Session: 05-04-01: Biomaterials and Tissue: Modelling, Synthesis, Fabrication and Characterization - I

Paper Number: 95610

95610 - Hydrophobicity Improvements of Polymers Used in Biomedical Applications 

Improvement in hydrophobicity is important for polymers used in various applications such as biomedical applications, as it can delay their degradation due to long-term exposure to moisture environments. Various surface modification techniques such as surface texturing have been employed over the years to improve the hydrophobicity of polymers. Although a number of surface modification techniques have been developed, their specific influences on hydrophobicity enhancement as well as long-term mechanical and tribological performances are yet to be fully understood. Introduction of textures on the surface may improve hydrophobicity; however, it’s impact on long-term tribological performance such as the wear and abrasion resistance of polymers used in prosthesis applications is complicated. In this study, surface textures, with variation in type and geometry, are introduced on Ultrahigh Molecular Weight Polyethylene (UHMWPE) and High Density Polyethylene (HDPE) surfaces to study the effect of surface modification on hydrophobicity and long-term mechanical and tribological performances. Theoretical study, using the Wenzel and Cassie-Baxter models, is conducted initially to investigate the feasibility of improving the hydrophobic properties by introducing various textures on polymer surfaces.

Based on the theoretical findings, protrusion and cavity surface textures of various types with difference in texture dimension are introduced on the surfaces of two model polymers, UHMWPE and HDPE, using a combination of laser engraving and hot pressing techniques. The textures introduced on the UHMWPE and HDPE polymer surfaces are analyzed using a digital microscope. The hydrophobicity of model polymer surfaces is measured using a custom-built water contact angle measurement setup since the hydrophobicity of a surface is characterized by the contact angle (θ) between a water droplet and the surface. The experimental results show that introduction of surface textures significantly improves the hydrophobicity of UHMWPE and HDPE. When comparing experimental results of protruding surface texture features with the theoretical models, the experimental results do not match well with the Wenzel model. However, the experimental results match well with the Cassie-Baxter model. For cavity surface texture features, the experimental results do not match well with both Wenzel and Cassie-Baxter models. The experimental results show significantly higher improvement in hydrophobicity compared to the Wenzel and Cassie-Baxter models for these cavity textures. Not much variation between protrusion and cavity textures could be found when comparing these two texture types for similar dimensions, for both UHMWPE and HDPE. Based on the comparison between the experimental results and theoretical models, it seems that a transition state (partially filling the voids of surface roughness, which is the transition state between Wenzel and Cassie-Baxter states) modeling is more suitable in describing the change in hydrophobicity with the addition of surface texture. Specific relationship between texture type and geometry, and improvement in hydrophobicity is also explored using the experimental results. The study provides useful guidelines to improve the hydrophobicity of polymers for biomedical applications as well as polymers used in automotive, aerospace, electronics, and household applications.

Presenting Author: Mohammad Hossain Texas A&M University-Kingsville

Presenting Author Biography: Mohammad Motaher Hossain is an Associate Professor in the Department of Mechanical & Industrial Engineering at Texas A&M University-Kingsville. His research mainly focuses on structure-property relationship in polymers, surface engineering, polymer tribology, contact mechanics, and fracture and failure analysis of polymeric materials, with more than 30 peer-reviewed publications in these fields. He received his Doctorate degree in Mechanical Engineering from Texas A&M University. His doctoral research focused on experimental and finite element analysis of polymer scratch behavior.

Authors:

Mohammad Hossain Texas A&M University-Kingsville
Vinay Reddy Lokasani Texas A&M University-Kingsville