WELD LINE STRENGTH OF FILLED & REINFORCED THERMOPLASTICS



THE LOCATION IN AN INJECTION MOLDED PART WHERE TWO FLOW FRONTS MEET IS COMMONLY CALLED A WELD LINE - THOUGH "WELD PLANE" MORE PROPERLY DESCRIBES THE PHENOMENON. IT'S WELL KNOWN THAT WELD LINES CREATE WEAK AREAS IN THE PART. THE MAGNITUDE OF THIS PROPERTY REDUCTION DEPENDS ON THE ABILITY OF THE TWO MELT FRONTS TO KNIT TOGETHER IN A HOMOGENEOUS FASHION DURING THE MOLDING PROCESS.


RESIN REINF % FILLER % SINGLE
GATE		 DOUBLE
GATE		 TENSILE STRENGTH PSI
% RETAINED
POLYSULFONE - - - - 9600 9600 100
POLYSULFONE GF 30 - - 16800 10400 62
SAN - - - - 11300 9025 80
SAN GF 30 - - 16180 6470 40
SAN GF 30 FR 10 13440 6100 45
PPRO - - - - 5400 4650 86
PPRO GF 20 - - 9100 4250 47
PPRO GF 30 - - 9800 3330 34
PPRO GF 15 GB 15 6500 2730 42
PPRO GF 30 PTFE 15 9700 2800 29
PPS - - - - 8840 7340 83
PPS GF 10 - - 10300 3920 38
PPS GF 20 - - 16000 5600 35
PPS GF 40 - - -20500 4100 20



GF = GLASS FIBER
GB = GLASS BEADS
PPRO = POLYPROPYLENE
PPS = POLYPHENYLENE SULFIDE
FR = FLAME RETARDANT

CONCLUSION:
THE HIGHER THE LOADING OF FIBER REINFORCEMENT, THE GREATER THE ABSOLUTE WELD-LINE STRENGTH, DESPITE THE INCREASING % LOSS IN STRENGTH !!

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