Fiber Reinforced TPU Composites


 Number/Link: WO 2018/104145

Applicant/Assignee:  Henkel

Publication date: 14 June 2018

Gist”: TPU based on a vicinal alkane diol together with an alkoxylated aromatic diol can be used as matrix material in a fiber composite

Why it is interesting: According to this invention a thermoplastic polyurethane with a high Tg (pref. >80°C) and a high stiffness (>1GPa) can be prepared from a short chain, sterically hindered, vicinal diol (e.g. 1,2-propanediol or 2,3-butanediol), an alkoxylated aromatic diol (e.g. alkoxylated bisphenol A or F) and an aromatic diisocyanate (e.g. 4,4’MDI) pref. mixed with some high functionality isocyanate (e.g. polymeric MDI) to control branching an molecular weight. The TPU composition can be used to make a fiber reinforced composite in an RTM-type process. The cured thermoplastic matrix has high mechanical properties but still allows for post-cure modification of the moulded part.


Ethoxylated Bisphenol F

Hybrid Polyisocyanurates for Composites and Coatings


 Number/Link:WO2018/087395 WO2018/087396  WO2018/087399 (German)

Applicant/Assignee:  Covestro

Publication date: 17 May 2018

Gist”:  Di-isocyanate trimer is reacted with hydroxymethacrylates and polyacrylates in the presence of a trimerization catalyst. 

Why it is interesting: According to these inventions a reaction system with two curing modes can be prepared by mixing high functionality oligomeric isocyanate, ethylenically unsaturated compounds, unsaturated compounds containing isocyanate-reactive groups, timerization catalyst and a free-radical initiator at an NCO index of 100 to 200. The system shows a relatively low viscosity and can e.g. be used in fiber-reinforced composites and in coatings. In the examples HDI trimer is reacted with hexanedioldimethacrylate and hydroxypropylmethacrylate in the presence of potassium acetate and a peroxybenzoic acid.

HDI isocyanurate


Aliphatic Polyisocyanurate Composites


 Number/Link: WO 2017/191216  (German)

Applicant/Assignee:  Covestro

Publication date: 9 November 2017

Gist”: Partially trimerized aliphatic diisocyanates are mixed with glass fiber and reacted using a trimerization catalyst

Why it is interesting: Conventional fiber-reinforced composites based on unsaturated polyesters, epoxies, polyurethane and the like are not weather-stable and need to be coated for outdoor use. Weather stable polyisocyanurate composites are known (WO2007/096216 – Huntsman) but are based on aromatic diisocyanates and show high reactivity and short ‘pot life’. According to this invention, PIR composites with improved reaction profile and weatherability can be prepared from partially trimerized aliphatic diisocyanates with a diisocyanate monomer content of less than 20% (w/w). In the examples commercially available HDI and IPDI trimer is used together with short glass fiber and a potassium acetate/PEG 400 blend as catalyst cured at a temperature of 160 to 180°C.

Isophorone diisocyanate (IPDI)


Triptycene Chain Extenders


 Number/Link: US20150191408

Applicant/Assignee: not yet recorded. Research supported by US Army

Publication date: 9-07-2015

Gist”: A novel primary diol derived from triptycene is useful as chain extender for polyurethanes and polyesters.

Why it is interesting: Polymers with increased mechanical properties and stiffness can be obtained by incorporating rigid structures in the polymer chain.  This however also results in increased glass transition temperature and reduced ductility because of reduced chain flexiblity and entanglements.  According to this invention polyurethanes (and copolyesters) with high modulus and good ductility at low temperatures can obtained by using triptycene-1,4-hydroquinone-bis(2-hydroxyethyl ether) or TD. In and example TD capped with PEG400 is reacted with a 4,4’MDI- PTMEG1000 prepolymer.  The resulting material indeed has a very low softblock Tg of  -65ºC and a much higher Y modulus compared to a PU made with HQEE as chain extender. According to the inventors the PU is highly suitable as a matrix material in KEVLAR or UHMWPE fiber composites.
In my opinion this is a very interesting chain extender as it appears to prevent H-bond formation and increase molar volume thereby substantially decreasing Tg. However lack of availability, and (most probably) price, will prevent this from becoming mainstream anytime soon.

Tryptycene-1,4-hydroquinone-bis(2-hydroxyethyl ether)

Triptycene-1,4-hydroquinone-bis(2-hydroxyethyl ether)


Steam-Treated Polyisocyanurate


 Number/Link: WO2014/160616

Applicant/Assignee: Dow

Publication date: 2-10-2014

Gist”: Treating PUR-PIR with hot water at superatmospheric pressure results in a Tg increase.

Why it is interesting: Fiber-reinforced phenol-formaldehyde composites are used to make pipes among other things.  They are however not completely stable in hot humid conditions so that they are less well suited for off-shore piping systems for example. According to this patent application, polyisocyanurate (PIR) or polyurethane-polyisocyanurate (PUR-PIR) systems are more suitable materials for such applications because properties of these materials remain stable and -surprisingly- glass transition temperature increases when subjected to high pressure water or steam. In the examples PUR-PIR systems based on polymeric MDI submerged in water at 120°C and 3500 kPa for 7 days show indeed an increase in Tg.  In my opinion it would be interesting to repeat the experiment with 4,4′-MDI based PUR/PIR.  Because 4,4′ MDI will show a higher conversion rate to PIR the ‘steam effect’ may well dissapear.

Isocyanurate group

Isocyanurate group