PVDF Fluoropolymer Film Tear Resistance via Core-Shell Modifiers
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Solution Overview
Problem
Greenhouse films made from fluoropolymers, such as PVDF, lack sufficient tear resistance, especially at low temperatures, while maintaining optical and chemical resistance properties.
Innovation Solution
Incorporating a core-shell type impact modifier into a polyvinylidene fluoride (PVDF) matrix to enhance tear resistance, with a mass rate of impact modifier between 2.5% and 40%, and using a multilayer film structure with modified and unmodified PVDF layers to achieve improved mechanical and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If fluoropolymer films (PVDF or VDF/HFP copolymers) are used for greenhouse applications, then good mechanical, optical, and chemical resistance properties are achieved, but tear resistance is insufficient, especially in the direction of extrusion (MD)
Solution Approach 1:
The patent applies composite materials by combining PVDF or VDF/HFP copolymer with elastomeric modifiers (such as polyethylene-graft-maleic anhydride, ethylene-propylene-diene monomer rubber, or butadiene-styrene rubber). This composite approach enhances tear resistance while preserving the inherent mechanical, optical, and chemical resistance properties of the fluoropolymer matrix, directly resolving the contradiction between maintaining reliability and improving strength.
2Strength
If multilayer fluorinated films with alternating copolymers of different crystallization temperatures are used, then tear resistance is significantly improved, but tear resistance remains insufficient at low temperature
Solution Approach 1:
The patent changes the chemical composition parameters by introducing elastomeric modifiers with specific glass transition temperatures and molecular structures. These modifiers remain flexible at low temperatures, allowing the film to maintain tear resistance in cold conditions while still benefiting from the improved tear strength provided by the multilayer or composite structure.
3Strength
If impact modifiers are added to improve tear resistance, then mechanical properties are enhanced, but visible light transmission and fire resistance must be maintained
Solution Approach 1:
The patent applies local quality by using elastomeric modifiers with specific properties (flexibility, compatibility) that are localized within the fluoropolymer matrix. These modifiers are selected to have refractive indices and optical properties similar to the base polymer, ensuring they enhance tear resistance locally without significantly affecting the overall visible light transmission of the film.
Solution Approach 2:
The patent carefully controls the concentration of impact modifiers (typically 5-50 wt%) and selects modifiers with appropriate molecular weights and chemical structures to optimize the balance between mechanical enhancement and optical property preservation, while also maintaining fire resistance characteristics of the fluoropolymer.
Data Source
AI summary
The present invention relates to a fluorinated film having properties that make it suitable for use outside, especially in the agricultural sector. The film according to the invention is a single-layer polymer film comprising a polyvinylidene fluoride (PVDF) matrix and at least one impact modifier having a polyorganosiloxane core and at least one thermoplastic shell, in which the weight content of impact modifier varies between 2.5% and less than 40%. According to one embodiment variant, the invention relates to multilayer films comprising at least one layer of said fluorinated film and at least one layer of unmodified PVDF.