Physical, Mechanical, and Thermal Properties and Characterization of Natural Fiber Composites Reinforced Poly(Lactic Acid): Miswak (Salvadora Persica L.) Fibers
Table 10
Challenge injection molders deals with PLA polymer.
Material
Challenge
Causes
Solution suggestion
PLA
Flow lines (patterns or lines appear on parts)
(i) Issue in varying flow rates as molten polymer moves through mold (ii) Changes in the thickness of the molds walls (iii) Injection speed to slow that cause molten polymer to solidify at different rates
✓ Increase the injection pressure and speeds to ensure cavities are filled evenly ✓ Increase temperature of the molten polymer or mold preventing polymer from quick cooling
Sink marks (small depression in thicker areas of the injection molding after there is shrinkage in the finished product)
(i) Issue with pressure inside cavity (ii) Incorrect mechanism or cooling time
✓ Decrease mold temperature ✓ Allow polymer to cool and cure longer inside the mold
Vacuum voids (air pockets trapped inside an injection molded part)
(i) Insufficient holding pressure that led to molten plastic to condense inside the mold
✓ Use less viscous polymer to avoid trapping gas ✓ Increase holding pressure and time
Warping (finished part are uneven in areas)
(i) Nonuniform cooling or varying cooling rates inside mold
✓ Cooling process are not rushed in term of time and speed
