Monoaxially Oriented Film Linear Tear Properties
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Solution Overview
Problem
Existing packaging films with high seal strengths are difficult to open by hand, often requiring scissors and can result in 'zippering' during opening, which leads to potential spillage, and methods like mechanical perforation or laser treatment compromise barrier properties and increase costs.
Innovation Solution
A monoaxially oriented film blend of low density polyethylene (LDPE) with propylene-based random copolymers, which maintains low seal initiation temperature and high seal strength while providing directional tear properties without the need for perforations or surface roughening, achieved through specific resin formulation and orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high seal strength is achieved through high seal initiation temperature, then sealing reliability is improved, but ease of operation deteriorates because the pouch becomes difficult to open by hand
Solution Approach 1:
The film structure incorporates an oriented polypropylene layer that provides directional tear properties only in the machine direction, while the transverse direction maintains high seal strength. This local differentiation allows the pouch to be easily opened in one direction without compromising sealing reliability in other directions.
Solution Approach 2:
The film is divided into functional layers with distinct properties: an oriented polypropylene layer for directional tear and a sealant layer for hermetic sealing. This segmentation allows each layer to optimize its specific function without interfering with the other, resolving the contradiction between ease of opening and sealing reliability.
2Ease of operation
If mechanical perforation or laser treatment is applied to enable easy opening, then ease of operation is improved, but barrier properties deteriorate and manufacturing cost increases
Solution Approach 1:
The oriented polypropylene layer inherently provides directional tear properties through its molecular orientation during film production, eliminating the need for additional perforation or laser treatment steps. The film structure itself enables easy opening without compromising barrier properties or requiring extra manufacturing processes.
3Strength
If the film is made entirely of polymeric films for retort packaging, then seal strength is improved, but ease of operation deteriorates because the pouch becomes difficult to open
Solution Approach 1:
The film structure incorporates an oriented polypropylene layer that provides directional tear properties only in the machine direction, while the transverse direction maintains high seal strength. This local differentiation allows the pouch to be easily opened in one direction without compromising sealing reliability in other directions.
4Ease of operation
If notches are used to enable hand opening, then ease of operation is improved, but the tear path becomes uncontrolled resulting in zippering and potential spillage
Solution Approach 1:
The oriented polypropylene layer creates a preferred tear path through its molecular orientation, guiding the tear to propagate linearly along the machine direction. This inherent directional guidance eliminates the need for notches while maintaining controlled tear paths and preventing zippering.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The film enables easy, controlled opening of packaging without zippering, maintains high seal strength and hermetic seals, and is cost-effective by avoiding additional processing steps, ensuring both consumer convenience and packaging integrity.
Implementation Method 1
The films include a blend of an incompatible polymer such as low density polyethylene (LDPE) with propylene-based random copolymers and/or terpolymers. The films, when mono-oriented, display the tendency to fibrillate.
Implementation Method 2
A monoaxially oriented film including a single layer (A) of a propylene random copolymer blended with an amount of low density polyethylene homopolymer (LDPE).
Implementation Method 3
These containers are commonly created using a heat sealing process, in which high pressure and temperature is applied to opposing polymer films or laminates to join them together.
Implementation Method 4
The temperature at which this seal is created can be relatively high depending on the melting or softening point of the polymer material used as a sealant.
Data Source
AI summary
A monoaxially oriented film including a propylene-based random copolymer and at least about 3 wt % of a low density polyethylene which is oriented at least about 2.5 times in one direction and exhibits excellent linear directional tear properties parallel to the orientation direction and excellent heat seal performance in terms of high heat seal strengths and low seal initiation temperature. This film formulation and orientation is suitable for pouch applications requiring an “easy-tear” linear tear feature and excellent hermetic seal properties.