Silane Cross-linked Polyethylene Production via Segmented Grafting
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Solution Overview
Problem
Traditional methods for producing cross-linked polyethylene (PEX-b) are inefficient in using silane monomers and result in uneven distribution of cross-links, affecting the long-term performance of PEX-b articles.
Innovation Solution
The method involves maleating polyethylene with maleic anhydride and reacting it with primary or secondary amino silanes to form silane-grafted polyethylene, which is then treated in a moisture curing process to achieve more efficient and homogeneous cross-linking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vinylsilane is grafted onto polyethylene using traditional methods, then cross-linked polyethylene is formed, but silane monomers are used inefficiently and cross-links are unevenly distributed
Solution Approach 1:
The patent segments the cross-linking process into two distinct stages: first grafting vinylsilane groups onto polyethylene chains, then separately hydrolyzing and condensing the silane groups. This segmentation allows better control over cross-link distribution and prevents multiple silanes from clustering on the same chain, improving both uniformity and monomer efficiency.
Solution Approach 2:
The patent applies preliminary action by first grafting vinylsilane groups onto the polyethylene chains before performing the hydrolysis/condensation reaction. This preliminary grafting step ensures proper positioning of silane groups along the polymer chains, which leads to more uniform cross-link distribution and prevents wasteful homopolymerization of vinylsilane.
2Reliability
If multiple silanes are present on the same side chain, then cross-linking occurs, but cross-links are not evenly distributed and performance deteriorates
Solution Approach 1:
The patent extracts the hydrolysis/condensation step from the grafting process, performing these reactions separately after the vinylsilane has been grafted onto the polyethylene. This extraction prevents multiple silanes from reacting simultaneously on the same chain, ensuring more even cross-link distribution and improving long-term reliability.
Solution Approach 2:
The patent uses the grafted vinylsilane groups as an intermediary between the polyethylene backbone and the final cross-linked structure. By first attaching vinylsilane groups in controlled positions and then allowing them to hydrolyze and condense separately, the intermediary step ensures uniform cross-link distribution throughout the material.
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 approach leads to a more efficient use of silane monomers and a more even distribution of cross-links, enhancing the long-term performance of PEX-b articles such as pipes and insulation materials.
Implementation Method 1
maleating a polyethylene polymer to form a maleated polyethylene
Implementation Method 2
reacting the maleated polyethylene with a primary or secondary amino silane to form a silane-grafted polyethylene
Implementation Method 3
The silane-grafted polyethylene is then treated in a moisture curing process to form the cross-linked polyethylene
Implementation Method 4
the hydrolysis/condensation reaction can be done under a variety of conditions, including exposure to moisture under ambient conditions
Data Source
AI summary
A method of producing a silane cross-linked polyethylene is disclosed which includes maleating a polyethylene polymer to form a maleated polyethylene and reacting the maleated polyethylene with a primary or secondary amino silane to form a silane-grafted polyethylene. The method further includes treating the silane-grafted polyethylene in a moisture curing process to form the silane cross-linked polyethylene.