Acylurea-Capped PBT Resin for Stable β-Crystal Formation
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Solution Overview
Problem
Current technologies lack effective methods to regulate the formation of β-crystal form in melt-crystallized polybutylene terephthalate (PBT) resin, necessitating the use of specific composite nucleating agents, and there is a need for PBT resins with improved mechanical properties.
Innovation Solution
A PBT resin capped with an aromatic carbodiimide functional group capping agent, controlling the content of acylurea and carboxyl end groups, is produced through a twin-screw extrusion process, enabling the formation of β-form crystals and enhancing mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a composite nucleating agent is used to promote β-crystal form formation in PBT, then the melting point is reduced and processing temperature can be lowered, but the formation of β-crystal form becomes irregular and mechanical properties deteriorate
Solution Approach 1:
The invention changes the chemical composition parameters of the nucleating agent system by specifying precise proportions of dibenzyl sorbitol (0.01-0.1 wt%) and sodium benzoate (0.01-0.1 wt%), along with controlling carboxyl end group content (≤20 mol/t). This parameter optimization enables regular β-crystal formation at lower processing temperatures while maintaining mechanical properties, resolving the contradiction between temperature reduction and strength preservation.
2Strength
If no specific nucleating agent is used, then the PBT resin maintains simple composition and good mechanical properties, but β-crystal form cannot be effectively formed and processing temperature remains high
Solution Approach 1:
The invention introduces minimal amounts of specific nucleating agents (dibenzyl sorbitol and sodium benzoate) with precisely controlled concentrations (0.01-0.1 wt% each), along with controlling carboxyl end group content. This subtle parameter change enables β-crystal formation and processing temperature reduction while preserving mechanical properties, avoiding the need for complex composite nucleating agents.
3Strength
If the content of acylurea end groups is increased to improve mechanical properties, then tensile strength increases, but the content of β-form crystals decreases
Solution Approach 1:
The invention optimizes the carboxyl end group content to ≤20 mol/t and acylurea end group content to 0.5-10 mol/t, creating a balanced composition that simultaneously achieves high tensile strength (≥55 MPa) and adequate β-form crystal content (≥3%). This parameter balance resolves the contradiction between strength enhancement and crystal stability.
Solution Approach 2:
The invention creates different end group distributions along the polymer chains, with controlled carboxyl and acylurea group concentrations. This local quality differentiation enables regions with high strength characteristics (acylurea groups) to coexist with regions favorable for β-crystal formation (low carboxyl content), resolving the contradiction between strength and crystal content.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting PBT resin contains 3.5-10% β-form crystals and exhibits superior mechanical strength, achieving tensile strengths up to 67 MPa.
Implementation Method 1
A PBT resin capped with an aromatic carbodiimide functional group capping agent, controlling the content of acylurea and carboxyl end groups
Implementation Method 2
The crystallization process can be divided into two stages: nucleation and crystal growth. According to the difference in the degree of chain folding, PBT has two crystal forms, α-crystal form and β-crystal form
Implementation Method 3
extruding the mixture through a twin-screw extruder to obtain the PBT resin; temperatures of the screw are set to ten zones as follows: a first zone with a temperature of 220-240° C.
Data Source
AI summary
The present disclosure provides a PBT resin, comprising an end group containing an acylurea group, where a content of the end group containing the acylurea group in the PBT resin is in a range of 0.5-10 mol/t, and a content of a carboxyl end group in the PBT resin is less than or equal to 20 mol/t. The PBT resin of the present disclosure is capped with a capping agent containing an aromatic carbodiimide functional group, and contains the carboxyl end group with a content of less than or equal to 20 mol/t, thereby obtaining PBT with a certain proportion of β-form crystal and excellent mechanical properties.