Finding the correct film type and film usage is just as important as choice of packaging method.
Flow Wrapping accommodates many types of products; from candy bars to medical devices, flow wrapping offers extensive benefits for production managers. Factors like cost-effectiveness, minimal waste and a high volume of production makes flow wrapping a preferred choice for packers.
While determining if flow wrapping is the right packaging technique for your product is important, it is equally critical to choose the correct film. The flow wrapping process wraps a product in a clear or printed Polyolefin, Polypropylene or laminate film, forming a 3-sided seal package to produce a light and flexible package. When considering the type of film to use in your flow wrapping, there are several factors to keep in mind.
- Dual films – Running dual films on a machine is efficient and increases flexibility.
- Selection – There should be a balance of quality, performance, efficiency, and cost. You should always match film selection to product and package characteristics.
- Characteristic questions to consider – Should you consider Oxygen Transmission Rate (OTR), Water Transmission Rate (WTR), or Modified Atmosphere Packaging (MAP)? Or is this application just to a cover or group the product/products?
- Further factors – Sealing method, throughput, preferred pack style, product heat sensitivity, quality, budget, production volume, and required sealing jaw profile are factors to consider when choosing the correct film.
- Product type – There are many products that accommodate flow wrapping. For example, in-store produce bags, baked goods, bags-in-a-box (film used to contain products for insertion into a folding carton or box); cook-in bags, overwrapped produce (such as bell peppers), candy and confectionery wrap, or meat, poultry and seafood packaging.
There are multiple common flow wrap films that are used:
- Polypropylene family (PP) – This film type is commonly used for snack foods, candy, baked good, etc. It can be transparent, printed or opaque. It’s combined with coating that helps protect the film and product. PP offers limited protection from moisture and oxygen.
- Polyethylene family (PE) – PE includes low density, linear low density and high-density types of films. Low and linear low-density films share similar properties: good clarity, highly flexible and can be heat sealed using special sealing systems. Both low and linear low-density films are used for stretch and shrink wraps, bags, pizzas, bakery goods among other similar applications. High density PE has lower clarity and is used along with EVA for wrapping frozen food, crackers, bread bags, cereal box liners, etc.
- Polyester Films (PET) – PET is often combined in laminations with other films as an outer layer. Metallicized packages for potato chips and pretzels or cook-in packaging are common uses. PET lamination offers light weight, resistance to water, and reflection of heat and UV. It preserves freshness and flavor while having scratch resistant properties for retail and transport.
The Right Seal
- Three common sealing elements – They are time, temperature, and pressure. A change in one element will affect another.
- Jaw seals – along with sealing elements, the type and method of jaw sealing needs to be considered. There are multiple types to consider, each with their unique benefits and drawbacks.
- Seal performance – Adjustment will need to be made when variables change. Worn sealing jaws, material changes or variations, sealing times or equipment speed changes are variables to consider.
- Hot and cold film seal – Using hot or cold film seal depends on individual product characteristics, material costs restrictions, production throughput (capacity/speed), required seal strength or integrity, and desired film barrier characteristics (Ultraviolet, Oxygen, etc.).
- Cold seals – This seal is produced by pressing together films using a base material with a glue layer. Cold seals don’t protect the product as well as heated seals and are more easily affected by environmental factors. However, heat sensitive products, like chocolate, require cold seals.
- Heated seals – Heated seals are the best choice for a high integrity seal. Temperature range is key: the wider the effective range, the less chance for seal failure.