Catalyst-doped sizing agent for preparation of high areal weight fiber shelf-stable prepreg or molding compound intermediates
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Solution Overview
Problem
High areal weight fiber intermediates face challenges in resin infusion due to decreased permeability, leading to under-cured regions and poor mechanical properties, particularly with the use of latent curatives like dicyandiamide, which are filtered out during the infusion process, resulting in non-uniform distribution and reduced composite homogeneity.
Innovation Solution
Coating the fiber material with a latent, particulate curative such as dicyandiamide improves resin flow and distribution, allowing for higher catalyst concentrations and uniform distribution within the thermosetting resin mixture, thereby enhancing the mechanical properties and curing efficiency of the composites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If latent curative particles are added to resin for high areal weight fiber infusion, then curing capability is improved, but fiber filtration of particles causes under-cured regions and poor homogeneity
Solution Approach 1:
The patent uses an intermediary carrier (such as silica particles or other inert substrates) to which the latent curative is bound. This intermediary serves as a transport medium that prevents direct filtration of curative particles by the fiber while delivering the curative to the resin system during infusion and curing, thereby resolving the contradiction between maintaining curing capability and achieving uniform distribution.
Solution Approach 2:
The patent changes the physical state and size parameters of the curative delivery system by binding curative to carrier particles with controlled size distribution (0.1-10 micrometers). This parameter modification allows the curative to pass through the fiber matrix without being filtered out, while still being released effectively during the curing process, thus improving both distribution homogeneity and curing reliability.
2Productivity
If fiber areal weight is increased to reduce layer count, then production efficiency is improved, but resin infusion difficulty increases due to decreased permeability
Solution Approach 1:
The patent modifies the resin system parameters by incorporating latent curative particles and adjusting viscosity characteristics. This allows the resin to maintain adequate flow properties through high areal weight fiber stacks while still achieving proper curing, thus enabling increased fiber areal weight without proportionally increasing infusion difficulty.
3Ease of manufacture
If resin temperature is increased to lower viscosity for infusion, then resin flow is improved, but hardener and accelerator activity becomes uncontrolled
Solution Approach 1:
The patent applies preliminary action by pre-coating the fiber with latent curative before resin infusion. This allows the resin to be infused at lower temperatures with controlled viscosity, while the latent curative on the fiber surface ensures proper curing occurs during the molding cycle without requiring high resin temperatures that would accelerate hardener reaction uncontrollably during infusion.
Solution Approach 2:
The patent introduces dynamic control of curative activity through the use of latent curative that remains inactive during infusion and only becomes active during the controlled curing cycle. This dynamic approach separates the resin flow phase from the curing phase, allowing independent optimization of each process parameter without interference.
4Manufacturing precision
If conventional solvents are used to dissolve curative for homogeneous distribution, then curative distribution is improved, but toxicity and volatility issues arise
Solution Approach 1:
The patent extracts the harmful solvent component from the curative delivery system while retaining the beneficial function of curative distribution. By using carrier-bound latent curative instead of solvent-based curative solutions, the system achieves homogeneous curative distribution through physical carrier distribution rather than solvent dissolution, thereby eliminating toxicity and volatility issues.
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
This approach enables the production of high areal weight prepregs with improved mechanical properties, increased permeability, and rapid curing at elevated temperatures, resulting in composites with enhanced heat resistance and dimensional stability.
Implementation Method 1
coating or sizing a fiber material with a latent, particulate curative or solid curative... infusing it with a resin mixture of one or more liquid epoxy resins and a hardener or catalyst
Implementation Method 2
infusing it with a resin mixture... dicy particles are retained and filtered out by the fiber intermediates at the point of entry of the resin
Data Source
AI summary
The present invention provides thermosetting resin pre-impregnated or infused fiber materials or prepregs comprising a thermosetting resin mixture and a fiber material component of a heat resistant fiber, such as carbon fiber, having an areal weight of from 500 to 3,000 g/m2 having a coating of from 0.5 to 4 phr of a latent, particulate curative or solid curative, preferably, dicyandiamide, wherein the prepregs are infused with a thermosetting resin mixture comprising (a) at least one liquid epoxy resin, and (b) a hardener and/or a catalyst, as well as methods of making the same. The prepregs of present invention enables the simple provision of lightweight composites having consistent resin cure throughout.