Splay marks

Special considerations moisture causes bubbles, streaking, and splay marks compounding with glass fiber has very little effect on PES heat deflection temperature and marginally increases LOI but tensile strength is improved in a broad spectrum of temperatures... 

Superior parts. The improved melt, free of volatiles, renders higher-quality parts with excellent appearance and better physical properties. Splay marks are eliminated from appearance parts and parts to be plated. 

Wavy surface appearance of an object molded from thermoplastic resins, caused by improper flow of the resin into the mold. Also see Splay marks. ... 

After drying the material it should not be placed into an open hopper for extended periods of time where it will reabsorb moisture for, when molding hygroscopic materials, such as ABS and PA66, this can produce moldings having splash or splay marks on their... 

Good resistance to heat normally, although it will tend to yellow if left to cook in the barrel, sk of decomposition at temperatures above 250° C (482° F). At a temperature of 250° C (482° F) the maximum residence time in the barrel should not exceed 5 minutes. When the temperature is 275° C (527° F) then the maximum residence time in the barrel should not exceed 1 to 2 minutes. Splay marks or streaks on moldings (similar to the effects of dampness) is an early indication of the material being overheated. 

A vented screw and barrel assembly can be used for this material, so as to eliminate drying. However it is important to use the correct temperature profile on the vented barrel assembly, for example, by keeping the vent zone lower than the other zones i.e. 230 to 250° C (446 to 482° F) so as to ensure that the moisture is exhausted from the vent section in order to produce moldings free from the characteristic splash/splay marks. 

Increased computer speed will also enable CAE vendors to offer optimization codes. Coupled with three-dimensional analysis, a real possibility exists of providing a virtual prototyping capability. The visualization capabilities of tomorrow s computers are also key to achieving this goal. We can expect in the near future to be able to link simulation results with visual defects such as splay marks and gloss variations. 

PAEK typically absorb around 0.5% moisture. This has a negligible effect on properties and will not cause chemical changes during processing. However, it will cause splay marks and other processing problems. Accordingly PAEK are typically dried for 3 hours at 150 °C or 2 hours at 160 °C before processing. 

Splay marks Circular pattern around gate High moisture in plastic, trapping of gas in rib... 

Problems and Troubleshooting - Injection Molding Flow chart 5.2.15 - Splay marks/Delamination... 

Splay Mark Also called silver streak. Fan-like or streaking on the surface of fabricated plastic parts. Causes include moisture in the plastic material, thermal degradation of plastic material, relatively cold plastic on mold or die surface due to fast an operation (called jetting), injection mold gate restriction, foam molding, etc. 

Another important and frequently used test throughout the industry is the moisture analysis test. This simple but effective test provides useful information regarding the processibility of plastic materials. Excessive moisture can cause many processing and visual problems such as splay marks. Bulk density tests and sieve analysis tests also help to predict the material s behavior during mixing, compounding, and processing. Chapter 7 discusses analytical tests often used in material characterization. 

The hygroscopic nature of plastic materials causes processing as well as dimensional stability problems. Materials like ABS and polycarbonate must be dried thoroughly before processing to avoid splay marks on molded parts, loss of impact strength, and loss of other properties. The presence of moisture also tends to produce a weak weld or knit lines, further weakening the molded part. Many processors conduct routine moisture analysis tests on materials prior to processing. Five basic methods have been developed and are most frequently used. 

The first ajid most im portant requirement for obtaining high quality PES is to lower the moisture content of the pellets. If the PES molding resin is allowed to absorb excessive amounts of water prior to molding, the mechanical properties uHti uppeuTuUce of tlie molded parts are impaired. Absorbed water can form steam that results in splay marks and internal bubbles in the molded parts. 

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