Low Gloss ABS Copolymer via Rubber Particle Size Control
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Solution Overview
Problem
Conventional acrylonitrile butadiene styrene (ABS) resins used in extrusion processes often exhibit high gloss, which is undesirable for applications like computer housings and automotive parts, and lack sufficient low gloss when thermoformed or vacuum formed, despite offering good impact resistance and stiffness.
Innovation Solution
A mass polymerized rubber-modified monovinylidene aromatic copolymer composition with a specific matrix and rubber particle size distribution, optimized through bulk polymerization techniques, to achieve a continuous low gloss finish across various fabrications, including extruded sheets and thermoformed articles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional ABS resins are used in extrusion processes, then good impact resistance and stiffness are achieved, but high gloss surface is produced which is undesirable for many applications
Solution Approach 1:
The patent changes the particle size parameter of the rubber domains from conventional smaller sizes to larger average sizes of at least 0.5 micrometers. This parameter change in the rubber particle dimensions directly affects the surface gloss by creating light-scattering centers, while the rubber content and composition are maintained to preserve impact resistance and stiffness properties.
2Illumination intensity
If mass process ABS resins are used, then inherently lower gloss is achieved, but the gloss is still not low enough when extruded into sheet and thermoformed
Solution Approach 1:
The patent applies preliminary action by pre-forming the rubber particle size distribution before the extrusion and thermoforming processes. The rubber domains are deliberately sized to at least 0.5 micrometers during resin formulation, so that when the material is subsequently extruded and thermoformed, the low gloss effect is already established and maintained through the fabrication process, ensuring consistent matte appearance in the final product.
3Illumination intensity
If larger rubber particle size is used to reduce gloss, then low gloss surface is achieved, but may affect other physical properties
Solution Approach 1:
The patent carefully adjusts multiple parameters simultaneously: rubber particle size (increased to ≥0.5 μm), rubber content (1-20 parts per 100 parts resin), and matrix composition (styrene-acrylonitrile copolymer with specific acrylonitrile content). This coordinated parameter optimization ensures that larger rubber particles provide the desired light scattering for low gloss while the controlled rubber concentration and matrix properties maintain the necessary mechanical strength, stiffness, and other physical properties.
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 solution provides a consistent low gloss appearance with maintained impact resistance and chemical resistance, suitable for diverse applications such as automotive and IT equipment parts, while maximizing the compositional effects for lower inherent gloss in fabricated articles.
Implementation Method 1
The large particle size of these rubbery domains is believed to be, in part, responsible for the lower gloss surface finish of mass produced ABS
Data Source
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AI summary
This invention relates to a mass polymerized rubber-modified monovinylidene aromatic copolymer composition compositions with an improved balance of aesthetic, physical and mechanical properties, in particular, a combination of low gloss and good impact resistance in (co)extruded sheet and thermoformed/vacuum formed articles therefrom. A method for preparing such compositions and articles is disclosed. The improved gloss performance is achieved by maintaining the following relationship between the average rubber particle size (RPS) and the weight average molecular weight (Mw) of the matrix polymer: Mw = 155 - 10-6 * RPS6.