Propylene Polymer Composition Stiffness Toughness Balance
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Solution Overview
Problem
Propylene polymer compositions used in small appliances and white goods face challenges in achieving a balance of stiffness, toughness, and surface quality, as the addition of mineral fillers increases stiffness but decreases toughness, promoting β-modification reduces stiffness while increasing toughness, and incorporating glass fibers compromises surface quality.
Innovation Solution
A propylene polymer composition comprising 70-98% heterophasic propylene copolymer with a high propylene content, 2-30% mineral filler, and 0.0001-1.0% β-nucleating agent, resulting in a composition with over 50% β-modification and significantly enhanced impact strength and stiffness, particularly at sub-zero temperatures, while maintaining excellent surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If mineral fillers are added to propylene polymer composition, then stiffness is increased, but toughness deteriorates
Solution Approach 1:
The patent changes the crystal modification parameter from alpha to beta by adding beta-nucleating agents (such as calcium pimelate, quinacridone, or dihydroquinacridone) at specific concentrations (0.0001-1.0 wt.-%). This parameter change enables the polymer to achieve both high stiffness (flexural modulus ≥1000 MPa) and high toughness (impact strength at -20°C at least 50% higher than copolymer alone) simultaneously, resolving the contradiction between stiffness and toughness that normally exists when mineral fillers are added.
2Strength
If β-modification is promoted in propylene copolymer, then toughness is increased, but stiffness is reduced
Solution Approach 1:
The patent applies parameter changes by controlling the beta-modification content within an optimal range (30-95 wt.-%, preferably 50-90 wt.-%) rather than maximizing it. This controlled parameter adjustment, combined with specific copolymer composition (Mw/Mw(XCS) ratio >0.8 and 5-35 wt.-% XCS content), achieves the counterintuitive result of simultaneously increasing both toughness and stiffness, overcoming the traditional trade-off where beta-modification promotion reduces stiffness.
3Strength
If glass fibers are added to increase stiffness and toughness, then surface quality deteriorates significantly
Solution Approach 1:
The patent extracts the harmful effect of mineral fillers on surface quality by eliminating glass fibers and other conventional reinforcements from the composition. Instead, it uses a refined copolymer composition with controlled molecular weight distribution and beta-nucleating agents, achieving high stiffness and toughness without the surface defects (fiber exposure, roughness, sink marks) that normally result from glass fiber addition.
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 achieves a substantial increase in both toughness and stiffness, with impact strength at least 50% higher than the propylene copolymer alone, and a flexural modulus of at least 1000 MPa, along with improved surface quality, as demonstrated by the 'delta total' value indicating a significant enhancement in mechanical properties.
Implementation Method 1
0.0001 to 1.0 wt.-% of a β-nucleating agent promoting the β-modification of the propylene copolymer
Data Source
AI summary
A propylene polymer composition having a high impact strength and a high stiffness for the manufacture of parts having an excellent surface quality comprisingA) 70 to 98 wt.-% of a heterophasic propylene copolymer with ethylene or an alpha-olefin with 4 to 12 carbon atoms, the propylene copolymer, which contains more than 60 wt.-% propylene, having a melt flow rate (MFR2) of 0.5 to 50 g/10 min and a ratio between elastomer molecular weight and total molecular weight expressed as Mw/Mw(XCS) of more than 0.8,Mw being the weight average molecular weight of the propylene copolymer andMw(XCS) being the weight average molecular weight of the propylene copolymer which is soluble in xylene at +23° C.,and the propylene copolymer further containing a portion of 5 to 35 wt.-% soluble in xylene at +23° C. (XCS content),B) 2 to 30 wt.-% of a mineral filler,C) 0.0001 to 1.0 wt.-% of a β-nucleating agent promoting the β-modification of the propylene copolymer,said composition having a content of β-modification of more than 50% determined by differential scanning calorimetry (DSC) and an impact strength at −20° C. which is at least 50% higher than the impact strength of the propylene copolymer (A).