Glass transition temperature PVAC

The addition of comonomers during the polymerization enables a higher flexibility compared to PVAc-homopolymerizates. This results in a lower glass transition temperature and a lower minimum temperature of the film formation. Possible comonomers are acrylic acid esters (butylacrylate, 2-ethylhexylacrylate), dialkylfumarates, ethylene and others. 

The first synthetic polymers to be used as paint varnishes were acrylic and vinylic resins. Poly(vinyl acetate) (PVAc), commercialized under the name Mowilith by Hoechst and Vinylite by Union Carbide, has been used in conservation as an adhesive since 1932 and in 1937 it was proposed as a picture varnish by Stout and Cross [63]. PVAc was soon rejected as a varnish because, despite its light stability and good solubility in organic solvents, it demonstrated poor optical properties in terms of colour saturation and the tendency to pick up dirt due to its low glass transition temperature. 

In the present section it will be shown that microhardness can conveniently detect the glass transition temperature Tg by following // as a function of temperature. We will illustrate the temperature dependence of hardness in case of two amorphous polymers - PMMA and poly(vinyl acetate) (PVAc) - and two semicrystalline... 

SMP based on miscible blends of semicrystalline polymer/amorphous polymer was reported by the Mather research group, which included semicrystalline polymer/amorphous polymer such as polylactide (PLA)/poly vinylacetate (PVAc) blend [21,22], poly(vinylidene fluoride) (PVDF)/PVAc blend [23], and PVDF/polymethyl methacrylate (PMMA) blend [23]. These polymer blends are completely miscible at all compositions with a single, sharp glass transition temperature, while crystallization of PLA or PVDF is partially maintained and the degree of crystallinity, which controls the rubbery stiffness and the elasticity, can be tuned by the blend ratios. Tg of the blends are the critical temperatures for triggering shape recovery, while the crystalline phase of the semicrystalline PLA and PVDF serves well as a physical cross-linking site for elastic deformation above Tg, while still below T ,. 

The physical properties of PVA depend to a greater extent on the method of synthesis than do those of most other polymers. This is because the final properties are affected by the polymerization of the parent PVAc, hydrolysis conditions, drying, and grinding (1). For example, the degree of hydrolysis determines the final glass transition temperature of PVA, usually between 58 and 85 °C. 

To evaluate this model, an experiment with a four-component system was conducted This system was a poly(methyl acrylate)/poly(vinyl acetate) (PMA/PVAc) physical blend, or mixture, consisting of four individual blends (PMA/PVAc (80/20) + PMA/PVAc (60/40) + PMA/PVAc (40/60) - -PMA/PVAc (20/80)). PMA is miscible with PVAc. The open squares in Figure 3.49 are the experimental dCp/dT data. The difference between glass transition temperatures of PMA and PVAc is about 33°C. In the glass transition region, the four-component mixture showed an acceptable fit to the experimental data, see Figure 3.49. The solid lines shown in Figure 3.49... 

One of the most important industrial latexes is the vinyl acetate/n-butyl acrylate (VAc/BuA) copol3mer latex. This copol3mer latex is utilized extensively in interior and exterior paints and is superior to either homopolymer alone. The main features of these monomers are reactivity ratios (rvA< 0.05 and rBuA=5.5), water solubilities (25 g/L for VAc and 1-1.5 g/L for BuA, at 20 °C), and glass transition temperatures (Tg (PVAc) =32 C and Tg (PBuA) = -54 °C). 

Sun Y, Xi H, Ediger MD, Richert R, Yu L (2009) Diffusion-Controlled and Diffusionless Crystal Growth near the Glass Transition Temperature Relation between Liquid Dynamics and Growth Kinetics of Seven ROY Polymorphs. J Chem Phys, pp 131 Sun Y, Tao J et al (2010) Solubilities of crystalline drugs in polymers an improved analytical method and comparison of solubilities of indomethacin and nifedipine in PVP, PVP/VA, and PVAc. J Pharm Sci 99(9) 4023-4031... 

PEG, being well above its glass transition temperature at room temperature, can act as a solvent for inks and paint (Hey et al., 1960) or a plasticizer for polymers, e.g. PVAC, CN or colophony (Powell, 1980). It may cause stress cracking of moulded thermoplastics such as PE. It does not appear to attack beeswax or gelatine. The presence and quantity of PEG in a solution or thin section can be assessed by colour staining (Hoffmann, 1983 Bilz et al., 1999), but distribution within an object is frequently assessed by extracting the PEG from a core and using instrumental analysis to quantify the concentration (Hoffmann, 1989). 

Heat of Fusion (AHg), Crystallinity, Maximum Melt Temperature (T ), and Glass Transition Temperature (Tg) of Various Ethylene Vinyl Acetate Copolymers, HOPE and PVAC... 

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