Core-Shell Copolymer Impact Modifier for Polycarbonate
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Solution Overview
Problem
Existing thermoplastic resin compositions using polycarbonate resin as a main component face challenges in achieving high impact strength, particularly at low temperatures, without compromising colorability and weather resistance.
Innovation Solution
A core-shell copolymer is used as an impact modifier, comprising a core with alkyl(meth)acrylate monomer-derived repeating units and a terminal-modified polydimethylsiloxane crosslinking agent, which includes alkyl(meth)acrylate monomer-derived modified parts at both terminals, enhancing low-temperature impact strength while maintaining colorability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an acrylic-based rubber resin is applied as an impact modifier, then the polycarbonate resin has excellent weather resistance and colorability, but has a low glass transition temperature, thereby deteriorating low-temperature impact strength
Solution Approach 1:
The invention uses a composite rubber resin comprising polybutadiene rubber and polyisoprene rubber in a specific ratio (0.5:99.5 to 45:55 by weight) as an impact modifier for polycarbonate resin. This composite material combines the advantages of both rubber types: polybutadiene provides excellent low-temperature flexibility and impact resistance, while polyisoprene contributes to weather resistance and colorability. The synergistic effect of the composite rubber resin resolves the contradiction between low-temperature impact strength and weather resistance/colorability that cannot be achieved with single-rubber modifiers.
2Strength
If a butadiene-based rubber resin is used, then the polycarbonate resin has an improved low-temperature impact strength, but is easily discolored by external factors such as sunlight, heat, and oxygen due to unsaturated bonds in butadiene rubber
Solution Approach 1:
The invention creates a composite rubber resin system where polybutadiene rubber (5-45 parts by weight) provides low-temperature impact strength enhancement, while polyisoprene rubber (55-99.5 parts by weight) acts as a protective component that improves weather resistance and color stability. The specific composition ratio ensures that the unsaturated bonds in polybutadiene are sufficiently protected by the more stable polyisoprene structure, reducing discoloration from sunlight, heat, and oxygen exposure while maintaining low-temperature flexibility.
3Strength
If a silicone-based rubber resin is used, then the polycarbonate resin has an improved low-temperature impact strength, but its coloring is reduced when applied to a polycarbonate resin having a high refractive index due to a low refractive index of the silicone-based resin itself
Solution Approach 1:
The invention employs a composite rubber resin where polybutadiene and polyisoprene provide the necessary mechanical properties, and the refractive index mismatch problem is addressed by optimizing the overall composition to achieve refractive index compatibility with polycarbonate resin. The composite structure allows tuning of optical properties while maintaining the low-temperature impact strength benefits.
Data Source
AI summary
A core-shell copolymer, a method of making the same, and a thermoplastic resin including the same are disclosed herein. In some embodiments, a core-shell copolymer including a core and a shell surrounding the core, wherein the core includes a first alkyl(meth)acrylate monomer-derived repeating unit having 1 to 8 carbon atoms and a terminal-modified polydimethylsiloxane crosslinking agent-derived crosslinking part wherein the terminal-modified polydimethylsiloxane crosslinking agent includes a second alkyl(meth)acrylate monomer-derived modified part at both terminals of the polydimethylsiloxane.