What Is A 7 Layer And Why Is It Better?
A 7-layer film is one where seven extruders are simultaneously extruding polymers to form 7 concentric rings of molten polymers that solidify to form one film. If the film cross-section is seen under a microscope, seven separate layers can be observed.
We believe that, for farmers, 7-layer greenhouse film is a better option than 3 or 5 layer films for four reasons. Firstly, the 7-layer film gives superior mechanical properties thus giving longer life. Secondly, the 7-layer film gives more uniform lighting & optical properties, thus creating conditions for uniform crop growth. Thirdly, the special properties of the film like anti-drip and anti-dust, are strongly expressed and last longer than conventional films. Fourthly, the 7-layer film allows us to better control raw materials and optimize the same for superior performance while maintaining cost-effectiveness.
Film quality depends significantly on the quality of the machine itself. Bandera is a worldwide leader in extrusion lines since 1947, and their 7 layer blown film machines are among their latest high technology machines. Our Bandera machine is Asia’s first 7-layer wide-width blown film plant and is one of the few in the world. It is equipped with multiple technological features to ensure consistency and uniformity viz. automatic thickness control from K-Design; 32 component dosing system from Doteco; and width control technology with internal and external bubble cooling systems.
The 7-layer Bandera machine allows us to separately extrude pure resins in each layer that translates into better performance, unlike the mixing of many resins in a single layer as is the case in a 3-layer or 5-layer film. Additives such as Anti-drip, UV absorbers, UV stabilizers can be applied on separate layers resulting in minimal interference between the additives, and each additive gives a stronger and longer-lasting expression as compared to the same in a 3 or 5 layer.
One of the most beneficial factors of the 7-layer film is downgauging, attributed to precision control in the layer-wise formulation. Generally, we can down gauge a film’s thickness by up to 15 %, and still achieve the same mechanical strength and durability in a 7-layer film as compared to a similar 3 or 5-layer film. This enables customers to save costs on applications.
As per technology and scientific improvements in the blown film industry, an increased number of layers always provides enhanced properties and control in making technical & specialized films for the agricultural/ packaging industry.