Heat Distortion Improving Agents

Typical examples of heat distortion improving agents are shown in Table 12.7. The agent is incorporated in amounts of 0.01-3%. 

In addition, ASA may be blended with other polymers that themselves exhibit high heat distortion temperatures. For example, blends of poly(ether imide) and ASA exhibit an improved heat distortion temperature, improved flexural properties and tensile properties in comparison to the ASA component alone and have lower impact strengths as well (35). The statement above has been exemplified using Ultem 1000 as a poly(ether imide) resin and Geloy 1020 as ASA component. 

Conversely, ASA itself may serve as a heat distortion improver additive for poly(vinyl chloride) (PVC) (36). The increase of the heat distortion temperature is linearly dependent on the amount of ASA added. Therefore, it is easy to add just the amount needed without doing a lot of preliminary testing with various formulations. ASA can be used in a blend with PVC. Another approach is the coextrusion of the ASA with PVC in such a way that only ASA is exposed to high temperatures. 

Because of the enhanced weather resistance, ASA is used extensively in the automotive industries, and further in general for outdoor applications. In particular, ASA polymers have been widely applied to glossy colored outdoor products including (17)  

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Because the heat distortion temperature of cured epoxy resins (qv) increases with the functionality of the curing agents, pyromellitic dianhydride is used to cross-link epoxy resins for elevated temperature service. The dianhydride may be added as a dispersion of micropulverized powder in liquid epoxy resin or as a glycol adduct (158). Such epoxies may be used as an insulating layer in printed circuit boards to improve heat resistance (159). Other uses include inhibition of corrosion (160,161), hot melt traffic paints (162), azo pigments (163), adhesives (164), and photoresist compounds (165). 

Tpo maximize the utility of crosslinked cycloaliphatic epoxy resins in some of the more critical application areas, improved toughness is required. Such improvements can often be made through modification with various flexibilizing agents, but as a rule this improvement is accompanied by a severe degradation of the strength and heat distortion temperature of the cured system. 

Effect of Molecular Configuration of Elastomer. The extent of the impact and strength improvements of ERL-4221 depends on the chemical structure and composition of the elastomer modifier. The data shown in Table I indicate that the carboxyl terminated 80-20 butadiene-acrylonitrile copolymer (CTBN) is the most effective toughening and reinforcing agent. The mercaptan terminated copolymer (MTBN) is considerably less effective as far as tensile strength and heat distortion temperature are concerned. The mercaptan groups are considerably less reactive with epoxides than carboxyls (4), and this difference in the rate of reaction may influence the extent of the epoxy-elastomer copolymerization and therefore the precipitation of the rubber as distinct particles. 

To improve high temperature stability over amine cured systems and to give better physical and electrical properties above their heat distortion temperatures, it has been general practice in epoxy resin systems to use anhydride curing agents with DGEBA epoxy resins (8 ). Most anhydride formulations require elevated-temperature cures with the ultimate properties dependent on postcures at temperatures of 150 C or higher. 

Uses Crosslinking agent for actylic/vinyl resins PVC plastisol comonomer (reduces initial vise, and oil extractability. and improves ultimate hardness, heat distort., hot tear strength, and stain resistance) adhesion promoter hardener used in cast acrylic sheet and rod, contact lens, elastomers, ion exchange resins, dental polymers, adhesives, coatings (paper, plastic), cosmetics, paints, sealants, photopolymers, electronics (photoresists, solder masks)... 

Hyperfom HPN 210 M is a new nucleating agent for injection molded high-density polyethylene apphcations. It improves mechanical performance to the levels approaching those of polypropylene impact copolymers. It increases stiffness by up to 50%, heat distortion temperature by 10-40°C, and productivity. It has ability to create lamellar crystal orientation of PE in the polymer flow direction reducing shrinkage. ... 

Automotive interior element is produced from polypropylene with use of nueleating agent (talc in quantity of 0.1 to 1 wt%). The addition of nucleating agents brings about a considerable improvement in important physical-mechanical properties, such as flexural modulus, heat distortion temperature, tensile strength at yield and transparency ... 

The thermal expansion of plastics can be increased by the incorporation of reinforcing agents or fillers into the formulation. Thns, the incorporation of ceramic powder filler into polytetraflnroethylene (PTFE) rednces the coefficient of thermal expansion. On the other hand, the incorporation of 20% glass fiber into epoxy resins will increase the coefficient of cubical expansion from 0.5 mn/mn/°C x 10" to 2.0 mn/mn/°C x 10. Reinforcanent of perfluoroalkoxyethylene improved the heat distortion temperature at 0.45 MPa from 24 C to lOO C and at 1.8 MPa from 30°C to 58°C. This was accompanied by a nominal increase in tensile strength. 

To improve the flame retardant property of PLA, the effects of phosphorus reagents and metal hydroxides have been studied. In Figure 28.14, the correlation of heat distortion temperature and flame retardant content is shown in the case of the PLA/PC (40/60) alloy. As shown in Figure 28.14, thermal resistance tends to decrease although the flame retardance improves by adding the agent. 

Heat distortion resistance (fillers as well as reinforcing agents improve it but the effect of reinforcing agents is greater). 

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