One-Side Coextruded Scrim Coating for Roofing Underlayment
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Solution Overview
Problem
Roofing underlayment and lumber wrap products face challenges with standard two-side coated woven products, which experience weld failure due to stress when stretched, and lack sufficient coefficient of friction, leading to slippage and moisture permeability issues.
Innovation Solution
A multi-layer polyolefin-based coating is applied to one side of a scrim, with a copolymer of ethylene as the outermost layer for high friction and an embossed surface for enhanced grip, and a core layer of polypropylene for high temperature resistance, hydrostatic resistance, and toughness, allowing for lower melting point outer layers to reduce weld stress and improve peel strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard two-side coated woven product is used, then both sides have coating protection, but the welds fail when stretched over lumber due to stress
Solution Approach 1:
The coating is segmented into three distinct layers: an innermost layer adjacent to the scrim, a middle layer, and an outermost layer. This segmentation allows each layer to perform specific functions - the innermost layer bonds to the scrim while the outer layers provide weldability and strength, resolving the weld failure issue without requiring complex multi-side coating structures
Solution Approach 2:
Different layers of the coating have different local qualities optimized for specific functions. The innermost layer has properties optimized for bonding to the scrim substrate, while the outer layers have properties optimized for welding and mechanical strength. This local differentiation allows the coating to achieve high weld strength without the complexity of coating both sides of the scrim
2Reliability
If a coating is applied to provide moisture barrier, then moisture resistance improves, but the coefficient of friction is insufficient causing slippage
Solution Approach 1:
The coating structure provides different local qualities at different interfaces. The innermost layer provides moisture barrier properties adjacent to the scrim, while the outer layers provide high coefficient of friction for slip resistance. This local differentiation resolves the contradiction between moisture protection and friction performance
Solution Approach 2:
The coating uses composite material structure with multiple polymeric layers, each potentially composed of different polymer compositions. This composite structure enables the coating to simultaneously provide moisture barrier properties from the inner layers and high friction properties from the outer layers
3Ease of manufacture
If outer layers have lower melting point for easy welding, then weldability improves, but high temperature resistance decreases
Solution Approach 1:
The coating is segmented into layers with different melting points. The outer layers have lower melting points optimized for welding operations, while the inner layers have higher melting points that provide high temperature resistance. This segmentation allows the product to be easily welded while maintaining temperature resistance
Solution Approach 2:
The melting point parameter is differentiated across the coating layers. Outer layers are formulated with lower melting points for easy welding, while inner layers maintain higher melting points for thermal stability. This parameter differentiation resolves the contradiction between weldability and high temperature resistance
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
The solution provides a roofing underlayment and lumber wrap with improved slip resistance, increased peel strength of welds, and enhanced durability, outperforming existing products in friction and moisture resistance tests.
Implementation Method 1
a first layer of a copolymer of ethylene juxtaposed to the major surface of the scrim and penetrating the interstices thereof to define a portion of the second major surface of the scrim
Implementation Method 2
an embossed surface for enhanced grip
Implementation Method 3
a core layer of polypropylene for high temperature resistance
Implementation Method 4
hydrostatic resistance
Data Source
AI summary
Protective coverings are disclosed that have a scrim made up of warp and weft members that define a plurality of interstices coated on only a first major surface thereof by a multi-layer coating with a first layer of the multi-layer coating juxtaposed to the first major surface, and penetrating into the interstices of the scrim to co-define, with the warp and weft members, an opposing second major surface of the scrim. The first layer of the multi-layer coating has a melting point below 100° C. and comprises a copolymer of ethylene, and provides the co-defined opposing second major surface of the scrim with a coefficient of friction of at least 0.5 when tested with dry leather and at least 0.7 when tested with dry rubber.