Dimensional stability improvement

Improved dimensional stability Improved heat resistance Improved processability Improved toughness Improved weatherability Improved solvent resistance Improved flame resistance Improved moisture resistance Improved esthetics and appearance, etc. 

High loadings possible can improve strength, lower moisture absorption, elevate heat and dimensional stability, improve electricals... 

Wollastonite Improves strength, reduces moisture absorption, higher heat/dimensional stability. Improved electrical properties high loadings possible... 

Figure 3-30. Dimensional Stability (Coefficient of Expansion) of ABS as a Function of Glass Fiber Reinforcement (Dimensional stability improves substantially with the addition of up to about 30% of glass fiber.)...

Low atoisture absorption Industry standard for platable grades Cost-effective milled glass replacement Improved mold flow Uniform heat distribution Better dimensional stability Improved surface characteristics Higher heat-distortion temperature Upgraded mechanical properties Reduced wall thickness... 

It is important to minimize the rotation speed of the screw. High speeds can be used, in conjunction with the appropriate backpressure, to mold thin and/or long parts. Injection pressure should also be as low as possible. Dimensional stability improves when pressure is lowered because of a reduction in the residual stresses in the molded part. Injection pressure may have to be increased if an improvement in the weld line or a reduction in sink marks is desired. Part design and equipment capability should always be considered in the selection of injection pressure. Backpressure should be kept at the lowest possible value. Increasing it can sometimes help increase the stock temperature. 

The resin matrix of commercial dental composites has bis-GMA (bisphenol-A-glycidyldimethacrylate) as its predominant base monomer. Due to its high viscosity, bis-GMA is mixed with other dimethacrylates, such as TEGDMA, UDMA or other monomers of lower molecular weight [26, 50] to reduce viscosity. The monomers are heavily reinforced with filler particles, which add dimensional stability, improve wear and strength of the material, also reducing polymerization shrinkage [51]. 

Dimensional Stability. The wet heat resistance of PVA fiber is indicated by the wet softening temperature (WTS) at which the fiber shrinks to a specified ratio. At one time, the WTS was not more than 95°C for nonacetalized PVA fiber, but improvement of WTS has been achieved by improvement in heat-drawing and -treating techniques other methods proposed include suppression of polymerization temperature of vinyl acetate (36) and employment of alkafi spinning (37). 

Fibers have been used by humans for thousands of years, but only in the twentieth century has there been such an explosion in fiber types available to the textile manufacturer. The advent of synthetic fibers possessing improved resiliency and dimensional stability has placed natural fibers, particularly cotton (qv), at an ostensible disadvantage. Before synthetics, various means to control the shrinkage, dimensional stability, and smooth-dry performance of cotton had been investigated, but the appearance of synthetics such as polyester has placed a greater sense of urgency on cotton interests to focus on the perceived deficiencies of natural fibers. 

Other uses include impregnation of wood to improve dimensional stability and reduce water absorption, sealing of porous metal castings by impregnation, and coil impregnation, to give a rigid structure both heat and water resistant. 

Aminos. There are two basic types of amino plastics - urea formaldehyde and melamine formaldehyde. They are hard, rigid materials with good abrasion resistance and their mechanical characteristics are sufficiently good for continuous use at moderate temperatures (up to 100°C). Urea formaldehyde is relatively inexpensive but moisture absorption can result in poor dimensional stability. It is generally used for bottle caps, electrical switches, plugs, utensil handles and trays. Melamine formaldehyde has lower water absorption and improved temperature and chemical resistance. It is typically used for tableware, laminated worktops and electrical fittings. 

Materials with totally new property combinations may be achieved by blending two or more polymers together. Through blending of thermotropic main-chain LCPs with engineering thermoplastics, the highly ordered fibrous structure and good properties of LCPs can be transferred to the more flexible matrix polymer. LCPs are blended with thermoplastics mainly in order to reinforce the matrix polymer or to improve its dimensional stability, but LCP addition may modify several... 

Analog-to-glass fibers silanes are used as coupling agents for natural fiber polymer composites. For example, the treatment of wood fibers with product A-175 improves wood dimensional stability [53]. In contrast, a decrease of mechanical properties was observed for coir-UP composites after a fiber modification with di-chloromethylvinyl silane [54]. The treatment of mercer-... 

PPO is an engineering thermoplastic with excellent properties. To improve its mechanical properties and dimensional stability, PPO can he blended with polystyrene and glass fiber. Articles made from PPO could be used up to 330°C it is mainly used in items that require higher temperatures such as laboratory equipment, valves, and fittings. 

Cross-linking produces some dimensional stability and improves toughness in a noncrystalline type of plastic above the Tg, but... 

These characteristics can be further enhanced and their applications widened by fillers, additives, and reinforcements. Compounding properly will yield an almost limitless combination of an increased loadcarrying capacity, a reduced coefficient of friction, improved wear resistance, higher mechanical strengths, improved thermal properties, greater fatigue endurance and creep resistance, excellent dimensional stability and reproducibility, and the like. 

Dimensional stability There is plastics with very good dimensional stability, and they are suitable where some age and environmental dimensional changes are permissible. These materials include polyphenylene oxide, polysulfone, phenoxy, mineral-filled phenolic, diallyl phthalate, epoxy, rigid vinyl, styrene, and various RPs. Such products will gain from an after-bake for dimensional stabilization. Glass fillers will improve the dimensional stability of all plastics. 

By the term particulate composites we are referring to composites reinforced with particles having dimensions of the same order of magnitude. Particulate composites are produced from a polymeric matrix, into which a suitable metal powder has been dispersed, and exhibit highly improved mechanical properties, better electrical and thermal conductivity than either phase, lower thermal expansivity, and improved dimensional stability and behaviour at elevated temperatures. 

To improve the dimensional stability of the oligoethyleneoxy phosphazene/ metal salt complexes, some attempts have been reported which concern the chemical modification of the parent polymers, their chemical or radiation cross-linking, or the use of blends. 

---