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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A Smart Supervision Team Cares about and Invests in Its Workers

It’s usually easy to tell every time a company cares about its workers. It shows in how the supervisory staff handles the work force. While the actual company might limp along for a lot of years, when the management interacts with the employees as if they were slaves, indignation increases and lots of employees contain the predisposition to be passive aggressive in terms of their thinking. If the management along with the staff will be engaged in petty combat, regardless how refined it could be on the surface, it is a clear certainty that that business will never rech its potential as long as that battle is allowed to continue on. Supervision would certainly be smart to remember that old maxime that it’s easier to capture flies by using honey compared to with vinegar.

There are a lot of techniques that your operations staff that desires to signify very good will towards its personnel are able to do so. Probably the most important is usually to handle each and all of them with regard. Basically studying peoples’ names, working to make eye contact, smiling, and then stopping occasionally to actualy pass the time of day is certainly associated with wonderful benefit. Good functioning circumstances, excellent pay pertaining to sound work, opportunities with regard to advancement and the expression regarding real appreciation with regard to the particular work that workers do virtually all generate good results. Workers really should have a good break spot for them to have to benefit from.

Going in conjunction along with possibilities to progress within the company could be the offering of academic prospects, such as injection molding seminars. If staff members are provided the chance to boost themselves as well as take seminars for injection molding, or maybe injection molding classes, it frequently not just shows that the operations actually values these folks, but in addition, it demonstrates that management wants to invest in them, as people. Not simply will all the qualifications acquired from benefiting from opportunities like scientific molding seminars tend to make these individuals improved personnel, success from near the business’s standpoint, but in addition, it positions such individuals to gain raises, possibly be granted promotions and to proceed to completely new jobs throughout the corporation. It makes their current work less risky, and makes it easier for them to find new work if they turn out to have to move to a whole new region.

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Organized businesses might need to change a few of their policies in the event that they wish to contend today. Millennials are overtaking the employed pool plus they function in different ways when compared with prior generations. There are a few things about this population group companies must understand if they want to bring in them as well as retain all of them with the business for as much time as they can. The times wherein a individual got a career and remained with that employer all of their career are over. Millennials tend to be switching jobs in excess of every other age group. These people recognize there are several businesses available that want their expert services and will send their resignation should they do not sense satisfied. To retain these folks, organizations may well need to develop major changes that can anger the slightly older generation of employees. One change that could produce a significant affect and also attract talent on the company will be providing advantages which will help employees stay healthy. This particular age group is usually interested in new healthy ideas and may end up being attracted to a company that presented an on-site health and fitness center and versatile hours hence they could exercise each day. This kind of overall flexibility may seem counterproductive to more aged workers but based on www.forbes.com, it could possibly make it easier to keep young workers which place an increased benefit on their wellness. As outlined by Melissa Thompson, developing companies are currently giving their staff members the possibility to work at home. They have learned that supplying their staff this type of versatility can cause improved output. Even though they may not sit at a desk and work continuously for 8 hours in a row, staff members which have the ability to bypass the drive and workplace chatter have a tendency to be able to obtain more completed in one day than those who drive in to the place of work. The stress of commuting into the metropolis will make an employee less productive and take them a significantly longer time to start on their daily duties. Individuals who operate from the home office don’t have to bother about those ideas plus they begin a full day restored and able to deal with the job before them. Businesses which will find ways to incorporate these types of guidelines to their business strategy are more likely to draw in and maintain millennials.

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It’s actually extremely simple for an individual to be pulled over and arrested and charged with a DUI when they failed to even recognize that they had an excessive amount to drink. Whenever somebody has a few drinks, they may well not feel influenced at all. Nevertheless, they still might be above the legal limit for their region. Anytime this occurs, they might be arrested and will have to deal with the charges they are facing as soon as possible. It’s probably going to be a good option for them to employ an oui lawyer as soon as possible.

Evidence starts to disappear speedily after somebody will be arrested. If they think the tests were defective, they’ll desire to retain the services of a lawyer or attorney quickly so they can be retested before time runs out. This could enable them to have the charges dismissed in case the tests were really wrong. Additionally, the lawyer or attorney could check into the precision of the testing techniques along with the reason behind the stop to be able to make sure there were no mistakes made just before or even during the arrest. If perhaps virtually any mistakes were made, the charges could be dropped. This indicates the person is no longer facing any charges as well as the police arrest isn’t going to be a part of their own criminal background.

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If you were arrested as well as charged with DUI, be sure to make contact with a criminal defense lawyer as soon as possible. There is a lot they’re able to do to help you and also, even if you do end up with a guilty verdict, they could nevertheless help minimize your sentence to lessen the effect it’s going to have on your everyday life. Get a hold of a criminal defense attorney right now to be able to find out far more and also to be able to get started working on your situation.

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The next time you have an event planned you should think out purchasing custom printed t-shirts for everyone in your group. Some really cool custom printed t-shirts will definitely make you stand out from the crowd.

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Custom t shirts are such a great way to stand out no matter what the case may be. If you’ve got a business you definitely want to make an everlasting first impression on your customers. A sharp dressed crew will make people say, WOW, this company has really got it together. You may be bidding on a large contract and it may come down to rather your crew looks and acts professional. When you have your crew outfitted in custom printed t shirts they know that they are representing your company. That gives them a little incentive to perform at a level. People want to work for a company that knows how important it is to look your best while at work. It shows that you’re not just any other company. It shows that your company has great potential. That large contractor will notice that as well.

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Discover More About One Particular Company That Is Endeavoring To Develop Calgary

Commercial property investment organizations typically have an emphasis on the future. This is the same as the ASI firm that’s currently working on a variety of projects inside the Calgary location. For personal investors as well as investment companies looking to work together with a commercial property investor, this company will be one which is well worth a glance. The firm is actually focusing on generating brand-new projects after having completed winning projects before. A person who is actually serious about investing in commercial real estate could desire to discover more with regards to the company and also its CEO now.

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People that need to discover a lot more with regards to the CEO Frank Lonardelli could take a look at the ASI site in order to learn more with regards to both just how he started in commercial real estate property investments and also to discover much more about the existing projects for the organization. This will give somebody an idea of exactly what the company is doing now as well as exactly what they intend on accomplishing down the road. A prospective investor will certainly want to discover just as much as possible so they are able to be sure they will see a great return on their own investment and also in order to make sure this really is the appropriate kind of investment for them.

In case you want to learn a lot more concerning this organization or concerning the CEO, spend some time to be able to take a look at https://renx.ca/private-market-financing-pays-arlington-stre right now. When you Learn more about Frank Lonardelli, you’ll be able to notice exactly why it could be smart to help invest in the location as well as to be able to work together with a firm that is endeavoring to enhance the overall region for the advantage of every person who lives there. Have a look right now to find out far more with regards to their current as well as long term projects.

On the subject of Advertising, What a Business Logo Is Put on Makes a Difference in Profit

At times a a free item or perhaps a giveaway at a community circus is more than merely receiving a thing without paying for it. When you’re getting one thing at no cost that has a emblem on it, you happen to be utilizing innovative advertising. Each time you make use of that product you’re marketing that manufacturer. You happen to be checking out the logo. If you make use of it while in front of individuals certainly they almost certainly are reading the symbol. It’s a whole lot like a subliminal message. It is getting into your head. You’re recalling it. It may well just be at some point that you’ll require the merchandise or services it is marketing. What are you more than likely intending to think of? Yes, you are most probably to consider this label on the product or service you’ve been using. You chalk it up to dumb luck. It’s really not a coincidence. It can be advertising and marketing. Additionally, it is fantastic.

Precisely how amazing this specific marketing plan is actually depends on the item which includes the logo. By way of example, those who stay in a seaside town tend to be in no way likely to get much usage out of an ice scraper with a logo imprinted on the front. Nevertheless Drink coolers are one thing they could make use of each day. The coolers could barely get remove before they are really needed yet again. That’s effective marketing and advertising and receiving your emblem out to the right individuals.

Custom T-Shirts to Suit Your Style

You can now custom t-shirts online to make your style statement or for fun. These t-shirts are digitally printed and suit everybody’s budget. Just go online, choose the design you want for your t-shirt and ask for a quote. One of the customer care executives of the company will get back to you in no time, and if all goes well, the t-shirt will be delivered to you within the minimum possible time. Either get started by designing your own t-shirt or choose from the design templates.

Features

You can add your own text and art to the t-shirt you like and choose the color as well. Some sites also offer free shipping without a hidden fee. You can choose from thousands of clip art designs. What’s more, you can also receive a guarantee on the quality of screen printing, embroidery, and digital prints. If you do not receive the correct order, you can get your money back. For instance, if the t-shirt that you have received in the mail is different from the one you had designed online, you can get your money back. There are a huge variety of designs that you can have on your custom t-shirts, such as street art, add personal messages, slogans, social causes, custom tagging, political statement, or the picture of your favorite movie or rock star.

The custom t-shirts are delivered well in time and sometimes even within three days of the placement of the order. You can choose the color, design, and occasion for which you want to design your t-shirt, including parties, St. Patrick’s Day, a football match, Christmas, or a charity event. Most of the companies use the latest and most advanced technologies to give you the most vibrant colors and designs. These t-shirts are also durable and are available for a baby and even for a 60-year old.

Advantages

These custom printed shirts, apart from giving you a stylish look, also reveal what an attitude you have toward things, toward others, and toward life in general. Custom t-shirts also make for great gifts for your family and friends. Simply get that picture that you took at the Niagara Falls, paste on your customized order, and make your loved ones smile. These t-shirts do not dig a hole in the pocket, and their prices start as low as $10. If you are lucky, you may even bag a discount or be part of some other promotional offer.

There are some more benefits attached with these t-shirts. These t-shirts can be ordered in bulk for a discounted price. However, you do not have to order a minimum quantity. T-shirt printers are easy to use, and most of the sites will explain you how to go about printing t-shirt with the style you choose. The custom t-shirts are just perfect for businesses, teams, clubs, and events.

So let that out-of-the-box idea come out and get printed on your t-shirt. Also, do not forget to read rave reviews of satisfied customers on websites whose satisfaction bears testimony to the quality of these t-shirts. So custom t-shirts and flaunt that chic look.