One of the most wanted product for packaging of cargo on pallet is stretch hood. The stretch hood is a tubular film stretched and hauled on the pallet with cargo with goal of fixation and protection of the cargo. During the packaging stretch hood, which is delivered on roll, is cut on particular length, welded on upper side. Hood is then grabbed with fingers of the machine and stretched to the side bigger than the dimension of the pallet. After that follows the hauling of the cargo and pallet. The length of the hood is very important for correct fixation of the cargo.
The ability of adjusting the elasticity and holding force is what this hood making it ideal for packaging of various products, from empty PET bottles till sacks of cement, which are total opposite characteristics then in first case. Its most popularity and fast grow stretch hood has accomplish packaging of construction material and cargo in FFS (form fill seal) sacks. Today stretch hood is most used for packaging of various household appliances where there is this package more cost efficient then cardboard packaging.
The advantage of packaging in stretch hood is speed of packaging which is compared to normal stretch film for wrapping 40 % faster. Second very important characteristic is good water barrier and UV protection – because the cargo is protected from five sides which can have atmospheric impact. During manipulation of cargo very important are visual characteristic (transparency of the film), so that the wanted cargo can be fast detected. This reduces probability to make error during the selection or delivery of goods. In this case we have only one layer of film and if wrapped with stretch film it is not the case. During transportation it is very important stability of the pallet so that cargo comes to final destination unharmed and in one piece. The last requests are complied by the selection the right ratio between elasticity and holding force which depends of the dimension of the film and used materials.
In global stretch hood is a very demanding product because it has to comply a list of parameters including tear and puncture resistance. To comply all the requested demands it is necessary to use materials of the high quality, and adequate resin formulation for specific type of packaging. Film for stretch hoods are usually three layer film extruded on coex blow film extruder. Two outer layers have protection purpose and middle layer have high elasticity characteristics. Most of the resin producers suggest usage of high quality resin C8 LLDPE and combination of plastomers and elastomers, polyolefin elastomers or EVAc - ethylene-vinyl acetate copolymer in the middle layer. Outer layer are dictating the mechanical and visual characteristics and inner layer is used for getting the needed elasticity. Usual ratio is 20:60:20. Every resin producer has its own formulation and suggestions for the particular type of packed material, but because of the process of packaging the demands of the holding force and elasticity must be balanced on very thin borders. This means that several industrial tests have to be done before the real production. In any case stretch hood is the fastest growing product for industrial packaging. According Versalis–Internal Marketing Intelligence European stretch hood market in the period from 2011 till 2015 will grow 7,5 %, and stretch film market will grow only 0,7 %. A lot of different sources are forecasting similar grow which are clearly showing the future usage and development of this kind of industrial packaging.
In its laboratory MURAPLAST can make all needed testing for mechanical and elastic properties needed for this product and can simulate whole process of packaging.
Technical characteristics of stretch hood.