Injection Moulding Binder Composition for Dimensional Stability
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Solution Overview
Problem
In powder injection molding, the debinding process often distorts the preform, leading to unacceptable sintered parts with low relative density, and existing binders are not universally applicable for both metal and ceramic powders.
Innovation Solution
A binder composition consisting of 35% to 60% non-amphiphilic polymeric base, 30% to 55% non-amphiphilic wax, and less than 10% amphiphilic surfactant, with a specific copolymer of styrene-ethylene-butylene-styrene (SEBS) content, which limits deformation and enhances sintered part density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional binders are used for injection molding composition, then the preform can be formed and handled, but the debinding process causes preform distortion and produces sintered parts with low relative density
Solution Approach 1:
The patent modifies the binder composition parameters by incorporating specific polymers (polypropylene, polyethylene, SEBS copolymer), waxes (paraffin, microcrystalline), and surfactants in controlled proportions. This parameter optimization enables the binder to maintain preform structural integrity during debinding while ensuring complete binder removal, thereby preventing distortion and achieving high relative density sintered parts (≥95% theoretical density)
Solution Approach 2:
The invention creates a composite binder system combining multiple polymer types (thermoplastic polymers and elastomeric SEBS), waxes, and surfactants. This composite structure provides synergistic effects: the polymer matrix offers mechanical strength, the wax facilitates controlled degradation during debinding, and the surfactant ensures uniform distribution and complete removal, collectively preventing preform distortion and enabling high-density sintering
2Adaptability or versatility
If a binder is developed for metal powder molding composition, then it performs adequately for metal powders, but it is not applicable for ceramic powder molding compositions
Solution Approach 1:
The patent develops a universal binder formulation containing polypropylene, polyethylene, SEBS copolymer, paraffin wax, microcrystalline wax, and surfactant that effectively binds both metal and ceramic powders. The amphiphilic nature of the surfactant and the dual polymer-wax system enable the binder to adapt to different powder surface properties, providing consistent performance across diverse material types while maintaining optimal molding and debinding characteristics
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 proposed binder composition reduces deformation during debinding, facilitates high relative density in sintered parts, and minimizes costly rework operations, particularly for complex shapes.
Implementation Method 1
Its role is to facilitate the flow of the molding composition during injection molding in step B)
Implementation Method 2
provide sufficient mechanical strength to the preform to allow it to be handled
Implementation Method 3
by conventionally subjecting said preform to an attack by a solvent ('solvent' debinding)
Implementation Method 4
then a thermal attack (thermal debinding)
Implementation Method 5
sintering the at least partially debinded preform in order to obtain a sintered part
Data Source
Figure 1~2
AI summary
Disclosed is a binder for an injection moulding composition, the binder consisting of, in percentage by mass and for a total of 100%: 35% to 60% of a component (a), or "polymer base", consisting of a polymer or a mixture of polymers, each of said polymer being"non-amphiphilic" and having a mass average molar mass greater than or equal to 5000 g/mol, 30% to 55% of a component (b), or "wax", consisting of a polymer or a mixture of polymers, each of said polymers being non-amphiphilic and having a mass average molar mass less than 5000 g/mol, and less than 10% of an amphiphilic component (c), or "surfactant", and less than 10% of other components (d), the polymer base comprising 2% to 15% of a styrene-ethylene-butylene-styrene copolymer, or "SEBS", in percentage by mass based on the mass of the binder, the content by mass of styrene in the SEBS being greater than 15%, in percentage by mass based on the mass of the SEBS, the mass average molar mass of the SEBS being greater than 100,000 g/mol.