Recyclable Cross-Linked Polyethylene Films for Low-Shrink Sealing

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Solution Overview

Problem

Existing recyclable polyethylene films lack sufficient heat resistance and stiffness, leading to poor appearance, shrinkage, and non-hermetic packaging due to low barrier performance and poor heat seals, making them unsuitable for high-performance packaging applications.

Innovation Solution

Oriented and irradiatively cross-linked polyethylene films with a free shrink rate of less than 10% in both directions and improved heat resistance, combined with a sealant layer, to enhance mechanical properties and recyclability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If polyethylene structures are used to provide recyclable films, then recyclability is improved, but heat resistance and stiffness deteriorate

Engineering Contradiction:

ImproverecyclabilityVSAvoidheat resistance

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The patent applies irradiative cross-linking treatment to polyethylene films, fundamentally changing the chemical structure and physical properties of the material. This parameter change enables the film to achieve high heat resistance (withstanding temperatures up to 100°C or higher) while maintaining recyclability in polyethylene streams, directly resolving the contradiction between recyclability and heat resistance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite structure by combining oriented polyethylene with irradiation-induced cross-linked networks. This composite approach integrates the recyclability of polyethylene with the thermal stability of cross-linked structures, achieving both high heat resistance and recyclability simultaneously

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If polyethylene structures are used to provide recyclable films, then recyclability is improved, but stiffness deteriorates

Engineering Contradiction:

ImproverecyclabilityVSAvoidstiffness

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

Irradiative cross-linking fundamentally alters the molecular architecture of polyethylene by creating three-dimensional networks between polymer chains. This parameter change transforms the material from a flexible, low-stiffness polymer into a rigid, high-stiffness material that maintains structural integrity while remaining recyclable

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The cross-linked polyethylene structure functions as a composite material where the polyethylene matrix provides recyclability while the cross-linked network provides stiffness and mechanical strength, resolving the contradiction between these two properties

Inventive Principle:

Principle #40Composite materials

3Temperature

If oriented and irradiatively cross-linked polyethylene films are used, then heat resistance is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveheat resistanceVSAvoidmanufacturing complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The patent applies irradiative cross-linking as a preliminary treatment step during film manufacturing, before the film is converted into final packaging products. This preliminary action ensures heat resistance is built into the material structure itself, simplifying downstream processing and reducing the need for additional protective measures

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention replaces complex mechanical reinforcement systems with chemical cross-linking. Instead of adding layers, coatings, or structural supports to achieve heat resistance, the patent uses irradiation to create molecular-level bonds that provide thermal stability, thereby reducing overall manufacturing complexity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 films exhibit improved heat resistance, clarity, and limited shrinkage, allowing for high-performance packaging applications without compromising recyclability, and can withstand heat sealing variability in commercial machines.

Implementation Method 1

the base film being oriented, annealed and irradiatively cross-linked

Methodology Applied

Scientific EffectIrradiative cross-linking: Radiation

Implementation Method 2

the base film Being oriented, annealed and irradiatively cross-linked

Methodology Applied

Scientific EffectAnnealing: Annealing

Implementation Method 3

the base film has a free shrink rate of less than 10% in the machine direction and a free shrink rate of less than 10% in the transverse direction upon application of heat up to 90° C.

Methodology Applied

Scientific EffectThermal contraction resistance: Thermal Expansion

Data Source

PatentUS12391028B2Recyclable films and packaging

Publication Date: 2025.08.19 AMCOR FLEXIBLES NORTH AMERICA INC

AI summary

A recyclable film contains a base film of polyethylene that has been oriented, annealed, and irradiatively crosslinked, and a sealant. The base film has a free shrink rate of less than 10% in both the machine direction and the transverse direction when exposed to heat of 90° C. These recyclable films are ideal for use as packaging components that can be hermetically heat sealed to themselves or other packaging components, while maintaining low shrink and excellent appearance.