Propylene-Ethylene Polymer Composition for Flexible Footwear
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Solution Overview
Problem
Clear flexible PVC injection molded products, such as footwear, face challenges in achieving the desired modulus control, temperature resistance, low tackiness, and maintaining clarity while meeting specific Shore A hardness and re-crystallization temperature requirements without compromising flow properties.
Innovation Solution
A composition comprising a propylene/ethylene interpolymer, a propylene-based polymer, a plasticizing agent, and a third polymer such as a styrenic ethylene/butylene triblock copolymer, ethylene/α-olefin/diene interpolymer, or ethylene vinyl acetate copolymer, optimized in weight percentages to achieve the desired properties of Shore A hardness, haze, crystallization temperature, and melt flow rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If clear flexible PVC is used to achieve flexibility and clarity, then the material provides good flow properties and transparency, but it fails to achieve adequate modulus control and temperature resistance above 85°C
Solution Approach 1:
The patent uses a composite polymer system combining propylene/ethylene interpolymer (providing flexibility and low temperature performance), propylene-based polymer (providing modulus and structural stability), and third polymer (providing temperature resistance and crystallization control). This multi-component composite approach allows simultaneous achievement of Tc > 85°C and proper modulus control that clear flexible PVC cannot provide alone.
2Strength
If the Shore A hardness is reduced to less than 65 for flexibility, then the material becomes softer and more flexible, but the flow properties and clarity are negatively impacted
Solution Approach 1:
The patent applies local quality by assigning different functional roles to each polymer component: propylene/ethylene interpolymer (density 0.860-0.870 g/cc) provides localized flexibility and softness, while propylene-based polymer (density ≥ 0.885 g/cc) provides localized structural support and flow control. This spatial-functional differentiation allows Shore A hardness < 65 while maintaining adequate flow properties and clarity.
3Object-affected harmful factors
If phthalate-free polymeric options are used to meet safety requirements, then the product is safer for end users, but achieving the required re-crystallization temperature of at least 85°C becomes more difficult
Solution Approach 1:
The patent changes the chemical composition parameters by selecting specific polymer types and density ranges: propylene/ethylene interpolymer with density 0.860-0.870 g/cc and propylene-based polymer with density ≥ 0.885 g/cc. These parameter specifications ensure the composite achieves Tc ≥ 85°C while being inherently phthalate-free, meeting both safety and temperature performance requirements.
4Illumination intensity
If the composition is optimized for low haze to maintain clarity, then the material becomes more transparent, but the balance between flexibility and structural integrity is compromised
Solution Approach 1:
The patent achieves multi-functionality where the propylene-based polymer component simultaneously provides haze control (optical clarity) and modulus control (structural integrity). The specific density requirement (≥ 0.885 g/cc) ensures this polymer contributes to both transparency and mechanical strength, eliminating the need to sacrifice one property for the other.
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 composition effectively achieves a Shore A hardness less than 60, total haze of less than 30%, crystallization temperature between 75 to 95°C, and a melt flow rate greater than 20 g/10 min, enhancing the performance of injection molded articles like footwear.
Implementation Method 1
at least 85° C. DSC re-crystallization temperature (Tc)
Implementation Method 2
a plasticizing agent
Data Source
AI summary
A composition including (a) propylene/ethylene interpolymer having a density from 0.860 to 0.870 g/cc; (b) a propylene-based polymer selected from the group consisting of a homopolymer polypropylene, a random propylene/α-olefin interpolymer and any combination thereof and wherein the propylene-based polymer has a density ≥0.885 g/cc; (c) a plasticizing agent; and (d) a third polymer selected from the group consisting of the following (i) a styrenic ethylene/butylene triblock copolymer having a Tg (rubber block) greater than, or equal, −40° C., (ii) less than, or equal to, 15 wt %, based on the weight of the composition, of an ethylene/α-olefin/diene interpolymer, or an ethylene/propylene copolymer, (iii) an ethylene vinyl acetate copolymer, and (iv) any combination thereof is provided. Further provided is an injection molded article comprising the composition and a process for making an injection molded article.