Polyethylene Composition for Injection Molding Melt Flow
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Solution Overview
Problem
Existing polyethylene-containing materials, particularly recycled polyethylene, have low melt indices and high viscosities, making them unsuitable for injection molding, and existing methods to increase melt flow index often involve peroxide decomposition products or require decomposition.
Innovation Solution
A process involving thermal treatment of polyethylene-containing materials using a twin-screw extruder to increase the melt index and reduce viscosity using a twin-screw extruder with specific temperature and time settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard extrusion process is used on recycled polyethylene, then the material is processed, but the melt index decreases making it unsuitable for injection molding
Solution Approach 1:
The patent applies reactive extrusion with peroxide addition to chemically modify the polyethylene structure, changing parameters such as molecular weight and branching to increase melt index from typical PCR values (0.2-1.0 g/10min) to injection molding suitable values (5-50 g/10min), while maintaining processing capability
Solution Approach 2:
The patent uses peroxide as an intermediary substance that facilitates chain scission and crosslinking reactions during extrusion, enabling controlled modification of the polyethylene to achieve desired rheological properties for injection molding applications
2Productivity
If peroxide is added to increase melt flow index, then the melt index increases, but peroxide decomposition products and residuals remain causing contamination
Solution Approach 1:
The patent optimizes peroxide dosage and extrusion temperature parameters to achieve complete peroxide decomposition and desired melt index increase while minimizing harmful residuals, targeting a balance between processing improvement and material cleanliness
Solution Approach 2:
The patent utilizes controlled peroxide decomposition to achieve beneficial chain scission that increases melt flow, while the same decomposition process eliminates harmful peroxide residuals, converting the potential harm into a beneficial cleaning effect
3Productivity
If organic peroxide is used to increase melt index, then the melt flow improves, but branching and crosslinking occurs affecting material properties
Solution Approach 1:
The patent carefully controls extrusion temperature, residence time, and peroxide concentration to achieve the desired degree of branching and crosslinking that improves melt flow while maintaining structural stability and preventing excessive gel formation that would harm material properties
4Productivity
If high peroxide content is used to increase melt index, then the melt flow index increases significantly, but fire risk and safety hazards increase
Solution Approach 1:
The patent optimizes peroxide dosage to the minimum effective concentration required to achieve the target melt index increase, thereby reducing fire risk and safety hazards while maintaining processing improvement benefits
Solution Approach 2:
The patent utilizes controlled peroxide decomposition during extrusion to achieve the desired melt index increase while the same process eliminates excess peroxide that would pose fire risks, converting the hazardous substance into beneficial processing aid and then eliminating it
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 process increases the melt index and reduces the viscosity of the polyethylene-containing materials, thereby making them suitable for injection molding applications.
Implementation Method 1
A process involving thermal treatment of polyethylene-containing materials using a twin-screw extruder to increase the melt index and reduce viscosity
Data Source
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AI summary
Polyethylene composition comprising at least 50 wt.% of polyethylene based on the total weight of the polyethylene composition, and having a density of at least 0.910 g/cm3; a melt index MI2 ranging from 3.0 to 60.0 g/10 min; an unsaturation index higher than 2,000 wherein the unsaturation index is the product of the Mn in Dalton and the vinyl unsaturation units per 1,000 carbon atoms as determined by ASTM D6248-98:2004; a complex viscosity at 0.1 rad/sec at 190° C ranging from 200 to 20,000 Pa·s; and a ratio of complex viscosity at a frequency of 0.01 rad/sec to the complex viscosity at a frequency of 100 rad/sec of at most 8.0, said ratio being measured at 190°C..