Tool Handle Hardness Gradient Plasticizer Migration
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Solution Overview
Problem
Conventional handles with layered hardness gradients experience plasticizer migration, leading to changes in hardness and reduced friction, which affects the transmission of forces like torque.
Innovation Solution
The handle design maintains a limited plasticizer content gradient between layers, with the inner layer having a free plasticizer content of at least 60% to 130% of the outer layer's, and uses bound plasticizers or fillers to achieve desired hardness differences while preventing excessive migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If plasticizers are incorporated into the outer layer to achieve desired hardness, then the handle surface becomes softer and more comfortable, but plasticizer migration occurs leading to hardness changes and reduced friction
Solution Approach 1:
The patent applies parameter changes by carefully controlling the plasticizer content in both inner and outer layers within specific ranges (0-40 wt% for inner layer, 0-30 wt% for outer layer) and limiting the gradient between layers to maximum 10 wt%. This parameter optimization ensures the outer layer remains soft and comfortable while preventing excessive plasticizer migration that would cause hardness changes and friction reduction.
Solution Approach 2:
The patent uses composite materials by creating a two-layer structure where the inner layer and outer layer are made from different plastic compositions with different plasticizer contents. The inner layer has higher plasticizer content for structural flexibility, while the outer layer has lower plasticizer content for durability and friction maintenance. This composite approach allows each layer to perform its specific function while mitigating the drawbacks of using plasticized materials throughout.
2Shape
If a gradient in plasticizer content is created from inner to outer layer, then different hardness levels are achieved, but plasticizer migration occurs from softer to harder layer
Solution Approach 1:
The patent applies parameter changes by establishing specific plasticizer content ranges for each layer and limiting the gradient between layers. The inner layer contains 0-40 wt% plasticizer while the outer layer contains 0-30 wt% plasticizer, with the gradient between layers limited to maximum 10 wt%. This controlled parameter approach maintains the desired hardness gradient while preventing excessive migration that would compromise compositional stability.
3Ease of operation
If high plasticizer content is used in the outer layer, then the handle surface becomes softer for better feel, but friction coefficient decreases due to plasticizer film formation
Solution Approach 1:
The patent applies parameter changes by optimizing the plasticizer content in the outer layer to a maximum of 30 wt% and limiting the plasticizer gradient between layers to maximum 10 wt%. This controlled parameter approach ensures the outer layer remains soft and comfortable for handling while preventing excessive plasticizer migration to the surface that would form lubricating films and reduce friction necessary for torque transmission.
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
This approach stabilizes the handle's properties over time, maintaining a high coefficient of friction and ensuring effective force transmission without the formation of undesirable plasticizer films.
Implementation Method 1
there is a gradient in the plasticizer content from a softer layer to a harder layer. As a result of this gradient, plasticizer migrates from the softer layer to the harder layer
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The handle (1) has an outer layer (6) made of flexible plastic e.g. silicone rubber, with a non-porous structure and hardness in a range of 30 to 60 shore A, and an inner layer (5) made of flexible plastic with hardness in a range of 10 to 55 shore A. A handle core (3) is made of hard plastic. The plastic forming the inner layer in the core has a free softener content that amounts to 60-130 percentage of the content in the plastic forming the outer layer. A compound selected from a group consisting of olive oil, larch resin, castor oil, or paraffin oil, is provided as the softener.