Stretch and Shrink Wrap

The flatness, in particular, is critical tor high quality printing systems. The ability to produce uniform shrinkage in both directions is an important property tor shrink wrap applications, particularly tor printed shrink materials, including labels. 

A German company, Kuhne GmbH, has introduced a triple-bubble process, which uses infrared heat, rod heaters, and other annealing techniques in a thermofixa-tion station to impart precise shrink rates to coextruded film. 

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PVC Some stretch and shrink wraps for industrial Excellent clarity... 

Flexible packaging for frozen food Yogurt and cream containers Stretch and shrink wrap for pallets Industrial strapping Refuse sacks... 

Explain the similarities and differences between stretch and shrink wrap. 

Your instructor may ask you to bring a polymer sample of your own choice. If possible, these samples should be clear and as thin as possible (similar to the thickness of plastic sandwich wrap). Good choices of plastic materials include windows from envelopes, plastic sandwich wrap, sandwich bags, soft-drink bottles, milk containers, shampoo bottles, candy wrappers, and shrink-wrap. If necessary, the samples can be heated in an oven and stretched to obtain thinner samples. If you are bringing a sample cut from a plastic container, obtain the recycling code from the bottom of the container, if one is given. 

Materials handling, including stretch wrap and shrink wrap... 

Nonfood packaging categories include dmgs and pharmaceuticals, textile goods, bags (merchandise, shipping, carry-out, T-shirt, and laundry), shrink wrap, stretch wrap, clear boxes, and many more. 

Mica is shipped by tmck (20.4 t max) or railroad (27.2 t max). Bulk tmckloads and rail shipments, such as palletizing, bagging, and shrink- or stretch-wrappiag, are made to avoid extra costs. Mica is usually palletized and shrink- or stretch-wrapped for shipment. 

Further, they can be used for medical purposes, such as press-through packages, disposable syringes, liquid medicine vials, and infusion bags. They are suitable for electric or electronic materials, such as wire coating. In addition, packaging films, such as wrapping films, stretch films, shrink films, and blister packs can be produced. 

Polyethylene, as LDPE, LLDPE or a mixture or blend involving combinations of LDPE, MDPE, HDPE, EVA, etc., finds a wide usage in bags, sacks, sachets, overwraps, shrink wraps, stretch wraps, etc. Most deep freeze packs, for example, use LDPE or an LDPE mixture which is produced from a reel on a form fill seal type machine. However, as many of these packs are up to 100% printed, even ink of 2-5 Pm could be considered as a separate layer which modifies some of the physical and chemical properties. As all polyolefins need a surface (oxidative) treatment to ensure a good print key, this or any other surface treatment process may further modify the film properties. 

This is the most popular use of stretch wrapping, hence it is frequently compared with shrink wrapping in terms of advantages and disadvantages. All the methods previously outlined are employed with LLDPE being the predominantly used material, in conjunction with a pre-stretching operation. Gauges of 15 to 50 Pm are usually employed. 

Critical requirements for PE are rapid processing, thinner yet stronger films, ease of direct printing or adherence of labels, rapid heat sealing, high strain rate at high strain for stretch wrap, plastic memory for shrink wrap, cross-linkability to resist creep and stress relaxation, cross-linking to resist elevated temperatures when the... 

Over time, shrink wrap, like stretch wrap, tends to loosen somewhat, due to creep and stress relaxation, with the loss of holding power increasing at higher temperatures. 

Shrink wrap materials include PE, PP, and PVC, among others. Some shrink wrap is used for pallet-loads of goods, but that market is dominated by stretch him, due in part to its lower energy requirements. Most shrink-wrap is used for individual packages or small bundles of products. A nonpackaging use of shrink film is window insulation, where the film is placed on the inside of a window and then shrunk using a hair dryer. 

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