Properties shape retention

The mechanical properties of acryUc and modacryUc fibers are retained very well under wet conditions. This makes these fibers well suited to the stresses of textile processing. Shape retention and maintenance of original bulk in home laundering cycles are also good. Typical stress—strain curves for acryhc and modacryUc fibers are compared with wool, cotton, and the other synthetic fibers in Figure 2. 

Shape retention is a factor in almost all articles made from polymeric materials (cf. warping of plastic articles, deformation of films, etc.). In textiles the lack of shape retention is reflected in the sagging of curtains, the bagging of trousers, etc. Shape retention is determined by the viscoelastic properties of the polymer, especially under the influence of moisture plastic deformation and creep are highly undesirable, whereas resilience is favourable. 

It may be concluded that shape retention, wrinkle recovery and pleat and crease retention depend on well-known viscoelastic properties the existence of a transition range, stress relaxation, creep and permanent deformation, and a possible resilience by a change in external conditions. 

Loss by wear is dependent on the coefficient of friction, the stiffness, the resilience and the degree of brittleness. In order to assess the resistance to wear it has to be ascertained whether this property is in equilibrium with other properties, e.g. colour fastness and shape retention. If the durability is determined by the resistance to wear, the aesthetic and use properties must remain virtually constant during the life of the product. 

It has been found that Mesua ferrea L. seed oil-based thermoplastic hyperbranched polyurethane (HBPU) of the monoglyceride of the oil, PCL (M = 3000 g moT ), 2,4/2,6-toluene diisocyanate and glycerol with 30% hard segment (NCO/OH = 0.96), exhibit thermoresponsive shape memory properties. The shape recovery (88,91 and 95%) and shape retention (70, 75 and 80%) are also found to be different at different temperatures (50, 60 and 70°C respectively). Bisphenol-A-based epoxy resin modified... 

The ability to crosslink the compounds gives improved physical properties, better chemical resistance and shape retention at temperatures significantly above the melting point of the polymer resin itself This prolongs the life of the compound and its integrity in the event of a fire. One of three methods can be utilised in the cable industry peroxide, silane (either Monosil or Sioplas techniques) and electron beam each requiring a different compound to achieve the right properties. Each has positive points and drawbacks. 

Addition of a small amount of PSF to a variety of resins improves hardness, the notched Izod impact strength, plateabflity, hydrolytic stability, and shape retention at high temperatures. Many PSF blends of or with engineering resins have been developed, viz., with PA, PEST, PC, PPE, or POM. They have high HDT, heat resistance, strength, stiffness, mechanical properties, and ESCR. Polysulfone blends have been foamed using water and either N2 or CO2 (Bland and Conte... 

Titanium and its alloys have many biomedical applications due to their high strength and corrosion resistance, and are commonly incorporated in replacement hip joints and items such as bone pins [1]. Porous Ti foams have been explored for biomedical uses due to their enhanced adhesion to host tissue [15]. Surface-treatment of Ti and Ti alloys to enhance material properties, such as wear resistance, in a biomedical context has been examined [16]. In addition, titanium nitride-based materials could potentially serve as coatings for biomedical implants [17]. NiTi-based shape memory alloys are attractive candidates for biomedical materials due to their shape retention and pseudoelasticity, however, manufacturing and processing these memory alloys for biomedical apphcations is typically not straightforward [18]. 

The mechanical properties of acrylic fiber are deficient under hot-wet conditions. This is primarily due to the fact that the wet Tg of acrylonitrile copolymers is lower than the boiling point of water. Textile wet-processing must be carried out in such a way as to minimize yarn or fabric distortion. Shape retention and maintenance of original bulk under the lower temperatures in home laimdering cycles are acceptable. Typical stress-strain curves for acrylic fiber in air and in wet conditions are shown in Figure 3. 

The elastic recovery and crimp retention properties provide excellent shape retention and crease resistance. 

Viscoelasticity Viscoelasticity is a property characteristic of all plastics. Plastics have both sohd state properties such as elasticity, strength and shape retention and hquid properties such as flow, which is dependent on variables such as temperature and load. Materials that demonstrate both viscous and elastic behavior imder an applied stress are designated as viscoelastic. 

Bacterial cellulose has been investigated for its potential use as artificial blood vessels because it carries a lower risk of blood clots. Native bacterial cellulose has several mechanical properties that are superior to those of many currently used synthetic materials such as polypropylene, polyethylene terephtalate, and cellophane. These properties include shape retention and tear resistance. 

---