Hardness properties polymer glasses

Combining polymers with inorganic glass formers has recently been used to form ceramers [27]. These hybrid materials show many desirable properties for example, the optical properties of polymers, and the hardness/wear of glass. 

The aim of the present work was focused on the improvement of the mechanical properties as well as the water resistance of caseinate-based films. The first part of this study deals with the control of the mechanical properties through addition of a plasticizer. A plasticizer is defined as a low volatile organic compound which causes a decrease in polymer glass transition temperature (Tg) and an increase in flexibihty and extensibility. By decreasing intermolecular forces between polymer coils, plasticizers cause an increase in material flexibility and conversely a decrease in the barrier properties due to the augmentation of the free volume [13,14]. To summarize, an initially hard and brittle material becomes soft and flexible when sufficiently... 

At the glass transition point of an acrylic polymer, significant rotation in the backbone and side chain stops. The properties of a polymer alter considerably as the polymer passes through this temperature zone. Below its Tg the polymer is rigid, hard, brittle and glass like. Above its T, the polymer is softer, rubbery and flexible. 

Block resistance - wet/dry - ink to ink and ink to substrate The exposure time, pressure, and temperature are specified by the end use requirement (i.e. 3 min at 1034 bar, 50 °C for surface print ink (5.4) - The ink surface s resistance to heat and pressure is subjectively measured. Ink properties that effect blocking results are hardness , adhesion, cohesion, and slip. The polymer glass transition temperature (Tg), molecular weight, and surface compatibility effect the block resistance test... 

In the previous chapter, it was pointed out how the chemical structure of polymers influences their mechanical properties. The glass transition temperature and the rate of cooling from the melt determine whether the polymer will be a hard, stiff material, or a soft flexible material. These qualitative differences can be quantifled by measuring standard mechanical properties. The student, generally, is introduced to the subject of mechanical behavior through the study of linear elastic metals that exhibit solid behavior at normal operating temperatures and conditions. However, this study of polymers reveals that polymers exhibit fluid as well as solid behavior and are viscoelastic and viscoplastic at room temperature. The mechanical properties of polymers are strain rate sensitive and highly temperature dependent. 

Glass transition Transition region or state in which an amorphous polymer changed from (or to) a viscous or rubbery condition to (or from) a hard and relatively brittle one. Transition occurs over a narrow temperature region similar to solidification of a liquid to a glassy state. This transformation causes hardness, brittleness, thermal expansibility, specific heat, and other properties to change dramatically. 

---