I. Injection moulds

1. Poor processing of mold cavity
If the mold cavity has scars, microporous, wear, roughness and other deficiencies, it will inevitably react to the plastic parts, so that the plastic parts luster bad, for this, to carefully process the mold, so that the surface of the cavity has a small roughness, if necessary, polishing chrome plating.

2. cavity surface stains
If the surface of the cavity has oil, water stains, or too much mold release agent, it will make the surface of the plastic parts dark, no luster, in this regard, to remove the oil and water stains, and limited use of mold release agent.

3. The slope of mold release is too small
Mold release slope is too small will cause difficulties to release the mold, or too much force to release the mold, so that the surface of the plastic parts gloss * good, to increase the mold release slope.

4. Poor exhaust of the mold
If the exhaust is not good, it will cause too much gas to stay in the model, which will also lead to bad luster, for this, check and correct the mold exhaust system.

5. Improper gate or runner design
Gate or runner cross-sectional area is too small or sudden changes, the melt in which the flow of shear force is too large, is turbulent dynamic flow, resulting in poor gloss, for which, should be appropriate to increase the gate and runner cross-sectional area.

II. Injection molding process

1. Injection speed is too small
The injection speed is too small to cause the surface of the plastic part is not dense, appearing bad luster, in this regard, the injection speed can be increased appropriately.

2. Insufficient cooling of plastic parts
If the cooling of thick-walled plastic parts is not sufficient, the surface will be hairy and the luster will be dark, in this regard, the cooling system should be improved.

3. Improper pressure-holding operation
If the holding pressure is too small, the holding time is too short, so that the density of plastic parts is not enough and the luster is not good, which should increase the holding pressure and holding time.

4. If the melt temperature is too low
When the melt flow is too low, making poor mobility, easy to lead to bad luster, which should be appropriate to improve the melt temperature.

5. Uneven cooling of crystalline resin
Such as PE, PP, POM and other plastic parts, such as uneven cooling will lead to poor gloss, in this regard, the cooling system should be improved to make it uniform cooling.

6. Injection speed and gate area do not match
If the injection speed is too large and the gate cross-sectional area is too small, the vicinity of the gate will be dark and bad luster, which can be properly reduced injection speed and increase the gate cross-sectional area.


III. Raw materials

1. Large differences in particle size of raw materials
Large differences in particle size make it difficult to plasticize evenly, and the luster is not good, in this regard, the raw materials should be sieved.

2. Too much secondary material in raw material
Such as recycled material or water mouth material added too much, affecting the uniform plasticization of the melt and bad luster, which should reduce the amount of recycled material or water mouth material added.

3. Raw material temperature resistance is bad
Some raw materials will decompose and change color when adjusting the temperature, resulting in bad luster, for this, should use the raw materials with better temperature resistance.

4. Raw materials containing volatile substances
If the moisture or volatile content of raw materials is too high, volatile gas when heated, condensation in the cavity and melt, resulting in poor luster plastic parts, which should be pre-drying raw materials.

5. Additive dispersion is not good
The dispersion of some additives is too poor and make the plastic parts bad luster, which should be replaced with additives with better fluidity.

6. Impure raw materials
Such as raw materials mixed with foreign materials, miscellaneous materials or insoluble materials, they can not be mixed with their raw materials evenly together and lead to bad luster, which should be strictly excluded in advance these miscellaneous materials.

7. The amount of lubricant is too little
If the amount of lubricant is too little, the fluidity of the melt is poor, the surface of the plastic part is not dense, making the luster bad, for this, the amount of lubricant should be increased appropriately.

Xiamen LFT composite plastic Co., Ltd is a brand-name company that focuses on LFT&LFRT. Long Glass Fiber Series (LGF) & Long Carbon Fiber Series (LCF). The company's thermoplastic LFT can be used for LFT-G injection molding and extrusion, and can also be used for LFT-D molding. It can be produced according to customer requirements: 5~25mm in length. The company's continuous infiltration reinforced thermoplastics have passed ISO9001&16949 system certification,  and the products have obtained lots of national trademarks and patents.