Wet Friction Closure Using Polar Thermoplastic Elastomer
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Solution Overview
Problem
Closures for product containers made from thermoplastic polymers are inherently slippery, leading to slippage and poor engagement with the user's skin, especially in wet environments, and existing solutions either increase wet friction at the cost of dry tackiness or manufacturing issues.
Innovation Solution
A thermoplastic elastomer with specific properties, such as a high coefficient of friction when wet and low tack when dry, is integrated into the closure, featuring projections and a Shore A hardness of 35 to 50, which can be formed via injection molding or overmolding, to enhance user grip and adherence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermoplastic polymer is used for closure, then manufacturing is easy and cost is low, but coefficient of friction when wet is low causing slippage
Solution Approach 1:
The closure combines thermoplastic polymer (easy to manufacture) with thermoplastic elastomer (high wet friction) to create a composite structure that achieves both manufacturing ease and reliable wet grip. The elastomer layer is applied over the rigid polymer base, allowing each material to contribute its superior properties.
Solution Approach 2:
The thermoplastic elastomer is applied locally to the gripping surfaces of the closure where friction is needed, rather than making the entire closure from elastomer. This allows the rigid polymer body to maintain structural integrity while the elastomer provides enhanced grip only where contact with user occurs.
2Reliability
If thermoplastic elastomer is used to increase coefficient of friction when wet, then grip is improved, but tack when dry increases causing discomfort
Solution Approach 1:
The elastomer formulation is optimized with specific Shore A hardness (35-55) and viscosity parameters to achieve the desired balance. By controlling the viscosity average molecular weight and elastomer-to-polymer ratio, the material provides high wet friction while limiting excessive dry tackiness through precise parameter adjustment.
3Reliability
If closure thickness is increased to improve grip, then engagement with skin is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The thermoplastic elastomer is applied selectively to specific gripping surfaces and features of the closure rather than increasing the overall thickness of the entire closure structure. This localized application provides enhanced skin engagement where needed while maintaining a thin, simple overall closure design.
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 solution provides a secure, comfortable grip in wet conditions without stickiness when dry, improving user engagement and adherence to the container while maintaining durability and stability.
Implementation Method 1
a high coefficient of friction when wet and low tack when dry, which would improve engagement of the closure with a user's skin
Data Source
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AI summary
A product container (10) comprising a housing (20) defining a hollow interior and a closure (30) coupled to the housing such that the closure covers the hollow interior. The closure comprises a thermoplastic elastomer on at least a portion of the closure. The thermoplastic elastomer is polar and hydrophilic.