Silver Streak

Silver Streaks in a Clear GPPS Resin Injection-Molded Packaging Part... 

For optical applications requiring extreme clarity it is desirable to minimize silver streaking, and yellowing. For example, Topas 5013 can be modified pentaerythritol tetrastearate, pentaerythritol distearate, or zinc stearate in order to improve the optical properties (59). These blends are suitable for high precision optical applications. 

The man looked up, frowning and tilting his head as if listening to something. He was dusky and weathered he had silver streaks in his beard, but his face was lean, vulpine, and still dangerous. 

In semi-automatic moulding the operator may inspect each unit for features including colour, dispersion and uniformity of colour, standard and uniformity of gloss or mattness, and the presence or otherwise of defects like silver streaks or stringing. However, it is preferable if assessments can be made in numerical terms, expressed in units that may be compared quantitatively and subjected easily to statistical treatment and analysis. It is often convenient in the course of... 

Silver Streaks Melt temperature too low Mold too eold Condensation on mold Entrapped volatiles... 

Drying requirements of ABS-based blends vary widely, depending on the other components and their concentration. In general, the presence of moisture will produce surface defects such as silver streaks or blisters. With non hygroscopic... 

The desirable properties of Pis and poly(sulfone)s can be combined into a single resin, such as in a poly(etherimide sulfone)." These resins have low levels of residual volatile species and low levels of reactive groups. Thus articles may be prepared from these resins, which are essentially free of voids, bubbles, splay, silver streaks or other imperfections. Monomers that introduce the sulfone group into the polymer are shown in Table 15.4. 

Silver streaks, splay Wet material due to improper drying, high percent regrind, over wet virgin resin Follow resin manufacturer s drying instructions and dryer manufacturer s operating and maintenance instructions Use desiccant dryer... 

Marks or lines found on the surface of the part after molding that may be caused by overheating the material, moisture in the material, or flow paths in the part. Usually white, silver, or gold in color. Also called silver streaking. 

Injection molding. High moisture concentrations in thermoplastics that are injection molded can result in nozzle drool, foamy melt, lower melt viscosity, flow lines and silver streaks in the gate area, rough or scaly part surface, voids in the part, poor dimensional control, and reduced mechanical properties. 

A hot spot on a tube is usually caused by a partial loss of flow through one pass of a multipass heater. In most refinery services, a sudden reduction in flow will cause tubes to overheat. The low velocity combined with high tube-wall metal temperature results in localized coke lay-down. The layer of coke insulates the tube wall from the cooling effects of the process fluid. The insulated portion of the tube overheats. Typically, the hot spot looks like a silver streak or a silver dollar. 

A tube with a silver streak will begin to bulge at its hottest point. Eventually, the tube wall will thin out over the bulge and split open. Figure 15-10 illustrates this problem. Process-side hydrocarbons will spill into the firebox and ignite. Depending on the size of the leak and how quickly the operators shut the unit down, the heater may or may not burn down. 

Predrying at 100-120°C for 4-6 hours is necessary because excessive moisture may cause appearance of silver streaks. Cylinder temperatures of 250-270°C, and mold temperatures of 50-80°C are recommended. Mold shrinkage of TA series is 0.1-0.2% - larger than ABS therefore a careful mold design is important. 

Prediylng at 90-100°C for 2-4 hours is necessary before injection molding because insuflELdently diy material may cause appearance of silver streaks. Molding conditions of TB are suggested as follows Cylinder temperatm e nozzle - 230-260, front - 230-260, middle - 230-250, rear -210-230°C Injection pressm-e - 80-100 MPa Mold temperature 40-60°C. The mold shrinkage of TB is 0.5-0.8% compared with ABS 0.4-0.6% which indicates that a mold must be carefully designed. 

Predrying at 80°C for 4-6 hours is necessary because moisture may cause degradation of TPU, leading to appearance of silver streaks and reduction in physical properties. TPU tends to decompose at temperatures above 230°C. Therefore, material temperatures of 190-230°C are recommended during molding. Mold temperatures of 20-40°C are suggested. 

Splay is caused by moisture and shear. The shear splay is also known as silver streaks. Splay caused by moisture is related to raw material and the shear splay, i.e., silver streaks are caused by processing. In case of splay, proper drying of the... 

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. 

Silver streaks Melt temperature too low Increase heating... 

Texture surface mold may benefit from the optical effect of reducing the appearance of silver streak but making the bubble shearing worse. 

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