PVC Compound Molecular Weight Distribution for Chlorine Industry
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Solution Overview
Problem
Current materials like PVC-U and PVC-C have limitations in high-temperature resistance and chemical stability, especially in the chlorine industry, leading to costly and complex processing, and composite pipes with polypropylene inliners face issues with thermal expansion and corrosion, resulting in frequent failures.
Innovation Solution
A PVC composition with a specific molecular weight distribution and chlorine content, combined with a tin stabilizer, providing high chemical resistance and ease of processing, and a composite pipe design using a glass fiber reinforced thermoset resin with an adhesive bond, eliminating the need for glass fleece and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If PVC-U is used for plant construction, then it is cost-effective and easy to process, but it has an upper temperature limit of around 60°C to 70°C
Solution Approach 1:
The patent applies parameter changes by modifying the molecular weight distribution of the PVC resin, specifically using a number average molecular weight (Mn) of 60-70 kDa and weight average molecular weight (Mw) of 114-124 kDa. This parameter optimization allows the material to achieve a Vicat softening temperature above 80°C while maintaining good processability and weldability, thus resolving the contradiction between temperature resistance and ease of manufacture.
2Temperature
If PVC-C is used to withstand higher temperatures, then the Vicat softening temperature increases significantly, but it is significantly more expensive and more difficult to weld and thermoform
Solution Approach 1:
The patent applies parameter changes by optimizing the molecular weight distribution parameters (Mn: 60-70 kDa, Mw: 114-124 kDa) and chlorine content (56-62%) of the PVC resin. These parameter changes enable the material to achieve high Vicat softening temperature (>80°C) while maintaining good weldability and thermoformability, thus resolving the contradiction between temperature resistance and ease of manufacture.
3Temperature
If PVC-C is used for high temperature applications, then the Vicat softening temperature increases, but the chemical resistance profile is limited due to mandatory addition of impact modifiers
Solution Approach 1:
The patent applies parameter changes by optimizing the molecular weight distribution (Mn: 60-70 kDa, Mw: 114-124 kDa) and chlorine content (56-62%) of the PVC resin, which enables achieving high Vicat softening temperature (>80°C) without requiring impact modifiers, thus maintaining excellent chemical resistance particularly in the chlorine industry.
Solution Approach 2:
The patent applies the extraction principle by removing impact modifiers from the material composition. By optimizing the base PVC resin parameters, the material achieves both high temperature resistance and good impact resistance without needing additional impact modifier additives, thereby eliminating the chemical resistance limitations associated with PVC-C.
4Temperature
If polypropylene is used for basic media at higher temperatures, then it resists thermal expansion better, but it has increased sensitivity to stress cracks and requires slow stress relaxation
Solution Approach 1:
The patent applies parameter changes by optimizing the molecular weight distribution (Mn: 60-70 kDa, Mw: 114-124 kDa) of the PVC resin, which provides both thermal resistance for high-temperature applications and improved stress crack resistance, eliminating the need for slow stress relaxation periods required by polypropylene.
5Reliability
If a polypropylene inliner is used in composite pipes, then it provides chemical resistance, but thermal expansion differences cause high shear forces and frequent failures
Solution Approach 1:
The patent applies parameter changes by using PVC resin with optimized molecular weight distribution (Mn: 60-70 kDa, Mw: 114-124 kDa) and chlorine content (56-62%) as the inliner material. This provides chemical resistance while having a coefficient of thermal expansion closer to GRP, significantly reducing thermal stress and improving connection strength in composite pipe systems.
Data Source
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AI summary
Composition comprises a PVC resin with a number average molecular weight of 60-70 kDa, and weight average molecular weight of 114-124 kDa, where the composition comprises a chlorine content of 56-62%. An independent claim is included for a pipe, channel or container for the transmission and/or storage of chemically aggressive substances comprising the composition.