FGF Composite Material Melt Strength Enhancement
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Solution Overview
Problem
Fused granulate fabrication using semi-crystalline polylactic acid faces challenges with maintaining dimensional precision and strength due to high melt viscosity and shrinkage, especially when producing large objects with high printing speeds, as the material lacks sufficient cohesive strength and processability at elevated temperatures.
Innovation Solution
A composite material comprising semi-crystalline polylactic acid, wood-based cellulose fibers, polypropylene, and a melt strength enhancing agent based on vinyl acetate and vinyl versatate, or a terpolymer including ethylene, which adjusts rheological properties to enhance self-supporting capability and processability, allowing for higher printing speeds and larger object production without a mold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If semi-crystalline polylactic acid is used for fused granulate fabrication, then high stiffness and good adhesion to heated platform are achieved, but dimensional precision and strength are insufficient due to high melt viscosity and shrinkage
Solution Approach 1:
The patent uses a composite material system consisting of semi-crystalline polylactic acid combined with polypropylene and a melt strength enhancing agent. This composite approach allows the material to maintain the high stiffness and adhesion properties of PLA while incorporating PP and the melt strength agent to reduce shrinkage and improve dimensional precision during fabrication.
Solution Approach 2:
The patent modifies the rheological parameters of the material by introducing a melt strength enhancing agent that changes the melt viscosity and shrinkage characteristics. This parameter change enables the material to maintain coherence at elevated temperatures and reduces shrinkage during cooling, thereby improving dimensional precision.
2Productivity
If high printing speeds are used for large object production, then productivity increases, but material coherence and dimensional stability deteriorate due to insufficient melt strength
Solution Approach 1:
The patent introduces a melt strength enhancing agent that specifically modifies the rheological parameters of the material at elevated temperatures. This agent increases melt strength and reduces shrinkage during the rapid printing process, enabling high printing speeds while maintaining dimensional stability of the printed objects.
Solution Approach 2:
The patent applies the melt strength enhancing agent to specifically address the local issue of melt coherence during high-speed printing. The agent concentrates its effect on maintaining material coherence and reducing shrinkage during the critical extrusion and deposition phases, allowing high productivity without sacrificing dimensional stability.
3Ease of manufacture
If elevated temperatures are used for processing, then processability and printing speed improve, but material shrinkage and loss of cohesive strength increase
Solution Approach 1:
The patent uses a melt strength enhancing agent that specifically targets the temperature-dependent rheological properties of the material. This agent modifies the melt viscosity and shrinkage behavior at processing temperatures, enabling good processability and high printing speeds while counteracting the natural tendency of the material to lose cohesive strength and increase shrinkage at elevated temperatures.
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 composite material demonstrates improved self-supporting capability and dimensional stability at elevated temperatures, enabling the production of high-quality, large objects with enhanced mechanical properties and processability, suitable for fused granulate fabrication.
Implementation Method 1
which adjusts rheological properties to enhance self-supporting capability and processability
Implementation Method 2
heating the composition to a temperature Tsub above the melting point of the composition, thereby producing composite material at a melt state, decreasing the temperature of the composite material at the melt state below the melting point of the composition, thereby solidifying the composite material
Data Source
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AI summary
The invention relates to a method for manufacturing a composite material and to a product thereof, the composite material having a composition that comprises semi-crystalline polylactic acid, polypropylene and wood-based cellulose fibres, which composite material is suitable for fused granulate fabrication (FGF). Fused granulate fabrication enables efficient and automated printing of very large objects from composite melt without a mould, being a much faster method than a filament based extrusion method. A copolymer based on vinyl acetate and vinyl versatate or a terpolymer further based on ethylene, may be used to enhance the melt strength properties of the composite material for FGF In particular, a combination comprising both polybutyrate adipate terephthalate and said copolymer or said terpolymer may be used to provide a composite material which has a high self-supporting capability at melt state in elevated temperatures and high printing speeds, as demonstrated by viscoelastic properties of the material in a melt state, when shear strain is applied.