A Review of Biomedical Applications of Polyurethane Materials and Their Coatings
Chapter 1 Development History and Basic Properties of Polyurethane Materials
Polyurethane (PU), one of the most important synthetic polymer materials in the 20th century, has a development history that can be traced back to the significant discovery by German chemist Otto Bayer in 1937. Professor Bayer successfully achieved the industrial synthesis of polyurethane based on the reaction principle between isocyanates discovered by Wurtz in 1849. This milestone discovery laid the foundation for modern polyurethane chemistry and opened new avenues for subsequent developments in materials science.
From a chemical structure perspective, polyurethane is a polymer compound containing carbamate groups (-NHCOO-) formed through addition polymerization reactions between isocyanate groups (-NCO) and hydroxyl groups (-OH). This unique chemical structure endows polyurethane materials with a series of distinct performance advantages. In molecular design, precise control over the ratio between soft segments (long-chain polyols) and hard segments (reaction products from isocyanates with chain extenders) allows for continuous performance tuning from flexible elastomers to rigid plastics. This structural designability makes polyurethane one of the most customizable polymers available.
Entering the 21st century, global production capacity for polyurethanes has experienced explosive growth. According to statistical data, global annual production exceeded 23 million tons by 2021, covering numerous industries including construction, automotive, electronics, and healthcare. Notably within medical health fields, applications for polyurethane materials have grown at rates significantly higher than those seen in traditional sectors due to their excellent biocompatibility and degradable properties.
Chapter 2 Chemical Composition and Structural Characteristics of Polyurethanes
2.1 Main Chemical Components and Their Functions The synthesis process for polyurethanes involves complex multi-component reaction systems centered around three core raw material categories: isocyanates, polyols, and chain extenders. Isocyanates as key reactive components can be divided into aromatic or aliphatic types; aromatic isocyanates such as Toluene Diisocyanate (TDI) or Methylene Diphenyl Diisocyanate (MDI) exhibit high reactivity but suffer from poor light stability compared to aliphatic counterparts like Hexamethylene Diisocyanate (HDI) or Isophorone Diisocyanate (IPDI), which while more expensive provide better weather resistance and color stability. Multiple classes are commonly used industrially among polyol components categorized primarily into ether-based or ester-based types; ether-type polyols like Polytetrahydrofuran show superior hydrolysis stability whereas polyester-type options such as Polycaprolactone offer enhanced mechanical strength along with solvent resistance capabilities—both molecular weight alongside branching degree significantly influence final product characteristics where high-molecular-weight variants tend towards flexibility while low-molecular-weight choices facilitate rigidity formation. Chain extenders play crucial roles within this chemistry framework where common examples include short-chain diols/diamines like Butanediol(BD)/Ethylenediamine reacting against excess amounts present yielding hard segment structures forming physical crosslinked networks via hydrogen bonding providing exceptional mechanical attributes—selecting different extender types allows precision adjustments across hardness elasticity thermal stabilities etcetera critical metrics impacting overall material functionality! 2.2 Microphase Separation Structures & Performance Relationships One notable feature inherent amongst these polymers lies their microphase separation phenomena observed at molecular levels wherein alternating arrangements exist involving both soft/hard domains creating nanoscale separations internally! Hard regions form quasi-crystalline zones due strong intermolecular hydrogen bonds delivering tensile strengths heat resistances meanwhile softer areas maintain amorphous states contributing elasticities lower temperature performances thus enabling diverse applications across varying contexts! Such structuring's extent morphology undergoes influences stemming from several factors starting chiefly polar differences found amidst soft/hard phases greater disparities yield heightened degrees phase-separation effects additionally variations regarding molecular weights distributions also affect behaviors herein tighter distributions enhancing separative clarity furthermore processing parameters encompassing temperatures catalyst varieties curing conditions impact resultant microstructures considerably throughout each stage involved leading ultimately toward achieving desired outcomes fitting specific application needs! Overall viewpoint reflects how precisely tuned phase-separated designs allow simultaneous possession rubber-like elasticity coupled plastic-like strength thereby satisfying requirements spanning various use cases widely recognized especially within biomedical realms attracting attention extensively!
Chapter Three Biocompatibility & Degradation Features Associated With Polyurethanes
3.1 Mechanisms Evaluating Biocompatibility... [Content truncated] ...