Soft Polyolefin Composition for Geomembranes
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Solution Overview
Problem
Existing polyolefin compositions for geomembranes and roofing membranes have low flexural modulus and Shore hardness but require improved tensile properties, particularly tensile stress at break, to meet application demands.
Innovation Solution
A polyolefin composition comprising 15-40% of a propylene-hexene-1 copolymer with 2.5-10% hexene-1 and 60-85% of an ethylene copolymer with propylene or a C2-C8 α-olefin, where the ethylene copolymer has high solubility in xylene at room temperature, is used, along with stereospecific Ziegler-Natta or metallocene catalysts for polymerization, to achieve enhanced tensile properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If polyolefin compositions with high elastomeric fraction content are used to reduce flexural modulus and Shore hardness, then flexibility and softness are improved, but tensile stress at break deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of two specific copolymers: the propylene copolymer contains 2-15% comonomer with specific solubility (5-30% in xylene) and intrinsic viscosity (1.5-4.0 dl/g), while the ethylene copolymer contains 15-40% ethylene with high solubility (>70% in xylene). This precise parameter control allows achieving the optimal balance between flexibility and tensile strength that cannot be obtained by simply increasing elastomeric fraction content.
Solution Approach 2:
The patent uses composite materials by combining two specifically designed copolymers in a defined ratio (40-85% propylene copolymer and 15-60% ethylene copolymer). Each copolymer has distinct properties: the propylene copolymer provides flexibility through controlled comonomer content and solubility, while the ethylene copolymer with high solubility contributes to tensile strength. The synergistic combination resolves the contradiction between flexibility and tensile strength.
2Ease of operation
If inorganic fillers are added to polyolefin compositions to reduce hardness and flexural modulus, then flexibility is improved, but tensile properties deteriorate
Solution Approach 1:
The patent applies parameter changes by controlling the molecular and compositional parameters of the copolymers rather than adding inorganic fillers. The propylene copolymer is designed with specific comonomer content (2-15%), solubility (5-30% in xylene), and intrinsic viscosity (1.5-4.0 dl/g), while the ethylene copolymer has ethylene content of 15-40% and high solubility (>70% in xylene). These parameter optimizations achieve flexibility improvement through molecular structure control, avoiding the use of inorganic fillers that would compromise tensile properties.
Solution Approach 2:
The patent replaces inorganic fillers (which are essentially disposable additives that compromise long-term tensile properties) with organically designed copolymer systems. The flexible propylene copolymer and the high-solubility ethylene copolymer work together as an integrated organic system that provides both flexibility and maintained tensile strength, eliminating the need for inorganic filler additives.
3Ease of operation
If elastomeric copolymers with high comonomer content are used to achieve low flexural modulus, then softness is improved, but processing behavior and tensile properties worsen
Solution Approach 1:
The patent applies parameter changes by optimizing the comonomer content to a specific range (2-15% for propylene copolymer) rather than using high comonomer content elastomers. The solubility parameter (5-30% in xylene) and intrinsic viscosity (1.5-4.0 dl/g) are also controlled to ensure proper processing behavior. This balanced parameter selection achieves softness while maintaining good processing and tensile properties.
Solution Approach 2:
The patent applies local quality by assigning different functional roles to different copolymer components within the composition. The propylene copolymer with controlled comonomer content (2-15%) and specific solubility provides localized flexibility and softness, while the ethylene copolymer with high solubility (>70% in xylene) and 15-40% ethylene content provides localized tensile strength enhancement. This localized functional distribution allows the overall composition to achieve both softness and improved tensile properties.
Data Source
AI summary
A polyolefin composition having unusually low values of flexural modulus and shore hardness andcomprising, in percent by weight: A) 15-40% of a copolymer of propylene with hexene-1 containing from 2.5 to 10% of hexene-1 and having Melt Flow Rate (MFR, measured according to ISO 1133, 230°C/2.16 Kg) from 0.5 to 100g/10 min.; and B) 60-85% of an ethylene copolymer containing ethylene in a quantity equal to or lower than 40%, and having solubility in xylene at room temperature greater than 70%.