Mothers have high standards for the items they use to take care of their children, and so does the Food and Drug Administration (FDA) last updated in May 2019 in a guidance to provide additional information on how to prepare Food Contact Notifications (FCNs) for food contact substances that will come into contact with infant formula and/or human (breast) milk. Mother and child care products require materials that are hypoallergenic, durable, smooth and comfortable, and easy to clean. For these characteristics, liquid silicone rubber (LSR) has emerged as the material of choice.
LSR baby products include items like pacifiers, while mothers may find them in infant formula packaging, such as baby bottles, bottle inserts, nipples, and any other products used to collect and store baby formula or breast milk. The molecular structure of LSR makes it inherently resistant to many harmful agents, and the injection molding process allows for unique designs for a variety of products. Injection molding and LSR are the best options for many mother and infant care products.
Part of the reason LSR materials are so widely used is that they have a variety of benefits applicable to many products. The unique chemical structure of LSR offers an array of characteristics that help prevent bottles from harboring bacteria, nipple protectors from irritating the skin and pacifiers from deforming in the dishwasher, among other useful qualities:
· Biocompatible: LSR is compatible with the body and an ideal choice for parts with prolonged human contact.
· Hypoallergenic: LSR is also hypoallergenic, it will not cause skin irritation. Many products in the life sciences industry, particularly mother and child care products see extensive human contact.
· Hygienic: Many mother and child care parts do not necessarily require production in an environmentally-controlled or a clean room environment, however a clean, highly-automated manufacturing process with minimal human touch is important and contributes positively to the overall hygiene of the part.
· Inert: LSR is inert and does not react to other chemicals, making it water resistant and resistant to oxidization, UV and ozone radiation. Because LSR is also resistant to cleaning agents, it offers ease of cleaning – important for baby-related products.
· Thermal properties: LSR materials maintain their structure throughout a wide range of temperatures between -40 and 200 degrees Celsius. They maintain flexibility at both low and high temperatures. Mother and child care products benefit greatly from LSR’s performance in wide range of temperature, important for products exposed to cold and hot temperatures, such as refrigeration and frequent dishwashing or heat sterilization.
· Tasteless and odorless: Using tasteless and odorless materials is essential when designing parts such as bottle teats and sippy cups. A bad smell or taste can easily prevent a baby from accepting the food or medicine fed.
· Soft touch and comfort: The soft and smooth texture of LSR make it ideal for baby feeding and soothing products, and breast-feeding products for mothers.
· Durable: Food-grade LSR has a low compression set, meaning it can significantly withstand deformation from compression and temperature changes. This quality makes it ideal for parts like nipples and pacifiers that a baby will bite or suck on. Even after stretching and pulling, it returns to its original shape without breaking or becoming brittle.
BENEFITS OF LSR INJECTION MOLDING
The LSR injection molding process combined with the inherent properties of LSRs are used in a wide range of products, and especially favorable for mother and child care products. The following are examples of some of the custom solutions we’ve offered our customers in the mother and child care industry:
· Bottle teats (nipples)
· Nipple protectors
· Breast pump accessories
· Sippy cup spouts
Our LSR injection molding process is clean, highly automated and provides precision shot-to-shot consistency, process stability, and minimal to no human interference. With our advanced technology, automated manufacturing, and high capacity molds, SIMTEC is ideally suited for high-volume, hygienic production requirements.
LSR injection molding offers the flexibility needed to create parts with unique features such as the following:
· Thin walls and undercuts: Typically parts with thin walls and undercuts can be a challenge when removing the part from the mold during the molding process. Undercuts can be particularly problematic with a rigid material. With LSRs, the parts can be more easily removed without sustaining damage due to its good compression set and elongation properties. Because LSR maintains its shape, it works well for thin walls. The degree of thinness will vary depending on the part geometry, function/intended use and other design aspects including size and location.
· Soft and comfort attributes: LSR is soft and smooth and comfortable to the touch. When LSR is joined together with a hard thermoplastic in an overmolded or two-shot application, such as a soft grip handle or spout, it offers both the structural rigidity needed and the softness for more enjoyable use.
· LSR provides an easy integration of design features within the part e.g. Valves and membranes. This helps in manufacturing products with anti-colic features to keep babies gas-free during feeding and to create tight seals to prevent spilling
A true, two-shot injection molding process integrates LSRs with engineering thermoplastics, molding them together in the same process, creating multi-functional, multi-material components that offer the benefits of both materials. Child care products that use two-shot molding include sealed caps, sippy cup soft spouts and handles, and bottles designed with integrated LSR vents that prevent air penetration. Air penetration can cause gas in infants as they swallow air that becomes trapped in the milk. Venting can prevent this by adding small holes, slits or valves in certain locations on the bottle to allow the air to escape as the baby drinks. The two-shot process combines the components and offers the characteristics and property benefits of both the rigid plastic and LSR.
Our manufacturing process is highly automated, minimizing or eliminating human touch and the potential for the introduction of contaminants including bacteria, viruses and other germs. From the mixing and delivery of the raw material into the mold, and multi-axis robotics removing the parts, to the delivery of the parts to conveyors, ─ each step is performed without human intervention for full control of each part during the complete production process.
In addition to the hygienic benefits, our advanced molding technology also provides consistent and efficient manufacturing and process stability, reducing errors and ensuring identical products over and over ─ from the first part to the last.
The chemical reactions involved in processing LSRs create some byproducts “volatiles” that remain in the material. Some volatiles escape the material over time, however when LSR is exposed to heat, the driving out of the volatiles is controlled and fast. In the LSR molding process, the mold is subjected to elevated temperatures which drives out almost all of the volatiles in the material. Sometimes the finished parts are put in a static oven at around 200°C for post-curing. The length of time and temperature will vary depending on the type of product and the manufacturing process. The curing process serves to remove excess volatiles and can also serve to improve mechanical properties. The post-curing process drives off any remaining volatile content, bringing it to appropriate levels for food and medical use. During this process, volatiles evaporate from the material.
For standard LSR grades, post-curing is typically required when used in sensitive applications such as baby care or medical devices. The most notable reason is to reduce the volatile content to meet specific acceptable levels of volatiles.
While post-curing drives volatiles out of the molded product, new generation low-volatile LSRs can eliminate the need for post-curing. Low-volatile LSRs are a new grade of materials that have the volatiles already removed in the process of manufacturing the raw material thus complying with regulations requiring maximum 0.5 weight percent volatile content and also fulfilling challenging limits for migrating and extractable substances without the post-cure heat treatment.
The result is a product that does not require a second processing step reducing cost and risk of contamination.
This transparent, blue-tinged low volatile LSR has a variety of Shore hardnessess between 30 and 70A. The Shore hardness scale measures how well a material resists indentation, and is an essential factor in the degree of flexibility in the part. For volatile-sensitive products used in baby care, food, and medical products, the shore hardness typically required is within this range.
Conventional LSRs that are not post-cured can have around 1 to 2% volatile content by weight, the newer lower volatile LSR products have about a 0.2 to 0.3% volatile content by weight. The conventional LSRs may have Dx siloxanes of 7,000 parts per million (ppm), compared to the 500 ppm of their low-volatile counterparts. These low levels of volatiles can make post-curing a thing of the past.
Many industries have products that must meet rigorous standards for the maximum allowable volatile content in their products, and with standard LSR materials, post-curing is usually required to meet these requirements. While post-curing is effective in reducing volatiles, it also has risks. Post curing can increase the opportunity for contamination. Therefore, it would be beneficial for products that must meet hygienic standards, such as those in medical, food, and mother and child care industries, if the post-curing process could be eliminated. There is also a risk of potential fire or explosion that can occur if oven ventilation is poor, another advantage of eliminating the need for post curing.
The new low-volatile LSRs help meet the volatile content requirements for various products in a variety of industries, without the need for post-curing ─ from baby care applications to medical components.
With conventional LSRs, post-curing is a necessity, but with these new low-volatile LSR options they eliminate the need for a secondary post-curing step. Although low volatile grades are more expensive than standard grades of LSR, they offer some cost savings and eliminate the additional source of contamination associated with the post-curing process:
· Ovens: The capital investment in commercial-grade ovens can be significant, especially if multiple ovens are needed.
· Energy Costs: The associated cost of electricity to heat the ovens.
· Time: Post-curing adds time to the manufacturing process. Depending on the product and method, it’s possible some LSRs may require several days to post cure.
· Space: Between floor space for the ovens and racks and trays for cooling, post-curing can take up valuable space throughout a facility that could otherwise see more efficient use.
· Labor: Manpower needed for operating the ovens, moving the product and overseeing the process.
Eliminating the need for post-curing with low-volatile LSRs can offer time and cost savings, and contribute to an improved final product by reducing contaminants without the added risks incurred to achieve the characteristics that make it beneficial.