Polycarbonate Polyester Flame Retardant Composition
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Solution Overview
Problem
Polyalkylene terephthalate/polycarbonate compositions face challenges with inadequate flame retardancy, high moulding shrinkage, and unsatisfactory heat resistance, which hinder the production of parts with tight tolerances and suitable fire behavior.
Innovation Solution
A specific composition comprising 49-70 parts by weight of aromatic polycarbonate, 21-40 parts by weight of polyalkylene terephthalate with more than 2 carbons in the diol component, and 6-25 parts by weight of a salt of phosphinic acid, with a preferred ratio of polycarbonate to polyalkylene terephthalate and the inclusion of conventional additives, optimizing the balance for low moulding shrinkage, high chemical resistance, and good heat resistance while enhancing flame retardancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If organic aromatic phosphates are used as flame retardants, then flame retardancy is improved, but heat resistance deteriorates due to highly plasticising action
Solution Approach 1:
The patent changes the chemical parameter of the flame retardant from organic aromatic phosphates to inorganic phosphinic acid salts, which have different plasticising properties. This parameter change maintains flame retardancy while reducing the harmful plasticising effect that compromises heat resistance
Solution Approach 2:
The patent creates a composite material system combining polycarbonate and polyalkylene terephthalate with inorganic phosphinic acid salts. This composite approach allows the inorganic flame retardant to work synergistically with the polymer matrix, achieving both flame retardancy and maintained heat resistance that wouldn't be possible with organic phosphates alone
2Manufacturing precision
If polyalkylene terephthalate content is increased to reduce moulding shrinkage, then dimensional stability is improved, but flame retardancy deteriorates
Solution Approach 1:
The inorganic phosphinic acid salt acts as an intermediary that enables the polyalkylene terephthalate to contribute to reducing moulding shrinkage without compromising flame retardancy. The salt mediates between the dimensional stability benefits of polyester and the fire safety requirements
Solution Approach 2:
The patent uses a composite material system where polycarbonate, polyalkylene terephthalate, and inorganic phosphinic acid salts work together. This composite allows the polyester component to reduce moulding shrinkage while the inorganic flame retardant maintains fire safety, overcoming the limitation identified in prior art
3Strength
If impact modification is increased to improve impact strength, then toughness is improved, but flame retardancy deteriorates when component B content reaches 20 parts by weight and more
Solution Approach 1:
The patent changes the flame retardant parameter from organic to inorganic, which alters the interaction with impact modifiers. The inorganic phosphinic acid salt does not have the same detrimental effect on flame retardancy when combined with impact modifiers as organic phosphates do, allowing higher impact modification levels
Data Source
AI summary
The present invention relates to polyalkylene terephthalate/polycarbonate compositions, containingA) 49 to 70 parts by weight aromatic polycarbonate,B) 21 to 40 parts by weight polyalkylene terephthalate with more than 2 carbons in the diol component,C) 6 to 25 parts by weight of a salt of a phosphinic acid,D) 0 to 24 parts by weight conventional additives,all parts by weight in the present application being standardized such that the sum of the parts by weight of components A+B+C+D in the composition adds up to 100,and which are distinguished by an optimum combination of low molding shrinkage, high chemical resistance and good heat resistance together with good fire behavior, the use of the polycarbonate compositions for the production of moldings and the moldings themselves.