Five-Layer Polyolefin Film for Heavy Duty Sack Toughness
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Solution Overview
Problem
Conventional 3-layer films used in heavy duty shipping sacks fail to provide a suitable balance of toughness and creep resistance when the thickness of multilayer films is reduced, making it challenging to meet customer and industry requirements for physical properties such as dart, puncture, tear, and creep resistance.
Innovation Solution
A multilayer film composition with at least five layers, including a polyethylene core layer, where specific polyolefin layers are positioned to achieve a balance of stiffness and abuse properties, utilizing a polyethylene composition with distinct fractions and densities to maintain toughness and creep resistance even at reduced thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the thickness of multilayer film is reduced to lower material costs, then material cost decreases, but toughness and creep resistance deteriorate
Solution Approach 1:
The film is divided into five distinct layers with different polyolefin compositions, each layer serving specific functional requirements. The segmentation allows optimization of each layer's properties to contribute to overall toughness and creep resistance while maintaining reduced total thickness
Solution Approach 2:
The invention uses composite materials consisting of multiple polyolefin types (polyethylene, polypropylene, polybutylene, polystyrene) with different densities and molecular weights combined in a multilayer structure. This composite approach enables the film to achieve superior mechanical properties at reduced thickness compared to single-material films
2Ease of manufacture
If conventional 3-layer film structure is used, then manufacturing simplicity is maintained, but balance of toughness and creep resistance is insufficient
Solution Approach 1:
The film structure is segmented into five layers with specific thickness allocations (first layer: 5-20% of total thickness, second layer: 10-30%, third layer: 30-50%, fourth layer: 10-30%, fifth layer: 5-20%). This segmentation provides the reliability needed for heavy duty shipping applications while remaining compatible with standard extrusion manufacturing processes
Solution Approach 2:
Each layer is assigned specific local quality characteristics through selection of particular polyolefin compositions and thicknesses. The core layer (third layer) contains the polyethylene composition with specific density (0.915-0.940 g/cm³) and molecular weight parameters to provide toughness, while outer layers provide creep resistance and surface properties
Data Source
AI summary
Embodiments of the present disclosure are directed to multilayer films. Embodiments of the multilayer films may include a first layer comprising a first polyolefin, a second layer comprising a second polyolefin, a third layer comprising a third polyolefin, fourth layer comprising a fourth polyolefin, and a fifth layer comprising a fifth polyolefin. The second layer may be positioned between the first layer and the third layer; the third layer may be positioned between the second layer and the fourth layer; and the fourth layer may be positioned between the third layer and the fifth layer. Two or more of the first polyolefin, second polyolefin, third polyolefin, and fourth polyolefin may be the same or different. The third polyolefin may be a polyethylene composition having a density of 0.924 g/cm3 to 0.936 g/cm3 and a melt index (I2) of 0.25 g/10 minutes to 2.0 g/10 minutes.