Recycling of asbestos tailings used as reinforcing fillers in polypropylene based composites

Our plain-English summary of Recycling of asbestos tailings used as reinforcing fillers in polypropylene based composites, by W. Zhai, Y. Wang, Y. Deng, et al (Journal of Hazardous Materials, 2014).

The study

• Authors: W. Zhai, Y. Wang, Y. Deng, H. Gao, Z. Lin, M. Li
• Journal: Journal of Hazardous Materials
• Published: 2014;270:137-43
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In this work, asbestos tailings were recycled and used as reinforcing fillers to enhance the mechanical properties of polypropylene (PP). A silane coupling agent was used to chemically modify the asbestos tailings to increase the compatibility between asbestos tailings and polypropylene matrix. Both raw and chemically treated asbestos tailings with different loading levels (from 3 to 30 wt%) were utilized to fabricate composites. Mechanical properties of these composites have been investigated by dynamic mechanical analysis, tensile test and notched impact test. Results showed that hybridization of asbestos tailings in the composites enhanced the mechanical properties of neat PP evidently, and treated asbestos tailings/PP composites yielded even better mechanical properties compared with those of raw asbestos tailings/PP composites. This recycling method of asbestos tailings not only reduces disposal costs and avoids secondary pollution but also produces a new PP-based composite material with enhanced mechanical properties.

Copyright © 2014 Elsevier B.V. All rights reserved.

In plain English

This was a laboratory materials study, not a study of people or health. The authors used asbestos tailings from the Mangya Asbestos Mine in Qinghai Province, China. These mining wastes, the authors say, contain short asbestos fibers and ore fragments, mainly serpentine. They ground them, removed the magnetic part, and mixed them into polypropylene plastic at 3 to 30 percent by weight. Some tailings were first coated with a silane coupling agent (MPS); others were used raw. They tested stiffness, tensile strength, stretch before breaking and impact strength. Stiffness rose with more tailings. With treated tailings, tensile strength beat plain polypropylene at every level except 30 percent; stretch before breaking fell as tailings increased. Raw-tailings impact strength was about the same as plain polypropylene's; treated-tailings impact strength was higher, rising with loading up to 18 percent tailings, then falling. Weighing the mechanical properties together, the authors suggested 18 percent as the optimum content and concluded the method could eliminate the tailings' environmental threat. That was their conclusion, not a tested result; the paper reported no fiber-release or health measurements.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory materials-engineering experiment: making and mechanically testing plastic composites filled with asbestos tailings (no human or animal subjects)
• Who was studied: Asbestos tailings supplied by the Mangya Asbestos Mine, Qinghai Province, China, mixed into polypropylene from Beijing Yanshan Petrochemicals Factory; work done at Beihang University, Beijing (paper received 2013)
• Exposure: Asbestos tailings (asbestos mine residue with short asbestos fibers under 1.18 mm and ore fragments, major mineral serpentine), ground to under 80 mesh with the magnetic part removed. They were used raw or treated with the silane coupling agent MPS, at polypropylene-to-tailings weight ratios from 100:0 to 70:30.
• Main results:
  • Under the microscope, composites with 12 wt% raw tailings showed poor wetting of the filler and clumping of filler. Composites with 12 wt% treated tailings showed better dispersion with less clumping.
  • Raw tailings composites: tensile strength rose up to 3 wt% tailings, then decreased as loading increased further.
  • Treated tailings composites had higher tensile strength than plain polypropylene at all loadings except 30 wt%.
  • Tensile modulus (stiffness) increased with loading of either raw or treated tailings. Treated composites had higher modulus than raw ones.
  • Elongation at break (how far the plastic stretched before breaking) decreased steadily as tailings content increased.
  • Raw tailings composites had notched impact strength about the same as plain polypropylene.
  • Treated tailings composites had higher impact strength than untreated ones. Their impact strength increased with filler loading up to 18 wt% tailings, then decreased from 18 to 30 wt%.
• The authors' conclusion: The authors concluded that asbestos tailings could be used as a reinforcing filler in polypropylene. Based on comprehensive consideration of the mechanical properties, they suggested 18 wt% as the optimum tailings content. They also stated the technology could eliminate the environmental threat of the tailings while giving economic benefits. This was their stated conclusion, not a measured safety result.
• Limitations the authors state:
  • The authors noted that the composites are not attractive in appearance.
  • The authors noted that elongation at break was reduced by adding the tailings.

Topics

Medical terms in this study, explained in our Lexicon: Tailings.

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