• Plastic ( soft or malleable) at normal ambient temperatures
• A melting point above approximately 45 °C.
• A  relatively low viscosity when melted (unlike many plastics)
• Insoluble in water
• Hydrophobic

We shall be discussing here on the waxes which are only being used in the rubber and plastic industry. Beeswax, perhaps , is the first wax which used by human in the beginning of our civilization, was one of the important renewable source of fuel. The honey comb formed by bees has typical hexagonal geometric pattern (Fig.1). Bees wax is used in tire building drum, if the rubber is too sticky, it can also be used in two roll mill to take care of rubber sticking to the rolls. It is frequently being used in the BC, MC, PC, TB  inner-tube making industry during pre-forming operation in the green stage when inner-tubes are expanded under mild air pressure just before curing in mold.

The main commercial source of wax is, however, crude oil but not all crude oil refiners produce wax. "Mineral" wax can also be produced from lignite. Plants, animals and even insects produce materials sold in commerce as "wax". There are five categories of waxes being used in rubber industries :

• Bees Wax
• Paraffin Wax - made of long-chain alkane hydrocarbons
• Microcrystalline Wax - with very fine crystalline structure
• Chlorinated Paraffin Wax
• Polyethylene Wax
• Chlorinated Polyethylene Wax

The major uses of petroleum based waxes are in rubber, cosmetics and in Candle industry. They are generally white in color but show usual brown color (Fig.2) due to contaminated with oil traces. Two types of waxes, in general, are used in rubber industry, Paraffinic wax and Microcrystalline wax. Its normal dose is 1-3 phr and high level of wax impairs low temperature flexibility and compression set. Rubber compounder considers wax as a very important processing aid because it has following advantages:

• Improves mixing properties

  

   

• Improves dispersion of filler and other ingredients
• Improves extrusion properties
• Improves upon extrudate and calendared surface finish
• Protects surface and acts as antioxidant /antiozonate

Paraffin and Microcrystalline waxes are derived from petroleum. They are easy to recover and offer a wide range of physical properties that can often be tailored by refining processes. Most producers offer two distinct types of petroleum waxes: paraffins, which are distinguished by large, well formed crystals; and microcrystallines, which are higher melting waxes with small, irregular crystals. Microcrystalline wax contains substantial proportions of branched and cyclic saturated hydrocarbons in addition to normal alkanes.

Some producers also sell "intermediate" wax, in which the boiling range is cut where the transition in crystal size and structure occur. Petroleum wax producers also characterize wax by degree of refinement; fully refined paraffin has oil content generally less than 0.5% and fully-refined micro-crystalline less than 3%. Paraffin wax produced from petroleum is essentially a pure mixture of normal and iso-alkanes without the esters, acids, etc. found in the animal and vegetable-based waxes.

Paraffin wax (or simply "paraffin") is mostly found as a white, odorless, tasteless, waxy solid, with a typical melting point between about 47-64 °C  and having a density of around 0.9 g/cm³. It is insoluble in water, but soluble in ether, benzene, and certain esters. Paraffin is unaffected by most common chemical reagents, but burns readily. Paraffin wax is generally unbranched hydrocarbon having carbon above C₁₇ and  are solid at room temperature. Their carbon atoms typically ranges between C₁₇ - C₃₀ and having typical melting point around 60°C. All paraffinic wax are recovered from fractional distillation of petroleum.The name paraffin implies that it contains straight hydrocarbon structure but it has branch also. Branched paraffins are called ‘Isoparafins’ and cyclic parafins are called ‘Cresines’ or ‘Isoceresies’.

Pure paraffin wax dose in rubber compounding varies from 1-3 phr. Pure paraffin wax is rarely used these days in rubber industry as it has oozing character and in excess it causes blooming on green rubber components, that results in reduction in compound tack. They are frequently blended with microcrystalline wax in rubber compounding therefore.

Pure paraffin wax is an excellent electrical insulator, with an electrical resistivity of between 10¹³ and 10¹⁷ ohm meter. This is better than nearly all other materials except some plastics (notably teflon or polytetrafluoroethylene). It is an effective neutron moderator and was used in James Chadwick's 1932 experiments to identify the neutron. Paraffin wax (C₂₅H₅₂) is an excellent material to store heat, having a specific heat capacity of 2.14–2.9 J g^–1 K^–1 (joule per gram per kelvin) and a heat of fusion of 200–220 J g^–1(joule per gram). This property is exploited in modified drywall for home building material.

Microcrystalline waxes: This is produced by de-oiling petrolatum, as part of the petroleum refining process. Microcrystalline wax contains a higher percentage of isoparaffinic (branched) hydrocarbons and naphthenic hydrocarbons. It is characterized by the fineness of its crystals in contrast to the larger crystal of paraffin wax. It consists of high molecular weight saturated aliphatic hydrocarbons with comparatively higher melting point than paraffinic wax. It is generally darker, more viscous, denser, tackier and more elastic than paraffin waxes. The elastic and adhesive characteristics of microcrystalline waxes are related to the non-straight chain components which they contain. Typical microcrystalline wax crystal structure is small and thin, making them more flexible than paraffin wax. It is commonly used in rubber formulation and cosmetic formulations.

Its usual carbon atom ranges from C₄₀–C₇₀ , having comparatively higher melting point (Fig.4) between 80-105 ⁰C because they have higher number of carbon. Common dose in rubber compounding is between 1-3 phr. Some time higher dose of  100% Micro crystalline wax is difficult to process and as a result they are often blended with paraffinic wax for rubber use. Blending is also done for economical reasons as microcrystalline wax is comparatively costlier. Paraffinic wax, having smaller molecular weight bleeds faster in cured rubber article, whereas, 100% micro crystalline wax  will have inherent resistance to faster volatilization and eventually, blended wax will have an intermediate property. Refineries may also utilize blending facilities to combine paraffin and microcrystalline waxes. This type of activity is prevalent especially for industries such as tire and rubber industries.

Higher dose of antioxidant and anti ozonates are always advised to add along with microcrystalline wax because the later help slower migration of antioxidant and antiozonates on the product surface and thereby increase on the product durability against ageing process. Tire curing bladder is often blended with 1-3 phr of microcrystalline wax.

Chlorinated Paraffin Wax

Upon chlorination of paraffinic wax we get Chlorinated Paraffin Wax(CPW). This is available in batch process that is processed from effective exothermic reaction. This reaction generates a by-product hydrochloric acid that is later removed out of the solution. Finally stabilizer and solution is mixed that provide the required final product, which is used in various industrial applications. With 30 to 70% chlorine and insolubility in water, these CPWs have low vapor pressure. Chlorinated Paraffin Wax is highly inert, insoluble in water and they have low vapor pressure. Generally used as plasticizers in plastic and elastomers, where flame retardant property is important.

Polyethylene waxes (PE-Wax)

Polyethylene waxes or PE-Wax is same familiar polyethylene chemical structure (Fig.5) but with lower molecular weight , generally around or less than 3000.This is a processing aid in elastomer and plastics but basically they are a form of synthetic resins. It is a white solid product (Fig.6) appears in the market as powdery, lumpy, or flaky product. It is a non-toxic product having concentrated distribution of molecular weight of 1500 with specific gravity about 0.94 with high softening point but low fusion viscosity with melting point; 112 - 118°C, melt peak 110 °C, flash point 210°C, minimum. It has excellent stability against polishing, scratch resistance, metal mark resistance, scuff resistance. PE-Wax is resistant to water and chemical materials.

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Recovered carbon black is edging closer to mainstream adoption as ASTM International committee D36 on Recovered Carbon Black develops a new ash content standard, D8621. The test promises to slash analysis times from 18 hours to just a few, a change that could reshape productivity and quality control for tyre makers and rCB producers. Yet the push for faster monitoring also exposes a bigger challenge, as standardisation alone will not guarantee industry-wide adoption. With high capital investment, scaling hurdles and safety considerations, the new method sits at the intersection of technical progress, economic pressure and the tyre industry’s sustainability ambitions.

The ASTM International’s recovered carbon black (rCB) D36 committee developed and published a new standard called D8621, which will improve productivity of tyre makers and also enhance production process monitoring abilities.

Speaking exclusively to Tyre Trends, ASTM D36 Chair and Director of rCB at Circtec, Pieter Ter Haar, said, “The D1506 method was developed for regular carbon black, which typically has an ash content of <1 percent. rCB typically has an ash content between 15 and 30 percent.”

The new standard promises to cut testing times from 18 hours to just a few. Commenting on this, he said, “This rCB-specific test method requires less material, and by operating the furnace at a higher temperature, the rate-of-reaction is optimised for rCB, resulting in the significant reduction in time. Since ash content is one of the important product specifications, reducing the time to obtain results is of great help in quality control of the production process of rCB.”

“The main benefit is the significant reduced time required to obtain ash content information of the rCB sample from a tailor-made test method. The future bias and precision study will have to show if the method also has an improved standard deviation,” he added.

CONSENSUS BUILDING

The method’s creation reflects the convergence of some of the industry’s biggest players. “This standard was created by the globally leading rCB, carbon black and tyre manufacturers who come together in the committee. We will actively try to promote the use of this method going forward both for producers and users,” said Ter Haar.

He argued that the proposed standard could reshape the economics of rCB production, particularly in terms of reducing waste or lowering costs as more process control will typically result in less waste and a quicker ability to adjust feedstock ratio’s when changes need to be made.

“This new method will also help tyre manufacturers analyse rCB faster and this will, however, not likely play a role in competitiveness compared to virgin carbon black,” he stated.

According to Ter Haar, the temperature of the muffle furnace has increased from 550 degrees Celsius to 700 degrees Celsius, which is an important consideration for the manufacturer using this method when it comes to safe execution of this method. Besides, he wasn’t aware of any other potential risks or limitations that need to be considered.

Alluding to how critical is standardisation in gaining wider adoption of rCB within tyre production supply chains from Circtec’s perspective, Ter Haar explained, “Standardisation will not be the silver bullet for better understanding of rCB or overcoming the initial adoption phase of rCB in rubber compounds. However, when it comes to consistent supply of rCB, relevant rCB-specific specifications are crucial.”

SUSTAINABILITY PUSH

ASTM Standard D8621 fits neatly into the tyre industry’s strategic pivot towards greener materials. According to Ter Haar, the new standard is part of the wider industry development of the rCB producers and adaptation to the needs and requirements of the tyre industry for adoption of new raw materials for the construction of tyres.

He pointed to high levels of capital deployment, the emergence of reputable producers across global regions and platforms like ASTM as proof that rCB is on track to become a cornerstone of tyre sustainability.

“There are very few sustainable raw material options available for the tyre industry that seem to be developing into mature industries,” the spokesperson noted, stressing that rCB is now positioned as a key strategic material for fulfilling long-term sustainability and circularity objectives.

Circtec itself is pushing hard to lead the charge. Later this year, the company will open its third European factory in the Netherlands. The facility, built to a scale comparable with regular carbon black plants, is expected to convert around six percent of all waste tyres in Europe into sustainable products once it reaches full capacity.

“We will continue to focus on the global expansion of Circtec and the development of the sector when it comes to regulatory compliance, technical knowledge and producing high-quality rCB at large industrial scale,” he said.

INDUSTRY RECEPTION

The new standard has already won the backing of the tyre industry. “The tyre industry was an active participant in the development and approval process of this new standard,” Ter Haar emphasised.

The benefit is straightforward, which is more precise quality control. “Any time one of the raw material suppliers can improve their quality control, this is welcomed. The main objective of any new standard is that the test method is technically relevant and improves the ability to test rCB’s characteristics that actually correlate to in-rubber performance,” he explained.

For producers, the efficiency gains are significant. At Circtec’s Netherlands plant, for instance, output is expected to reach 10 tonnes of rCB per hour. At these production rates, quick quality control test methods are crucial.

While faster process monitoring will primarily benefit producers with scaled up production capacity, Ter Haar noted that the standard is not necessarily designed to spark innovation in rCB applications beyond tyres such as plastics or coatings.

Crucially, adopting the new standard won’t require expensive technical upgrades. “The benefit of this method and aim during the development is that for most producers or end-users, there would not be a need for any new investments in equipment. This method is based on the use of an affordable ashing muffle furnace with the ability to heat to 700 degrees Celsius,” he said.

ADOPTION DYNAMICS

ASTM standards remain voluntary, but Ter Haar expects uptake to be swift given the operational advantages. “This new standard is a tool to improve the speed of quality control. It is up to the individual parties to adopt this or any other ASTM method. Due to the clear advantages of this method, I would expect both producers and users to welcome using this test method moving forward,” Ter Haar said.

The development also represents a milestone in a broader strategic roadmap. The ASTM committee D36 on Recovered Carbon Black, formed eight years ago, initially issued guidance on which carbon black test methods could or should not be used.

“At the moment, most of the key product performance characteristics of rCB can be determined,” he observed, suggesting that D8621 could be a stepping stone towards a broader suite of rCB-specific standards on par with virgin carbon black testing.

As rCB moves into the mainstream, the combination of industrial-scale production, regulatory support and technical validation is setting the stage for what could become one of the tyre industry’s most significant sustainability transformations in decades.

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Members of the Global Platform for Sustainable Natural Rubber gathered for the organisation’s seventh General Assembly, marking what it described as a pivotal year for accountability and member-led sustainability across the natural rubber value chain.

A key development in 2025 was the launch of GPSNR’s risk-based Assurance System, which sets sustainability expectations, introduces independent verification and aims to drive continuous improvement beyond regulatory compliance. The system was developed collaboratively over several years and is intended to provide a globally applicable framework for sustainability in the sector.

At the assembly, end-user companies reaffirmed their support for the Assurance System and agreed on a structured pathway towards full implementation within their category.

“This year marks a turning point for GPSNR,” said Stefano Savi, chief executive of GPSNR. “The Assurance System gives our members a shared and trusted foundation for demonstrating progress across the value chain.”

Members also reflected on the first year of the Shared Investment Mechanism, a model that allows manufacturers to share the costs of large-scale capacity-building projects. The initiative is intended to deliver long-term benefits for upstream participants, particularly smallholder producers.

“Sustainability cannot be achieved by one part of the value chain alone,” Savi said. “By investing together, our members are enabling more inclusive and impactful outcomes worldwide.”

Looking ahead to 2026, GPSNR said it would focus on supporting the implementation of the Assurance System through data collection, member learning programmes, and stakeholder dialogue, to ensure the framework reflects operational realities and different business models.

The assembly concluded with members reiterating their commitment to building more equitable, resilient and sustainable natural rubber supply chains.

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The Tire Recycling Foundation has opened nominations for its first Circle of Change Awards, aimed at recognising organisations, teams and individuals advancing innovation and sustainability across the tyre recycling sector.

Nominations opened on 15 December and will be accepted until 8 February  2026. The awards will honour contributions spanning tyre recycling technologies, end-use market development and leadership in circular economy practices.

“The Circle of Change Awards will serve as a powerful way to recognise national visionaries and changemakers who have shaped the trajectory of the full tyre recycling value chain over the past two decades,” said Anne Forristall Luke, president of the Tire Recycling Foundation board. “We are thrilled to recognise trailblazers making a lasting impact on end-of-life tyre (ELT) recycling and the circular economy.”

Four award categories will be presented at the 10th Tire Recycling Conference, scheduled to take place in Denver, Colorado.

“By spotlighting the collective progress being made in tyre recycling, the Foundation hopes these inaugural awards will inspire and fuel accelerating momentum in exciting new markets for recycled tyres,” said Stephanie Mull, executive director of the Tire Recycling Foundation.

The Innovation in End-Use Technology Award will recognise technologies, products or processes that use recycled tyre rubber in new ways, with a focus on technological advancement, commercialisation and sustainability impact.

The Circular Economy Trailblazer Recognition, State Leadership in Tire Market Innovation category will honour state agencies or statewide programmes that demonstrate leadership and measurable impact in advancing tyre recycling within a circular economy framework.

The Market Development Excellence Award will recognise efforts to expand end-use markets for tyre-derived materials through education, policy, marketing or advocacy, with an emphasis on measurable market growth and long-term strategy.

The Value Chain Collaboration Award will acknowledge partnerships across the tyre recycling value chain that deliver measurable improvements in efficiency, economics or environmental performance.

The foundation said organisations and individuals that have made significant contributions to tyre recycling or developed innovative solutions for tyre-derived materials are encouraged to apply. Award recipients will be allowed to showcase their achievements and inspire further progress across the sector.

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The German Rubber Industry Association (wdk) has called for enhanced policies to unlock the full potential of tyre recycling in Germany. While acknowledging the existing successes of the circular economy in this sector, Stephan Rau, Technical Director of wdk, emphasised that significant untapped opportunities remain. Last year alone, Germany generated 533,000 tonnes of used tyres, with nearly 70 percent kept in circulation through reuse, retreading and recycling. The wdk advocates for a stronger framework to improve these material flows and boost the market for recycled materials.

A central pillar of the wdk’s position is the demand for a modern, science-based evaluation of recycled rubber products. Over 200,000 tonnes of used tyres are processed annually into granules and rubber flour, vital secondary raw materials for sustainable manufacturing. However, Rau argues that their broader market success is hindered by outdated assessment methods. The association urgently recommends a risk-based approach that evaluates chemical ingredients based on their actual bioavailability and migration, rather than their mere presence. This perspective, now supported by the German Federal Institute for Risk Assessment (BfR), necessitates establishing binding limit values determined through migration analysis to ensure both safety and commercial viability.

Furthermore, the wdk highlights a critical gap in the complete monitoring of tyre material flows. A notable proportion of used tyres exit Germany and Europe for processing, depriving domestic recyclers of valuable secondary raw materials. To address this leakage and strengthen the circular economy, Rau stresses the need for comprehensive tracking of all end-of-life tyres. The association’s commitment is reflected in its patronage of the Alliance for Future Tyres (AZuR), a European network of nearly 100 partners from industry, trade and science dedicated to advancing a sustainable tyre circular economy across all segments.

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