Modification Of Natural Rubber Latex With Water-soluble Chitosan And Waterborne Polyurethane

As a renewable natural resource, natural rubber latex (NRL) possesses excellent mechanical properties. It has been widely used in medical field, such as medical catheter, medical gloves and condoms. However, some defects of natural rubber products have been gradually exposed. They are not compactable enough to prevent certain viruses and bacteria from penetrating medical gloves, and their anti-aging, antimicrobial performances are weak. Another serious problem is that NRL contains some allergen—Water-soluble protein, which can easily induced contact dermatitis, urticaria, allergic asthma, etc. These allergic reactions will cause severe anaphylactic shock, and even death.Chitosan has been gained a growing number of attention, because of its biocompatibility, biodegradability and non-toxicity accompanying with its antimicrobial activity and low immunogenicity. Focusing on those drawbacks of NR procucts, we introduced chitosan into NRL. By use of heterocoagulation method, we wrapped up NR particles with water-soluble chitosan and prepared a stable blending emulsion. Furthermore, the irritability was studied by cytotoxicity, skin irritatin and extracted protein tests and the surface of modified films was characterized by contact angle and scanning electron microscope. The results show that: water-soluble chitosan was successfully wrapped in the outer surface of the rubber microspheres, and formed a core-shell structures. Such structure endowed films with compactness, excellent mechanical strength and solvent resistance. Extracted protein concentration and cell toxicity testing showed that the water-soluble chitosan can effectively prevent water-soluble protein extracting from films, and make extracted protein concentration lower than the minimum sensitization concentration.Waterborne polyurethane(WPU) has many advantages, such as, environment-friendly, non-toxic, excellent mechanical performance, and good compatibility. Both anionic waterborne polyurethane particles and NR particles are negatively charged, and can blend in any ratio. We added waterborne polyurethane into NRL in order to improve the compactness, mechanical strength, solvent resistance and to reduce extracted protein concentration. Four kinds of waterborne polyurethane were systhesised. When polytetrahydrofuran as soft segment, WPU films had the best mechanical property. Applying this kind of WPU to modify NRL, tensile strength of these films was significantly higher than that of NR films, but elongation at break had a slightly decrease and extracted protein concentration of films significantly reduced. Solvent resistance testing and AFM spectrum showed that modified films had a compact structure and smoother surface.