Abrasive resistance of polyetherurethane ureas

The relationship between the structure of the polymer chains and the abrasion resistance of segmented polyurethane ureas based on polyoxytetramethylene oligoether was studied. Experimental data were obtained for systems with the hard segments content above 39%. It was found that the function of the volumetric wear of polyurethane-urea samples on the content of hard segments had an extremum; at high contents of these segments (more than 35%), a further increase in this content lead to a deterioration in the abrasion resistance. The reasons for this effect can be associated with a sharp deterioration in the strength and strain properties of the studied elastomers when additional amounts of diisocyanate are introduced into the system, which can lead to the formation of excessive interchain bonds.

Silver- and Zinc-Decorated Polyurethane Ionomers with Tunable Hard/Soft Phase Segregation

Segmented polyurethane ionomers find prominent applications in the biomedical field since they can combine the good mechanical and biostability properties of polyurethanes (PUs) with the strong hydrophilicity features of ionomers. In this work, PU ionomers were prepared from a carboxylated diol, poly(tetrahydrofuran) (soft phase) and a small library of diisocyanates (hard phase), either aliphatic or aromatic. The synthesized PUs were characterized to investigate the effect of ionic groups and the nature of diisocyanate upon the structure–property relationship. Results showed how the polymer hard/soft phase segregation was affected by both the concentration of ionic groups and the type of diisocyanate. Specifically, PUs obtained with aliphatic diisocyanates possessed a hard/soft phase segregation stronger than PUs with aromatic diisocyanates, as well as greater bulk and surface hydrophilicity. In contrast, a higher content of ionic groups per polymer repeat unit promoted phase mixing. The neutralization of polymer ionic groups with silver or zinc further increased the hard/soft phase segregation and provided polymers with antimicrobial properties. In particular, the Zinc/PU hybrid systems possessed activity only against the Gram-positive Staphylococcus epidermidis while Silver/PU systems were active also against the Gram-negative Pseudomonas aeruginosa. The herein-obtained polyurethanes could find promising applications as antimicrobial coatings for different kinds of surfaces including medical devices, fabric for wound dressings and other textiles.

Thermal, Mechanical and Electrical Properties of Carbon Fiber Fabric and Graphene Reinforced Segmented Polyurethane Composites

Thermal conductive materials with reliable and high performances such as thermal interface materials are crucial for rapid heat transferring in thermal management. In this work, carbon fiber fabric and graphene reinforced segmented polyurethane composites (CFF-G/SPU) were proposed and prepared to obtain superior thermal, mechanical and electrical properties using the hot-pressing method. The composites exhibit excellent tensile strength and can withstand a tensile force of at least 350 N without breaking. The results show that, comparing with the SPU material, the thermal conductivity is increased by 28% for the CFF-G/SPU composite, while the in-plane electrical conductivity is increased by 8 orders of magnitude to 175 S·m−1. The application of CFF-G/SPU composite as a winding thermal interface material with electric-driven self-heating effect presents good performances of fluidity and interface wettability. The composite has great advantages in phase transition and filling the interfacial gap in the short time of few seconds under the condition of electrical field, with the interface temperature difference between two layers significantly reduced.

Using the method of pyrolytic mass spectrometry in the study of biodegradable polymeric materials

The results of pyrolytic mass spectrometry studies of biodegradable polymeric materials based on polyolefins and segmented polyurethanes with various functional additives are summarized. The structure and composition of initial and after exposure in soil, climate chamber and after exposure to microorganisms (bacteria, yeast) composites are characterized. In the research presented, influence of acetates and complexonates of metals, including cobalt, copper and zinc, on the structural changes in the high pressure polyethylene (HPPE) occurring under the impact of factors such as temperature, humidity and UV-radiation is investigated. It was established, that samples of HPPE, modified by cobalt acetate and cobalt and copper complexonates are responsive and most sensitive to the action of above-mentioned physical factors. Investigation of a segmented polyurethanes (SPU) of a different chemical structure influenced by a factors, modeling of the environmental conditions was conducted. It was shown using pyrolytic mass-spectrometry method and monitoring of samples’ weight loss that under the influence of above-mentioned environmental factors in the SPU occurs processes, resulting to changing its micro heterogeneous structure. It is established that SPU having ester links in its structure and being exposured in soil for 120 days is predominantly attacked by microorganisms, then the main active factor appears to be soil’ pH value – after 300 days in soil with alkaline or acid solution SPU sample decomposes into a separate fragments. Features of the chemical structure of urethane polymers synthesized on the base of hydroxylated rapeseed oil (polyol) were examined. Analysis of the results showed that the macromolecular compounds obtained are segmented polyurethanes which thermal degradation occurs in two stages: hard blocks are destroyed at the first stage, while polyol part (soft blocks) decomposes at the second stage, allowing to identify the temperature area of polymer destruction and thus its temperature region of operation. It is shown that the most suitable from the viewpoint of environmental friendly is polyurethane composition containing more than 50% of polyol. Thermal mass-spectrometry (TMS) has been employed to investigate processes of thermal destruction of segmented polyurethane and it’s compositions filled by polysaccharides: starch, dextrin, chitosan. The features of thermal destruction for segmented polyurethane and related compositions before and after their storage in a soil have been determined. Application TMS is shown to permit the processes of biodegradation of polymeric materials to investigate.