Polyorganosiloxane Core-Shell Impact Modifier for Polycarbonate
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Solution Overview
Problem
Polycarbonate resin compositions face challenges with poor flowability due to high melting points, leading to deteriorated impact resistance, and existing impact modifiers either degrade at high temperatures or provide poor coloration and low-temperature impact resistance.
Innovation Solution
An impact modifier comprising a polyorganosiloxane core and a styrenic polymer shell, where the core includes an acrylate and styrenic polymer, and the shell is formed through polymerization and grafting processes, offering enhanced impact resistance and coloration without copolymer formation, with a refractive index between 1.49 and 1.59.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a butadiene rubber-based impact modifier is used to improve impact strength, then impact resistance is improved, but heat stability and weather resistance deteriorate due to degradation at molding temperatures over 300°C
Solution Approach 1:
The invention uses a composite impact modifier consisting of a polyorganosiloxane core and an acrylate rubber shell. This composite structure combines the high-temperature stability of polyorganosiloxane with the impact resistance of acrylate rubber, resolving the contradiction between impact strength and heat stability that plagues single-material modifiers like butadiene rubber.
Solution Approach 2:
The impact modifier employs a core-shell structure where the inner polyorganosiloxane core provides heat stability and the outer acrylate rubber shell provides impact resistance. Each material is placed in the location where it best performs its function, allowing the modifier as a whole to simultaneously achieve both impact strength and heat stability.
2Reliability
If an acrylate rubber-based impact modifier is used to improve heat stability and weather resistance, then reliability is improved, but coloration property and low-temperature impact resistance deteriorate
Solution Approach 1:
The composite core-shell structure allows the polyorganosiloxane core to provide heat stability while the acrylate rubber shell provides low-temperature impact resistance and acceptable coloration properties, overcoming the limitations of using acrylate rubber alone.
Solution Approach 2:
By placing acrylate rubber in the outer shell region, the modifier achieves good coloration and low-temperature impact resistance where these properties are most needed, while the inner core maintains heat stability.
3Ease of manufacture
If polycarbonate resin is processed at high temperature to improve flowability, then ease of manufacture is improved, but impact resistance deteriorates
Solution Approach 1:
The composite impact modifier with polyorganosiloxane core and acrylate rubber shell maintains stability at high processing temperatures, allowing polycarbonate to be processed at lower temperatures without compromising impact resistance, thus resolving the contradiction between flowability and impact strength.
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 impact modifier provides excellent coloration and impact resistance at low temperatures, maintaining glass transition temperature and refractive index, while preventing diffusion and ensuring stable morphology, thus addressing the limitations of existing impact modifiers.
Implementation Method 1
polymerizing the polymerizable styrenic compound within the particle to provide a styrenic polymer
Implementation Method 2
polymerizing the polymerizable acrylic compound within the polyorganosiloxane particle to provide an acrylate polymer
Implementation Method 3
grafting a polymerizable compound onto the polyorganosiloxane particle to provide a shell substantially surrounding the polyorganosiloxane particle
Data Source
AI summary
Disclosed herein is an impact modifier for a polymer composition and a method of preparing the same. The impact modifier includes a core comprising a polyorganosiloxane, an acrylate polymer and a styrenic polymer; and a shell generally surrounding the core, the shell comprising a polymer attached to the core. The method includes providing a silicone rubber particle; adding a polymerizable styrenic compound into the silicone rubber particle; polymerizing the polymerizable styrenic compound within the particle to provide a styrenic polymer; adding a polymerizable acrylic compound into the silicone rubber particle; polymerizing the polymerizable acrylic compound within the silicone rubber particle to provide an acrylate polymer; and grafting a polymerizable compound onto the silicone rubber particle to provide a shell substantially surrounding the silicone rubber particle comprising the styrenic polymer and the acrylate polymer.