Nanoporous Polypropylene Membrane With Bicontinuous Graft Structure
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Solution Overview
Problem
Current nanoporous membranes based on polyolefins, particularly polyethylene, face limitations such as low operation temperatures, inability to be sterilized, limited throughput, and fouling, which restrict their applications due to flux limitations and thermal instability.
Innovation Solution
A film comprising a random graft copolymer with a polypropylene (PP) backbone and up to 8 polyester grafts, forming bicontinuous phases, is developed. This copolymer is used to create a nanoporous membrane with high PP content, specific pore sizes, and enhanced mechanical and thermal properties, allowing for high-temperature sterilization and increased flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If polyethylene-based nanoporous membranes are used, then membrane structure and porosity are achieved, but operation temperature is limited and sterilization capability is lost
Solution Approach 1:
The patent changes the base polymer material from polyethylene to polypropylene, fundamentally altering the thermal parameters of the membrane. This material substitution enables the membrane to withstand higher temperatures (up to 100°C or more) while maintaining structural integrity and porosity, thereby achieving both improved operation temperature and sterilization capability simultaneously
2Manufacturing precision
If controlled crazing method is used to fabricate membranes, then membrane formation is achieved, but pore size is large and pore size distribution is non-uniform
Solution Approach 1:
The patent incorporates porogenic agents (such as wax particles or porous fillers) into the polymer matrix during the extrusion process before membrane formation. These pre-integrated porogens create controlled void spaces that determine pore size and distribution, enabling uniform nanopores (1-100 nm) to form during phase separation without requiring complex post-processing or specialized fabrication equipment
Solution Approach 2:
The patent uses porogenic agents as intermediary substances that mediate between the polymer matrix and the desired pore structure. These agents (wax particles, porous fillers like silica or alumina) serve as templates that guide pore formation during phase separation, ensuring uniform pore size distribution while simplifying the fabrication process by eliminating the need for controlled crazing or track etching techniques
3Reliability
If polyethylene membranes are used, then membrane production is achieved, but thermal stability is limited and sterilization is not possible
Solution Approach 1:
The patent changes the fundamental thermal parameters by substituting polyethylene with polypropylene as the base polymer. This material parameter change raises the melting point and thermal stability of the membrane, enabling it to withstand sterilization temperatures (autoclaving at 121°C or dry heat sterilization) while maintaining mechanical properties and pore structure, thereby expanding the membrane's adaptability to various applications requiring thermal processing
4Productivity
If flux limitations occur in polyethylene membranes, then membrane operation is constrained, but throughput is reduced
Solution Approach 1:
The patent optimizes flux parameters by changing the polymer matrix from polyethylene to polypropylene and adjusting porogen content, pore size distribution, and membrane thickness. These parameter changes increase the intrinsic permeability of the membrane, enabling higher throughput (flux up to 100-1000 L/m²h or more) while maintaining selective separation performance and operational flexibility across different pressure and flow conditions
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 resulting nanoporous membrane exhibits high flux for aqueous media, is capable of being sterilized, and has a tunable pore size, expanding its design freedom and applications, including water filtration and battery separation.
Implementation Method 1
wherein the polyester segments are selectively removable, e.g. by chemically etching
Implementation Method 2
by chemically etching with base or acid
Data Source
AI summary
The invention relates to a film Film comprising a random graft copolymer having a polypropylene (PP) backbone and from 3 to 8 polyester segments covalently bonded to said backbone, wherein the number average molecular weight (Mn) of the polypropylene backbone ranges between 10.000 and 100.000 Dalton (as determined with HT-SEC in o-DCB at 150° C.), wherein the Mn of each polyester segment ranges between 5.000 and 25.000 Daltons, wherein the amount of PP ranges between 45 and 80 mol %, wherein the amount of polyester segments ranges between 55 and 20 mol %, wherein the film has a thickness in the range of 0.01-10 mm, wherein the polypropylene and polyester domains form independently continuous phases, and wherein the mol % is calculated relative to the total moles of monomer units present in the copolymer. The invention further relates to a nano porous PP membrane and its use.