Blown Film Extrusion Introduction

Blown Film Extrusion Introduction
Blown film extrusion is a technology that is the most common method to make plastic films, especially for the packaging industry. The process involves extruding a tube of molten polymer through a die and inflating to several times its initial diameter to form a thin film bubble. This bubble is then collapsed and used as a lay-flat film or can be made into bags. Usually polyethylene is used with this process, and other materials can be used as blends with these polymers. A diagram of a polyethylene chain is shown in Figure 1 to the right.
Background Theory on Polymers

In the cooling step of blown film extrusion, the amorphous, transparent melt crystallizes to form a translucent, hazy, or opaque film. The point where opacity begins in the bubble is known as the frost line. 
Fig 1: Model of polytheylene chain frompolyethylene Wikipedia article.The frost line height is controlled by several parameters: the air flow, film speed, and temperature difference between the film and the surroundings. Properties of the film, such as tensile strength, flexural strength, toughness, and optical properties, drastically change depending on the orientation of the molecules. As the transverse or hoop direction properties increase, the machine or longitudinal direction properties decrease. For instance, if all the molecules were aligned in the machine direction, it would be easy to tear the film in that direction, and very difficult in the transverse direction.

The Film Blowing machine Process

Fig 2: Schematic of set-up from User:J.Chiang.

Typically, blown film extrusion is carried out vertically upwards, however horizontal and downward extrusion processes are now becoming more common. Figure 2 shows a schematic of the set-up for blown film extrusion. This procedure consists of four main steps: The polymer material starts in a pellet form, which are successively compacted and melted to form a continuous, viscous liquid. This molten plastic is then forced, or extruded, through an annular die. Air is injected through a hole in the center of the die, and the pressure causes the extruded melt to expand into a bubble. The air entering the bubble replaces air leaving it, so that even and constant pressure is maintained to ensure uniform thickness of the film. The bubble is pulled continually upwards from the die and a cooling ring blows air onto the film. The film can also be cooled from the inside using internal bubble cooling. This reduces the temperature inside the bubble, while maintaining the bubble diameter. After solidification at the frost line, the film moves into a set of nip rollers which collapse the bubble and flatten it into two flat film layers. The puller rolls pull the film onto windup rollers. The film passes through idler rolls during this process to ensure that there is uniform tension in the film. Between the nip rollers and the windup rollers, the film may pass through a treatment centre, depending on the application. During this stage, the film may be slit to form one or two films, or surface treated. Advantages Blown film generally has a better balance of mechanical properties than cast or extruded films because it is drawn in both the transverse and machine directions. Mechanical properties of the thin film include tensile and flexural strength, and toughness. The nearly uniform properties in both directions allow for maximum toughness in the film.
Blown film extrusion can be used to make one large film, two smaller ones, or tubes that can be made into bags. Also, one die can make many different widths and sizes without significant trimming. This high level of flexibility in the process leads to less scrap material and higher productivity. Blown films also require lower melting temperatures than cast extrusion. Measured at the die opening, the temperature of cast film is about 220 C, where as the temperature of blown film is about 135 C. Furthermore, the cost of the equipment is approximately 50% of a cast line.

Blown Film Extrusion Disadvantages Blown film has a less effective cooling process than flat film. Flat film cooling is done by means of chill rolls or water, which have significantly higher specific heat capacities than the air that is used in the blown film cooling process. The higher specific heat capacity allows the substance to absorb more heat with less change in the substance temperature. Compared to cast film, blown film has a more complicated and less accurate method to control film thickness; cast film has a thickness variation of 1 to 2% versus the 3 to 4% for blown film. The resins used for casting typically have a lower melt flow index, which is the amount of polymer that can be forced through a standard die in 10 minutes according to a standard procedure. The melt flow index for cast film is about 5.0 g/10 min where as for blown film it is about 1.0 g/10 min. Consequently, the production rates for cast film are higher: cast film lines can reach production rates of up to 300m/min where as blown film lines are usually less than half this value. And finally, cast film has better optical properties, including transparency, haze, and gloss.

Common Problems Air entrapment between film layers and rollers – this may cause film scratching or wrinkling, or processing problems when winding up the film due to reduced friction. Possible solutions to this is using a vacuum to remove entrapped air or by using winding rolls with a diamond shaped groove in the rubber cover to increase surface area and decrease amount of entrapped air in the film. Large output fluctuations from the die – this causes thickness variations, and can be prevented by keeping the extruder clean and by using more consistently shaped pellets in the extruder. Melt fractures – these appear as roughness or wavy lines on the film surface, and can be eliminated by lowering the viscosity of the polymer melt. This can be done by increasing the melting temperature or by adding an internal lubricant to the material composition. Thickness variations in the film – this can be avoided by centering the die in the extrusion line before every run, adjusting the air speed of the cooling system, or by using heated die lips. Die lines on the surface of the film – this defect reduces the aesthetic appeal of the film, reduces optical properties, and weakens mechanical properties such as tear strength. This can usually be avoided by routinely cleaning the inner surfaces of the die and by refinishing scratched or roughened flow surfaces. Gels – these defects are small, hard globules encapsulated in the film or stuck on the film surface and reduce the aesthetic appeal of the film and cause stress concentration points which may result in premature failure. These are caused by overheating to the point of polymer degradation in the die, and can therefore be avoided by cleaning the inner surfaces of the die on a regular basis. Optimization of the Process Coextrusion One way to improve the line efficiency of blown film extrusion is to implement coextrusion. This is the process of extruding two or more materials simultaneously through a single die. The orifices in the die are arranged such that the layers merge together before cooling. This process saves time because it extrudes two or more layers at the same time, and it provides a method with fewer steps to produce multilayer films. The production rate for a coextruded multilayer film of three layers is about 65m/min, and the production rate for a single layer of blown film is about 130m/min. Thus, in order to produce 10 000m of a three layer multilayer film, it would take almost 4 hours using a single layer blown film process, and only 2 and a half hours using the coextrusion process. Furthermore, the film produced from the single layer process would require an extra step to glue the layers together using some sort of adhesive. Coextrusion is the least expensive means of producing layered films and the coextrusion system is capable of quick changeovers to minimize production line down time.

Minimizing the Melt Temperature
The efficiency of blown film extrusion can be improved by minimizing the temperature of the polymer melt. Reduction of the melt temperature causes the melt to require less heating in the extruder. Normal extrusion conditions have a melting temperature at about 190 C despite the fact that the temperature of the melt only needs to be about 135 C. However, it is not always practical to decrease the melting temperature by that much. By decreasing the melt temperature 2 to 20 C, the motor load can be decreased by about 1 to 10%. Furthermore, reduction of the melt temperature causes less need for cooling, so there is a reduced use of the cooling system. Moreover, removing heat from the bubble is usually the rate-limiting factor in this extrusion process, so by having less heat in the polymer to remove, the rate of the process can be increased, thus yielding higher productivity. A way to maintain the melt temperature at a minimum is to choose an extruder that is matched to the specific processing conditions, such as the material of the melt, pressure, and throughput.

Heated Extrusion Die Lips
Typically, solutions to melt fractures involve decreasing the output or increasing the melt temperature to decrease the shear stress in the extruder. Both of these methods are not ideal because they both reduce the efficiency of the blown film line. Heated extrusion die lips can solve this problem. This targeted heating method allows for film extruders to be run at higher production rates with narrower die gaps while eliminating melt fractures. Direct heat is applied to the surface of the polymer melt as it exits the die so that viscosity is reduced. Therefore, melt fractures, which are caused when trying to extrude too much of the polymer at one time, will no longer act as a limiting factor to increasing the production rate. Furthermore, heated die lips use less energy than increasing the melting temperature because only the surface of the melt is heated and not the bulk of the liquid. Another benefit of using heated die lips is that thickness variations can be controlled by adding heat to certain areas along the die circumference to make the film at that position thinner. This would ensure that no excess material is used.
Determine how much energy each of these processes can save per given volume of material. 

Above article from www.appropedia.org

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Learning Benefits of Online Cannabis Dispensaries

There are many changes currently been brought by advancing technology. You will note that acquisition of the marijuana products has become quite easy due to the improvement of technology. The invention of the internet has also been the main reason unto the popularity of the online dispensary. You are assured of obtaining multiple cannabis products with a few clicks on your networks. You will need to have sufficient packages to be able to acquire and obtain the products available for sale.

It is simple to obtain an extensive range of marijuana products if you do it online. You will note that the numbers of suppliers approved to sell the marijuana products are rising day in day out. Besides, the best way to find a clinic that sells marijuana is by use of Google maps. It is crucial that you check the customer reviews of all the available cannabis dispensaries. You can get in touch with the right dispensary based on your conclusions.

The good thing with the online dispensary is the fact they sell products which have been legalised by the relevant authorities. With online shopping, it is also possible for such patients to acquire the products without any hassles. You need to adapt the online shopping if you want to access the benefits that result. Currently, the Medical cannabis sector has been improving at a considerable rate. The internet comes in handy in enabling cannabis entrepreneurs to record an increase in the profits and revenue.

You can see the meaning of running the dispensary the online way if you take time to research in depth. It is vital to note that getting to know the benefits of online cannabis dispensary if you take time to read this article. Highly valued marijuana products are obtained if you buy them from the online shop. You are assured of obtaining highly valued marijuana products if you buy them online. Clients can get satisfaction upon buying the marijuana products from online cannabis dispensary.

In case you want to acquire affordable marijuana products, it is advisable to shop online. Clients who shop online can buy products which are reasonably priced and those of high quality. In case you want to save more cost of travelling, it is advisable to go for online marijuana products. Clients who consider shopping for marijuana products get to enjoy the free shipping benefits to their destinations. It is also beneficial to shop from the online marijuana shop if you want the products to be wrapped uniquely.

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Waist Training Tips

When you need to know how to waist train, you shall have so much to learn. This shall be necessary even before you buy a waist trainer. Here are some key areas that shall need your attention.
The comfort levels of the waist trainer are an important consideration. Since you shall be wearing it for a while, it needs not to be uncomfortable throughout that period. You need to for one know where the pins and hooks are located, to make it easy for you to wear it. The fabric type used should be durable and breathable. You need to then check that the boning, which is the support and structure of the trainer, is durable. You are better off going for steel and not plastic. There should be no errors in getting those measurements if the trainer is to work well for you. You need to make sure you can breathe and move with no restrictions. There are other comfort choices to make, which you shall find on this site.
You need to then be clear on your style. You shall find a wide range of styles to choose from in the market. You will find things like the over-bust style, which works well for those with bigger chests. The under-bust is less restrictive, and thus can be worn for longer. If you shall find yourself doing plenty of vigorous activities such as a workout, then you need to go for the rubber or latex choices.
The size of the waist trainer is another important consideration. This shall determine how well the waist trainer chosen shall work for you. You shall suffer health-wise if you choose something not right. Use your natural waist as a measure of the right size to buy. This shall then allow you to pick one that is about 5 inches smaller than what your natural waist measurement was. You need to also consider your torso length. You need to settle only for one that fits well, no matter how long or short your torso happens to be. This length is a measure of the distance between the lower part of your breast and the point where your leg bends naturally when you lift it. but for those who shall be partaking in more vigorous pastimes like exercising, they will need to go for something a bit shorter. This will see them move with less strain each time.
Another important consideration is how you shall be wearing the waist trainer. This calls for you to determine the style and duration of wearing it. You will be glad to learn that waist trainers can be worn under your clothes, as long as you pick the right one. It is however important that if you shall wear it under your clothes, to go for the most comfortable fabrics you can find.

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Discovering The Truth About Services

How to Choose a Suitable Web Development Company

Most businesses are at much speed when hiring web development companies, something they most regret for. By considering the factors highlighted below, you will choose a suitable web development company.

Consider the web of the website development company. The website of a web development company should be one of the things you get drawn most to hiring it. It is crucial to ensure that the company you are hiring has a website that is in line with the claims a company makes. If the website of the company is substandard and has errors they include grammatical and spelling, do not settle for it. If the company has not delivered on its website, it cannot deliver on yours.

Make sure you are certain about what your business needs. Before settling for any website development company, ensure you are clear about your requirements. This is crucial in hiring a company whose website generating strategies fulfill your requirements. It is this wise to know what your business is in need of and the reason it is necessary for it to have a website.

Ensure you are attentive to the level of competency of a company. Before making any commitment, you need to check the methodology a web development company uses. You have to meet the team that will have the responsibility of working on your project. Ensure you are keen to know the strengths and weaknesses of the developers to know if they suit for your projects. In addition, check the digital marketing strategies a potential company will apply in your project.

Contact past clients for testimonials. Before you choose a web development company, check testimonials of its old clients. Make sure you know past customer’s experience in meeting deadlines, project management, and availability. Testimonials will help you access honest information concerning the performance of a company and the quality of services it offers.

Check if the company is proficient in digital marketing. Check beforehand whether a potential company offers digital marketing services. A suitable web development company will have tools for digital advertising such as pay-per-click advertising, mobile advertising, video display ads, and banner ads.

Pay attention to web hosting. You should be attentive as to whether a web development company provides hosting services for the webs it develops since this will save you from hassles of hiring different companies to do different works. If the company hosts, look into the security measures put in place to ensure your website is secure from viruses and hackers. Also, be attentive into if you will be provided with website backup.

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Why No One Talks About Attorneys Anymore

What are the Advantages of Finding the Best Law Firm?

If you know about the law, then you definitely know that without it, it is almost impossible for a society to function – this is why the law is held in high importance in most parts of the world. The law is very deep and broad, and one might not be surprised, only worried, when he or she brushes against it, and finds himself or herself facing a very serious court case. If you are facing an accusation for the first time, then, and you are feeling very worried because you know that it can entail really serious consequences, it is a good idea for you to find a good law firm which will give you the chance to get a lawyer to defend you. Those who find the best law firm in their area, then, can be sure to gain a lot of benefits from it.

The first thing that people will be able to gain when they find the best law firm is the benefit of getting help with a number of different cases. People might know that it is important to hire a specific lawyer for a specific case, whether it is medical malpractice, personal injury, offshore drilling accidents, family law, and so on. They will be happy to know that when they find a reputable law firm, they can find different lawyers who specialize in different areas.

Another thing that people will be able to gain when they find a law firm like this is the benefit of knowing that lawyers who work there will have so much experience. You can be sure that when you hire a lawyer with experience, nothing will be able to surprise him or her, having had so many cases that are just like yours. If you want to have the assurance that you do not end up lost and confused as you try to sort your case, then, you should hire a professional from a reputable law firm like this one.

One who hires a lawyer from the best law firm will also be glad to know that when he or she does so, it will be possible to enjoy the best peace of mind. The reason why this is so is because a good lawyer will be dedicated and passionate when it comes to protecting you.

If one needs help because he or she is facing serious charges, then, one should not settle for less than a law firm like this one, one that promises all of these satisfying benefits, and much more.

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Being Introduced To Contract Manufacturing And Its Advantages

Contract manufacturing is basically outsourcing a manufacturer to produce your goods. The use of this business strategy has increased rapidly over the years since it provides a lot of benefits to the business. In this article, you will know each of them.

For those who are just starting their business, it is highly advantageous to let an expert produce the goods. They may even give helpful advice for improvements and how you are able to cut down costs. Also, these manufacturers are will be in charge of handling your project from start to finish, detect flaws and spot potential risks throughout the supply chain.

They will have more skilled workers. There will be lesser errors during the production.

It will free up a lot of your time. You do not have to think about how you are able to create your products and you can focus on creating better marketing ideas or ways on how you are able to boost your sales.

It will not only save you time but also space. You can use this space for an office.

There will be a decrease in your operating expenses. This is due to the reason that you will not have to hire additional employees for the labor work. Also, manufacturers can purchase materials in bulk quantities thus they will be able to produce more goods at a lower price. This will result to cheaper offers that the customers would want.

You do not have to invest in the types of equipment needed to produce the goods. You do not have to purchase the raw materials since they will do it for you.

Established manufacturers frequently update the technology of their types of equipment. It is much easier for you to provide your customers with better service.

All of the products will undergo the required testing before being released to the public. They have complete knowledge of producing quality materials for various industries.

You will not have to ship the items yourself. There will be no risk of damaging the products during the delivery.

It is also a good idea to do contract manufacturing from foreign countries. You will have access to the raw materials that is not available in your country. A good example is Starbucks who is known to sell coffees. Starbucks does not own its own coffee farm which is why its coffee, cocoa, and tea ingredients are sourced from farmers and suppliers worldwide.

You are not the only one who can enjoy its benefits but also the manufacturer. You are able to create or help maintain jobs and stimulate the economy.

Finally, the manufacturers are able to produce more goods quickly since they have been doing it for a long time. They have already built a relationship with the suppliers. You are able to meet the number of demands from the customers.

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Why not learn more about Resurfacing?

Tips for Choosing the Best Bathtub Refinishing Services in Lincoln

Refinishing services are the best someone can get if you have a worn out bathtub. If you do not want to spend a lot of money on replacement, then it is important for you to do this rather than replacing everything. Refinishing is not only for the worn out bathtubs, even those that do not look good can have the refinishing.

The big problem comes when you have to choose the person who will help you with the refinishing in Lincoln. Remember, the bath refinishing team that you hire might bring the change that you want or bring a worst look.

Here are some tips that you should always look at before hiring any bathtub refinishing service provider.
Like any other services, one can easily find the perfect bathtub refinishing firm through recommendations from the people who are close to you. One can use the online platform if there is no one who can recommend you to the perfect service provider. When looking for any service provider, it is recommendable to use the internet, since to has something for everyone. You can easily locate the best service provider who is near you from the internet.

It is important for someone to choose experience when you are hiring some service provider. Note that those who will be offering you the kind of services that you want are the ones who will make your bathtub to be perfect or worst. If you go for people with no experience you are likely to be disappointed with the end results. It would be good if you choose people with some experience.

You should at least see some of the work the company has completed for other people. You should have the courage to ask for the photos from the company without fear. From the pictures you should admire their work. From the time the company started to the time you get to hire them, their work should be improving. It will be easy for you to know if they will give you what you want.

Reputation is also something else that you should look at. It would be good if you make sure you have an idea of what other people have to say about the firm. What people say about a certain firm is always according to the kind of services that they have been offering their customers for quite some time. It is not wise for someone to pick any firm that does not have good reputations from other clients.

Consider the communication with your team. If they are not good at communication before you hire them, then you should change and go to another team. Poor communication will not give you the best results.

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What You Know About Car Dealers

For your needs in a car as well as the parts, you will note that the use of the known dealer will be all that you will need. Getting the perfect place that will have all the needs that you have in check will be an essential thing to consider.

You should know that it will be for your own good if you will stand to have the perfect kind of the place that will be able to work well with the needs that you have as a person.

You should know that with the right dealer, you will stand to have all that you need. When it comes to the top dealer company, you will stand to have the services and products that you have and hence a gain on your side.

Here are some of the reasons that will make you consider choosing the right motor dealer for your needs such as Viking motors. You should know that it with the right kind of the company you will stand to have a place that will be able to sort your needs.

With the best dealer, you will have the car of your choice with the same. The dealer will have a variety of the cars that you can choose from.

The brand that you want, will be all that the top dealer will have. Moreover, you will be having a perfect choice in new and used cars.

More so you should know that getting all the choices at your place, you will stand to make the right kind of the choice when it comes to your needs. Moreover, you should know that if you need some spare parts when it comes to your car, you will have the perfect place to get the same.

The best dealer in the place will have all the parts for the brand of the cars that it has. It is crucial to understand that you will be able to get some genuine parts for your use.

With the best dealer, you should know that you will stand to have a choice of new and used parts as well. If you need to have some regular car maintenance, you should know that you will have the right kind of the place to do the same.

The use of the best kind of the dealer will be a massive gain in the quality of services and products at a better pricing. It is essential to note that it will be crucial to have the best dealer at your services.

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How You Can Find the Best Company for Website Development and Marketing Services

A lot of people have a problem when it comes to website development and marketing services and it is essential that they get to look for the best company that can offer them the best services. Typically, there is increased use of the Amazon platforms by so many business persons so that they can have an increased sale drive and so that you be competent on this platform you need to hire the company that specializes in this task. So that you find the best web services providers that you can hire it is essential that you get to consider doing your own investigation as that will significantly lead you to locate the best company. It is essential that you look at the tips outlined below as they will help you in finding the best websites services provider that will ensure you are having the best profile online.

The first factor that you need to consider looking at is the license. At all times, you are supposed to consider hiring the web designer that is licensed to offer website services and online marketing as that will ensure you are getting the most appropriate services. It is advocated that you incorporate the licensed website designer as that will ensure the services offered to you are in line with your business needs and your aims will be attained.

It is also essential that you get to consider looking at the services that are offered. When it comes to online marketing services more so based on the websites every company has its own services it is essential that you get to incorporate the company that will be able to offer you the services that you deserve.

It is crucial to consider reading the reviews. There is a need for you to consider looking at the reviews as they will aid you in finding the most appropriate company that you can hire is services and ensure you are satisfied. When you incorporate the right company you will be able to have all your business products viewed by a high number of customers online and chances of increasing sales are high.

Besides, it is essential that you get to consider referrals. Always ensure that you are asking for leads from your close friends that you trust so that they can help you in finding the most appropriate company that you can hire its services when it comes to marketing and website services. To find the best recommendations ensure those that you ask for leads you can trust them. Therefore, you have to make sure that you are considering the above factors as they will play a significant role in helping you find the best company that you can hire its services.

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Hire a Limo Service for Your Special Occasion

One major part of the planning process for your wedding is getting reservation for limo service for your special day. It is essential that you choose the appropriate mode of transportation if you want to keep in style when you arrive at the ceremony as well as at the reception. When you book for a reservation, there are a few things you have to take into consideration like the schedule for the whole day, the number of passengers for each trip, and the style and size that you are looking for.

Desired Style of Your Limo

Picking a limo style is totally up to you. You have all the option whether you want to match it with the theme of your wedding or just opt for a limo that you have always wanted to ride. You can choose either a hummer style or a stretch style limo. The decision should be based on what you want since it is your special day.

Schedule for the Whole Day

On your special day, expect that there are different things going on. You need to get dressed, take photos, see to it that everyone is ready for the wedding party, and that you arrive on time. Decisions need to be made before you can make a reservation for your desired limo. Others want to have a transportation arranged for the bride and her family members to the ceremony. When you are making the reservation, make sure that you give enough time for the driver to get there, get everyone loaded, and the drive to the venue.

In addition, you may also want to get transportation for the bride and groom from the ceremony to the reception in case they are held in separate places. It can be quite difficult to know exactly when the ceremony will be done and all the pictures taken, but see to it that you give enough time for the second limo to arrive. Appoint someone to make sure that your limo will be at the reception so that it can be decorated and the two of you can leave in it together after the event.

Whole Number of Passengers

Take note how many people will the first trip have. Other attendants will take their own car to the ceremony and the reception, so there is no need for you to include them in the number. However, you will also have to provide a ride for the parents of the bride and groom as well as grandparents and other relatives, so you may have to get a bigger limo to take this number of people. Make sure that no one is stranded at the ceremony and reception.

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