Development of polyurethane‐based sheets by phase inversion method for therapeutic footwear applications: Synthesis, fabrication, and characterization

Abstract

It has been proved that polyurethane (PU) foam and viscoelastic PUs are offering better cushioning and shock absorption properties than other materials such as foam rubbers, polyethylene, ethylene vinyl acetate, and polyvinyl chloride which are used currently as insole materials in therapeutic footwear for diabetic and orthopedic patients to ''offload'' or redistribute high pressure under the foot. The aim of this research work was to prepare viscoelastic materials based on PUs having the highest degree of phase separation that provides for the elastomeric nature of these polymers. Polymer structures with a high concentration of amide groups can be made with the addition of hydrazine or a diacid hydrazide to a diisocyanate. We had prepared various PUs by chain extending the isocyanate-terminated prepolymer with terepthalic dihydrazide, 5-hydroxy isothalic dihydrazide, and 1,4-butanediol. Polymers were developed into sheets by phase inversion method using dimethyl formamide as solvent and water as nonsolvent. To improve the mechanical properties of PU sheets the polymer solution was blended with polyester-based PU Desmopan 8078 (CPU) in 1 : 1 ratio and the solution mixture was developed into sheet by the same method. Further PU sheets based on only CPU were also developed with various concentrations of PU. The synthesized PU and their blends with CPU were characterized by infrared spectroscopy, differential scanning calorimetry, thermo gravimetric analysis, gel permeation chromatography, and dynamic mechanical analysis. Morphological characteristics of PU sheets were studied by scanning electron microscopy.

Influence of Contoured Insoles with Different Materials on Kinematics and Kinetics Changes in Diabetic Elderly during Gait

“…The structural design and material properties of these insoles are particularly essential and are related to the efficacy of foot orthotic interventions for DFUs and gait alteration. With advances in materials sciences in recent years, a wide range of materials have been introduced to the market, such as ethylene vinyl acetate (EVA; e.g., Nora ® (Weinheim, Germany)), polyethylene (e.g., Pe-Lite ® (Algeos, Liverpool, UK)), and polyurethane (e.g., PORON ® (Dr. Jill's Foot Pads, London, UK)) [23][24][25][26]. These insole materials are available in a wide range of hardnesses, thicknesses, and densities, with different structural and mechanical properties for a diversity of different usages.…”

Effects of custom‐made textile insoles on plantar pressure distribution and lower limb EMG activity during turning

“…Foot orthotic treatment is one of the primary means to handle various foot problems such as reducing the occurrence or recurrence of ulceration which is due to the excessive shearing together with abnormal levels of repeated pressure that occur within the foot leading to severe damage to soft tissue [9,10]. Even though some previous studies have been carried out to evaluate the effectiveness and applications of orthotic insoles as well as different types of orthotic materials in various clinical symptoms [11][12][13][14][15], much clinical attention has been focused primarily on the foot loading characteristics and their effects on posture during gait at straight line walking [16][17][18][19][20], and thus little is known about the footfootwear interface during turning. Specifically, very few studies have attempted to examine the implications of foot orthotic inventions on plantar pressure and muscle activation pattern so as to improve the turning function and safety of the wearers.…”

Optimization of 3D printable cellular array structures for cushioning

“…Conventionally, porous cushioning materials are manufactured chemically (foams) or by expansion/corrugation of sheet material (honeycombs) [19]. The relative density and properties can be altered by mixing polymer solution with other substances [20]. As seen in Figure 1-1a and 1-1b, the resulting pore microstructures are normally disordered.…”

“…Cushioning materials are widely used in various applications which include packaging [77], automotive safety features [78] and therapeutic footwear [20]. Cushioning materials are also utilized in the sports industry, in the soles of running shoes [79], gym mats [80], helmets [81], etc.…”