Molecular weight and glass transition temperature

Substituted nonheat-reactive resins do not form a film and are not reactive by themselves, but are exceUent modifier resins for oleoresinous varnishes and alkyds. Thein high glass-transition temperature and molecular weight provide initial hardness and reduce tack oxygen-initiated cross-linking reactions take place with the unsaturated oils. 

Polymer characteristics such as glass transition temperature and molecular weight... 

Glass Transition Temperature and Molecular Weight Distribution of Polymers obtained from Anionic Microemulsions... 

Poly(vinyl ethers). Homopolymers of vinyl ethers are produced via carbocationic polymerization. Polymerization is carried out either in bulk or solution using BF3 or its complexes, AICI3, or SnCh. Commercially important poly(vinyl ethers) are made of methyl, ethyl, isobutyl, and octadecyl vinyl ethers [Tg = -34, -42, -19, and 50°C (1)]. Depending on their glass-transition temperature and molecular weight, commercial poly(vinyl ethers) are viscous oils, tacky resins, or... 

Omelczuk MO, McGinity JW (1992) The influence of polymer glass transition temperature and molecular weight on drug release from tablets containing poly (DL-lactic add). Pharm Res... 

The glass transition temperatures determined with these polyesteramide resins appeared to be strongly dependent on the type of anhydride used and of their molecular weight. Figure 10 shows the dependence of glass transition temperature on molecular weight for hyperbranched polyesteramides based on hexahydrophthalic anhydride. In general, the Tg for HHPA- and THPA-based resins were about 45-90°C, PA based resins about 70-100°C, and SA and GA about 20-40°C. 

Fig. 10. Dependence of the glass transition temperature on molecular weight of hyperbranched polyesteramides based on HHPA and diisopropanolamine, measured for different samples and intrapolated...

FIGURE 10-61 Schematic plot of glass transition temperature versus molecular weight [redrawn from the data of T. G. Fox and P. J. Flory, J. Appl Phys., 21, 581 (1950)1. 

On the basis of this relatbn. Fox and Loshaek (32) developed a relation for the variation of the glass transition temperature with molecular weight. Subsequently, Gibbs and DiMarzio (34) have shown that while B is not precisely constant, it is very nearly so over a wide range of molecular weights. 

Figure 3.3 a) Melting and glass transition temperature versus molecular weight of PLLA, content. ... 

Polymer Chemical category and classification Glass transition temperature (T,) Molecular weight (MW) Solubility Hygroscopicity Solubility parameter Degradation temperature Technologies... 

Figure 15.19 Dependence of polymer properties and melting and glass transition temperatures on molecular weight.

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... 

Heat resistance test at 100 °C - Sentinel heat seal tester Set-up a Sentinel heat sealer according to heat pressure and time interval specified. A one by three inch (2.5 cm X 7.5 cm) print sample is folded ink surface-to-ink surface and placed between the sealer bars. The heat sealer is operated. After the sample has been cooled, the sheets are separated and a subjective comparison is made for cling, ink transfer and picking. The jxjlymer glass transition temperature (Tg), molecular weight, and surface compatibility affect heat resistance. 

Below T polymers are stiff, hard, britde, and glass-like above if the molecular weight is high enough, they are relatively soft, limp, stretchable, and can be somewhat elastic. At even higher temperatures they flow and are tacky. Methods used to determine glass-transition temperatures and the reported values for a large number of polymers may be found in References 7—9. Values for the T of common acrylate homopolymers are found in Table 1. 

Solution Polymers. Acryflc solution polymers are usually characterized by their composition, solids content, viscosity, molecular weight, glass-transition temperature, and solvent. The compositions of acryflc polymers are most readily determined by physicochemical methods such as spectroscopy, pyrolytic gas—liquid chromatography, and refractive index measurements (97,158). The solids content of acryflc polymers is determined by dilution followed by solvent evaporation to constant weight. Viscosities are most conveniently determined with a Brookfield viscometer, molecular weight by intrinsic viscosity (158), and glass-transition temperature by calorimetry. 

Carbon Cha.in Backbone Polymers. These polymers may be represented by (4) and considered derivatives of polyethylene, where n is the degree of polymeriza tion and R is (an alkyl group or) a functional group hydrogen (polyethylene), methyl (polypropylene), carboxyl (poly(acryhc acid)), chlorine (poly(vinyl chloride)), phenyl (polystyrene) hydroxyl (poly(vinyl alcohol)), ester (poly(vinyl acetate)), nitrile (polyacrylonitrile), vinyl (polybutadiene), etc. The functional groups and the molecular weight of the polymers, control thek properties which vary in hydrophobicity, solubiUty characteristics, glass-transition temperature, and crystallinity. 

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