PMMI Copolymers Stabilize Filled Polycarbonate Against Oxide Degradation
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Solution Overview
Problem
Aromatic polycarbonate compositions filled with metal or metalloid oxides experience molecular weight degradation during processing, leading to adverse effects on mechanical, thermal, and optical properties, with existing stabilizers either failing to prevent degradation or compromising the reinforcing effect of fillers and causing yellowing.
Innovation Solution
Incorporating PMMI copolymers into the polycarbonate compositions to inhibit molecular weight degradation without impairing the mechanical and thermal properties, and potentially improving them, while maintaining the reinforcing effect of the fillers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional process stabilizers (phosphites or phosphonites) are used to stabilize polycarbonate compositions, then molecular weight degradation is inhibited, but they are unsuitable for preventing filler-induced degradation
Solution Approach 1:
The patent changes the chemical parameters of the stabilizer by using oxidized acid-modified polyolefinic (co)polymers with specific functional groups (carboxylic acid, carboxylic anhydride, or sulfonic acid) instead of conventional phosphites or phosphonites. This parameter change enables the stabilizer to effectively counter filler-induced degradation while maintaining inhibition of molecular weight degradation
Solution Approach 2:
The patent creates a composite stabilizing system by combining oxidized polyolefinic (co)polymers with specific acid functionalities into a multi-functional stabilizer that addresses multiple degradation mechanisms simultaneously, making it suitable for filler-based polycarbonate compositions
2Reliability
If inorganic acids (e.g., phosphoric acid or phosphorous acid) are added to stabilize polycarbonate compositions, then molecular weight degradation is inhibited, but excessive amounts cause cleavage of carbonate units and degradation
Solution Approach 1:
The patent changes the acidity parameter by using oxidized acid-modified polyolefinic (co)polymers with controlled acid functionality instead of strong inorganic acids. This provides sufficient stabilization while avoiding excessive acidity that would cause carbonate unit cleavage
Solution Approach 2:
The oxidized polyolefinic (co)polymers act as intermediary stabilizers that provide the necessary acid functionality to counter filler-induced degradation without the excessive acidity of inorganic acids, thus mediating between stabilization needs and protection of carbonate units
3Reliability
If organic acids (e.g., citric acid) are used to stabilize polycarbonate compositions, then molecular weight degradation is inhibited, but they decompose far below the typical processing temperature of polycarbonate
Solution Approach 1:
The patent changes the thermal stability parameter by using oxidized acid-modified polyolefinic (co)polymers that maintain structural integrity at polycarbonate processing temperatures (260-400°C), unlike organic acids such as citric acid that decompose at much lower temperatures
Solution Approach 2:
The patent replaces short-lived organic acids that decompose at low temperatures with thermally stable oxidized polyolefinic (co)polymers that can withstand the full processing temperature range of polycarbonate without decomposing
4Reliability
If olefinic waxes are added to stabilize filled polycarbonate compositions, then molecular weight degradation is inhibited, but they have a plasticizing effect and reduce mechanical and thermal properties
Solution Approach 1:
The patent changes the molecular weight and structural parameters by using oxidized acid-modified polyolefinic (co)polymers instead of low molecular weight olefinic waxes. This eliminates the plasticizing effect while maintaining stabilization effectiveness, as the modified polymers do not reduce the reinforcing effect of fillers
5Reliability
If oxidized acid-modified polyolefinic (co)polymers are added in high concentrations to achieve stabilization, then molecular weight degradation is inhibited, but miscibility with polycarbonate decreases rapidly leading to clouding
Solution Approach 1:
The patent optimizes the concentration parameter by using oxidized acid-modified polyolefinic (co)polymers at controlled low levels (0.01-5% by weight based on filler content). At these optimized concentrations, the stabilizers provide effective protection against filler-induced degradation while maintaining sufficient miscibility with polycarbonate to avoid clouding
Data Source
AI summary
The invention relates to the use of PMMI copolymers for reducing the molecular weight degradation of the polymer induced by oxides such as titanium dioxide or silicon dioxide in compositions based on aromatic polycarbonate. The mechanical, optical and rheological properties of the thermoplastic composition remain good and are in some cases even improved despite the addition of the PMMI copolymer.