Shaped Articles from Crumb Rubber Polyolefin Matrix
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Solution Overview
Problem
Existing methods for forming shaped articles from crumb rubber and thermoplastic materials often result in uneven distribution of crumb rubber within the polymer matrix, leading to inconsistent mechanical, physical, and visual properties, and environmental concerns due to high PAH emissions.
Innovation Solution
A method involving a double grind process of crumb rubber and granular polyolefin, where the mixture is extruded, cooled, and then regrinded to form a homogeneous dispersion of crumb rubber within a polyolefin matrix, followed by injection molding to create shaped articles with improved esthetic and environmental characteristics, including reduced porosity and PAH emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If crumb rubber and thermoplastic materials are mixed and formed using conventional methods, then shaped articles can be produced, but the crumb rubber is unevenly distributed within the polymer matrix
Solution Approach 1:
The mixing process is divided into two distinct stages: initial dry blending of crumb rubber with thermoplastic granules, followed by a second mixing stage after extrusion. This segmentation allows each stage to optimize for different aspects of dispersion, ultimately achieving more uniform distribution of crumb rubber throughout the polymer matrix.
Solution Approach 2:
Crumb rubber is pre-mixed with thermoplastic granules in a dry state before extrusion, creating a preliminary homogeneous blend. This preliminary action ensures that crumb rubber particles are evenly distributed on the surface of granules before melting, which prevents clumping and promotes uniform dispersion in the final product.
2Manufacturing precision
If conventional mixing and forming methods are used, then production can proceed, but the surface texture is irregular and porosity is high
Solution Approach 1:
A preliminary dry mix is created before extrusion, ensuring uniform distribution of crumb rubber on thermoplastic granule surfaces. This preliminary preparation prevents surface irregularities and reduces porosity during the forming process, achieving smoother surfaces without significantly increasing process complexity.
Solution Approach 2:
The process controls and optimizes parameters including mixing ratio, extrusion temperature, and cooling rate to achieve dense, uniform structures with smooth surfaces. By carefully adjusting these parameters, the method reduces porosity and eliminates surface irregularities while maintaining manufacturing efficiency.
3Object-affected harmful factors
If crumb rubber from recycled tires is used, then environmental benefits are achieved, but PAH emissions and environmental compliance become concerns
Solution Approach 1:
The extrusion temperature and processing parameters are optimized to minimize thermal degradation of crumb rubber and reduce PAH emissions. By controlling temperature profiles and residence time, the process achieves environmental compliance while maintaining the benefits of using recycled tire rubber.
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 method achieves a substantially homogeneous dispersion of crumb rubber within the polyolefin matrix, resulting in shaped articles with desirable properties such as even surface texture, weather resistance, and reduced PAH emissions, compliant with environmental standards like REACH.
Implementation Method 1
The mixture is extruded, cooled, and then regrinded
Implementation Method 2
extruded under heat into a sheet/film/ribbon having the crumb rubber substantially evenly dispersed within/throughout a polyolefin matrix
Implementation Method 3
cooled and then further mechanically processed into a regrind composition
Data Source
AI summary
Methods of making an environmentally acceptable shaped article. In an embodiment method comprises machining a sheet comprising crumb rubber within a polyolefin matrix into a plurality of particles to form a reground mixture; and processing the reground mixture at an elevated temperature into a mold to form said shaped article, wherein the shaped article has a substantially more evenly dispersed mixture of said crumb rubber within the matrix of said shaped article than within the matrix of said sheet or the particles of the reground mixture.