High Melt Strength Polypropylene Fogging Reduction
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Solution Overview
Problem
High melt strength polypropylene (HMS-PP) experiences fogging due to the decomposition of dialkyl peroxydicarbonates at higher temperatures, leading to reduced visual transparency in applications such as food packaging and automotive interiors.
Innovation Solution
Introducing an anhydride into or onto the polypropylene during heat treatment in the presence of a dialkyl peroxydicarbonate, with a specific molar ratio, to reduce fogging and enhance melt strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If dialkyl peroxydicarbonate is used to improve melt strength of polypropylene, then melt strength is enhanced, but fogging occurs due to decomposition products evaporating and condensing on surfaces
Solution Approach 1:
Anhydride acts as an intermediary substance that reacts with the alcoholic decomposition products of dialkyl peroxydicarbonate. The anhydride captures these volatile alcohols through chemical reaction, preventing them from evaporating and condensing on surfaces to form fog. This mediator approach allows the peroxydicarbonate to maintain its melt strength enhancement function while the anhydride neutralizes its harmful fogging side effect.
Solution Approach 2:
The invention converts the harmful alcoholic decomposition products into beneficial reaction products. By introducing anhydride, the volatile alcohols that cause fogging are transformed into non-volatile ester compounds through chemical reaction. This converts a harmful substance (volatile alcohol causing fog) into a beneficial outcome (reduced fogging, improved transparency) while maintaining the original melt strength benefits.
2Strength
If heat treatment temperature is increased to enhance melt strength, then melt strength improves, but decomposition of dialkyl peroxydicarbonate increases leading to more fogging
Solution Approach 1:
The anhydride is introduced into the polypropylene system before or during the heat treatment process, positioned to preemptively counteract the fogging issue. As the dialkyl peroxydicarbonate decomposes at elevated temperatures, the pre-present anhydride immediately reacts with the released alcoholic decomposition products, preventing them from reaching surfaces and forming fog. This preliminary anti-action occurs throughout the heat treatment process.
3Object-generated harmful factors
If anhydride is introduced to reduce fogging, then fogging is reduced, but the process complexity increases
Solution Approach 1:
The invention modifies the chemical composition parameters of the polypropylene system by introducing anhydride at specific concentrations (0.1-5 wt%). This parameter change transforms the system's behavior regarding fogging without fundamentally altering the processing methodology. The anhydride content is optimized to achieve fogging reduction while maintaining compatibility with existing extrusion and heat treatment processes, thus limiting the increase in process complexity.
Data Source
AI summary
Process for reducing fogging from high melt strength polypropylene (HMS-PP) obtained by heat treating polypropylene at a temperature between 150° C. and 300° C. in the presence of a dialkyl peroxydicarbonate, said process involving the introduction of an anhydride to said high melt strength polypropylene.