Starch-Based Films Directional Alignment Extrusion
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Solution Overview
Problem
Current methods fail to incorporate starch-based polymeric materials into directionally oriented plastics without compromising mechanical properties or processing capabilities, due to starch materials' high molecular weight and complex molecular characteristics, which affect rheological properties and melt strength.
Innovation Solution
Development of a method to extrude and directionally align a composition including starch-based polymeric materials with high molecular weight, using a thermoplastic diluent to maintain desired rheological characteristics, such as melt strength and elongational viscosity, allowing for processing at commercial speeds and shear rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If starch-based polymeric materials are incorporated into directionally oriented plastics, then biodegradability and sustainability are improved, but mechanical strength and rheological properties deteriorate
Solution Approach 1:
The patent applies parameter changes by carefully controlling the molecular weight of the starch-based polymeric material (specifically using high molecular weight starch with Mw > 10^6) and adjusting processing parameters such as extrusion temperature, draw ratio, and heating rate to achieve optimal mechanical properties while maintaining biodegradability
Solution Approach 2:
The patent creates a composite material system by combining starch-based polymeric materials with conventional polyolefin resins in specific ratios, where the starch provides biodegradability and the polyolefin provides mechanical strength and processability, resolving the contradiction between these two properties
2Reliability
If starch-based polymeric materials are incorporated into directionally oriented plastics, then sustainability is improved, but processing capabilities deteriorate
Solution Approach 1:
The patent changes processing parameters including using specific extrusion temperatures (180-220°C), controlled draw ratios (1.5-3.0 in machine direction, 1.0-2.5 in transverse direction), and heating rates to ensure proper melt strength and extensional viscosity during directional orientation processing
Solution Approach 2:
The patent performs preliminary action by pre-drying the starch-based polymeric material to reduce moisture content below 10% before extrusion, and by preparing the resin composition with proper mixing and distribution of starch granules before the directional orientation process to prevent processing defects
3Quantity of substance
If conventional starch materials are used in polyolefin resin blends, then renewable content is increased, but extensional viscosity and melt strength deteriorate
Solution Approach 1:
The patent applies parameter changes by using high molecular weight starch (Mw > 10^6) instead of conventional lower molecular weight starch, and by controlling the starch content in the resin blend to maintain extensional viscosity and melt strength necessary for directional orientation processing
Solution Approach 2:
The patent substitutes the mechanical properties of conventional starch with those of high molecular weight starch-based polymers that exhibit strain-hardening behavior, providing the necessary extensional viscosity and melt strength for processing without compromising renewable content
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 method enables the production of directionally oriented films and sheets with starch-based polymeric materials that exhibit strength comparable to traditional materials, while being biodegradable and processed on conventional equipment, enhancing sustainability and biodegradability.
Implementation Method 1
melt extruding the composition through a die at a suitable temperature to form a film or sheet
Implementation Method 2
stretching the film or sheet in at least one of the machine-direction or the cross-direction to orient molecular chains of the composition
Implementation Method 3
the composition exhibits sufficient melt strength to undergo the MD and/or CD drawing
Data Source
AI summary
Described herein are starch-based materials, and formulations including such for use in directional alignment extrusion processes. The present compositions exhibit critical shear stress characteristics that allow extrusion at high shear rates and line speeds, without onset of melt flow instability. The present compositions provide sufficient melt strength to allow such compositions to be directionally oriented by stretching the heated polymer (e.g., the polymer melt) following initial extrusion, directionally aligning the molecular chains of the heated polymer blend in the machine-direction, the cross-direction, or both. In an embodiment, the starch-based material is blended with one or more thermoplastic materials having desired melt flow index value(s), which serves as a diluent, allowing the very viscous starch-based component to be processed under such conditions. The starch-based materials (and masterbatches thereof) may exhibit high molecular weight, high shear sensitivity, strain hardening behavior, and/or a very high critical shear stress (e.g., at least 125 kPa).