Thermal properties softening point

Mechanical and Thermal Properties. The first member of the acrylate series, poly(methyl acrylate), has fltde or no tack at room temperature it is a tough, mbbery, and moderately hard polymer. Poly(ethyl acrylate) is more mbberflke, considerably softer, and more extensible. Poly(butyl acrylate) is softer stiU, and much tackier. This information is quantitatively summarized in Table 2 (41). In the alkyl acrylate series, the softness increases through n-octy acrylate. As the chain length is increased beyond n-octy side-chain crystallization occurs and the materials become brittle (42) poly( -hexadecyl acrylate) is hard and waxlike at room temperature but is soft and tacky above its softening point. 

Vitreous sihca has many exceptional properties. Most are the expected result of vitreous sihca being an extremely pure and strongly bonded glass. Inert to most common chemical agents, it has a high softening point, low thermal expansion, exceUent thermal shock resistance, and an exceUent optical transmission over a wide spectmm. Compared to other technical glasses, vitreous sihca is one of the best thermal and electrical insulators and has one of the lowest indexes of refraction. 

The thermal properties are of interest to both the user of the end-product and to the processor. From the user s point of view the principal features are the very low thermal conductivity (approx. 0.13 W/mK) and the comparatively low softening point. Standard tests give softening points of about 90°C, that is below the boiling point of water. In addition many properties are affected by temperature Figure 16.11). 

Adding plasticizer, like dioctyl phthalate, is generally accomplished by mechanical methods. Permanent or chemical plasticization can be done by copolymerization of VCM with monomers such as vinyl acetate, vinylidene chloride, methyl acrylate, or methyl rhethacrylate. Comonomer levels vary from 5-40%. The purpose of the co-polymers, of course, is to change the properties such as softening point, thermal stability, flexibility, tensile strength, and solubility. 

Thermal properties Vicat softening point ( C) ASTM D1525 (DSC method) 39 52 66... 

While untreated wood meal shows a thermal softening point of 260°C, esterified wood meals prepared in the N204-DMF-pyridine solution have a softening point of around 100 C or less and a thermal flow temperature of 220-250°C [98]. The flow temperature shows a tendency to decrease with increase in the C number of acyl group. This was first found by Shiraishi et al. [98] that wood meal is converted as a whole to thermoplastic material. In this case, a very high degree of acylation is not always required to provide wood with the thermally meltable property. The products become thermoplasticized materials when almost one-third of the hydroxyl groups in wood are acylated [99]. 

Other properties such as calorific value, carbon residue, specific heat, softening point, flash point, molecular weight, and thermal conductivity are also used to determine the suitability of the bitumen for conversion options. 

Thermal Properties. Some wholly N-methylated aromatic polyamides have been reported previously and found to be considerably lower in thermal stability than the corresponding unsubstituted polymers. Thus, Koton reported that the softening point of VII was 247°C, a temperature much below that of PPD-T, which shows no softening point below 400°C. 

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