and for additional UV curing adhesive to create a quick fix	661
For bonding metal and plastic parts and additional UV curing adhesive to create a fast fix	3920, 366

The strength of the bonding joint is generally not affected by dry air. With an increase in the polymerization process, the rate of production slows down. Using air recirculation systems in the workplace, you can create the desired level of humidity. On acidic surfaces (pH < 7) the curing process may slow down or even stop, while on alkaline surfaces (pH > 7) curing will be accelerated.

Influence of relative humidity on the polymerization of cyanoacrylate adhesives

The polymerization process in cyanoacrylate adhesives proceeds as follows: some consistency (1). Surface moisture neutralizes the stabilizer (2) and starts the polymerization process (3). The formation of a large number of polymer chains begins, which are firmly intertwined (4).

After applying the adhesive, the parts should be connected as quickly as possible, as the polymerization process starts after a few seconds. The time during which the free movement of parts is possible depends on the atmospheric humidity, the humidity of the surfaces to be bonded, the type of adhesive and the ambient temperature. Due to their rather high curing speed, cyanoacrylate adhesives can be used when bonding small parts.

Cyanoacrylate adhesives are very economical in use. To achieve the best bonding, it is enough to apply glue to any of the surfaces to be bonded in a small amount, sufficient to fill the gap.

We have already mentioned that the rate of curing is affected by the humidity of the bonding surface. Activators can be used to eliminate dependence on atmospheric humidity and to speed up curing. Excess adhesive or drops of adhesive that have not reacted (for example, when gluing wires) can also be cured in a few seconds using activators.

Activators for cyanoacrylate adhesives:

Cyanoacrylates have the following properties:

• very high tensile and shear strength

• very fast curing (set in seconds)

• can be used on almost any material

• good aging resistance

Cyanoacrylate applications:

About activator cured adhesives (modified acrylics)

These adhesives cure at room temperature with activators. Depending on the type of adhesive used, both the activator and the adhesive can be applied to the surface either individually or after pre-mixing. There are adhesives used with low viscosity activators. These formulations are not recommended to be pre-mixed. The activator and adhesive are always applied separately to the surfaces to be bonded. After joining the parts, the adhesive begins to cure.

The same density of adhesive and activator prevents the components from running off. These are 2-component systems in which adhesive and activator are applied separately – strip on strip or strip on strip. When connecting the parts to be glued, the mixing of the components occurs when one part is shifted relative to the other. If the adhesive, combined with the activator, remains viable for 5 minutes or more, then a static mixer is used for mixing. This has the advantage that the pre-mixed adhesive is already ready and there is no need to move already connected parts.

Application conditions determine the choice of one of the methods: a) or b). Parts A and B of the adhesive should in any case be mixed at the time of joining.

Modified acrylic adhesives have the following features:

• very high tensile and shear strength

• good impact resistance

• wide operating temperature range: -55 – +120 degrees Celsius

• the ability to bond almost any material

• good gap filling (particularly evident with premixed acrylics)

• good environmental resistance

Applications for modified acrylic adhesives:

About Ambient Humidity Curing Adhesives

These types of adhesives/sealants generally cure by a condensation reaction, the reaction of the compound with ambient humidity.

There are two main types of chemical adhesives in this category:

1. Silicones:

These materials are cured by atmospheric humidity at room temperature. Unlike the anionic reaction of cyanoacrylates, in which moisture is neutralized by a stabilizer, silicones use water molecules to create intermolecular bonds. That is, water molecules must enter the silicone in the place where the vulcanization process will take place. After water molecules come into contact with silicone molecules, a by-product is formed.

The chemical composition of the polymerization components affects the properties of the resulting by-product, which can be neutral (eg alcohol or oxime), basic (eg amine), or acidic (eg acetic acid).

The cure rate of these adhesives is affected by relative humidity.

The nature of the polymerization mechanism provides silicone vulcanization from the surface layer into the depth of the bonded seam. Due to the need for moisture to enter the place of formation of intermolecular bonds, the polymerization depth is limited to 10-15 millimeters.

Relationship between relative humidity and polymerization rate.

Cured silicones (or silicone elastomers) have the following properties:

• excellent temperature resistance (over 230 degrees Celsius)

• elasticity, elasticity, high extensibility

• come from low modulus to medium

• are effective sealants for use in a variety of fluids

• excellent gap filling

Fig. 17: Typical silicone bonding.

Applications for silicones:

About polyurethanes:

In most cases, the formation of polyurethanes occurs as a result of the reaction between water and additives that contain isocyanate groups. In silicones, water molecules must be incorporated into the adhesive to form a crosslink. Similarly, the polymerization process occurs in polyurethanes, with the exception of the formation of by-products as a result of the reaction. The rate of polymerization of polyurethanes is also affected by relative humidity.

Polyurethanes have the following properties:

• superior strength

• elasticity, high extensibility

• excellent gap filling

• paintable after curing

• good chemical resistance

To obtain the best and highest adhesion strength, suitable cleaners and primers (adhesion accelerators) must be used. The type of surface determines the use of certain primers.

About heat curing adhesives

Heat curing generally uses single component adhesives. An example is the heat polymerization of epoxy resins. The temperature of the polymerization process depends on the type of composition used. The minimum polymerization temperature is usually in the order of 100 degrees Celsius.

The polymerization temperature and the polymerization time are related: as the temperature increases, the polymerization time decreases. As a rule, a minimum temperature is required to activate the hardener and start the polymerization process.

Applications for polyurethanes:

Curing time versus temperature.

In addition to adhesives that cure solely by heat, there are other types of adhesives that use heat curing as an additional mechanism. For example, In anaerobic adhesives, the curing process occurs at a temperature of 120 degrees Celsius.