Polyethylene Film for Polysilicon Packaging
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Solution Overview
Problem
Commercial packing machines fail to maintain the purity of chunk polysilicon during packaging due to contamination from composite films, and the sharp-edged, non-free-flowing nature of the material often damages or penetrates standard plastic bags, leading to transport issues.
Innovation Solution
Development of a plastic bag with specific properties, including a PE film thickness of 150-900 μm and a weld seam strength of 25-150 N/15 mm, produced using temperature-regulated pulse sealing and a heat-sealing welding device with a nonmetallic sheathed weld wire, to prevent contamination and damage during transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard plastic bags are used for packing chunk polysilicon, then the packing process is simple and cost-effective, but the sharp-edged polysilicon penetrates and damages the bags during transport
Solution Approach 1:
The patent changes the physical parameters of the plastic film by specifying precise thickness ranges (150-900 μm) and mechanical property ranges (fracture force, fracture energy, tensile stress, elongation at break) to create bags that can withstand the mechanical stress of sharp-edged polysilicon during transport while maintaining the simplicity of the packing process
2Productivity
If composite films with chemical additions are used in commercial packing machines, then the packing process is efficient, but the chemical additions cause contamination of the chunk polysilicon
Solution Approach 1:
The patent applies local quality by using pure PE film without chemical additives in the critical area where polysilicon contacts the packaging material, while still maintaining efficient packing through controlled welding parameters and process optimization
Solution Approach 2:
The patent uses a composite approach by combining pure PE material with specific welding techniques (temperature-regulated pulse sealing) to create a packaging system that maintains both efficiency and purity, avoiding contamination from chemical additives while ensuring secure sealing
3Quantity of substance
If thin plastic films are used to reduce material cost, then the packing cost is lower, but the films are easily damaged by sharp-edged polysilicon chunks
Solution Approach 1:
The patent optimizes the film thickness parameter to a specific range (150-900 μm) that provides sufficient mechanical strength to resist penetration by sharp-edged polysilicon while avoiding excessive material consumption, achieving a balance between cost and durability
Solution Approach 2:
The patent specifies elongation at break parameters (300-2000% longitudinal, 450-3000% transverse) that indicate the film's ability to deform and absorb impact energy through elastic deformation, preventing catastrophic failure when contacted by sharp edges
4Strength
If thick plastic films are used to prevent damage from sharp-edged polysilicon, then bag strength is improved, but manufacturing cost and material consumption increase
Solution Approach 1:
The patent establishes an optimized thickness range (150-900 μm) with specific mechanical property thresholds that provide sufficient protection against sharp-edged polysilicon damage while minimizing material consumption and cost, avoiding the need for excessively thick films
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 bags exhibit improved resistance to damage and contamination, with 0% leakproof failure after 2000 km of transport in Example 1, demonstrating enhanced operational reliability and reduced contamination risks.
Implementation Method 1
welding the bag by pulse sealing with a contact pressure by means of welding jaws greater than 0.01 N/mm2, resulting in a weld seam having a weld seam strength of 25-150 N/15 mm
Data Source
AI summary
A bag contains polysilicon, has been welded and includes at least one weld seam and a polyethylene film having: a thickness of 150-900 μm; a stiffness at a flexural modulus Fmax of 300-2000 mN and Ft of 100-1300 mN; a fracture force F determined by dynamic penetration testing of 200-1500 N; a fracture energy Ws of 2-30 J; a penetration energy Wtot of 2.2-30 J; a film tensile stress at 15% longitudinal and transverse elongation of 9-50 MPa; an Elmendorf longitudinal film tear resistance of 10-60 cN; an Elmendorf transverse film tear resistance of 18-60 cN; a longitudinal film elongation at break of 300-2000%; a transverse film elongation at break of 450-3000%; and a weld seam strength of 25-150 N/15 mm. A method includes filling a bag with polysilicon, and welding by pulse sealing with contact pressure greater than 0.01 N/mm2 to obtain a 25-150 N/15 mm weld seam strength.