When it comes to packaging your product, it’s natural to think first about design, shelf appeal, or cost. But there’s another critical factor that often flies under the radar – chemical compatibility, especially when it comes to your product’s pH level.
Getting this right isn’t just about making sure your packaging looks good – it’s about protecting your product, your customers, and your brand reputation. Choosing the wrong plastic could mean leaching, swelling, cracking, or worse—your packaging breaking down entirely.
That’s where understanding the science of plastics becomes so valuable. At Weltrade Packaging, we work closely with brands and contract fillers to help navigate these choices – because the right packaging protects your product and adds long-term value to your business.
So, what plastics should you be looking at – and why does pH matter?
Let’s break down four of the most common plastics we supply – PET, HDPE, LDPE, and PP – and explore how they handle different formulations and pH levels.
PET (Polyethylene Terephthalate)
PET is a favourite for skincare, supplements, and beverages, thanks to its strength and clear finish. But it’s not just clear – PET handles acids as it is meant to.
✅ Great for: Vitamin C serums, AHA/BHA exfoliants, kombucha, juices, essential oils.
✅ Why? It resists acids, offers a strong oxygen barrier, and doesn’t absorb your product—keeping everything stable.
🚫 Avoid: High-pH products like bleach or strong alkaline cleaners – PET just can’t handle them long-term.
♻ Highly recyclable (Resin Code #1) – a great option if sustainability is part of your brand story.
HDPE (High-Density Polyethylene) – Tough Enough for Alkaline Formulas
If you’re packing shampoos, cleaning agents, or other alkaline products, HDPE is your go-to. It’s durable, resistant, and built for the tougher jobs.
✅ Great for: Soaps, body washes, detergents, dairy-based products.
✅ Why? HDPE resists alkaline ingredients and stands up to knocks and drops.
🚫 Watch out: It’s not ideal for essential oils – over time, they can weaken the plastic and will suck in the sides of the bottle or panel.
♻ Recyclable (Resin Code #2) and widely used in household and personal care packaging.
LDPE (Low-Density Polyethylene) – Perfect for Squeeze & Flex
LDPE is super flexible – making it ideal for tubes and soft packaging – but it does have its limits.
✅ Great for: Gels, lotions, personal care products with mild formulas, sauce bottles and ultra sound gel bottles.
✅ Why? It’s soft, squeezable, and user-friendly.
🚫 Avoid: Essential oils or harsh ingredients – they’ll eventually cause warping or breakdown.
♻ Recyclable (Resin Code #4), though it’s less commonly accepted in kerbside collections, commonly councils accept 1, 2 and 5.
PP (Polypropylene) – Versatile, Reliable, and pH-Friendly
PP is the jack-of-all-trades. It works well with both acidic and alkaline products, making it ideal for pumps, closures, and even complete containers.
✅ Great for: Vitamin-rich serums, active skincare, caps and closures for almost any formulation.
✅ Why? Excellent chemical resistance and durability.
♻ Lightweight, recyclable (Resin Code #5), and highly versatile.
Why Should This Matter to You?
At the end of the day, packaging isn’t just a container – it’s an extension of your brand. Choosing the right plastic keeps your product stable, extends shelf life, and protects your investment. Get it wrong, and you risk leaching, contamination, or costly product recalls.
Whether you’re a growing brand or a contract filler looking for a reliable packaging partner, we’re here to help you make the smart choice from the start.
Let’s Work Together
At Weltrade Packaging, we pride ourselves on being more than just a supplier. We’re here as your partner – offering advice, support, and the expertise you need to nail the right packaging, whether it be Jars, Bottles, Tubes or lids, for your product, your customers, and your market.
We look forward to working with you and being part of your journey – helping you protect your products and elevate your brand with packaging that truly performs.
Weltrade Packaging is an industry leader in Sustainability, Innovation, Local manufacturing and Quality (ISO9001 and HACCP approved). Please use our available tools to help you find something that is compatible for you https://weltradepackaging.com.au/plastic-compatibility/
Reach out anytime – we’d love to chat 07 5597 0102.