"Joe! I need you to order 2,000 poly cover-bags for our shipment on the 15th!" the operations manager yells at 3:30 on a Friday afternoon. Being the purchasing agent for his company, it is inferred that Joe knows what a "poly cover-bag" is or what will be the best type, thickness, color or size to protect his product. If you know nothing about the polyethylene packaging industry, are looking for a specific answer like "how to measure" or are simply keeping up on recent market trends, this is the article for you.
Pallet Covers are used to protect your company's product during transportation and storage. These days, pallet covers also serve as an effective means of advertisement as well as oversized trash bags. This article will teach you everything your manufacturer knows regarding this product. Therefore, it guarantees you will be a more effective buyer!
Pallet Covers and Bin Liners are often listed on subsequent pages in packaging supply catalogs. This is done because, in most cases, a liner is simply an inverted cover. First we'll cover some basics of polyethylene custom films.
Polyethylene (PE) is a thermoplastic polymer, which is today's most widely used plastic. Even the now nearly obsolete plastic grocery bag is a form of PE. I say nearly obsolete as the plastic grocery bag has begun to give way to the Non-Woven Polypropylene (PP) shopping bag as a green alternative. There are several different sub-categories of Polyethylene; 10 to be more specific. I do not intend to bore you with a chemistry lesson (nor am I qualified to teach one) so we will discuss the few that are used most often in the packaging industry. There are three sub-classifications you will most likely be interested in, depending on your specific packaging needs.
They are linear low density polyethylene (LLDPE), low density polyethylene (LDPE) and high density polyethylene (HDPE). LLDPE is known to have a higher resistance to punctures and higher overall strength than that of a LDPE. LLDPE is commonly used to make thin films due to its high strength. LLDPE can be found in stretch films, plastic wraps and nearly all polyethylene markets. Negatives for LLDPE are its smaller heat-sealing abilities and production challenges. Pallet cover users typically prefer LDPE for its "burly" chemical characteristics. It can also be found in many other applications such as playground slides and computer components. LDPE is not as dense as LLDPE and also has a lower tensile strength that requires a higher thickness be used in many applications. HDPE is more likely to be used in the manufacturing of extremely thin films such as t-shirt bags or grocery bags as it relates to our industry. Outside of the packaging industry, HDPE has many different applications and is seen as a very versatile product. We will move on with the LDPE (don't forget Joe still has to get those bags ordered!).
What color? How many MIL thick? What is a MIL? Do I need a UVI additive? Should it be a shrink blend? What size? How many do I have to buy? How much will it cost? How "green" is it? Can I get my company info printed on it? How many print colors? How many print sides? Is it safe in cold weather? What is a gusseted cover? What is a center-fold and m-fold? How are they packaged? Don't worry, we'll get there.
Our friend Joe is employed by an industry leader in the manufacturing of dog food. His company is located in Miami, FL. Knowing the what, where, how long and size are a couple of determining factors in choosing the correct liner, or in this case cover.
Let's say Joe has 40 lb bags of dog food that are produced in mass quantity, then loaded on skids and shipped to distributors all over the continental U.S. For this order, Joe will be going with a Low Density Polyethylene. If we were just looking for the lowest cost and not concerned with presentation or longevity a black, LDPE, "Repro-Blend" would be the route to go. Given today's economy coupled with our nation's concern with staying "green", this has become a very popular choice.
The company's owners are more concerned with marketing and presentation than just getting a low price. Now that we know we're looking for a LDPE film, lets get more specific. Polyethylene resins can be "virgin" or a "virgin/repro blend" in this case. Many manufacturers only use virgin resin due to its quality and aesthetic value. Plus they are unable to quote on Repro products, as they do not have poly regrind machinery. When looking for the most economical choice, it is always good to find if your source has the capability to produce a product using recycled resin. Using a resin made partially of recycled polyethylene does allow your company to market it as a "green" product. Yes, it is a "plastic bag" which for some is the farthest thing from environmentally friendly. However, if your cover will eventually be used as a trash bag or disposed of shortly after being installed this may be the most economical route.
Polyethylene pallet covers can be manufactured in a wide array of colors. They also can be "Opaque" or "tinted", which of course, refers to the color density. The pantone color system (PMS) is the most common color system used to choose these colors. As with anything, the more bells and whistles you add, the more your costs rise. If your product will spend a great deal of time sitting at its destination prior to being unpacked, an opaque color with artwork should be an option to consider. In Joe's case, the owner wants both a good looking cover and increased marketing potential. White is always a great background for any print or logo to stand out on. So Joe should suggest white opaque film be used.
Shrink covers and bags are used to cover anything from a 30' boat to a 2" wide toy. A shrink cover is made of a film that does just that when heat is applied to it. In some applications the material is covered with a shrink film and moved through a heat tunnel. Other companies will use a heat gun to shrink the material around the product. If the decision is made to go with a shrink cover, additional tools will need to be purchased. Heat tunnels and heat guns do come with a high initial investment. Shrink products include; bags, covers, tubes and films. These items are installed to keep the pallet load secure and clean during transit and storage. Joe's product is wrapped with stretch film prior to having the pallet cover installed. When this is the case, a shrink cover is not typically needed, as the load is secured by stretch film.
We learned earlier that Joe's company is located in Florida and it transports throughout the country. This is relevant information as we begin to discuss a couple of additives often used in the manufacture of pallet covers. If the company was located in Minnesota, and the product sat in sub-freezing temperatures for long periods of time, EVA would be needed. EVA (Ethyl Vinyl Acetate) is an additive to prevent hardening and cracking due to the cold. Another common additive option requested in pallet cover production is UVI (Ultra Violet Inhibitor). This is needed if a covered load will be exposed to the sun, wind or salt spray for long periods of time. Purchasing an opaque cover does provide a degree of resistance to the sun's damaging rays. However, if you really need to be confident that the cover will protect your product from color changes due to fading, or you with to reduce bag deterioration, then the addition of a UVI is a must. Depending on the size, color and type of material, a variable amount of the additive is combined in the production of covers. For each amount there is a corresponding duration assigned to the cover's shelf life. A 6-month UVI additive and 12-month UVI additives are the most common amounts requested, as most products are either used or sold during the first 12 months. In Joe's case, the dog food bags are only exposed to the sun during transit. This, coupled with the fact that he has already chosen a white opaque film, will provide ample protection from the sun's rays.
Now that we've narrowed down the materials to be used, let's discuss measuring and a couple of more manufacturing options. How to measure for a pallet cover, or to determine the cover size required means that we first need to measure our palletized product. A gusseted pallet cover is typically used for 48"x48" pallets and many other similar sizes. Gusseted covers are very popular as they are form fitted to the product providing a nice clean look. We will cover this type of cover first. Simply measure the height, width and depth of the pallet (for depth number always use the shorter side). Once you have the width (the wider side) measured add 1"-2" for ease of installation. Next, find the depth and again add 1" -2". To find the length of the cover measure the height of the pallet and add 1/2 of the depth. In example: a pallet that measures 48" wide by 48" deep by 48" tall would result in a pallet cover size of 51" x 49" x 72". This size is very common and stocked by many distribution companies. Consider adding a couple inches to the height if you would like the pallet cover to be long enough to cover a portion of the pallet itself. If your cover will be in windy conditions it may be a good idea to order the cover a bit longer, then use a bundling film to secure the bottom of the cover to the wood pallet.
A centerfold cover is commonly used for larger, longer pallet loads. For this cover we again need to find our width, length and height. For a pallet 48" wide x 96" long x 48" high, we will measure the width plus 1/2 the depth, add 1" - 2" and use that number for the overall height of the bag. To find the length of the bag we measure the pallet length (96") then add 1/2 of each side depth (24"+24") this gives us a length of 144", we then add 4" - 6". This gives us a centerfold cover size: 150" x 74". The additional 4" - 6" in length are added for ease of installation, as this is needed for larger pallet loads. Most manufacturers' size capabilities restrict them from producing a gusseted cover for a pallet this size. The centerfold cover differs from the gusseted cover in that it is 2 dimensional and sometimes known as a lay flat bag or cover. Since we are installing a lay flat cover over a 3 dimensional pallet small amounts of extra material remain at the top of both ends. This extra material is commonly referred to as "dog ears" and doesn't affect the functionality or longevity of the cover. However, if you have a large load and would like a cover without "dog ears" and cannot go with a typical gusseted cover, an M-Fold cover is another option.