5 Critical Mistakes in Plastic and Rubber Processing That Shorten Product Lifespan

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Plastics and rubber are the foundation of modern manufacturing, but their processing requires a precise approach. Even minor deviations from technological parameters can cause serious defects—from reduced mechanical resistance to chemical degradation. Problems often begin during raw material storage or incorrect setup of processing machinery. In this article, we focus on the five most common errors that lead to premature material failure and show how to systematically prevent them. The practical advice is based on real-world experience from manufacturers and suppliers of chemical additives who address the quality of final products on a daily basis.

1. Improper raw material storage: How moisture and temperature destroy polymers

Polymers and rubber compounds are sensitive to storage conditions, with moisture and temperature fluctuations being the most common causes of degradation. Polyamides, polycarbonates, or polyurethane systems absorb moisture from the air, leading to hydrolysis during processing—resulting in bubbles, reduced strength, or a dull surface finish of products. For example, polyamide 6 can absorb up to 3% water when stored in an environment with relative humidity above 50%, which during subsequent processing causes the breakdown of polymer chains.

Storage temperature should be stable, ideally between 15–25 °C. Excessively low temperatures cause brittleness in some elastomers (e.g., natural rubber), while high temperatures accelerate oxidation and shorten the lifespan of additives such as antioxidants or plasticizers. Store raw materials in their original sealed packaging, on pallets away from direct sunlight and heat sources. For sensitive materials (e.g., polyurethane prepolymers), use air dryers or climate-controlled spaces. Regularly check humidity using hygrometers and follow manufacturer recommendations—these often specify a maximum storage period (typically 6–12 months) and conditions.

2. Incorrect Material Preparation Before Processing: Why Drying and Homogenization Matter

Many production defects in plastics and rubber processing arise even before the actual processing—due to insufficient drying or poor homogenization of raw materials. Hygroscopic polymers (e.g., PET, ABS, polycarbonate) require drying to a moisture level below 0.02–0.05% before entering the extruder or injection molding machine. Excess moisture causes hydrolytic degradation, which manifests as a reduction in molecular weight, deterioration of mechanical properties, and the formation of surface defects. Hot-air or vacuum dryers are used for drying, with temperatures of 80–120 °C for 2–6 hours, depending on the material.

Another critical step is the homogenization of mixtures, especially in rubber compounds or composites with fillers (carbon black, chalk, glass fibers). Uneven distribution of additives leads to local overheating, poor melt flow, or uneven curing. Use mixing equipment with controlled temperature and mixing time, or masterbatch for uniform dispersion of pigments or stabilizers. Before processing, always verify the moisture content using standard test methods and visually inspect the mixture’s homogeneity—lumps or separation are warning signs.

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3. Melt overheating: How temperature and processing time affect quality

Overheating of polymers during processing is a common cause of degradation, which manifests as yellowing, reduced strength, or increased brittleness. Each polymer has a specific processing temperature range—for example, polypropylene is processed at 200–260 °C, while temperatures above 280 °C cause decomposition and the release of volatile substances. In rubber compounds, overheating leads to premature crosslinking (scorching), which prevents further processing.

Not only temperature but also the residence time of the material in the hot zone is important. Long processing times (e.g., at low screw speeds) increase the risk of thermal degradation. To minimize risks, follow the recommended temperature profiles for the specific material, use thermocouples for precise melt temperature measurement, and regularly check the condition of the screw and barrels—worn components cause local overheating. For sensitive materials (e.g., PVC), add thermal stabilizers and process them at the lowest possible temperatures.

4. Neglecting Additive and Polymer Compatibility: When Components Don’t Mix

Additives such as plasticizers, stabilizers, fillers, or colorants can significantly improve the properties of plastics and rubber, but their incorrect combination leads to chemical reactions, migration, or loss of functionality. For example, some plasticizers (e.g., phthalates) are not compatible with polyolefins and may cause embrittlement or surface exudation. Similarly, improperly selected antioxidants can react with the polymer and accelerate its degradation instead of protecting it.

Always verify the compatibility of additives with the polymer using technical data sheets and manufacturer recommendations before use. It is also important to consider processing conditions—some additives degrade at high temperatures or react with moisture. When developing blends, perform compatibility tests, such as differential scanning calorimetry (DSC) or rheological measurements. For rubber compounds, pay attention to interactions between crosslinking agents, accelerators, and fillers—an incorrect combination can lead to insufficient crosslinking or premature curing.

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5. Ignoring internal stress and improper cooling: Why even high-quality parts crack

Internal stresses in plastic and rubber components are a silent killer of longevity. They arise during uneven cooling of the melt, when different parts of the product solidify at varying rates. A typical example is thin-walled parts with thick ribs – while the ribs are still hot and soft, the thin walls have already hardened. The result is permanent stress, which only becomes apparent later: the product cracks under mechanical stress, deforms with temperature changes, or corrodes more quickly. In rubber, this also leads to so-called 'frozen' stress, which reduces elasticity and shortens the lifespan of seals and hoses.

The solution is controlled cooling with respect to the geometry of the part. For injection-moulded plastics, gradual reduction of mould temperatures (e.g., from 80 °C to 40 °C over 30 seconds) and the use of cooling channels with uniform flow have proven effective. For extruded profiles, symmetrical cooling is key – ideally combining water sprays and air knives. For rubber products, slow cooling in climate-controlled chambers is recommended to prevent sudden shrinkage. It is also important to follow the recommended temperature profiles for specific polymers – for example, polyamides require longer cooling than polyolefins due to higher crystallinity.

6. Neglecting Maintenance of Processing Machinery: How Worn Screws and Moulds Destroy Material

Worn screws in injection moulding machines, scratched moulds, or clogged extruder filters are common causes of polymer degradation. As the material passes through damaged parts, local overheating, shear stress, and the formation of unwanted degradation products occur. For example, a worn screw can cause part of the melt to linger in 'dead zones' and overheat, while the rest of the material is processed correctly. The result is dark spots, reduced strength, or increased brittleness of the product. In rubber, premature vulcanisation also occurs in areas with high friction.

Regular maintenance should include checking the screw geometry (especially for highly filled polymers), mold polishing, and replacing filters at least every 500 operating hours. For injection molding machines, it is critical to monitor screw wear – if the thread depth decreases by more than 10% of the original value, it is time for replacement. For extruders, it is recommended to use filters with a fineness corresponding to the processed material (e.g., 40–60 microns for polyolefins, 20–30 microns for engineering plastics). It is also important to calibrate temperature sensors – a deviation of just 5 °C can lead to degradation of additives or the polymer.

7. Improper Handling of Recyclate: When Savings Come at the Cost of Quality

Using recycled polymers is ecological and economical, but without the right approach, it can dramatically reduce the lifespan of products. The most common mistake is mixing recyclate with primary material without considering compatibility and the quality of the input raw material. For example, recycled polyethylene from packaging may contain residues of adhesives, dyes, or other polymers, which cause phase separation and weaken the structure. In rubber, the problem is contamination with metal particles or residues of vulcanizing agents, which accelerate aging.

The key to successful recyclate utilization is its thorough characterization and pretreatment. Before mixing, it is necessary to verify rheological properties (e.g., melt flow index), impurity content, and mechanical parameters. For plastics, it is recommended to use recyclate with a maximum of 10% impurities and to dry it to a moisture content below 0.05% before mixing. For rubber, it is essential to remove metal particles by magnetic separation and perform thermal regeneration to eliminate residues of vulcanizing agents. Ideally, recyclate should be processed in the middle layer of multilayer products (e.g., pipes or packaging), where it does not affect surface properties.

Ensure Quality Raw Materials

Every raw material from GCG Group is supplied with complete technical documentation and safety data sheets, which include precise parameters for processing and storage. Our experts will be happy to advise you on the selection of additives and the optimization of your production process to help you avoid unnecessary losses and complaints. Contact us – or browse our catalog of over 1,300 products right away.