The minimum and maximum wall thicknesses that can be achieved depend, in particular, on the thermal energy stored in the metal immersion cores heated in the furnace and the components to be coated, the dwell time of the metal cores and components as they are immersed and cool down in the immersion tank, and the geometry and viscosity of the PVC material.
Generally speaking, thicker insert cores – for example, round insert cores with larger diameters used in the manufacture of round caps – also allow for greater wall thicknesses to be achieved. To protect screw connections, Round caps for the construction of wind turbines manufactured, for example, with a length of 400 mm and a wall thickness of 4.5 mm.
When coating components with geometries that are sometimes complex, the wall thicknesses of the coating must be determined through practical trials.
To ensure that the dip-moulded parts can be easily removed from the differently shaped mould cores after the gelation process, they must have a sufficient minimum wall thickness. If the wall thickness is too small, the dip-moulded part may become deformed or turn inside out during demoulding.
The required minimum wall thickness depends on the specific geometry of the die-cast part. We therefore specify the technically necessary minimum wall thickness in our quotations.
Depending on the geometry of the part being dipped, the dipping cores are immersed in and removed from the dipping tank at different speeds and to different depths.
If the immersion core remains in the immersion tank for too short a time, the resulting PVC layer will be too thin to allow the part to be demoulded subsequently without deformation and in a process-reliable manner. In such cases, the dwell time is increased to ensure a sufficiently thick wall.
The wall thickness of our dip-moulded parts is measured non-destructively at the open end of the component. To do this, we use a calliper whose measuring jaws make only light contact with the inner and outer surfaces of the soft PVC part. This method provides reliable results and is entirely sufficient for dip-moulded parts. Compared with injection-moulded parts, the wall thicknesses are designed with a comparatively generous tolerance of ± 0.2 mm. As the requirements for dimensional accuracy are generally less stringent, this measurement method enables reliable and practical quality control.
No. Neither the PVC dip moulding process nor PVC dip coating allows for a completely uniform wall thickness to be achieved along the entire length of a product.
The wall thickness is influenced by various factors, including the dwell time of the dip-moulded part or the component to be coated in the plastisol, the thermal energy stored in the mould or component, the geometry of the dip-moulded part or component, and the viscosity of the soft PVC used.
Generally speaking, the greatest wall thickness occurs where the heated dip core or component first comes into contact with the plastisol. This area remains in the dip tank for the longest time during the dipping process, allowing the thickest layer of PVC to build up there.
In the case of a simple cylindrical cap, the wall thickness is therefore greatest at the closed end and decreases gradually towards the open end.
As the coating is built up predominantly through the thermal energy stored in the dip core or the component to be coated, and as the PVC layer that has already formed acts as a thermal insulator, there are physical limits to the wall thickness that can be achieved. Minor variations in wall thickness are therefore inherent to the process and cannot be avoided from a technical point of view.
Local variations in thickness occur at edges and tips, and these cannot be avoided. The smaller the angle between two adjacent surfaces, the thinner the layer of material over the edge will be. In the case of acute angles and sharply protruding geometries, there is a risk that the layer build-up will be insufficient to achieve a functionally effective and continuous wall thickness.
For custom-made parts, the wall thickness distribution is influenced by the shape of the dip mould or the component to be coated. Areas with a greater volume of material store more thermal energy and cool down more slowly. As a result, PVC can accumulate there over a longer period, leading to locally thicker walls. In the corners where adjacent surfaces meet, the viscous, slow-flowing material adheres, leading to further material build-up.
Drip marks and flow marks are phenomena inherent to the PVC dip-coating and coating process. After the dipping core or the coated component has been removed from the plastisol, excess material slowly flows downwards under the influence of gravity and tends to collect in recesses, grooves, at corners and at the lowest points of the component.
The extent of this effect depends, amongst other things, on the viscosity of the soft PVC used. Materials with a higher Shore hardness are generally more viscous and flow more slowly. This can lead to localised build-up of material, sagging or slight flow marks.
These characteristics are due to technical factors and cannot be completely avoided during the dipping and coating process.
When immersing the mould cores, care must be taken to ensure that no air is drawn into the depths of the plastisol due to geometric undercuts and cavities. The liquid plastisol displaces the air as it is immersed. Air bubbles adhering to the core are washed away by the plastisol. After demoulding, the bubbles are clearly visible on the wall of the inner contour. The invisible inner contour of the dip-moulded parts is a replica of the surface of the dip moulds.
If the dipping cores are lowered into the dipping tank too quickly, air bubbles may detach from them. As the bubbles rise only slowly to the surface of the viscous plastisol, the PVC dipping paste becomes increasingly interspersed with bubbles. Surface defects on the visible outer contour of the dipped parts are caused by excessive immersion speeds and a lack of care when immersing the cores.
When stored correctly, PVC caps can be kept for many years without their performance characteristics being significantly impaired. This requires temperatures that remain as constant as possible and are close to room temperature, protection from direct sunlight and UV radiation, and avoiding contact with solvents or other chemical influences.
For long-term storage, we recommend keeping the parts in sealed, sturdy storage containers. The shipping packaging is primarily designed for cost-effective transport and is not always suitable for storage over several years. Particularly with larger quantities, the weight of the parts themselves can lead to compressive stress and permanent deformation of the caps underneath. Transferring the parts to suitable storage boxes can significantly reduce this risk.
Soft PVC is particularly suitable for processing by extrusion, injection moulding, dipping, coating, thermoforming, thermal bonding and solvent-based bonding. Due to its softness and temperature sensitivity, PVC requires specific manufacturing process parameters to prevent thermal decomposition of the material.
Our processes in detail:
Injection moulding: Soft PVC is melted in the barrel of an injection moulding machine (approx. 160–200 °C) and injected into moulds to produce precise and complex moulded parts (e.g. seals or plugs). Find out more about PVC—Injection moulding process
Dipping & Coating: Metals or other substrate materials suitable for heating in a furnace are dipped into liquid soft PVC (plastisol) to produce durable, shock-absorbing coatings or flexible dipped parts. Find out more about the Immersion process and the PVC coating
Joining & Bonding: PVC parts can be joined thermally (e.g. hot-air welding) or chemically (bonding). Special adhesives suitable for use with plasticisers are used for this purpose.
The key difference lies in the method and precision of the moulding process: In injection moulding, molten, hot plastic is forced under high pressure into a closed, cooled hollow mould and, once cooled, is demoulded as a finished moulded part with excellent accuracy in reproducing the internal and external contours. In the dip-moulding process, a pre-heated component or heated dip mould is immersed in an unheated bath of liquid PVC plastic (plastisol) and remains in the dipping tank until, without the application of pressure, a sufficient amount of material has adhered to the metal surface, which is wetted by the liquid and cooling slowly. The internal contour exhibits good accuracy, whilst the external contour tends to be rounded and less precise.
At the PVC dipping and coating processes Gelling, or the gelling process, refers to the transition of liquid PVC plastisol into a solid, rubber-like state when exposed to temperatures of 80°C or above.
When cold, the finest PVC particles, plasticisers and other formulation components are evenly and loosely distributed within the liquid-paste-like PVC plastisol. When a highly heated workpiece is immersed in the paste, contact with the hot surface causes the PVC particles to absorb plasticisers, swell and adhere to the hot surface. This very quickly forms a gel-like layer on the surface of the metal part as it cools slowly. The physical and mechanical properties of PVC grades are achieved following a final heat treatment at temperatures above 150°C in the furnace.
The task at hand is the key difference when comparing the two manufacturing processes. Whilst in the Coating where a component that has been heated beforehand is coated with a functional layer (e.g. corrosion protection, electrically insulating coating) by immersion in a plastisol dip bath (dip coating) and the coating remains on the component, the aim of the Immersion process of a preheated moulded part (dip moulding), and, once the material has gelled, to be able to remove a functional part (cover cap, paint protection or impact protection) from the dip mould and use it for any components.
When applying a PVC coating to metal components, care is taken to ensure that they are as free as possible from grease and oil-based contaminants. The components are heated in an oven and then immersed in a tank filled with plastisol. Under the influence of heat, the PVC gels and fuses to form a continuous, firmly adhering plastic layer which, following the final heat treatment, protects the component against corrosion and mechanical stress.
Further information for buyers, technicians, design engineers and developers is available on the product page PVC coating and rubberising Ready.
The coating can be applied primarily to metals (steel, structural steel, stainless steel, aluminium, copper, brass), as well as Glass and ceramics, as well as some heat-resistant plastics. In industrial practice, however, it is predominantly metal parts that are used in the PVC dipping process coated, because they can withstand the required process temperatures and store the thermal energy needed for the gelling process.
The suitability of galvanised or powder-coated metal parts for Coating with PVC This must be tested in practice, as the quality of the pre-treatment is also crucial to the quality of the coating. As a powder coating acts as a bonding agent between the metal and the PVC layer, the process parameters for the PVC coating should be determined on uncoated raw parts. Visible discolouration on uncoated areas of galvanised parts, as well as possible blistering on poorly powder-coated metal parts, cannot be entirely ruled out.
Some high-temperature-resistant plastics, such as PEEK and PET, can be coated under certain conditions. Even if the softening temperature is above 200 °C, the wall thickness in the area to be coated on the plastic parts must be sufficiently large to store and slowly release the thermal energy required for the PVC particles to gel on the moulded part’s wall.
Yes, a second layer of PVC in a different colour can be applied using the dip-coating process. This process is used when multi-coloured layers, decorative effects or additional functional layers of varying hardness are required.
First, a component or a moulded dip mould is dipped into the PVC plastisol containing the first colour, and the first layer is allowed to gel to the desired thickness. Depending on the process, the cooled component or dip mould is either reheated to a lower temperature or maintained at a defined temperature whilst the process is ongoing. This is followed by a second dipping process in the plastisol using a different colour. The second layer gels onto the surface of the existing first PVC layer. During the final heat treatment, both layers are thermally bonded together.
Completely dipping the item in a second colour usually results in the first colour being covered. Two-colour designs are therefore often created by partial dipping or by covering (masking) specific functional areas. Examples of applications include tool handles with a coloured grip zone or protective caps subject to mechanical stress, which allow wear to be detected in good time.
Yes, soft PVC can be welded. It is a thermoplastic and softens or becomes fusible when heated, allowing two parts to be joined by material bonding. Most commonly, the joint surfaces are heated with a hot wedge and then pressed together under pressure. However, caution is advised: overheating the joints can lead to the thermal decomposition of PVC. This decomposition releases, amongst other things, hydrogen chloride (HCl), which is why effective extraction is essential. As the bead-like joint formed during welding requires mechanical finishing, we recommend bonding the parts together.
Soft PVC is generally easy to bond, although the choice of adhesive is more important than with rigid PVC, as the plasticisers it contains can adversely affect the bonded joint. In most cases, two soft PVC parts are bonded using solvent-based PVC adhesives. It is crucial that the adhesive is suitable for PVC containing plasticisers, so that the joint remains permanently flexible and strong at the bonding point once the solvent has evaporated. In contrast to the welding of soft PVC parts, when Bonding only a very slight ridge-like thickening at the joint.
Yes, both soft PVC dip-moulded parts and PVC-coated components can, in principle, be used in the pad printing process can be printed on. The 1- or 2-component ink system is perfectly suited to the surface characteristics of the glossy, smooth standard types, as well as to the matt, pearlescent finish of the two special types of soft PVC and the plasticisers they contain. No pre-treatment (e.g. cleaning, flame treatment, corona or plasma treatment) is required for our PVC products.
Yes, undercuts can often be achieved in soft PVC dip-moulded parts, and indeed much more easily than in many injection-moulded parts. Light to moderate undercuts, or so-called forced demoulding with thin walls, are often achievable without difficulty in soft PVC dip-moulded parts, as the material is sufficiently flexible and elastic. When being removed from the dipping core, the dipped part – which is fitted with a locking groove or a circumferential bead – can be temporarily deformed (stretched) and subsequently returns to its original shape.
In the case of pronounced undercuts, such as those found in a bellows, we have to determine the geometry based on material hardness, wall thickness and Plunger core design be assessed.
Soft PVC (plasticised polyvinyl chloride) Soft PVC (plasticised polyvinyl chloride) is a flexible and durable plastic. It is characterised by its high elasticity, good weather resistance, as well as its resistance to moisture absorption and resistance to chemicals, cleaning agents and disinfectants. Furthermore, soft PVC is ideally suited for processing into rubber-like products using dip-coating, coating and injection moulding processes.
Soft PVC contains plasticisers, which make it elastic, pliable and flexible. Hard PVC does not contain any plasticisers and is therefore rigid, dimensionally stable and particularly durable. Whilst soft PVC is frequently used for hoses, films, Immersion parts and Coatings Rigid PVC is primarily used in pipes, window profiles and technical components.
Soft PVC derives its elasticity from special plasticisers. For health and consumer protection reasons, the use of certain phthalate plasticisers is now restricted, particularly in products for children, consumer goods and applications involving close skin contact, phthalate-free formulations used.
Yes. The international abbreviation for polyvinyl chloride is PVC. The letter ‘C’ in this stands for the halogen chlorine. This applies to both rigid PVC and flexible PVC. The chlorine is firmly bound within the molecular structure of the plastic and is not released during normal use. It is only upon thermal decomposition and immediate reaction with water or atmospheric moisture that caustic and corrosive hydrogen chloride (HCl) is produced as a decomposition product.
Products made from soft PVC typically have a continuous temperature resistance of 60–80 °C and can withstand temperatures of up to 90–100 °C for short periods. Temperatures above this range cause the material to soften and products made from soft PVC to deform. A soft PVC specially formulated with additives In accordance with VW test standard P 1300, it can be subjected to temperatures of up to 200°C for a period of 45 minutes, which is sufficient as an alternative to silicone caps in certain applications.
Yes, caps can in principle also be made from diving materials such as silicone or natural rubber, both of which have a higher long-term temperature resistance than soft PVC, but are not used by Hamco.
As conventional products made of soft material soften at temperatures above 90–100 °C and deform under stress, a Special-grade soft PVC which can be used for extended periods at higher temperatures. In accordance with the thermal stability test standard set out in VW specification P 1300, this special type can withstand a temperature of 200°C for a period of 45 minutes. For every 10 K reduction in test temperature, the operating time doubles (to 90 minutes at T = 190 °C / to 180 minutes at T = 180 °C). In many cases, this is sufficient as an alternative to injection-moulded or dip-coated silicone caps.
Particularly in the case of coloured soft PVC products which, when used outdoors in accordance with their intended application, are exposed to prolonged and intense UV radiation, specific UV stabilisers must be added to the soft PVC formulations prior to processing, to counteract both premature colour fading and a loss of mechanical properties. Black soft PVC exhibits good UV and weather resistance.
Soft PVC is a durable, flexible plastic with good resistance to ageing. PVC does not absorb water, is resistant to many chemicals and withstands weathering over long periods. However, the actual service life of moulded parts and coatings made from soft PVC depends on the operating conditions, in particular UV radiation, temperature exposure and mechanical stress. The use of suitable stabilisers can further improve resistance to ageing.
Yes, soft PVC is resistant to water and seawater. The material absorbs virtually no water and retains its physical and mechanical properties even when in constant contact with moisture. Furthermore, soft PVC is largely resistant to salt water, which is why it is frequently used in maritime applications or, for example, for Protective caps, PVC castings or coated components used in coastal or offshore wind turbines is used.
Soft PVC is characterised by good chemical resistance to many acids, alkalis, salt solutions and water-based chemicals. Furthermore, soft PVC exhibits good weather resistance and resistance to water and salt water. However, its resistance to oils, fats, fuels and some organic solvents may be limited, depending on the specific substance, its concentration and the conditions of use.
Depending on the requirements and function of the submerged component, a wider range of soft PVC grades with Shore A hardness levels from 55 to 96 is available to help you select the most suitable material. For the manufacture of smooth-running bellows, we recommend the use of a soft Plastisol-type with approx. 55 Shore A. The Standard hardness of 67 Shore A covers the vast majority of applications for cover caps and protective caps across a wide range of industrial sectors and Industries . When it comes to parts that are subjected to less mechanical stress, such as grip sleeves for hand tools, or when coating components where the focus is on corrosion protection rather than impact protection, or on ensuring a good grip on the surface, a Hardness of 75 Shore A a good choice. Where coated components are subject to high mechanical stress and are required to offer both good abrasion resistance and excellent electrical insulation properties, a Plastisol with a hardness of 85 Shore A is used. The hardest of these, and therefore just about still classed as a soft PVC type, Plastisol type with a Shore A hardness of 96 is ideal when the immersed parts need to offer high rigidity and abrasion resistance.
As well as their hardness, the various types of soft PVC also differ in their composition. Phthalate-free soft PVC types, in particular, open up new possibilities for the use of soft PVC in the the medical technology and therapeutic sectors, for toys and products that come into prolonged contact with the skin.
Soft PVC has inherently good fire-retardant properties due to its chlorine content. The material is flame-retardant and self-extinguishing once the ignition source is removed. However, please note: in the event of a fire, harmful fumes are released which must never be inhaled. In normal use, however, PVC-coated parts do not pose a risk; risks only arise in the event of severe thermal decomposition.
Yes, soft PVC is also available in electrically conductive grades as an option. By adding special additives to existing plastisol formulations, the electrical resistance can be specifically reduced so that electrostatic charges are safely dissipated. Electrically conductive soft PVC is used, for example, for Coatings for hand tools used in applications where protection against electrostatic discharge (ESD) is required.
Detectable soft PVC contains metallic or magnetically detectable additives, so that material residues from mechanically damaged or lost protective caps can be detected by metal detectors or X-ray systems – particularly in the food, pharmaceutical and packaging industries – and removed to protect consumers.
For soft PVC dip-moulded parts containing magnetic particles, the applications are almost exclusively those that require the detectability and do not require the use of an actual magnetic function.
Soft PVC is ideally suited for insulating components against electrical voltage and protecting the user. The material’s dielectric strength is at least 15–20 kV per mm of material thickness, making it entirely comparable to silicone, if not slightly superior.
Special additives can be used to tailor the electrical properties specifically, for example for applications requiring electrical conductivity or detectability.
In many regions, small quantities of used soft PVC dip-moulded parts can be disposed of as part of a private household’s general waste. For larger quantities and commercial plastic waste, the relevant local disposal and recycling regulations apply. Soft PVC is generally recyclable and should, where possible, be sent for appropriate recycling.
Yes, soft PVC is generally recyclable. Whether and in what form recycling is possible depends on the material composition, the degree of contamination and the recycling options available in your region. Please observe the waste disposal and recycling regulations that apply to you.
To ensure that a PVC round cap To ensure that it is easy to fit and, at the same time, sits securely on the component so that it cannot be lost, the outer diameter of the component and the inner diameter of the cap must be matched. For easy manual fitting, we recommend that the inner diameter of the protective cap be 0.2–0.5 mm smaller; for secure transport protection, we recommend selecting an inner diameter that is 0.5–1.0 mm smaller.
As a general rule, the internal diameter of the round cap should be selected to be slightly smaller than the external diameter of the component to be protected. Due to the elasticity of the soft PVC, the cap expands slightly during fitting and then fits snugly against the surface of the component with a certain amount of pre-tension. This creates the desired secure hold.
As well as the diameter, the length of the cap also plays an important role. Longer round caps generally provide a larger contact area and therefore fit more securely than shorter versions. It is often better to choose a slightly longer cap rather than reducing the diameter significantly.
With harder PVC materials and longer caps, the difference in dimensions between the cap and the component should be smaller, so that the cap can still be fitted without any problems.
PVC rectangular caps PVC rectangular caps are fitted onto the end of a standardised square tube or rectangular profile. Whilst this may sound simple, the ease with which this can be done varies depending on the dimensions of the protective caps, but it can always be done without the need for any tools. To ensure that the rectangular caps sit securely and cannot be lost, the caps must be pre-tensioned on the component. This pre-tension is achieved by making the longer side of the rectangular cap slightly undersized. For an 8 x 12 mm rectangular cap, the 12 mm dimension is manufactured undersized. The narrower side of the rectangular cap can initially be fitted onto the square tube with ease. Using the flat of the palm and applying a little thrust towards the longer dimension, the cap is pushed right up to the edge and then slipped over it with a little effort. A little water with a splash of washing-up liquid on the surface of one of the two components is sufficient to make the assembly a little easier.
The casting process is particularly suitable for solid plastic parts where injection moulding would be less practical, either economically or technically, due to thick walls, significant variations in wall thickness or low production volumes.
HAMCO processes high-quality PVC plastisols from the Covytec® range. These are specially tailored to meet the specific requirements in terms of hardness, flexibility and intended application.
Technical tool surfaces are reproduced very well. However, areas not in contact with the tool may have a slightly uneven surface. The process is therefore only of limited suitability for decorative high-gloss surfaces.
The PVC casting process is particularly cost-effective for small production runs, pre-production runs, spare parts and regularly recurring production orders involving manageable quantities.
The production of these moulds is significantly more cost-effective than that of complex injection moulds. This means that even smaller projects can be carried out cost-effectively.
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