Nitroxide Peroxide Composition for Scorch Delay in Elastomers
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Solution Overview
Problem
Premature crosslinking (scorching) during the preparatory phase of elastomeric and thermoplastic materials using peroxides leads to imperfections and reduced productivity, as existing solutions either prolong curing time or decrease final crosslinking density.
Innovation Solution
A composition comprising a nitroxide and organic peroxide in specific weight ratios (1:0.01 to 1:0.1) is used to retard scorching without harming crosslinking density, allowing for high productivity and improved mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If organic peroxide is used for crosslinking elastomeric and thermoplastic materials, then crosslinking density and mechanical properties are improved, but premature crosslinking (scorching) occurs during the preparatory phase
Solution Approach 1:
A nitroxide compound is introduced as an intermediary substance that temporarily prevents the peroxide from decomposing and causing premature crosslinking during the preparatory phase. The nitroxide acts as a protective mediator that allows safe blending and extrusion, then is removed before final crosslinking to enable complete curing without scorching.
Solution Approach 2:
The nitroxide compound is added in advance during the preparatory phase to prevent scorching before the actual crosslinking process. This preliminary protective action allows the material to be processed at high temperatures without premature crosslinking, and the nitroxide is subsequently removed before final crosslinking occurs.
2Object-generated harmful factors
If additives are incorporated to reduce scorching tendency, then scorching time is extended, but curing time increases and final crosslinking density decreases
Solution Approach 1:
The nitroxide serves as a temporary intermediary that only protects during the preparatory phase, then is completely removed before crosslinking. This differs from conventional additives that remain in the final product and continuously interfere with crosslinking. The intermediary is removed, allowing full crosslinking density to be achieved without productivity loss.
Solution Approach 2:
The nitroxide compound is discarded after serving its protective function during the preparatory phase. It is completely removed from the material before the crosslinking step, allowing the crosslinking process to proceed to completion without interference, thus maintaining both productivity and crosslinking density.
3Object-generated harmful factors
If initiator with long half-life time is used to prevent scorching, then scorching is reduced, but productivity decreases due to long curing time
Solution Approach 1:
The nitroxide provides preliminary protection during the preparatory phase, then is removed to allow rapid crosslinking. This separates the protection function from the crosslinking function, allowing each to be optimized independently, unlike long half-life initiators that inherently slow down the crosslinking process.
Solution Approach 2:
The system changes the state of the nitroxide from present (protective) to absent (allowing crosslinking). This parameter change enables the material to transition from a protected state during processing to an active crosslinking state, achieving both scorch prevention and fast curing without the trade-off inherent in using long half-life initiators.
Data Source
AI summary
The invention relates to scorch prevention and, more specifically, to a composition which comprises a nitroxide and at least one organic peroxide and which can be used to delay scorching prior to crosslinking of thermoplastic compositions and/or elastomers. The invention also relates to a crosslinkable composition and to a crosslinking method.