UHMWPE Sheet Production via Heated Calender Rolls
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Solution Overview
Problem
The production of ultra high molecular weight polyethylene (UHMWPE) sheets wider than 1-2 inches requires expensive and complex equipment for powder compaction, which is necessary for subsequent rolling and drawing processes, but results in products that are not fully dense and unsuitable for further processing.
Innovation Solution
A process involving feeding polyolefin powder into the nip between heated calender rolls, rolling it into a coherent sheet, and adjusting temperature to achieve specific tensile and elongation properties, eliminating the need for compaction and enabling further drawing without tearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If powder compaction is used to produce UHMWPE sheets, then the sheets have sufficient tenacity for rolling and drawing, but the equipment becomes massive, complex and expensive
Solution Approach 1:
The invention extracts and eliminates the compaction step from the traditional process sequence. By applying heat directly to the polyolefin powder in the nip between calender rolls, the process achieves sheet formation without requiring the separate compaction operation, thereby removing the need for massive compaction equipment while maintaining sufficient sheet tenacity for subsequent drawing operations
Solution Approach 2:
The invention changes the temperature parameter in the rolling operation itself. By heating the calender rolls to temperatures above the melting point of polyolefin powder (typically 150-200°C), the powder becomes sufficiently plastic to form coherent sheets directly in the nip, eliminating the need for low-temperature compaction while achieving the required sheet strength for drawing
2Ease of manufacture
If powder compaction is used to produce UHMWPE sheets, then the sheets can be introduced into rolling operation, but the sheets are relatively friable and require subsequent calendering or drawing to achieve good strength and durability
Solution Approach 1:
The invention changes the temperature parameter from below-melting-point compaction to above-melting-point rolling. By maintaining the calender rolls at temperatures sufficient to keep the polyolefin powder plastic (above melting point), the resulting sheets exhibit superior strength and durability properties directly from the rolling operation, eliminating the need for subsequent calendering or drawing to achieve acceptable mechanical properties
Solution Approach 2:
The invention combines the heating and rolling operations into a single continuous process step. The polyolefin powder is heated and rolled simultaneously in the nip between heated calender rolls, producing sheets with inherent strength and durability without requiring separate subsequent processing steps to enhance mechanical properties
3Area of stationary object
If compaction equipment is used for UHMWPE sheets wider than 1-2 inches, then the sheets can be produced, but capital expenditures and operating and maintenance expenses increase significantly
Solution Approach 1:
The invention makes the calender rolls multi-functional by designing them to perform both heating and rolling operations simultaneously. The calender rolls are heated to temperatures above the melting point of polyolefin powder, enabling them to directly form coherent sheets from powder without requiring separate compaction equipment, thereby producing wide sheets (greater than 1-2 inches) with reduced capital and operating costs
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
This process produces virtually full-density UHMWPE sheets suitable for drawing, achieving high tenacity and orientation with reduced capital and operating expenses, and producing materials with high heat of fusion, tensile strength, and low entanglement.
Implementation Method 1
feeding a metered amount of polyolefin powder into the nip between two vertically stacked and heated calender rolls
Implementation Method 2
rolling the powder through the nip until a coherent sheet of polyolefin sheet is produced
Data Source
AI summary
A process for the production of virtually full density polyolefin suitable for further processing by drawing to form a high tenacity, highly oriented polyolefin sheet comprising: a) feeding a metered amount of polyolefin powder into the nip between two vertically stacked and heated calender rolls through application of the polyolefin powder to the apex of the topmost of the two heated calender rolls; b) rolling the powder through the nip until a coherent sheet of polyolefin sheet is produced: and c) once a coherent polyolefin sheet exits the nip adjusting the temperature in the nip to obtain specific tensile and elongation properties. Apparatus for the performance of such a process is also described.