Multilayer HDPE Bottle Wall for Weight Reduction
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Solution Overview
Problem
Multilayer polymer articles require a balance of mechanical strength, impact resistance, and environmental stress cracking resistance (ESCR) while being cost-effective, but existing methods like bimodal resin technology are costly and inefficient for high-volume production.
Innovation Solution
A molded multilayer polymer structure comprising a body wall with a first layer of copolymer HDPE, a second layer of homopolymer HDPE, and a third layer as a mix of both, where the third layer is between the first and second layers, with a total weight content of homopolymer HDPE at least 30 wt-%, and includes regrind and post-consumer resin for enhanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copolymer HDPE is used to improve ESCR properties, then environmental stress cracking resistance is improved, but mechanical strength deteriorates
Solution Approach 1:
The container is divided into multiple layers with different polymer compositions. The inner layer uses copolymer HDPE for ESCR, the outer layer uses homopolymer HDPE for mechanical strength, and intermediate layers provide transition and reinforcement. This segmentation allows each layer to contribute its specific properties without compromising the other.
Solution Approach 2:
The invention uses a composite multilayer structure combining copolymer HDPE and homopolymer HDPE in specific layers. This composite approach leverages the ESCR benefits of copolymer while maintaining the mechanical strength of homopolymer, creating a material system that exhibits both properties simultaneously.
2Strength
If homopolymer HDPE is used to improve mechanical strength, then mechanical strength is improved, but environmental stress cracking resistance deteriorates
Solution Approach 1:
The container wall is segmented into multiple functional layers. Homopolymer HDPE is placed in outer layers where mechanical strength is critical, while copolymer HDPE is placed in inner layers contacting the product where ESCR is critical. This spatial segmentation resolves the contradiction by assigning each polymer to its optimal functional zone.
Solution Approach 2:
Different regions of the container wall are assigned different polymer compositions based on local requirements. The outer surface receives homopolymer for strength and stiffness, while the inner surface receives copolymer for chemical resistance. This local quality differentiation allows the structure to meet varying performance demands at different locations.
3Strength
If bimodal resin technology is used to combine homopolymer and copolymer HDPE properties, then both mechanical strength and ESCR are improved, but manufacturing cost increases
Solution Approach 1:
Instead of using expensive bimodal resin throughout, the invention segments the structure into layers using standard homopolymer and copolymer resins. This approach achieves the same performance benefits as bimodal resin but at lower material cost and with simpler processing suitable for high-volume production.
Solution Approach 2:
The invention replaces expensive bimodal resin technology with more economical standard polymers arranged in a multilayer configuration. This substitution maintains performance while reducing material costs and making the process suitable for cost-effective high-volume manufacturing of consumer product articles.
4Use of energy by moving object
If container weight is reduced to lower shipping energy consumption, then energy consumption is reduced, but mechanical strength may deteriorate
Solution Approach 1:
The multilayer structure optimizes material distribution locally, placing high-strength homopolymer where structural integrity is critical and lighter copolymer where chemical resistance is prioritized. This optimized material distribution reduces overall weight while maintaining necessary mechanical strength through efficient structural design.
Solution Approach 2:
The composite multilayer construction provides high strength-to-weight ratio by combining polymers with complementary properties. The structure achieves sufficient mechanical strength with reduced material quantity, enabling weight reduction for lower shipping energy consumption without sacrificing performance.
Data Source
AI summary
Molded multilayer polymer compositions and structures are provided, including a body portion having a body wall. The body wall has a first layer comprising a copolymer HDPE, a second layer comprising a homopolymer HDPE, and a third layer comprising a mix of the copolymer HDPE of the first layer and the homopolymer HDPE of the second layer, wherein the third layer is disposed between the first layer and the second layer, and a total weight content of the homopolymer HDPE is at least about 30 wt-% of the body wall. The body wall has an overall wall thickness T, the first thickness is about 10% of the overall wall thickness T, the second thickness is about 20% of the overall wall thickness T, and the third layer has a third thickness of about 70% of the overall wall thickness T.