Bioabsorbable Polymer Blend for Dimensional Stability
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Solution Overview
Problem
Conventional bioabsorbable polymers used in medical devices often suffer from inferior mechanical properties, dimensional instability, and residual stresses during thermal injection molding, leading to issues like warpage and shrinkage, especially when exposed to ethylene oxide sterilization or elevated temperatures.
Innovation Solution
A novel bioabsorbable polymer blend comprising 76-92 weight percent of a lactide-rich polymer and up to 24 weight percent of poly(p-dioxanone), calculated using the expression Weight Percent Poly(p-dioxanone)=(215.6212/Mol Percent Polymerized Lactide)^2.7027, which provides enhanced dimensional stability and mechanical properties through controlled crystallization and stress reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional thermal injection molding processes are used to manufacture medical devices from bioabsorbable polymers, then manufacturing efficiency is improved, but dimensional stability deteriorates due to residual stresses and warpage
Solution Approach 1:
The patent modifies the chemical composition parameters of the polymer blend by specifying precise weight percentages of poly(p-dioxanone) (5-24 wt%) and lactide-rich copolymer (76-92 wt%), along with controlled molecular weights and crystallinity levels. These parameter changes enable the material to maintain dimensional stability during thermal injection molding while preserving manufacturing efficiency.
Solution Approach 2:
The patent creates a composite polymer blend combining poly(p-dioxanone) with lactide-rich copolymer (polylactide or poly(glycolide-co-lactide)). This composite material leverages the complementary properties of both polymers: poly(p-dioxanone) provides mechanical strength and crystallinity, while the lactide-rich copolymer ensures bioabsorbability and processability, resolving the contradiction between manufacturing efficiency and dimensional stability.
2Reliability
If polymeric components with low glass transition temperature are used to enhance bioabsorbability, then bioabsorption rate is improved, but mechanical properties and dimensional stability deteriorate
Solution Approach 1:
The patent employs a composite material system where poly(p-dioxanone) (with higher Tg providing mechanical stability) is blended with lactide-rich copolymer (with lower Tg providing enhanced bioabsorbability). The specific composition ratios and molecular weight distributions are controlled to achieve synergistic effects, allowing the material to simultaneously exhibit good mechanical properties and rapid bioabsorption.
Solution Approach 2:
The patent precisely controls the glass transition temperature parameters through selection of specific polymer components and their proportions. By adjusting the molecular weight distribution (weight average molecular weight to polydispersity index ratio) and crystallinity (30-70%), the material achieves optimal balance between mechanical strength and bioabsorption rate.
3Manufacturing precision
If high glass transition temperature polymers are used to resist warpage during sterilization, then dimensional stability is improved, but bioabsorbability and mechanical flexibility deteriorate
Solution Approach 1:
The patent uses a composite polymer blend where poly(p-dioxanone) (higher Tg component providing thermal stability during sterilization) is combined with lactide-rich copolymer (lower Tg component maintaining bioabsorbability). The controlled composition ratios ensure that the material achieves dimensional stability during ethylene oxide sterilization while preserving enhanced bioabsorption characteristics.
4Productivity
If residual stresses are introduced during injection molding to improve filling speed, then productivity is improved, but warpage and shrinkage increase
Solution Approach 1:
The patent modifies the material parameters including molecular weight distribution (weight average molecular weight to polydispersity index ratio of 1.05-2.0), crystallinity (30-70%), and composition ratios to enable the polymer blend to be processed at optimized temperatures and pressures. These parameter changes allow for faster filling speeds while minimizing residual stresses and subsequent warpage.
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 polymer blend achieves superior breaking strength retention, dimensional stability, and bioabsorption rates, maintaining structural integrity during sterilization, storage, and in vivo use, while minimizing warpage and shrinkage.
Implementation Method 1
controlled crystallization and stress reduction
Implementation Method 2
controlled crystallization and stress reduction
Implementation Method 3
breakdown in vivo and are either metabolized or otherwise broken down, for example by hydrolysis, and excreted from the patient's body
Data Source
AI summary
Novel bioabsorbable polymeric blends 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 poly(p-dioxanone) polymer. The novel polymeric blends provide medical devices having dimensional stability. Also disclosed are novel bioabsorbable medical devices made from these novel polymer blends, as well as novel methods of manufacture.