Material Drying
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ABS product brittle cracking——excessive regrind ratio
Problem Phenomenon
The product has poor toughness and breaks easily, concentrated after increasing the regrind ratio; the melt index rises, the fluidity improves, but the strength decreases.
Cause Analysis
ABS regrind undergoes multiple thermal histories, the molecular chains break and the molecular weight decreases; too high a regrind ratio or the use of multiple-times regenerated material directly lowers the overall toughness; crushed material contains moisture and dust and plasticizes unevenly, further aggravating performance fluctuations.
Solution
①Generally control the regrind ratio within 30%, use new material for key load-bearing parts; ②avoid using multiple-times regenerated material; ③fully and uniformly mix the regrind with new material and re-dry; ④appropriately lower the melt temperature and shorten the residence time to reduce secondary degradation; ⑤establish a ledger corresponding regrind batches to performance.
Key Takeaway
ABS regrind is not unusable, but the ratio and thermal history must be controlled; the improvement in fluidity is precisely a signal of molecular weight decrease; don't be fooled by 'easy to mold'——the performance account must be calculated with impact and tensile data.
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