What causes discoloration on plastic?

What causes discoloration on plastic?

Exposure to UV radiation can cause plastics to change color (turn yellow), crack, break, shatter or even melt! When it comes to yellowing, however, UV light is often the primary culprit.

What are the defects in plastics?

Common Defects

• Blister. A blister is a raised area on the plastic surface, very similar to the medical condition of the same name.
• Burn Marks. Burn marks are generally caused by problems similar to blistering.
• Burrs.
• Embedded contaminates.
• Flow marks.
• Lamination.
• Sink marks.
• Short mold.

How do you fix drag marks in injection molding?

Drag Marks Unfortunately, this may mean that a redesign and adjustment to the part and mold must be made to increase the draft angle or change the position of the parting line. In some cases, a mold release agent may help to reduce drag.

What are ejector pin marks?

Ejector pin marks, sometimes called pin push, are the glossy or white imprints caused by the ejector pins that show on the class-A surface of the part. These marks can easily crack during the use of the actual products, so you want to prevent ejector pin marks before they happen.

How do you fix discolored clear plastic?

Cleaning Yellowed Plastic Containers With Vinegar

1. In the sink, add a tablespoon of Dawn, two cups of vinegar, and water.
2. Allow the plastic containers to soak for 15-30 minutes.
3. Use the bristle brush to scrub the containers.
4. Rinse with water and dry.

How do you clean discolored plastic?

Make a solution of water and bleach, using one tablespoon of bleach per cup of water. Let the containers and other items soak in the solution for one or two hours. After the stains are gone, wash the containers thoroughly, rinse, and dry.

What are sink marks?

Sink Marks are areas in a molded part where the surface is deformed into a depression. Sink marks are areas in a molded part where the surface is deformed into a depression. The depressions typically occur in areas of thick geometry and are caused by uneven cooling of the injection material.

What are the disadvantages of plastic in points?

Disadvantages of Plastic:

• They are non renewable resources.
• They produce toxic fumes when burnt.
• They are low heat resistant and poor ductility.
• They are non biodegradable.
• They harm the environment by choking the drains.
• The poisonous gaseous product produced by the decomposition plastic can causes CANCER.

How do you remove flash from plastic parts?

Dry ice blasting effectively removes various flash or burrs Despite its gentle touch, dry ice effectively removes flash and burrs from a variety of surfaces. Dry ice has been successful on most plastics and some rubbers, especially thermoset polymers.

How do you stop plastic parts from warping?

The general rule is the plastic that cools the slowest shrinks the most.

1. Cooling Rate. When the plastic cools in the mold, the molecules move closer together.
2. Cavity Pressure. Cavity pressure is always highest near the gate.
3. Fill Rate. Plastic molecules tend to orient when they flow.
4. Melt Temperature.

What is the injection pin?

Ejector Pins
What Are Injection Molding Ejector Pins? Ejector pins are vital in creating parts. They are an integral component of the ejection system in mold, which determines the final outcome of products in an injection molding process.

What causes drag marks on a plastic mold?

Drag marks – Scratches that occur when the part is ejected from the mold usually due to an improperly designed ejector system or one that is out of alignment. Burn marks – Black or brown blemishes that are caused by improper ventilation or prolonged heating in the mold.

What causes a plastic part to have a distorted shape?

Warping – A part with a distorted shape can be due to a poor cooling system in the mold. When the plastic material is cooled unevenly, the result is a bowing effect. Almost every defect that we listed can be fixed by making changes to the processing, the material, or the mold itself.

What causes flow marks on a plastic part?

Discoloration – This can occur when the hopper and feed zone have not been flushed properly to remove and residual color. Flow marks – This is a wavy pattern or discoloration caused by a slow injection speed which allows the material to cool too quickly.

What causes burn marks on injection molded plastic?

Image From ParallelDesign.com. Causes: Burn marks are caused either by the degradation of the plastic material due to excessive heating or by injection speeds that are too fast. Burn marks can also be caused by the overheating of trapped air, which etches the surface of the molded part.