Polypropylene Blend for Syringe Barrel Radiation Stability
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Solution Overview
Problem
Existing polypropylene compositions for syringe barrels face challenges in achieving a balance of rigidity, impact resistance, optical clarity, and radiation stability, while also maintaining processability during injection molding.
Innovation Solution
A polypropylene blend comprising 90-99wt% of a random propylene copolymer with a melt flow rate of 15-40 g/10min and 1-10wt% of an ethylene-based plastomer with specific density and melt index ranges, optimized to provide improved mechanical and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polypropylene is blended with other polymers to improve radiation tolerance, then radiation stability is improved, but impact resistance and stiffness may deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ethylene content (1.5-2.5wt%) and MFR (15-40 g/10min) of the random propylene copolymer, and the density (860-915 kg/m³) of the plastomer to achieve optimal balance between radiation stability and mechanical properties
Solution Approach 2:
The patent creates a composite material system by blending random propylene copolymer with ethylene-based plastomer in specific ratios (90-99wt% copolymer, 1-10wt% plastomer), where each component contributes different properties: the copolymer provides radiation stability while the plastomer enhances impact resistance
2Ease of manufacture
If lower crystallisation temperature is used to improve processability, then injection moulding is easier, but cycle time increases reducing productivity
Solution Approach 1:
The patent optimizes the crystallisation temperature parameter by selecting specific MFR ranges (15-40 g/10min) and comonomer content (1.5-2.5wt% ethylene) to achieve a balance between processability and cycle time, avoiding both excessively high and low crystallisation temperatures
3Strength
If blend composition is optimized for impact resistance, then mechanical strength is improved, but optical properties such as clarity and haze may worsen
Solution Approach 1:
The patent uses parameter changes by controlling the plastomer density (860-915 kg/m³) and blend ratio (1-10wt%) to achieve the right balance between impact resistance and optical clarity, where the specific density range ensures proper phase separation and morphology for both mechanical and optical properties
Data Source
AI summary
A composition is disclosed comprising a blend of 90 - 99 wt%, based on the blend, of a random propylene copolymer having an melt flow rate (MFR 230°C/2.16kg) of 15 - 40 g/10min and containing 1.5 – 2.5 wt% ethylene, and 1 - 10 wt%, based on the blend, of an ethylene based plastomer having a density of 860 - 915 kg/m3 and an MI2 (190°C/2.16kg) of 0.5 to 25 g/10 min. The blend preferably has an MFR of 15-35 g/10min and a flexural modulus of 700-1300 MPa.