Clays scratch resistance

The incorporation of nano-clay in polymer has improved the scratch resistance and toughness significantly, with the retention of transparency, which facilitates its use for UV filter films. 

The use of silanization as treatment for clays prior to their use in UV-curable formulations is based on the availability and reactivity of hydroxyl groups in the clay strucmre. Thus, the surface modification of MMT by glycidyl-propyl-triethoxysylane (GPTS) allowed new highly dispersed epoxy resin-based nanocomposites with enhanced scratch resistance and low susceptibility to crack formation and propagation [240]. 

Simultaneous improvements of tensile strength, scratch resistance, storage and loss modulus, gas barrier behavior, thermal stability, and flame retardancy can be achieved for many common polymers by dispersing into them less than 5% of clay. ° These improvements are only observed and transparency of the material is only maintained if the individual silicate sheets of clay are nanodispersed, that is, if they form an intercalated or exfoliated stmcture (Figure 18). However, a majority of industrial polymers is unpolar and thus incompatible with the silicate sheets, which carry negative surface charges. Silica sheets do not disperse in such polymers unless the silica surface is modified by a surfactant. 

A dramatic increase in the hardness of dried cancrinite products occurs after treatment with tetraethyl silicate (TES). Soaking the can-crinite-clay mixture in TES for several hours, either at room temperature or at 100 °C, gives a product which is difficult to scratch and which is more water resistant. Samples treated with TES do not appear to soften even when soaked in water for months. 

Bisphenol-A-based epoxy with a poly(amido amine) hardener system cured Mesuaferrea L. seed oil-based hyperbranched polyurethane (HBPU)/ clay nanocomposites obtained by an ex situ solution technique, was also reported. The partially exfoliated nanocomposites showed a two-fold improvement in adhesive strength and scratch hardness, 10 MPa increments in tensile strength and thermostability at 112°C with little effect on impact resistance, bending and elongation at break compared to a pristine epoxy-modified HBPU system. However, similar epoxy-cured Mesua ferrea L. seed oil-based HBPU/clay nanocomposites exhibited a two-fold increase in tensile strength, a 6°C increase in melting point and thermostability at 111°C after nanocomposite formation using an in situ technique. An excellent shape recovery of about 96-99% was observed for the nanocomposites. The above observations confirm that the performance characteristics of nanocomposites are influenced by their preparation technique. 

Nano-clay incorporated polymer coatings are important for modifying properties of surfaces. Nano-clay incorporated thermoset polymer nanocoatings exhibit superior properties such as super-hydrophobicity, improved wettability, excellent resistance to chemicals, corrosion resistance, improved weather resistance, better abrasion resistance, improved barrier properties and resistance to impact, scratches, etc. [116]. The parameters such as dipping time, temperature, nature of surfactant, and purity of nanomaterials decides the coating thickness. Clay-epoxy coating... 

Stoneware. The combined NOMENCLATURE (q.v.) is Stoneware, which, though dense, impermeable and hard enough to resist scratching by a steel point, differs from porcelain because it is more opaque, and normally only partially vitrified. It may be vitreous or semi-vitreous. It is usually coloured grey or brownish because of impurities in the clay used for its manufacture, and is normally glazed . A translucency (q.v.) test is specified. Water absorption is to be 3 wt %. The body consists either... 

Despite the apparent limitations of nano-clays compared to more conventional anisotropic fillers, the nano-clays appear to combine their effects with other benefits such as good surface finish and better scratch and mar resistance than can be achieved with talc, mica or glass fibres and thus, if the costs are not too high, they appear to have a good future in applications where these are important considerations. 

Dasari A, Lim S H, Yu Z-Z and Mai Y-W (2007) Toughening, thermal stability, flame retardaiicy, and scratch-wear resistance of polymer-clay nanocomposites, Aust J Chem 60 496-518. 

Polymer nanocomposites are commonly defined as the combination of a polymer matrix and additives that have at least one dimension in the nanometer range. The additives ean be one-dimensional (examples include nanotubes and fibres), two-dimensional (which include layered minerals like clay), or three-dimensional (ineluding spherical particles). Over the past decade, polymer nanocomposites have attracted considerable interests in both academia and industry, owing to their outstanding mechanical properties like elastic stiffness and strength with only a small amount of the nanoadditives. This is caused by the large surface area to volume ratio of nanoadditives when compared to the micro- and macro-additives. Other superior properties of polymer nanocomposites include barrier resistance, flame retardancy, scratch/wear resistance, as well as optical, magnetic and eleclrical properties. 

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