Polyolefin Blends with Crystalline Block Copolymer Compatibilizer
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Solution Overview
Problem
Polypropylene (PP) and high density polyethylene (HDPE) blends in the post-consumer recycle industry often exhibit poor mechanical properties, such as impact strength and tensile toughness, due to incompatibility, and modifying them with elastomers can compromise other properties, particularly at temperatures below freezing.
Innovation Solution
A composition comprising 10 wt% to 86 wt% ethylene component, 10 wt% to 86 wt% propylene component, 2 wt% to 22 wt% octene component, and 2 wt% to 20 wt% crystalline block composite, which includes a crystalline ethylene based polymer, a crystalline alpha-olefin based polymer, and a block copolymer with crystalline ethylene and alpha-olefin blocks, is used to enhance the mechanical properties of PP/HDPE blends while minimizing loss of modulus-related properties at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If elastomers are added to PP/HDPE blends to improve toughness, then impact strength and tensile toughness are improved, but modulus-related properties deteriorate
Solution Approach 1:
A compatibilizer comprising a block copolymer with crystalline ethylene and propylene blocks is introduced as an intermediary substance between PP and HDPE phases. This compatibilizer reduces interfacial tension and improves adhesion between incompatible phases, enabling toughness enhancement without proportionate loss of modulus. The block copolymer structure allows it to blend with both polypropylene and polyethylene phases, creating a stabilized morphology that maintains structural integrity.
Solution Approach 2:
The invention creates a multi-phase composite material system consisting of PP, HDPE, elastomer, and compatibilizer phases. By carefully controlling the composition ratios and phase morphology, the composite achieves synergistic properties where the elastomer provides toughness while the compatibilizer maintains continuity and load transfer, preventing excessive modulus loss. The crystalline block copolymer forms a structured composite architecture that balances soft and hard phases.
2Strength
If elastomers are added to PP/HDPE blends to improve toughness, then mechanical properties at low temperatures are improved, but other properties are compromised
Solution Approach 1:
The crystalline block copolymer compatibilizer acts as a mediator that stabilizes the multi-phase morphology at low temperatures. Its crystalline structure provides thermal stability and maintains phase dispersion integrity when the material is exposed to freezing conditions, ensuring that toughness improvements are maintained without triggering other property deteriorations.
Solution Approach 2:
The invention optimizes specific composition parameters including the ratio of PP to HDPE, the amount of elastomer added, and the concentration of block copolymer compatibilizer. By precisely controlling these parameters within specific ranges, the material achieves enhanced low-temperature mechanical properties while maintaining overall property balance and reliability across different service conditions.
Data Source
Figure 1
AI summary
A composition comprising from 10 wt% to 86 wt% of an ethylene component including at least one ethylene based polymer having an ethylene content of at least 50.0 wt%, a melt index from 0.1 g/10 min to 100.0 g/10 min, and a density from 0.935 g/cm3 to 0.965 g/cm3; from 10 wt% to 86 wt% of a propylene component including at least one propylene based polymer having a propylene content of at least 50.0 wt% and a melt flow rate from 0.5 g/10 min to 200.0 g/10 min; from 2 wt% to 22 wt% of an octene component including at least one octene based polymer having an octene content of at least 80 wt%; and from 2 wt% to 20 wt% of a composite component including at least one selected from the group of a crystalline block composite and a specified block composite, derived from at least ethylene and an alpha-olefin.