Heterophasic Polypropylene Pipe Stiffness Impact Strength
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Solution Overview
Problem
Non-pressure pipes, such as sewage pipes, face challenges in achieving high stiffness while maintaining acceptable impact strength, especially at low temperatures, due to the conflicting properties of stiffness and impact resistance in polypropylene materials.
Innovation Solution
A heterophasic polymer composition is developed, comprising a propylene homopolymer or copolymer matrix with a low amount of comonomer units and an elastomeric polypropylene dispersed within, featuring an amorphous fraction with specific ethylene-derived comonomer units and a xylene cold soluble fraction, which enhances the tensile modulus and impact strength of the pipes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tensile modulus of PP pipe material is increased to improve stiffness, then the pipe can withstand earth load better, but the impact strength decreases especially at low temperature
Solution Approach 1:
The invention changes the chemical composition parameters of the polypropylene material by controlling comonomer content (0.5-2.0 wt%) and introducing specific additives (0.1-5.0 wt% of compound (I) and 0.1-5.0 wt% of compound (II)). These parameter changes enable the material to achieve both high tensile modulus (improved stiffness) and maintained impact strength, resolving the contradiction between these two properties.
Solution Approach 2:
The invention creates a composite polymer material system consisting of polypropylene base material combined with specific comonomer units and additive compounds (I) and (II). This composite approach allows the material to exhibit both high stiffness and good impact resistance, overcoming the limitation of pure PP materials where increasing stiffness inevitably reduces impact strength.
2Weight of moving object
If polymer materials like PVC or PE are used to reduce weight compared to ceramics or concrete, then the pipe becomes lighter and easier to handle, but the stiffness may be insufficient to withstand earth load without internal pressure support
Solution Approach 1:
The invention optimizes the compositional parameters of polypropylene-based pipe material by controlling comonomer content (0.5-2.0 wt%) and adding specific compounds (0.1-5.0 wt% each of compounds (I) and (II)). These parameter adjustments enable the pipe to achieve high tensile modulus values that provide sufficient stiffness to withstand earth loads, while maintaining the lightweight advantage of polymer materials over ceramics or concrete.
Data Source
AI summary
The present invention relates to a heterophasic polymer composition which comprises (i) a matrix comprising a propylene homopolymer and/or a propylene copolymer having an amount of comonomer units of less than 1.0 wt%, and (ii) an elastomeric polypropylene which is dispersed within the matrix and comprises comonomer units derived from ethylene and/or a C4 to C12 alpha-olefin; and wherein the heterophasic polymer composition has an amorphous fraction AM in an amount of 2.0 to 7.5 wt%, and the amorphous fraction AM has an amount of ethylene- and/or C4 to C12 alpha-olefin-derived comonomer units of 20 to 45 wt%.