Absorbable Polymer Blend Dimensional Stability
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Solution Overview
Problem
Conventional absorbable polymer blends used in medical devices often suffer from inferior mechanical properties, dimensional instability, and residual stresses due to manufacturing processes like injection molding, which can lead to warpage and shrinkage, especially when exposed to ethylene oxide sterilization or elevated temperatures.
Innovation Solution
A novel absorbable polymer blend comprising a lactide-rich polymer and a poly(p-dioxanone-co-glycolide) copolymer, synthesized using a mixture of mono- and di-functional initiators, which enhances crystallization rates and crystallinity, providing improved dimensional stability and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional injection molding processes are used to manufacture absorbable medical devices, then manufacturing efficiency is improved, but dimensional stability and mechanical properties deteriorate due to residual stresses and warpage
Solution Approach 1:
The patent modifies the chemical composition parameters of the polymer blend by incorporating poly(p-dioxanone-co-glycolide) copolymer with specific dioxanone-to-glycolide ratios (90:10 to 95:5). This compositional parameter change enables the material to maintain dimensional stability while being processed through conventional injection molding, resolving the contradiction between manufacturing efficiency and dimensional precision.
Solution Approach 2:
The patent creates a composite polymer blend system combining lactide-rich polymer with poly(p-dioxanone-co-glycolide) copolymer. This composite material approach allows the blend to exhibit improved crystallization behavior and reduced residual stresses during injection molding, simultaneously achieving high manufacturing efficiency and dimensional stability.
2Duration of action of moving object
If poly(p-dioxanone) is added to increase absorption rate, then absorption performance is improved, but stiffness and mechanical strength deteriorate
Solution Approach 1:
The patent changes the chemical structure parameter of the dioxanone-containing polymer by introducing glycolide units to create poly(p-dioxanone-co-glycolide) copolymer. This parameter change allows the material to maintain higher stiffness and mechanical strength while preserving the desired absorption rate, thus resolving the contradiction between absorption performance and mechanical strength.
3Ease of manufacture
If thermal injection molding is used to manufacture devices, then manufacturing capability is improved, but mechanical properties and breaking strength retention deteriorate due to flow-induced residual stress
Solution Approach 1:
The patent modifies the thermal and rheological parameters of the polymer blend by optimizing the copolymer composition with controlled dioxanone and glycolide ratios. This parameter modification reduces the melt viscosity and improves flow characteristics, allowing thermal injection molding to proceed with reduced flow-induced residual stresses, thereby preserving breaking strength retention while maintaining manufacturing capability.
4Manufacturing precision
If high glass transition temperature materials are used to reduce distortion, then dimensional stability is improved, but absorbability deteriorates
Solution Approach 1:
The patent creates a composite polymer system where poly(p-dioxanone-co-glycolide) copolymer is blended with lactide-rich polymer. This composite approach allows the material to achieve dimensional stability through controlled crystallization behavior rather than relying on high glass transition temperature, thereby maintaining good absorbability while preventing distortion during sterilization and storage.
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 novel polymer blend achieves superior dimensional stability and mechanical properties, reducing warpage and shrinkage, and maintaining stability under conditions like sterilization and storage, while allowing for lower poly(p-dioxanone) content for increased stiffness.
Implementation Method 1
Approaches that have been employed include: (1) attempting to crystallize the part while still in the mold to increase the mechanical rigidity to resist distortion
Implementation Method 2
The absorbable polymers are designed to have a chemistry such that the polymers breakdown in vivo and are either metabolized or otherwise broken down, for example by hydrolysis, and excreted from the patient's body
Data Source
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Figure 5A~5C
AI summary
Novel absorbable polymeric blends made from components wherein at least one of the components is synthesized using mixtures of mono- and di-functional initiators are disclosed. The blends have a first component that is a polylactide polymer or a copolymer of lactide and glycolide and a second component that is either poly(p-dioxanone) homopolymer, or a poly(p-dioxanone-co-glycolide) copolymer. The novel polymeric blends provide medical devices having dimensional stability. Also disclosed are novel absorbable medical devices made from these novel polymer blends, as well as novel methods of manufacture.