By Qian Bin, Sinopec Chemical Commercial Holding Company East China Branch

As the automobile industry is heading toward green, environmental-protection, safety and energy-saving development, it has led to constant innovations in modified polypropylene (PP) applications for autos. For countries, with developed automobile industry, the consumption volume of PP in autos has been increasing, to one third of the total plastic consumption and larger than any other plastic materials used in finished autos.      

Impacts from the COVID-19 on auto industry 

   The rampant COVID-19 pandemic has taken a toll on the world automobile industry, causing hundreds of automakers to halt production and shuttered over 3 000 spare parts companies across the globe. Auto sales have posted a year-on-year slump. China’s domestic automobile market is expected to fall in the early part of 2020 and is likely to regain some steam in the second half of the year, with shrinking demand resulting in an overall slow recovery in auto sales. China’s auto sales have dropped for two consecutive years and showed some signs of picking-up at the end of 2019. But the virus outbreak, which was gradually taken under control in March has crippled auto sales for the whole first quarter of 2020. The pent-up demand may start to release in the second quarter, likely to resume the growth in auto sales. Overseas auto orders almost grinded to a halt, as the virus also pummeled auto exports.    

   China’s auto production and sales reached 3.47 million units and 3.668 million units, respectively during January-March 2020, down by 45.2% and 42.4% year on year, respectively. Details are shown in Table 1. 

   Table 1  China’s domestic auto sales in 2019-2020 (Unit: 10 000 Units)

Three major applications of PP in automobiles

   PP has three major applications in autos. They are external applications and trims, internal applications and trims and applications under the hood. 

   The typical external application is found in bumper. The PP panel covers the surface of the hydraulic shock absorption system or honeycomb and foam system components. This kind of PP material is usually prepared by blending and modifying with specialty rubber or thermoplastic elastomer.

   PP also occupies most of the auto interior applications market, due to its good processing performance, processing coloring performance, and higher heat resistance, low gloss, and scratch resistance under light-weight conditions. Typical applications include PP instruments dial, door panel, column cover, console and seat back, etc.

   Applications under the auto hood include battery boxes, antifreeze, brake fluid, car wash fluid bottles, front-end modules for installing cooling fans and headlight covers, and car chassis shells.

Auto-use PP makes great headway

   Riding the tide of light autos, plastics, especially PP, boasting excellent properties, wide range of applications and great freedom in design have made substantial progress and their using volume in autos has been on the rise. At present, the research and development hotspots mainly include long glass fiber reinforced PP (LFRP), low-emission, low-odor PP, and scratch-resistant PP.

   1. LFRP

   LFRP is widely used in auto components, such as instrument frame panels, door assemblies, front-end components, body door panel modules, roof panels, seat frames, etc. because of its higher strength, stiffness, toughness, and dimensional stability.

   The highly integrated LFRP plastic door panel module can reduce the weight by 1.65 kilograms (kg) or 30%, compared with the steel door module; at the same time, it integrates the number of spare parts and reduces the cost by 10%, which can reduce the weight of each auto by 6 kg. At present, it has been widely used in high-end models, such as Mercedes-Benz, Audi and Wrangler.

   2. Low-emission, low-odor PP and scratch-resistant PP

   With people's pursuit of premium automobile quality, vehicle-use PP need to meet not only mechanical properties, but also high requirements on appearance and environmental protection.

   In October 2018, the draft of the mandatory national standard "Guidelines for Air Quality Assessment in Passenger Cars" jointly formulated by China’s Ministry of Ecology and Environment and the General Administration of Quality Supervision, Inspection and Quarantine was officially released to solicit opinions. From January 1, 2019, all newly-formed vehicles must strictly implement the standard.

   Air quality problems are mainly caused by toxic substances, released by the interior materials used in autos. At present, low-emission, low-odor PP materials are dominated by Basell and Borealis. China’s domestically made products have a long way to go to replace the imports. 

   The manufacture of high-scratch-resistant auto interior materials requires, on the one hand, the use of imported PP materials with higher surface hardness, and on the other hand to add additives to improve the smoothness of the surface of the material. The core of the problem still hinges on the performance of the base material PP.  

Development and research hotspots for auto-use PP

   China’s auto sales reached 25.769 million units in 2019, down by 8.2% year on year. The bleak outlook of the automobile industry calls for accelerating the pace of upgrading and replacing imported PP for domestic materials.

   1. High flow-ability, high modulus, high toughness PP

   In 2017, Sinopec Zhenhai Refinery developed M60RHC, with melt-index at 60g/10min and flexural modulus above 1800MPa. Around 80 kt of such product have been put into the market by the first quart of 2020. In the meantime, Zhenhai Refinery has successfully developed M100RC, with melt-index at 100g/10min. PP of high flow-ability, high modulus and high toughness will become the mainstream material used in autos. 

   2.  Low-emission, low-odor PP

   Auto interior parts must meet four requirements of emission performance, namely odor score no higher than 3; formaldehyde content no larger than 10mg/Kg; condensation component no larger than 2mg; total carbon content no higher than 50μgC/g. Sinopec Zhenhai Refinery’s low-emission, low odor PP M50RH has an odor score closer to 3, which can almost replace its counterparts from ExxonMobil and Basell. The sales of M50RH have exceeded 30 kt by the first quarter of 2020. 

   3.  PP foam

   PP foam displays the advantages of light weight and heat resistance. Auto-use PP foam materials are mainly chemical microcellular foam, including injection microfoam, blow molding microfoam and extruded microfoam. Among them, injection micro-foam is suitable for various auto interior and exterior trims, such as body door panels, tail doors, air ducts, etc.; extruded micro-foam is appropriate for sealing strips, ceilings, etc.; blow-molded micro-foam is suitable for automobile air ducts, etc.

   The use of micro-foaming technology can reduce the weight of PP products by 10% to 20%. It can achieve a weight reduction of up to 50%, compared with traditional materials, making the design of products and molds more flexible.

   4. Antibiotic PP

   The COVID-19 outbreak has brought antibiotic PP application in auto interior parts to the forefront and this may become a hotspot for auto-use PP development.