RTP reports progress in engineered PLA compounds

"Can we get bio-content into high performance engineered products?," asked Mark Bennick, Technology Manager at the Singapore operation of RTP Company (Winona, MN). Judging from his presentation at the recent 3rd International Conference for South & Southeast Asia on Innovations in High Performance Engineering Plastics in Singapore the answer is yes.

Bennick introduce a polylactic acid (PLA) grade‑RTP2099 X 124789 E‑ incorporating a copolymer impact modifier that boasted performance on a par with high impact polystyrene used in LCD TV housings where a notched impact strength of 2.0 ft.lb./in. is required. "The 95% bio-content PLA grade clears this, as well as tensile and flexural requirements, although heat deflection temperature at 66 psi is 151 deg F (66 deg C) versus 190 deg F (88 deg C) f0r HIPS.

A second such PLA grade‑ RTP2099 X 124789 F‑has been developed as an alternative to ABS in food processors and juicer housings. Whereas ABS delivers 4.0 ft.lb./in. of impact strength, the 90% bio-content PLA grade comes in at 5.9 ft.lb./in. Tensile and flexural properties are on a par, whereas HDT is 140 deg F (60 deg C) versus 2o0 deg F (93 deg C) for ABS.

Moving further up the performance spectrum, RTP is targeting PLA substitution for PC/ABS alloys in cellphone applications, for example, where a high notched impact strength of 13 ft.lb./in. is required. Grade RTP2099 X 124789 E is an 85% bio-content impact-modified PLA with flexural and tensile properties on a par with PC/ABS and notched impact strength of 16 ft.lb./in. It lags in HDT, however, at 140 deg F versus 240 deg F (116 deg C) for PC/ABS.

To raise the HDT, RTP's solution is to compound in PC with a compatibilizer, which raises HDT to 247 deg F (119 deg C), although bio-content declines to 32%. "A 90%-plus bio-content is possible if post-consumer recycled PC is employed," says Bennick. "

To raise the HDT of grades targeting ABS substitution, RTP has turned to mineral fillers. Specifically, 10% calcium carbonate-filled grade RTP2099 X 124790 E features an improved HTD of 175 deg F (79 deg C), while a 10% talc filling in grade RTP2099 X 124790 A features an HDT of 243 deg F (117 deg C) on a par with ABS.

In glass filled grades, RTP has worked with PLA and a nucleator to improve strength, modulus and heat performance. Grade RTP2099 X 124793 A is a 30% glass-filled grade with a flexural modulus of 1.6 million psi (versus 1.2 million psi for 30% glass-filled PBT and PA), tensile strength of 15,800 psi (versus 18,000 psi and 23,000 psi for the same PBT and PA grades), and an HDT of 327 deg F (164 deg C). The PBT and PA grades both have an HDT of 420 deg F (216 deg F). Further, the PLA grade is superior to glass filled PP in most respects except impact strength (1.1 ft.lb./in. versus 2.0 ft.lb./in..‑mpweditorial@ubm.com