Composite heat deflection temperature

Class Resin Type Composition Heat-Deflection Temperature ( 0... 

Thermal Properties. Thermal properties include heat-deflection temperature (HDT), specific heat, continuous use temperature, thermal conductivity, coefficient of thermal expansion, and flammability ratings. Heat-deflection temperature is a measure of the minimum temperature that results in a specified deformation of a plastic beam under loads of 1.82 or 0.46 N/mm (264 or 67 psi, respectively). Eor an unreinforced plastic, this is typically ca 20°C below the glass-transition temperature, T, at which the molecular mobility is altered. Sometimes confused with HDT is the UL Thermal Index, which Underwriters Laboratories estabflshed as a safe continuous operation temperature for apparatus made of plastics (37). Typically, UL temperature indexes are significantly lower than HDTs. Specific heat and thermal conductivity relate to insulating properties. The coefficient of thermal expansion is an important component of mold shrinkage and must be considered when designing composite stmctures. 

The selection of monomers for preparation of copolyesters is based on applying established structure/property principles and is usually driven by new market needs and applications with specific end-use properties in mind. Thus, attempts to develop amorphous or semicrystalline CHDM-based polyester compositions for applications requiring greater heat resistance or higher heat deflection temperatures have generally followed the theme of incorporating bulky or rigid constituents to further enhance the desirable thermal properties of CHDM-based... 

Most acrylonitrile-butadiene styrene terpolymer (ABS) is produced as a graft of SAN onto a butadiene polymer backbone. This graft copolymer may be blended with more SAN or acrylonitrile elastomer (NBR) to improve its properties. ABS is more ductile than SAN. The Tt and the heat deflection temperature of ABS vary with the composition, and ABS may have one set of values for the PBD domains and another set for the SAN matrix. The permeabilities of ABS to oxygen, nitrogen, and carbon dioxide are much less than those of hope. 

As shown in Table 13.2, the heat deflection temperature of ABS is increased by the incorporation of fibrous glass. The copolymer reinforced with 20% fibrous glass has a lower coefficient of linear expansion (2.0 X 10 5 on/cm C) and higher compressive, flexural, and tensile strengths than unfilled SAN. These improvements are related to the amount of fibrous glass present in the composite. 

These products are produced by the reaction of partially hydrolyzed PVAc with aldehydes. The acetal rings on these random amorphous polymer chains restrict flexibility and increase the heat deflection temperature to a value higher than that of PVAc. The heat deflection temperature of polyvinyl formal is about 90 C and is dependent on the specific composition of this complex polymer. Because of the presence of residual hydroxyl groups, commercial polyvinyl formal has a water absorption of about 1%. Polyvinyl formal has a Tg of 10S . It has a solubility parameter of about 10 H and is soluble in solvents with similar solubility parameters, such as acetone. 

Figure 7.8 shows the relationship between the heat deflection temperatures (HDT) and PVDF content of PVDF/PMMA blends. HDT is the starting temperature at which the polymer begins to deform under a certain stress. A minimum HDT is observed at a PVDF content of 50 wt %. The sharp increase in HDT is most likely due to the crystallization of PVDF in solid blends when the PVDF composition exceeds 50 wt %. The crystallites serve as temporary crosslinking sites to limit the mobility of polymer segments and thus to increase the heat resistance of PVDF/PMMA blends. When a blend has a PVDF content greater than 65 wt %, the material provides a heat resistance exceeding that of PMMA. 

A flexibilized thermohardening composition contained ca. 90% BPA/DC and a polyester from dimerized fatty acids and hexanediol. Elongation at break and impact strength increased considerably, whereas the heat deflection temperature was only little decreased [139],... 

Special considerations glass composites have very high LOI= 47% glass fiber reinforcement increases heat deflection temperature by more than 150°C to over 260°C at 40 wt% glass fiber... 

Heat deflection temperature is influenced by (i) blend composition, (ii) flUers/reinforcing agents,... 

Figure 12.30. Variation of heat deflection temperature with PC/ABS blend composition (curves 1 and 2 are obtained with loads 4.6 and 18.2 kg.f/cm, respectively).

The effect of wood species on the wood-polymer interface and on properties of WPCs has received little attention in the literature. Stark and Berger [13] evaluated the effect of ponderosa pine, loblolly pine, maple, or oak on the mechanical properties of polypropylene WPCs. In general, WPCs made with maple or oak exhibit slightly better tensile and flexural properties and heat deflection temperatures than either of the pines. Composites elaborated with coconut flber and polyurethanes have shown good results. Coconut flber acts as reinforcement and active part of the matrix system, improving the interface... 

Flame retardants based on phosphorous show certain disadvantages. Some of them have to be included in large amounts in order to achieve the desired grade of flame retardancy, however, undesired side effects then emerge. For example, resorcinol diphosphate plasticizes the composition and significantly reduces the heat deflection temperature of the formulation. Examples for phosphorous-based flame retardants for PPE include resorcinol diphosphate, bisphenol A diphosphate, tetraxylyl piperazine di-phosphoramide, ete. Organoclay additives show synergistic effects with phosphates with respeet to flame retardancy. For this reason, the amount... 

Poly(styrene), saturated polyalicyclic resins, and terpene phenol reduce viscosity and impart high flow to the resulting composition. For this reason, the polymers added are sometimes addressed as flow promoters. The materials have some adverse effect as they reduce the heat deflection temperature of the product and increase the flammability. High flow polyphenylene ether resin compositions have been described... 

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