Molded Catching Elements High Flexural Modulus Thermoplastic
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing hook-shaped or mushroom-shaped touch-and-close fastener elements from thermoplastic materials face challenges in producing elements with a thick head, as they either fail to withstand stress or are damaged during demolding, especially when using amorphous or substantially amorphous thermoplastics with high flexural modulus.
Innovation Solution
A method involving molding a thermoplastic material within a cavity at a temperature between the glass transition temperature minus and plus 30 degrees Celsius, allowing for demolding and subsequent cooling to ambient temperature, which enables the production of catching elements with high flexural modulus without deformation, suitable for large-scale production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick head is obtained in mushroom-shaped catching elements, then the catching ability and stress resistance are improved, but the element cannot be stripped from the molding cavity
Solution Approach 1:
The patent applies parameter changes by controlling the temperature of the thermoplastic material during molding to be between Tg-30°C and Tg+30°C (where Tg is the glass transition temperature). This temperature control modifies the material's physical state, allowing it to be sufficiently rigid during molding to maintain thick head geometry, yet flexible enough to enable demolding without damage. The temperature parameter is the key variable being adjusted to resolve the contradiction between structural integrity and manufacturability.
2Strength
If amorphous or substantially amorphous thermoplastic with high flexural modulus is used, then the rigidity and catching quality are improved, but the hooks are too degraded after stripping to have catching ability
Solution Approach 1:
The patent uses parameter changes by precisely controlling the temperature parameter during the molding and demolding process. By maintaining the thermoplastic temperature between Tg-30°C and Tg+30°C, the material exhibits optimized mechanical properties that allow high rigidity during molding while remaining sufficiently ductile during demolding to avoid degradation. This temperature parameter control enables the use of amorphous thermoplastics with high flexural modulus without suffering from post-demolding degradation.
Solution Approach 2:
The patent applies preliminary action by pre-heating the thermoplastic material to the specific temperature range (Tg-30°C to Tg+30°C) before molding and maintaining this temperature during the demolding process. This preliminary temperature preparation ensures the material has the appropriate mechanical properties for both molding thick-headed hooks and successfully demolding them without degradation, preventing the reliability issue before it occurs.
3Productivity
If simple ejection demolding is used, then large-scale manufacture is favored, but hooks made from rigid amorphous thermoplastic are too degraded to have catching ability
Solution Approach 1:
The patent resolves this contradiction by changing the temperature parameter during the ejection demolding process. By maintaining the thermoplastic at Tg-30°C to Tg+30°C during ejection, the material temporarily exhibits reduced rigidity and increased ductility, allowing simple ejection demolding to proceed without degrading the hook structure. After demolding, the material returns to its normal rigid state, preserving catching ability. This parameter change enables both high productivity through simple ejection and high manufacturing precision through preserved hook integrity.
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 method allows for the successful manufacture of catching elements with high catching ability from rigid amorphous thermoplastics, overcoming the limitations of previous methods by ensuring the elements are not damaged during demolding and maintaining their structural integrity.
Implementation Method 1
the temperature of the thermoplastic inside the molding cavity is regulated to a value Tmold comprised between Tg-ΔTg and Tg+ΔTg, Tg being the glass transition temperature of the thermoplastic
Implementation Method 2
the demolded element is left to cool at a temperature lower than Tmold, notably at ambient temperature
Data Source
AI summary
The invention relates to a catching element of a male-female or male-male self-gripping device, which comprises a rod portion (1) and a catching portion (2), the rod portion extending in an axis that is transverse to a base strip (B) and the catching portion projecting laterally from the rod portion, characterized in that at least the catching portion is made of a thermoplastic material having a bending modulus of more than 1000 MPa, specifically more than 1200 MPa, in particular more than 1500 MPa at 25° C., the catching element being produced by molding, specifically by injection molding, and when the thermogram is plotted for the hook, in other words when differential scanning calorimetry is carried out, an absence or almost-absence of relaxation enthalpy near the glass transition can be seen during the first rise in temperature.